Journal articles: 'Planarian flatworms'

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Kreshchenko, Grebenshchikova, and Karpov. "INFLUENCE OF SEROTONIN ON PLANARIAN PHOTORECEPTORS’ REGENERATION." THEORY AND PRACTICE OF PARASITIC DISEASE CONTROL, no. 20 (May 14, 2019): 278–83. http://dx.doi.org/10.31016/978-5-9902340-8-6.2019.20.278-283.

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The paper presents data on the effect of biogenic amine, serotonin, on morphogenetic processes in planarians Schmidtea mediterranea and Girardia tigrina(Turbellaria, Platyhelminthes). For the study, cut-off median and tail fragments of the planarian body were used, in which eye regeneration was observed. Photoreceptor recovery occurred from the 3rd to the 6th day of regeneration. In experimental specimens exposed to serotonin at a concentration of 0.1–1 μM, acceleration of the photoreceptor regeneration process was observed. The stimulating effect was observed at 4–5 days after surgery. Planaria (Turbellaria, Platyhelminthes) are free-living flatworms related to parasitic trematodes, cestodes and monogenges. In addition to the nervous, muscular, digestive, excretory and reproductive systems, they have a pair of simple eyes (photoreceptors), so they can distinguish the intensity and direction of the light flux and are oriented in space [1]. Planarium eyes are located on the dorsal surface of the head part of the body and consist of photoreceptor and pigment cells that form an "eye cup". Planaria can regenerate the whole organism from a small fragment. In the process of regeneration, the planarium can completely restore the head ganglion (brain), as well as other organs, including the eyes.Our task was to study the dynamics of photoreceptor differentiation in planarians Schmidtea mediterranea, and to investigate the possible morphogenetic function of serotonin in S. mediterranea and G. tigrina

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Kim, Iana V., Sebastian Riedelbauch, and Claus-D. Kuhn. "The piRNA pathway in planarian flatworms: new model, new insights." Biological Chemistry 401, no. 10 (September 25, 2020): 1123–41. http://dx.doi.org/10.1515/hsz-2019-0445.

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AbstractPIWI-interacting RNAs (piRNAs) are small regulatory RNAs that associate with members of the PIWI clade of the Argonaute superfamily of proteins. piRNAs are predominantly found in animal gonads. There they silence transposable elements (TEs), regulate gene expression and participate in DNA methylation, thus orchestrating proper germline development. Furthermore, PIWI proteins are also indispensable for the maintenance and differentiation capabilities of pluripotent stem cells in free-living invertebrate species with regenerative potential. Thus, PIWI proteins and piRNAs seem to constitute an essential molecular feature of somatic pluripotent stem cells and the germline. In keeping with this hypothesis, both PIWI proteins and piRNAs are enriched in neoblasts, the adult stem cells of planarian flatworms, and their presence is a prerequisite for the proper regeneration and perpetual tissue homeostasis of these animals. The piRNA pathway is required to maintain the unique biology of planarians because, in analogy to the animal germline, planarian piRNAs silence TEs and ensure stable genome inheritance. Moreover, planarian piRNAs also contribute to the degradation of numerous protein-coding transcripts, a function that may be critical for neoblast differentiation. This review gives an overview of the planarian piRNA pathway and of its crucial function in neoblast biology.

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Kreshchenko, Skavulyak, Bondarenko, and Ermakov. "MELATONIN MODULATES DYNAMICS OF PLANARIAN STEM CELL PROLIFERATION." THEORY AND PRACTICE OF PARASITIC DISEASE CONTROL, no. 21 (May 29, 2020): 157–63. http://dx.doi.org/10.31016/978-5-9902341-5-4.2020.21.157-163.

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Melatonin is a derivate of biogenic amine of serotonin identified in all classes of animals including flatworms. Melatonin demonstrates different physiological functions the main of which is circadian rhythm regulation. Via specific G-protein coupled receptors, melatonin affects the target cells changing the levels of other hormones. On early stages of embryonic development, biogenic amines as well as melatonin play a role of specific signal cell molecules that regulate processes of cellular renewal. This work has studied physiological function of melatonin in free-living flatworms, planarian Schmidtea mediterranea. The influence of melatonin on diurnal dynamics of stem cells proliferation was investigated using an immunocytochemical method and confocal laser scanning microscopy. The specific antibodies against H3 phosphohistones were applied for immunocytochemical identification of proliferative cells. It was shown that melatonin (1 µМ) decreased the total number of proliferative cells in planarians. It was also found that the diurnal dynamics of cells proliferation in planarians was changed by melatonin: regular rhythmic oscillations observed in the control group of animals were smoothening. Further researches are required to clarify mechanisms of melatonin actions.

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Adell, Teresa, Emili Saló, Jack J. W. A. van Loon, and Gennaro Auletta. "Planarians Sense Simulated Microgravity and Hypergravity." BioMed Research International 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/679672.

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Planarians are flatworms, which belong to the phylumPlatyhelminthes.They have been a classical subject of study due to their amazing regenerative ability, which relies on the existence of adult totipotent stem cells. Nowadays they are an emerging model system in the field of developmental, regenerative, and stem cell biology. In this study we analyze the effect of a simulated microgravity and a hypergravity environment during the process of planarian regeneration and embryogenesis. We demonstrate that simulated microgravity by means of the random positioning machine (RPM) set at a speed of 60 °/s but not at 10 °/s produces the dead of planarians. Under hypergravity of 3 g and 4 g in a large diameter centrifuge (LDC) planarians can regenerate missing tissues, although a decrease in the proliferation rate is observed. Under 8 g hypergravity small planarian fragments are not able to regenerate. Moreover, we found an effect of gravity alterations in the rate of planarian scission, which is its asexual mode of reproduction. No apparent effects of altered gravity were found during the embryonic development.

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Sluys, Ronald. "The evolutionary terrestrialization of planarian flatworms (Platyhelminthes, Tricladida, Geoplanidae): a review and research programme." Zoosystematics and Evolution 95, no. 2 (September 29, 2019): 543–56. http://dx.doi.org/10.3897/zse.95.38727.

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The terrestrialization of animal life from aquatic ancestors is a key transition during the history of life. Planarian flatworms form an ideal group of model organisms to study this colonization of the land because they have freshwater, marine, and terrestrial representatives. The widespread occurrence of terrestrial flatworms is a testament to their remarkable success occupying a new niche on land. This lineage of terrestrial worms provides a unique glimpse of an evolutionary pathway by which a group of early divergent aquatic, invertebrate metazoans has moved onto land. Land flatworms are among the first groups of animals to have evolved terrestrial adaptations and to have extensively radiated. Study of this terrestrialization process and the anatomical key innovations facilitating their colonization of the land will contribute greatly to our understanding of this important step in Metazoan history. The context and scientific background are reviewed regarding the evolutionary terrestrialization of land flatworms. Furthermore, a framework of a research programme is sketched, which has as its main objective to test hypotheses on the evolution of land planarians, specifically whether particular anatomical and physiological key innovations have contributed to their evolutionary successful terrestrial colonization and radiation. In this context special attention is paid to the respiration in aquatic and terrestrial planarians. The research programme depends on a comprehensive phylogenetic analysis of all major taxa of the land flatworms on the basis of both molecular and anatomical data. The data sets should be analyzed phylogenetically with a suite of phylogenetic inference methods. Building on such robust reconstructions, it will be possible to study associations between key innovations and the evolutionary terrestrialization process.

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Molina, M. Dolores, and Francesc Cebrià. "Decoding Stem Cells: An Overview on Planarian Stem Cell Heterogeneity and Lineage Progression." Biomolecules 11, no. 10 (October 17, 2021): 1532. http://dx.doi.org/10.3390/biom11101532.

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Planarians are flatworms capable of whole-body regeneration, able to regrow any missing body part after injury or amputation. The extraordinary regenerative capacity of planarians is based upon the presence in the adult of a large population of somatic pluripotent stem cells. These cells, called neoblasts, offer a unique system to study the process of stem cell specification and differentiation in vivo. In recent years, FACS-based isolation of neoblasts, RNAi functional analyses as well as high-throughput approaches such as single-cell sequencing have allowed a rapid progress in our understanding of many different aspects of neoblast biology. Here, we summarize our current knowledge on the molecular signatures that define planarian neoblasts heterogeneity, which includes a percentage of truly pluripotent stem cells, and guide the commitment of pluripotent neoblasts into lineage-specific progenitor cells, as well as their differentiation into specific planarian cell types.

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Verma, Prince, Court K. M. Waterbury, and Elizabeth M. Duncan. "Set1 Targets Genes with Essential Identity and Tumor-Suppressing Functions in Planarian Stem Cells." Genes 12, no. 8 (July 29, 2021): 1182. http://dx.doi.org/10.3390/genes12081182.

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Tumor suppressor genes (TSGs) are essential for normal cellular function in multicellular organisms, but many TSGs and tumor-suppressing mechanisms remain unknown. Planarian flatworms exhibit particularly robust tumor suppression, yet the specific mechanisms underlying this trait remain unclear. Here, we analyze histone H3 lysine 4 trimethylation (H3K4me3) signal across the planarian genome to determine if the broad H3K4me3 chromatin signature that marks essential cell identity genes and TSGs in mammalian cells is conserved in this valuable model of in vivo stem cell function. We find that this signature is indeed conserved on the planarian genome and that the lysine methyltransferase Set1 is largely responsible for creating it at both cell identity and putative TSG loci. In addition, we show that depletion of set1 in planarians induces stem cell phenotypes that suggest loss of TSG function, including hyperproliferation and an abnormal DNA damage response (DDR). Importantly, this work establishes that Set1 targets specific gene loci in planarian stem cells and marks them with a conserved chromatin signature. Moreover, our data strongly suggest that Set1 activity at these genes has important functional consequences both during normal homeostasis and in response to genotoxic stress.

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Morris, Johnathan, Elizabeth J. Bealer, Ivan D. S. Souza, Lauren Repmann, Hannah Bonelli, Joseph F. Stanzione III, and Mary M. Staehle. "Chemical Exposure-Induced Developmental Neurotoxicity in Head-Regenerating Schmidtea mediterranea." Toxicological Sciences 185, no. 2 (November 13, 2021): 220–31. http://dx.doi.org/10.1093/toxsci/kfab132.

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Abstract The growing number of commercially used chemicals that are under-evaluated for developmental neurotoxicity (DNT) combined with the difficulty in describing the etiology of exposure-related neurodevelopmental toxicity has created a reticent threat to human health. Current means of screening chemicals for DNT are limited to expensive, time-consuming, and labor-intensive traditional laboratory animal models. In this study, we hypothesize that exposed head-regenerating planarian flatworms can effectively and efficiently categorize DNT in known developmental neurotoxins (ethanol and bisphenol A [BPA]). Planarian flatworms are an established alternative animal model for neurodevelopmental studies and have remarkable regenerative abilities allowing neurodevelopment to be induced via head resection. Here, we observed changes in photophobic behavior and central nervous system (CNS) morphology to evaluate the impact of exposure to low concentrations of ethanol, BPA, and BPA industry alternatives bisphenol F, and bisguaiacol on neurodevelopment. Our studies show that exposure to 1% v/v ethanol during regeneration induces a recoverable 48-h delay in the development of proper CNS integrity, which aligns with behavioral assessments of cognitive ability. Exposure to BPA and its alternatives induced deviations to neurodevelopment in a range of severities, distinguished by suppressions, delays, or a combination of the 2. These results suggest that quick and inexpensive behavioral assessments are a viable surrogate for tedious and costly immunostaining studies, equipping more utility and resolution to the planarian model for neurodevelopmental toxicity in the future of mass chemical screening. These studies demonstrate that behavioral phenotypes observed following chemical exposure are classifiable and also temporally correlated to the anatomical development of the CNS in planaria. This will facilitate and accelerate toxicological screening assays with this alternative animal model.

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Cao, Zhonghong, Hongjin Liu, Bosheng Zhao, Qiuxiang Pang, and Xiufang Zhang. "Extreme Environmental Stress-Induced Biological Responses in the Planarian." BioMed Research International 2020 (June 11, 2020): 1–11. http://dx.doi.org/10.1155/2020/7164230.

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Planarians are bilaterally symmetric metazoans of the phylum Platyhelminthes. They have well-defined anteroposterior and dorsoventral axes and have a highly structured true brain which consists of all neural cell types and neuropeptides found in a vertebrate. Planarian flatworms are famous for their strong regenerative ability; they can easily regenerate any part of the body including the complete neoformation of a functional brain within a few days and can survive a series of extreme environmental stress. Nowadays, they are an emerging model system in the field of developmental, regenerative, and stem cell biology and have offered lots of helpful information for these realms. In this review, we will summarize the response of planarians to some typical environmental stress and hope to shed light on basic mechanisms of how organisms interact with extreme environmental stress and survive it, such as altered gravity, temperature, and oxygen, and this information will help researchers improve the design in future studies.

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Sluys, Ronald, Masaharu Kawakatsu, Marta Riutort, and Jaume Baguñà. "A new higher classification of planarian flatworms (Platyhelminthes, Tricladida)." Journal of Natural History 43, no. 29-30 (July 21, 2009): 1763–77. http://dx.doi.org/10.1080/00222930902741669.

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Kreshchenko, Grebenshchikov, Grebenshchikova, and Karpov. "SEROTONIN ACCELERATES HEAD END REGENERATION IN PLANARIAN SCHMIDTEA MEDITERRANEA AND GIRARDIA TIGRINA (PLATYHELMINTHES)." THEORY AND PRACTICE OF PARASITIC DISEASE CONTROL, no. 20 (May 14, 2019): 284–89. http://dx.doi.org/10.31016/978-5-9902340-8-6.2019.20.284-289.

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Free-living flatworms – planarians posses fascinated regenerative ability amongst metazoan. They can regenerate whole organism from small body piece. Precise mechanisms of its regeneration remain poorly investigated. The results of the experiments on head blastema growth, which was formed in regenerating planarians Schmidtea mediterranea and Girardia tigrina after decapitation, have been presented. Planarians were operated with thin scalpel under dissecting microscope and left for regeneration. Animals from control group were kept in normal water. And to the experimental group of animals the solutions of the serotonin in concentration of 0.1 and 1 μM have been added. The experiments were repeated several times. With the methods of vital computer morphomethry the areas of blastemas were measured in regenerating control and experimental (treated with serotonin) planarians. The results were analyzed by t-Student statistical method. The observation indicated the acceleration of blastema growth under serotonin treatment (0.1–1 μM) in two planarian species – S. mediterraneaand G. tigrina. Stimulating effect of serotonin has attained the level of significance on day 2 or day 3 after the operation. Serotonin is known as regulator of neural development in vertebrate organisms. In present work the morphogenetic action of biogenic amine, serotonin, in lower metazoan is postulated.

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Sarnat, Harvey B., and Martin G. Netsky. "The Brain of the Planarian as the Ancestor of the Human Brain." Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 12, no. 4 (November 1985): 296–302. http://dx.doi.org/10.1017/s031716710003537x.

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ABSTRACT:The planarian is the simplest living animal having a body plan of bilateral symmetry and cephalization. The brain of these free-living flatworms is a biiobed structure with a cortex of nerve cells and a core of nerve fibres including some that decussate to form commissures. Special sensory input from chemoreceptors, photoreceptor cells of primitive eyes, and tactile receptors are integrated to provide motor responses of the entire body, and local reflexes. Many morphological, electrophysiological, and pharmacological features of planarian neurons, as well as synaptic organization, are reminiscent of the vertebrate brain. Multipolar neurons and dendritic spines are rare in higher invertebrates, but are found in the planarian. Several neurotransmitter substances identified in the human brain also occur in the planarian nervous system. The planarian evolved before the divergence of the phylogenetic line leading to vertebrates. This simple worm therefore is suggested as a living example of the early evolution of the vertebrate brain. An extraordinary plasticity and regenerative capacity, and sensitivity to neurotoxins, provide unique opportunities for studying the reorganization of the nervous system after injury. Study of this simple organism may also contribute to a better understanding of the evolution of the human nervous system.

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MORI, EMILIANO, GIULIA MAGOGA, and GIUSEPPE MAZZA. "NEW RECORDS BASED ON CITIZEN-SCIENCE REPORT ALIEN LAND PLANARIANS IN THE THREE REMAINING ITALIAN REGIONS AND PANTELLERIA ISLAND, AND FIRST RECORD OF DOLICHOPLANA STRIATA (PLATYHELMINTHES TRICLADIDA CONTINETICOLA GEOPLANIDAE) IN ITALY." Redia 105 (June 16, 2022): 91–95. http://dx.doi.org/10.19263/redia-105.22.12.

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Mori E., Magoga G., Mazza G. - New records based on citizen-science report alien land planarians in the three remaining Italian regions and Pantelleria island, and first record of Dolichoplana striata (Platyhelminthes Tricladida Contineticola Geoplanidae) in Italy. Alien land planarians have been recorded in most of Europe and, in Italy, in 17 out of 20 regions. In this work, after collecting new data through a citizen-science approach, we report for the first time the presence of at least one alien planarian species in Molise, Basilicata, and Aosta Valley and we update the distribution range provided in our previous work. Amongst new sites, alien planarians were also found on a small island in Southern Italy, Pantelleria, which is included in a National Park rich in endemic species, thus deserving particular attention. Moreover, we report the first record of Dolichoplana striata in Italy. The increase of distribution range of alien planarians in Italy needs to be tightly monitored, as these introduced worms are responsible for impacts on native soil biodiversity. Accordingly, an e-mail address has been created ad-hoc (planarieitaliane@gmail.com) to collect all the records and to keep the distribution of alien species updated. Key Words: Biological Invasions, Citizen Science, Italy, Land flatworms, Planarians

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Kustov, Leonid, Kharlampii Tiras, Souhail Al-Abed, Natalia Golovina, and Mikhail Ananyan. "Estimation of the Toxicity of Silver Nanoparticles by Using Planarian Flatworms." Alternatives to Laboratory Animals 42, no. 1 (March 2014): 51–58. http://dx.doi.org/10.1177/026119291404200108.

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Mateos, Eduardo, Ronald Sluys, Marta Riutort, and Marta Álvarez-Presas. "Species richness in the genus Microplana (Platyhelminthes, Tricladida, Microplaninae) in Europe: as yet no asymptote in sight." Invertebrate Systematics 31, no. 3 (2017): 269. http://dx.doi.org/10.1071/is16038.

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This study forms a major step towards a comprehensive morphological and molecular analysis of the species diversity of European microplanid land planarians. It presents a molecular phylogenetic tree on the basis of information from the genes Cox1, 18S, 28S and elongation factor 1-α, and applies molecular and morphological species delimitation methodologies for Microplana specimens sampled over a wide geographic range within Europe. The study suggests that as yet there is no plateau or asymptote in the accumulation curve for European Microplana species, as our results facilitated an integrative delimitation of seven new species as well as the diagnosis of new populations of three already known species and one doubtful or problematic species. In some cases, the new records considerably enlarged the known range of a species. An integrative account is provided of each of these species. Molecular sequence information on newly collected land flatworms may quickly point the planarian systematist to taxa that need to be examined morphologically and thus may considerably reduce laborious and time-consuming histological analyses.

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Kreshchenko, Mitkovskii, Grebenshchikova, Vykidanets, and Terenina. "MORPHOMETRIC STUDY OF SEROTONERGIC NERVOUS COMPONENTS IN PLANARIANS GIRARDIA TIGRINA." THEORY AND PRACTICE OF PARASITIC DISEASE CONTROL, no. 22 (May 19, 2021): 276–81. http://dx.doi.org/10.31016/978-5-6046256-1-3.2021.22.276-281.

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The serotonergic components in the nervous system of planarian Girardia tigrina was shown by immunocytochemical method. The whole-mounts are used to extract the maximum information and conduct a quantitative morphometric analysis of serotonin-immunopositive elements in different body regions. The planarian nervous system is represented by cephalic ganglion in the anterior body part and a pair of well-defined ventral nerve cords running along the body. The density of serotonin components is greatest in the head region, which reflects in thickness of cephalic ganglion arch (123–94 µm) and of nerve cords, gradually decreasing from head (111–97 µm) to middle (83–42 µm) and tail (64-28 µm) zones. Nerve nodes contain 4–10 serotonergic neurons in different body regions and connected by a few transverse commissures with a distance from 70 to 145 µm. Results supplement the available data and can be useful for comparative analysis of serotonergic components in free-living and parasitic flatworms.

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Magley, Robert Alan, and Labib Rouhana. "Tau tubulin kinase is required for spermatogenesis and development of motile cilia in planarian flatworms." Molecular Biology of the Cell 30, no. 17 (August 2019): 2155–70. http://dx.doi.org/10.1091/mbc.e18-10-0663.

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Cilia are microtubule-based structures that protrude from the apical surface of cells to mediate motility, transport, intracellular signaling, and environmental sensing. Tau tubulin kinases (TTBKs) destabilize microtubules by phosphorylating microtubule-associated proteins (MAPs) of the MAP2/Tau family, but also contribute to the assembly of primary cilia during embryogenesis. Expression of TTBKs is enriched in testicular tissue, but their relevance to reproductive processes is unknown. We identified six TTBK homologues in the genome of the planarian Schmidtea mediterranea ( Smed-TTBK-a, -b, -c, -d, -e, and -f), all of which are preferentially expressed in testes. Inhibition of TTBK paralogues by RNA interference (RNAi) revealed a specific requirement for Smed-TTBK-d in postmeiotic regulation of spermatogenesis. Disrupting expression of Smed-TTBK-d results in loss of spermatozoa, but not spermatids. In the soma, Smed-TTBK-d RNAi impaired the function of multiciliated epidermal cells in propelling planarian movement, as well as the osmoregulatory function of protonephridia. Decreased density and structural defects of motile cilia were observed in the epidermis of Smed-TTBK-d(RNAi) by phase contrast, immunofluorescence, and transmission electron microscopy. Altogether, these results demonstrate that members of the TTBK family of proteins are postmeiotic regulators of sperm development and also contribute to the formation of motile cilia in the soma.

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Filippova, Kristina O., Artem M. Ermakov, Anton L. Popov, Olga N. Ermakova, Artem S. Blagodatsky, Nikita N. Chukavin, Alexander B. Shcherbakov, and Vladimir K. Ivanov. "Mitogen-like Cerium-Based Nanoparticles Protect Schmidtea mediterranea against Severe Doses of X-rays." International Journal of Molecular Sciences 24, no. 2 (January 8, 2023): 1241. http://dx.doi.org/10.3390/ijms24021241.

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Novel radioprotectors are strongly demanded due to their numerous applications in radiobiology and biomedicine, e.g., for facilitating the remedy after cancer radiotherapy. Currently, cerium-containing nanomaterials are regarded as promising inorganic radioprotectors due to their unrivaled antioxidant activity based on their ability to mimic the action of natural redox enzymes like catalase and superoxide dismutase and to neutralize reactive oxygen species (ROS), which are by far the main damaging factors of ionizing radiation. The freshwater planarian flatworms are considered a promising system for testing new radioprotectors, due to the high regenerative potential of these species and an excessive amount of proliferating stem cells (neoblasts) in their bodies. Using planarian Schmidtea mediterranea, we tested CeO2 nanoparticles, well known for their antioxidant activity, along with much less studied CeF3 nanoparticles, for their radioprotective potential. In addition, both CeO2 and CeF3 nanoparticles improve planarian head blastema regeneration after ionizing irradiation by enhancing blastema growth, increasing the number of mitoses and neoblasts’ survival, and modulating the expression of genes responsible for the proliferation and differentiation of neoblasts. The CeO2 nanoparticles’ action stems directly from their redox activity as ROS scavengers, while the CeF3 nanoparticles’ action is mediated by overexpression of “wound-induced genes” and neoblast- and stem cell-regulating genes.

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Kreshchenko and Mitkovskii. "SEROTONIN STRUCTURES IN THE NERVOUS SYSTEM OF PLANARIANS POLYCELIS TENUIS: MOPHOMETRIC RESEARCH." THEORY AND PRACTICE OF PARASITIC DISEASE CONTROL, no. 23 (April 18, 2022): 271–75. http://dx.doi.org/10.31016/978-5-6046256-9-9.2022.23.271-275.

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The serotonergic components in the nervous system of the planarian Polycelis tenuis were studied by the indirect immunocytochemical method for staining frozen tissue sections and their analysis using a fluorescence microscope. Morphometric measurements were conducted on microphotographs taken from stained serotonin immune-positive sections using a digital photo camera. The P. tenuis central nervous system is represented by a pair of cerebral ganglia connected by a commissure having together a butterfly-like shape and prominent ventral nerve cords that lie along the whole planarian’s body. Each cerebral ganglion had a size of 132–310 µm on serial sections. From 12 to 17 serotonin components were visible in one ganglion on one tissue section. The thickness of the nerve cords was 138 to 60 µm in different areas of the body. Nerve knots located along the way of the ventral nerve cords had 5–6 up to 8 serotonergic neurons of 11 to 23 µm. The obtained results can be useful for comparative analysis of the nervous system in free-living and parasitic flatworms to define their evolutionary development aspects.

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Negrete, Lisandro, Silvana Vargas Do Amaral, Giovana Gamino Ribeiro, Juliana Wolmann Gonçalves, Victor Hugo Valiati, Cristina Damborenea, Francisco Brusa, and Ana Maria Leal-Zanchet. "Far away, so close! Integrative taxonomy reveals a new genus and species of land flatworm (Platyhelminthes: Geoplanidae) from southern South America." Zoological Journal of the Linnean Society 189, no. 3 (November 28, 2019): 722–44. http://dx.doi.org/10.1093/zoolinnean/zlz131.

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Abstract Land flatworms usually show low ability to disperse and high endemicity, displaying many singletons in studies on land planarian assemblages. Thus, many species have been described based on specimens sampled in a single locality and/or on a few specimens. Based on phylogenetic analyses of concatenated COI and 18S rRNA genes and morphological analyses, a new genus and species of geoplaninid land planarian is described from central–east Argentina and southern Brazil. Winsoria gen. nov. shows, among its most outstanding features, a ventral cephalic retractor muscle and a subneural muscle layer that extends throughout the anterior region of the body. In addition, characters of the reproductive system and the phylogenetic analyses support the erection of this new genus. According to molecular phylogenies,Winsoria bipatria sp. nov. is closely related to species of Luteostriata, Supramontana and Issoca, taxa that also possess a cephalic retractor muscle. Despite its disjunct distribution, phylogenetic analyses, genetic divergence and morphological features show that the allopatric populations studied herein belong to a single species. We argue that the occurrence of W. bipatria in localities separated by hundreds of kilometres and a geographical barrier should be explained by passive dispersal.

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Hoffmann, Karl B., Anja Voss-Böhme, Jochen C. Rink, and Lutz Brusch. "A dynamically diluted alignment model reveals the impact of cell turnover on the plasticity of tissue polarity patterns." Journal of The Royal Society Interface 14, no. 135 (October 2017): 20170466. http://dx.doi.org/10.1098/rsif.2017.0466.

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The polarization of cells and tissues is fundamental for tissue morphogenesis during biological development and regeneration. A deeper understanding of biological polarity pattern formation can be gained from the consideration of pattern reorganization in response to an opposing instructive cue, which we here consider using the example of experimentally inducible body axis inversions in planarian flatworms. We define a dynamically diluted alignment model linking three processes: entrainment of cell polarity by a global signal, local cell–cell coupling aligning polarity among neighbours, and cell turnover replacing polarized cells by initially unpolarized cells. We show that a persistent global orienting signal determines the final mean polarity orientation in this stochastic model. Combining numerical and analytical approaches, we find that neighbour coupling retards polarity pattern reorganization, whereas cell turnover accelerates it. We derive a formula for an effective neighbour coupling strength integrating both effects and find that the time of polarity reorganization depends linearly on this effective parameter and no abrupt transitions are observed. This allows us to determine neighbour coupling strengths from experimental observations. Our model is related to a dynamic 8-Potts model with annealed site-dilution and makes testable predictions regarding the polarization of dynamic systems, such as the planarian epithelium.

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Sluys, Ronald, Miquel Vila-Farré, Jochen Rink, and John E. J. Rasko. "An intriguing, new planarian species from Tasmania, with a discussion on protandry in triclad flatworms (Platyhelminthes, Tricladida)." Acta Zoologica 99, no. 4 (February 2, 2018): 404–14. http://dx.doi.org/10.1111/azo.12243.

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Cao, Zigang, Yunlong Meng, Fanghua Gong, Zhaopeng Xu, Fasheng Liu, Mengjie Fang, Lufang Zou, et al. "Calcineurin controls proximodistal blastema polarity in zebrafish fin regeneration." Proceedings of the National Academy of Sciences 118, no. 2 (December 29, 2020): e2009539118. http://dx.doi.org/10.1073/pnas.2009539118.

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Planarian flatworms regenerate their heads and tails from anterior or posterior wounds and this regenerative blastema polarity is controlled by Wnt/β-catenin signaling. It is well known that a regeneration blastema of appendages of vertebrates such as fish and amphibians grows distally. However, it remains unclear whether a regeneration blastema in vertebrate appendages can grow proximally. Here, we show that a regeneration blastema in zebrafish fins can grow proximally along the proximodistal axis by calcineurin inhibition. We used fin excavation in adult zebrafish to observe unidirectional regeneration from the anterior cut edge (ACE) to the posterior cut edge (PCE) of the cavity and this unidirectional regeneration polarity occurs as the PCE fails to build blastemas. Furthermore, we found that calcineurin activities in the ACE were greater than in the PCE. Calcineurin inhibition induced PCE blastemas, and calcineurin hyperactivation suppressed fin regeneration. Collectively, these findings identify calcineurin as a molecular switch to specify the PCE blastema of the proximodistal axis and regeneration polarity in zebrafish fin.

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Dattani, Anish, Divya Sridhar, and A. Aziz Aboobaker. "Planarian flatworms as a new model system for understanding the epigenetic regulation of stem cell pluripotency and differentiation." Seminars in Cell & Developmental Biology 87 (March 2019): 79–94. http://dx.doi.org/10.1016/j.semcdb.2018.04.007.

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Cloutier, Jennifer K., Conor L. McMann, Isaac M. Oderberg, and Peter W. Reddien. "activin-2 is required for regeneration of polarity on the planarian anterior-posterior axis." PLOS Genetics 17, no. 3 (March 29, 2021): e1009466. http://dx.doi.org/10.1371/journal.pgen.1009466.

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Planarians are flatworms and can perform whole-body regeneration. This ability involves a mechanism to distinguish between anterior-facing wounds that require head regeneration and posterior-facing wounds that require tail regeneration. How this head-tail regeneration polarity decision is made is studied to identify principles underlying tissue-identity specification in regeneration. We report that inhibition ofactivin-2, which encodes an Activin-like signaling ligand, resulted in the regeneration of ectopic posterior-facing heads following amputation. During tissue turnover in uninjured planarians, positional information is constitutively expressed in muscle to maintain proper patterning. Positional information includes Wnts expressed in the posterior and Wnt antagonists expressed in the anterior. Upon amputation, several wound-induced genes promote re-establishment of positional information. The head-versus-tail regeneration decision involves preferential wound induction of the Wnt antagonistnotumat anterior-facing over posterior-facing wounds. Asymmetric activation ofnotumrepresents the earliest known molecular distinction between head and tail regeneration, yet how it occurs is unknown.activin-2RNAi animals displayed symmetric wound-induced activation ofnotumat anterior- and posterior-facing wounds, providing a molecular explanation for their ectopic posterior-head phenotype.activin-2RNAi animals also displayed anterior-posterior (AP) axis splitting, with two heads appearing in anterior blastemas, and various combinations of heads and tails appearing in posterior blastemas. This was associated with ectopic nucleation of anterior poles, which are head-tip muscle cells that facilitate AP and medial-lateral (ML) pattern at posterior-facing wounds. These findings reveal a role for Activin signaling in determining the outcome of AP-axis-patterning events that are specific to regeneration.

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Barzaghi, Benedetta, Davide De Giorgi, Roberta Pennati, and Raoul Manenti. "Planarians, a Neglected Component of Biodiversity in Groundwaters." Diversity 13, no. 5 (April 22, 2021): 178. http://dx.doi.org/10.3390/d13050178.

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Underground waters are still one of the most important sources of drinking water for the planet. Moreover, the fauna that inhabits these waters is still little known, even if it could be used as an effective bioindicator. Among cave invertebrates, planarians are strongly suited to be used as a study model to understand adaptations and trophic web features. Here, we show a systematic literature review that aims to investigate the studies done so far on groundwater-dwelling planarians. The research was done using Google Scholar and Web of Science databases. Using the key words “Planarian cave” and “Flatworm Cave” we found 2273 papers that our selection reduced to only 48, providing 113 usable observations on 107 different species of planarians from both groundwaters and springs. Among the most interesting results, it emerged that planarians are at the top of the food chain in two thirds of the reported caves, and in both groundwaters and springs they show a high variability of morphological adaptations to subterranean environments. This is a first attempt to review the phylogeny of the groundwater-dwelling planarias, focusing on the online literature. The paucity of information underlines that scarce attention has been dedicated to these animals. Further revisions, including old papers and books, not available online will be necessary.

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Counts, Jenna T., Tasha M. Hester, and Labib Rouhana. "Genetic expansion of chaperonin-containing TCP-1 (CCT/TRiC) complex subunits yields testis-specific isoforms required for spermatogenesis in planarian flatworms." Molecular Reproduction and Development 84, no. 12 (November 10, 2017): 1271–84. http://dx.doi.org/10.1002/mrd.22925.

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Grosbusch, Alexandra L., Philip Bertemes, Bob Kauffmann, Clemens Gotsis, and Bernhard Egger. "Do Not Lose Your Head Over the Unequal Regeneration Capacity in Prolecithophoran Flatworms." Biology 11, no. 11 (October 28, 2022): 1588. http://dx.doi.org/10.3390/biology11111588.

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One of the central questions in studying the evolution of regeneration in flatworms remains whether the ancestral flatworm was able to regenerate all body parts, including the head. If so, this ability was subsequently lost in most existent flatworms. The alternative hypothesis is that head regeneration has evolved within flatworms, possibly several times independently. In the well-studied flatworm taxon Tricladida (planarians), most species are able to regenerate a head. Little is known about the regeneration capacity of the closest relatives of Tricladida: Fecampiida and Prolecithophora. Here, we analysed the regeneration capacity of three prolecithophoran families: Pseudostomidae, Plagiostomidae, and Protomonotresidae. The regeneration capacity of prolecithophorans varies considerably between families, which is likely related to the remaining body size of the regenerates. While all studied prolecithophoran species were able to regenerate a tail-shaped posterior end, only some Pseudostomidae could regenerate a part of the pharynx and pharynx pouch. Some Plagiostomidae could regenerate a head including the brain and eyes, provided the roots of the brain were present. The broad spectrum of regeneration capacity in Prolecithophora suggests that head regeneration capacity is not an apomorphy of Adiaphanida.

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Pietak, Alexis, and Michael Levin. "Bioelectric gene and reaction networks: computational modelling of genetic, biochemical and bioelectrical dynamics in pattern regulation." Journal of The Royal Society Interface 14, no. 134 (September 2017): 20170425. http://dx.doi.org/10.1098/rsif.2017.0425.

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Gene regulatory networks (GRNs) describe interactions between gene products and transcription factors that control gene expression. In combination with reaction–diffusion models, GRNs have enhanced comprehension of biological pattern formation. However, although it is well known that biological systems exploit an interplay of genetic and physical mechanisms, instructive factors such as transmembrane potential ( V mem ) have not been integrated into full GRN models. Here we extend regulatory networks to include bioelectric signalling, developing a novel synthesis: the bioelectricity-integrated gene and reaction (BIGR) network. Using in silico simulations, we highlight the capacity for V mem to alter steady-state concentrations of key signalling molecules inside and out of cells. We characterize fundamental feedbacks where V mem both controls, and is in turn regulated by, biochemical signals and thereby demonstrate V mem homeostatic control, V mem memory and V mem controlled state switching. BIGR networks demonstrating hysteresis are identified as a mechanisms through which more complex patterns of stable V mem spots and stripes, along with correlated concentration patterns, can spontaneously emerge. As further proof of principle, we present and analyse a BIGR network model that mechanistically explains key aspects of the remarkable regenerative powers of creatures such as planarian flatworms. The functional properties of BIGR networks generate the first testable, quantitative hypotheses for biophysical mechanisms underlying the stability and adaptive regulation of anatomical bioelectric pattern.

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Issigonis, Melanie, Akshada B. Redkar, Tania Rozario, Umair W. Khan, Rosa Mejia-Sanchez, Sylvain W. Lapan, Peter W. Reddien, and Phillip A. Newmark. "A Krüppel-like factor is required for development and regeneration of germline and yolk cells from somatic stem cells in planarians." PLOS Biology 20, no. 7 (July 15, 2022): e3001472. http://dx.doi.org/10.1371/journal.pbio.3001472.

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Sexually reproducing animals segregate their germline from their soma. In addition to gamete-producing gonads, planarian and parasitic flatworm reproduction relies on yolk cell–generating accessory reproductive organs (vitellaria) supporting development of yolkless oocytes. Despite the importance of vitellaria for flatworm reproduction (and parasite transmission), little is known about this unique evolutionary innovation. Here, we examine reproductive system development in the planarian Schmidtea mediterranea, in which pluripotent stem cells generate both somatic and germ cell lineages. We show that a homolog of the pluripotency factor Klf4 is expressed in primordial germ cells (PGCs), presumptive germline stem cells (GSCs), and yolk cell progenitors. Knockdown of this klf4-like (klf4l) gene results in animals that fail to specify or maintain germ cells; surprisingly, they also fail to maintain yolk cells. We find that yolk cells display germ cell–like attributes and that vitellaria are structurally analogous to gonads. In addition to identifying a new proliferative cell population in planarians (yolk cell progenitors) and defining its niche, our work provides evidence supporting the hypothesis that flatworm germ cells and yolk cells share a common evolutionary origin.

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Uppaputthangkul, Pimrak. "REGENERATIVE ABILITIES OF PLANARIANS AND ITS INFLUENCE ON THE FUTURE OF REGENERATIVE MEDICINE." International Journal of Advanced Research 10, no. 07 (July 31, 2022): 337–41. http://dx.doi.org/10.21474/ijar01/15038.

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The regenerative abilities of a particular species of flatworm, the planarian, have been a topic of discussion and interest among scientists. These animals can regenerate parts of their body that have been cut off. This review includes the general introduction of planarians, the types of stem cells in its body, its basic anatomy and physiology, behavior, regeneration process, and applications to the medical field. We also predict the future of regenerative medicine that could be achieved by studying this particular animal model.

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Reuter, Maria, and Natalia Kreshchenko. "Flatworm asexual multiplication implicates stem cells and regeneration." Canadian Journal of Zoology 82, no. 2 (February 1, 2004): 334–56. http://dx.doi.org/10.1139/z03-219.

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The phenomenon of asexual multiplication is rare in the animal kingdom, but it occurs in all main flatworm taxa. In the present paper, we review data regarding the presence of different forms of asexual multiplication in flatworms and argue that the presence of a population of totipotent or pluripotent stem cells, "neoblasts", is a primitive feature of decisive importance for the developing potential of flatworms. Next we present information on the role of stem cells in fission, head regeneration, and pharynx regeneration of planarians. Furthermore, the tracing of neoblasts in lower flatworms and cestodes is presented, and the results indicating heterogeneity of the neoblast pool are discussed. Finally, the mode by which the neoblasts are stimulated to divide, migrate, and differentiate and the nature of the interactions are discussed. We focus on (i) biogenic amines and neuropeptides, (ii) the role of neuropeptides in the early stage of regeneration, (iii) the evidence for the influences of growth factors and nitric oxide, and (iv) the influence of weak electromagnetic fields. We discuss the pattern in which a gradient system of morphogens and (or) a hierarchical system of inductions is expressed in development.

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Lewallen, Melissa, and Warren Burggren. "Metabolic physiology of the freshwater planaria Girardia dorotocephela and Schmidtea mediterranea: reproductive mode, specific dynamic action, and temperature." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 319, no. 4 (October 1, 2020): R428—R438. http://dx.doi.org/10.1152/ajpregu.00099.2020.

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Planarians are widely used animal models for studies in regeneration, developmental biology, neurobiology, and behavior. However, surprisingly little is known about other aspects of their basic biology, even though such information might help validate these flatworms as a general animal model. We hypothesized that planaria, although dependent on simple diffusion of O2 across the integument for O2 uptake, would nonetheless show changes in oxygen consumption (V̇o2) associated with reproductive mode (sexual or asexual), feeding (specific dynamic action; SDA), temperature (Q10 values), and photoperiod typical of those responses of more complex invertebrates. In the current experiments, routine V̇o2 was measured over the range of 13-28°C in Schmidtea mediterranea and Girardia dorotocephala. At the long-term maintenance temperature of 18°C, routine V̇o2 was ~13 µL O2·g−1·h−1 in the two asexual strains, but approximately twice as high (27 µL O2·g−1·h−1) in the sexual strain of S. mediterranea, suggesting a metabolic cost for sexual reproduction. Metabolic temperature sensitivity, measured by Q10, was about one to three for all three groups. All three groups showed a large (~2- to 3-fold) increase in V̇o2 within a day following feeding, suggesting a large SDA effect. Starvation, causing “degrowth” in some planaria, resulted in a loss of one-third of body mass in sexual S. mediterranea but no body mass loss in either asexual strains. Collectively, these data indicate that, while being a relatively simple flatworm with no dedicated respiratory or circulatory system, their metabolic physiological responses are quite similar to those shown by more complex invertebrates and vertebrates, contributing to their validation as an animal model.

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Chaisiri, K., S. Dusitsittipon, N. Panitvong, T. Ketboonlue, S. Nuamtanong, U. Thaenkham, S. Morand, and P. Dekumyoy. "Distribution of the newly invasive New Guinea flatworm Platydemus manokwari (Platyhelminthes: Geoplanidae) in Thailand and its potential role as a paratenic host carrying Angiostrongylus malaysiensis larvae." Journal of Helminthology 93, no. 6 (September 20, 2018): 711–19. http://dx.doi.org/10.1017/s0022149x18000834.

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AbstractInvasive species constitute one of the most serious threats to biodiversity and ecosystems, and they potentially cause economic problems and impact human health. The globally invasive New Guinea flatworm, Platydemus manokwari (Platyhelminthes: Geoplanidae), has been identified as a threat to terrestrial biodiversity, particularly soil-dwelling native species (e.g. molluscs, annelids and other land planarians), and is listed among 100 of the world's worst invasive alien species. We report here, for the first time, P. manokwari occurrences in many locations throughout Thailand, using voluntary digital public participation from the social network portals associated with the Thailand Biodiversity Conservation Group and collections of living flatworm specimens. Mitochondrial cytochrome c oxidase subunit I (COI) sequences confirmed that all collected flatworms were P. manokwari and placed them in the “world haplotype” clade alongside other previously reported specimens from France, Florida (USA), Puerto Rico, Singapore, French Polynesia, New Caledonia, and the Solomon Islands. In addition, infective stage larvae (L3) of the nematode Angiostrongylus malaysiensis were found in the flatworm specimens, with a 12.4% infection rate (15/121 specimens examined). Platydemus manokwari occurrence in Thailand and its capacity to carry L3 of Angiostrongylus should be of concern to biodiversity conservation and human health practitioners, because this invasive flatworm species may be involved in the life cycle of angiostrongylid worms in Thailand.

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Steiner, Jessica Kathryne, Junichi Tasaki, and Labib Rouhana. "Germline Defects Caused by Smed-boule RNA-Interference Reveal That Egg Capsule Deposition Occurs Independently of Fertilization, Ovulation, Mating, or the Presence of Gametes in Planarian Flatworms." PLOS Genetics 12, no. 5 (May 5, 2016): e1006030. http://dx.doi.org/10.1371/journal.pgen.1006030.

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Segev, Ori, Ariel Rodríguez, Susanne Hauswaldt, Karen Hugemann, and Miguel Vences. "Flatworms (Schmidtea nova) prey upon embryos of the common frog (Rana temporaria) and induce minor developmental acceleration." Amphibia-Reptilia 36, no. 2 (2015): 155–63. http://dx.doi.org/10.1163/15685381-00002992.

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Amphibians vary in the degree of pre-metamorphic developmental plasticity in response to risk of predation. Changes in hatching time and development rate can increase egg or tadpole survival respectively by shortening the duration of the more vulnerable stages. The intensity of predator induced developmental response and its direction, i.e. delayed, accelerated, or none, varies considerably between amphibian and predator species. We surveyed freshly deposited clutches of the European common frog Rana temporaria in a population in Braunschweig, Germany and found that 62% (N = 20) of the clutches contained planarians (Schmidtea nova), with an average of 3.94 ± 0.79 and a maximum of 13 planarians per clutch. A laboratory predation experiment confirmed that this planaria preys on R. temporaria eggs and early embryos. We further exposed freshly laid egg masses to either free, caged, or no planarians treatments using floating containers within a breeding pond where the two species co-occur. After 10 days exposure, embryos showed developmental stages 14-25 along the Gosner scale with statistically significant positive effects of both predator treatments. The observed effect was rather slight as predator-exposed individuals showed an increase by a single Gosner stage relative to those raised without planarians. The detected trend suggests that direct and indirect cues from flatworms, rarely considered as anuran predators, might induce a developmental response in R. temporaria early developmental stages.

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Drees, Leonard, and Jochen C. Rink. "The planarian flatworm Schmidtea mediterranea." Nature Methods 20, no. 1 (January 2023): 3–5. http://dx.doi.org/10.1038/s41592-022-01727-5.

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Drobysheva, I. M. "Ultrastructure of Neoblasts in Turbellarian Geocentrophora wagini Timoshkin, 1984 (Lecithoepitheliata: Plathelminthes)." Proceedings of the Zoological Institute RAS 320, no. 2 (June 24, 2016): 176–92. http://dx.doi.org/10.31610/trudyzin/2016.320.2.176.

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Acoelomorpha and Plathelminthes have a unique system of stem cells (neoblasts), which is believed to represent a common proliferative compartment of somatic and germ line cells. Meanwhile, on the electron-microscopic level, these cells are not studied in most taxa of Turbellaria. In this study, I describe the ultrastructure of neoblasts in Geocentrophora wagini Timoshkin, 1984 (Lecithoepitheliata, Plathelminthes), an endemic turbellarian from Lake Baikal. The neoblast-like cells showed a high nucleus/cytoplasm ratio. The cytoplasm revealed the features of undifferentiated cells. Particularly, there were free ribosomes and mitochondria, while other organelles were rare and did not occur in all the cells studied. Based on their cytoplasmic and nuclear organization, three main types of parenchymal neoblasts have been distinguished. In type 1, the nuclei had a complex, highly branched configuration. The peripheral heterochromatin was not developed. A large loose structure of fibrous nature and a tiny Golgi apparatus with several secretory granules could be observed in the type 1 neoblast cytoplasm. The nuclei of the type 2 neoblasts had much simpler outlines than those of type 1, despite some processes or invaginations. The poor development of peripheral condensed chromatin was observed and distribution density of the heterochromatin clumps tended to be slightly higher, as compared to type 1. A cluster of small dense granules or a little loose body occasionally could be seen in the proximity to nuclear membrane. Type 3 neoblasts had the most compact nuclei and their heterochromatin was seen as large, irregular clumps of extremely high electron density. Many of these clumps were connected with each other and with the nuclear membrane. The scarce cytoplasm contained only mitochondria and ribosomes. Undifferentiated cells in the gastrodermis were similar to the type 2 neoblasts in the parenchyma. For the first time outside Tricladida special structures were found in the neoblast cytoplasm. These loose fibrous bodies and clusters of granules are likely to be functionally identical to the planarian chromatoid bodies. The obtained results contribute to the comparative morphology of the stem cells in flatworms and basic Bilateria and confirm the heterogeneity of the proliferative compartment in Turbellaria.

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Bertemes, Philip, Alexandra L. Grosbusch, and Bernhard Egger. "No head regeneration here: regeneration capacity and stem cell dynamics of Theama mediterranea (Polycladida, Platyhelminthes)." Cell and Tissue Research 379, no. 2 (September 11, 2019): 301–21. http://dx.doi.org/10.1007/s00441-019-03094-8.

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Abstract Research on the regeneration potential of flatworms (Platyhelminthes) has been mainly undertaken with planarians (Tricladida), where most species can regenerate a head and no proliferation takes place in the blastema, i.e. the early undifferentiated regenerative tissue. Only few studies are available for an early-branching group within the Platyhelminthes, the Polycladida. Head regeneration in polyclads is not possible, with a single exception from a study performed more than 100 years ago: Cestoplana was reported to be able to regenerate a head if cut a short distance behind the brain. Here, we show that ‘Cestoplana’ was misdetermined and most likely was the small interstitial polyclad Theama mediterranea. We revisited regeneration capacity and dynamics of T. mediterranea with live observations and stainings of musculature, nervous system, and proliferating and differentiating stem cells. In our experiments, after transversal amputation, only animals retaining more than half of the brain could fully restore the head including the brain. If completely removed, the brain was never found to regenerate to any extent. Different from planarians, but comparable to other free-living flatworms we detected cell proliferation within the posterior regeneration blastema in T. mediterranea. Similar to other free-living flatworms, proliferation did not occur within, but only outside, the differentiating organ primordia. Our results strongly imply that brain regeneration in the absence of the latter is not possible in any polyclad studied so far. Also, it appears that proliferation of stem cells within the regeneration blastema is a plesiomorphy in flatworms and that planarians are derived in this character.

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Miles, Rhea, and Tonya Little. "Investigating the Effects of an Energy Drink on Flatworms." American Biology Teacher 81, no. 6 (August 1, 2019): 430–34. http://dx.doi.org/10.1525/abt.2019.81.6.430.

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One of the goals of the Science Education Against Drug Abuse Partnership (SEADAP) is to increase student knowledge about drugs through the implementation of an inquiry-based curriculum. A science teacher who was a participant in the SEADAP program served as a facilitator for middle school students participating in an after-school program to assist them with designing their own experiment using planarians (flatworms) exposed to caffeine, sugar, and an energy drink. Results indicated that the average velocity of the planarians in 1 mM caffeine, 1 mM sucrose, and 0.1% Monster Energy drink increased in comparison to their behavior in spring water. The students also learned that substances such as energy drinks can be lethal to planarians.

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Inden, Masatoshi, Yoshihisa Kitamura, Takashi Taniguchi, Kenji Watanabe, and Kiyokazu Agata. "Parkinsonian model of planarian, an invertebrate flatworm." International Congress Series 1260 (February 2004): 291–95. http://dx.doi.org/10.1016/s0531-5131(03)01574-7.

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Sedwick, Caitlin. "Alejandro Sánchez Alvarado: Bootstrapping flatworms into the molecular age." Journal of Cell Biology 194, no. 4 (August 22, 2011): 510–11. http://dx.doi.org/10.1083/jcb.1944pi.

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Ermakov, Artem M., Kristina A. Kamenskikh, Olga N. Ermakova, Artem S. Blagodatsky, Anton L. Popov, and Vladimir K. Ivanov. "Planarians as an In Vivo Experimental Model for the Study of New Radioprotective Substances." Antioxidants 10, no. 11 (November 4, 2021): 1763. http://dx.doi.org/10.3390/antiox10111763.

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Ionising radiation causes the death of the most actively dividing cells, thus leading to depletion of the stem cell pool. Planarians are invertebrate flatworms that are unique in that their stem cells, called neoblasts, constantly replace old, damaged, or dying cells. Amenability to efficient RNAi treatments, the rapid development of clear phenotypes, and sensitivity to ionising radiation, combined with new genomic technologies, make planarians an outstanding tool for the discovery of potential radioprotective agents. In this work, using the well-known antioxidant N-acetylcysteine, planarians are, for the first time, shown to be an excellent model system for the fast and effective screening of novel radioprotective and radio-sensitising substances. In addition, a panel of measurable parameters that can be used for the study of radioprotective effects on this model is suggested.

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do Amaral, Silvana Vargas, Giovana Gamino Ribeiro, Victor Hugo Valiati, and Ana Maria Leal-Zanchet. "Body doubles: an integrative taxonomic approach reveals new sibling species of land planarians." Invertebrate Systematics 32, no. 3 (2018): 533. http://dx.doi.org/10.1071/is17046.

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Records of cryptic species have continued to emerge in the scientific literature, often revealed by the use of molecular phylogenetic analyses in an integrative taxonomic approach. This study addresses a group of four striped flatworms from the genus Pasipha Ogren & Kawakatsu, showing a pale median stripe on a dark dorsal surface. Based on morphological and molecular analyses from the cytochrome c oxidase subunit I gene (COI), we establish that we are dealing with sibling species that are closely related to P. brevilineata Leal-Zanchet, Rossi & Alvarenga, 2012, a recently described species with a similar colour pattern. Thus, we describe three of the studied flatworms as new species and propose one new unconfirmed candidate species based on molecular data. In addition, sequence analysis revealed 40 nucleotide autapomorphies supporting the species studied herein. Considering anatomical and histological features, the three new species are differentiated from their congeners mainly by details of the copulatory apparatus, such as the occurrence of an epithelium of pseudostratified appearance lining the female atrium and the shape and position of the proximal portion of the prostatic vesicle.

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Farrell, Martilias S., Kirsti Gilmore, Robert B. Raffa, and Ellen A. Walker. "Behavioral characterization of serotonergic activation in the flatworm Planaria." Behavioural Pharmacology 19, no. 3 (May 2008): 177–82. http://dx.doi.org/10.1097/fbp.0b013e3282fe885e.

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Juan Antonio, Pujol, and Ubero-Pascal Nicolás. "Non-indigenous terrestrial flatworms in Torrevieja (Alicante): presence of Bipalium cf. kewense Mosely, 1878 (Platyhelminthes, Tricladida, Geoplanidae)." Anales de Biología, no. 41 (October 3, 2019): 69–72. http://dx.doi.org/10.6018/analesbio.41.09.

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Se cita por primera vez en la provincia de Alicante (península ibérica) la especie de planaria terrestre exótica Bipalium cf. kewense Moseley, 1878. Con esta presencia aumenta el área de distribución de la especie en la Comunidad Valenciana, siendo la más meridional. Dado que la especie está considerada en esta comunidad autónoma como especie exótica invasora, se valora el riesgo potencial de colonización de ambientes naturales limítrofes a la zona de observación (jardín privado en zona urbanizada). The non-indigenous terrestrial flatworm Bipalium cf. kewense Moseley, 1878 is reported in Alicante province (Iberian Peninsula) for the first time. This occurrence is the most meridional from the Comunidad Valenciana, enlarging its distribution in this area. As the species is considered an invasive alien species in this region, the potential risk of colonizing natural environments closer to the observation area is evaluated.

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Sluys, Ronald, Lauryne J. Grant, and David Blair. "Freshwater planarians from artesian springs in Queensland, Australia (Platyhelminthes, Tricladida, Paludicola)." Contributions to Zoology 76, no. 1 (2007): 9–19. http://dx.doi.org/10.1163/18759866-07601002.

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Two new species of triclad flatworm are described from artesian springs in Queensland, Australia, viz. Dugesia artesiana Sluys and Grant, sp. nov. and Weissius capaciductus Sluys, gen. et sp. nov. Some historical biogeographic scenarios are discussed that may explain the occurrence of the new species and their close relatives in Australia.

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DORIGO, LUCA, TOMMASO DAL LAGO, MATTIA MENCHETTI, and RONALD SLUYS. "First records of two alien land flatworms (Tricladida, Geoplanidae) from Northeastern Italy." Zootaxa 4732, no. 2 (February 12, 2020): 332–34. http://dx.doi.org/10.11646/zootaxa.4732.2.8.

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During a period of intense rainfall (May 2019), several specimens of land flatworms were collected from a private garden in Palazzolo dello Stella (Friuli Venezia Giulia, Udine, Italy: 45°47’40.5”N, 13°05’17.2”E). Planarians were found both in a cultivated part of the garden and in a part covered with gravel and with trees and shrubs (Pyracantha sp., Olea europaea, Pyrus communis). The animals were observed under branches, stones, tufa blocks, and pots close to a small artificial pond, but also in other parts of the garden, as well as inside buildings.

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CHEN, JIA-JIA, WEI-XUAN LI, RONALD SLUYS, MING-QI WU, LEI WANG, SHUANG-FEI LI, and AN-TAI WANG. "Two new species of marine flatworm from southern China facilitate determination of the phylogenetic position of the genus Nerpa Marcus, 1948 and the histochemical structure of the nervous system in the genus Paucumara Sluys, 1989 (Platyhelminthes, Tricladida, Maricola)." Zootaxa 4568, no. 1 (March 19, 2019): 149. http://dx.doi.org/10.11646/zootaxa.4568.1.9.

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Two new species of flatworm, collected from a beach at eastern Shenzhen, China, were studied through an integrative approach by combining morphological, histological, histochemical (acetylcholinesterase, AChE), and molecular (18S r- DNA) data. These species belong to two genera of marine triclads, previously unrecorded from China, viz. Nerpa Marcus, 1948 and Paucumara Sluys, 1989. Nerpa fistulata Wang & Chen, sp. nov. is characterized by: transparent body; principally pentamerous intestine with three distinct commissures; two very large, prepharyngeal testis follicles; a semi-circular lens in each eye cup; a penis papilla provided with a chitinized, pointed stylet; lateral bursae communicating with the oviduct and opening ventrally to the exterior via a duct. Phylogenetically N. fistulata groups with one member of the family Bdellouridae. This new, Chinese species of Nerpa introduces a major geographic disjunction, as the type species N. evelinae was described from the bay of Santos, Brazil, so that the genus is now known from both Atlantic as well as Pacific coasts. The species Paucumara falcata Wang & Li, sp. nov. is characterized by: three distinct pale yellow transverse pigmentation bands on its dorsal side, between which some snowflake-like specks are randomly distributed, and a brown transverse band anteriorly to the eyes; 8–11 testicular follicles on either side of the body, the follicles extending from immediately behind the ovaries to half-way along the pharyngeal pocket; a musculo-parenchymatic organ with a sclerotic, curved tip projecting from the anterior wall of the male atrium, ventrally to the root of the penis papilla. Phylogenetically P. falcata groups with its congener P. trigonocephala, with the genus Paucumara forming the sister taxon of the genus Ectoplana. Comparison of the nerve structure of P. falcata, as revealed by AChE histochemistry, with that of eight other species of triclad suggested that the nervous system of marine planarians is simpler than that of species of freshwater planarians, but revealed also that the nerve structure is rather variable among species. The copulatory position exhibited by two partners in Paucumara falcata is remarkable in that they intertwine, with their heads pointing downwards and the tails pointing upwards, the entire process lasting about 10 min. Such a copulatory position has never before been reported for triclad flatworms.

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Cheng, Xiu-Zhen, Dan Jin, Li-Li Duan, Wen-Song Xu, and Hong-Chun Pan. "The complete mitochondrial genome of a planarian flatworm Girardia tigrina (Tricladida: Dugesiidae)." Mitochondrial DNA Part B 6, no. 9 (August 12, 2021): 2615–16. http://dx.doi.org/10.1080/23802359.2021.1962757.

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Journal articles on the topic 'Planarian flatworms'

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