Academic literature on the topic 'Amblyrhynchus'

The objective of this study was to demonstrate the importance of chironomid (Diptera, Insecta) larvae as food resource for Leporinus amblyrhynchus Garavello & Britski, 1987 (Anostomidae, Characiformes) and Pimelodus maculatus Lacépède 1803 (Pimelodidae, Siluriformes) and to call attention for the importance of the trophic relation between fish and chironomids assemblages in Miranda reservoir in Araguari River (Minas Gerais State, Brazil), focusing on the influence of the dam on the structure and taxonomic composition of chironomid assemblage. A total of 318 stomach contents of L. amblyrhynchus and P. maculatus were checked of which 108 had chironomid larvae. The number of chironomid larvae observed in stomach contents was higher for L. amblyrhynchus (86.3%) than for P. maculatus (52.7%). The recorded taxonomic richness of chironomid larvae in the stomach contents, suggest that these two fish species invest considerable time and energy feeding on chironomid larvae, thus consisting an important food resource. The recorded data constitute important additional information on the biology of the two studied fish species. Key words: Chironomidae, Fish diet, Dam impacts, Biodiversity.

The effects of the direct interaction between hybridization and speciation—two major contrasting evolutionary processes—are poorly understood. We present here the evolutionary history of the Galápagos marine iguana ( Amblyrhynchus cristatus ) and reveal a case of incipient within-island speciation, which is paralleled by between-island hybridization. In-depth genome-wide analyses suggest that Amblyrhynchus diverged from its sister group, the Galápagos land iguanas, around 4.5 million years ago (Ma), but divergence among extant populations is exceedingly young (less than 50 000 years). Despite Amblyrhynchus appearing as a single long-branch species phylogenetically, we find strong population structure between islands, and one case of incipient speciation of sister lineages within the same island—ostensibly initiated by volcanic events. Hybridization between both lineages is exceedingly rare, yet frequent hybridization with migrants from nearby islands is evident. The contemporary snapshot provided by highly variable markers indicates that speciation events may have occurred throughout the evolutionary history of marine iguanas, though these events are not visible in the deeper phylogenetic trees. We hypothesize that the observed interplay of speciation and hybridization might be a mechanism by which local adaptations, generated by incipient speciation, can be absorbed into a common gene pool, thereby enhancing the evolutionary potential of the species as a whole.

A new species of the genus Leporinus Agassiz, 1829 (Characiformes, Anostomidae) is described. The new species is similar to Leporinus amblyrhynchus, L. taeniatus, L. taeniofasciatus, L geminis, L. unitaeniatus, L. vanzoi, by having a dark longitudinal midlateral stripe and dark transversal bars on dorsum. However, the new species is distinguished from Leporinus amblyrhynchus by having four teeth on dentary (vs. three); from L. taeniatus by having 12 circumpeduncular scale series (vs. 16) and 37 to 39 scales on lateral line (vs. 36 to 37); from L. taeniofasciatus by having 12 circumpeduncular scale series (vs. 16); from L. geminis, L. unitaeniatus and L. vanzoi by having three teeth on premaxilla (vs. four), 37 to 39 scales on lateral line (vs. 40 to 43), four or five scale series above lateral line (vs. six), and 12 circumpeduncular scale series (vs. 16). The new species is distributed in the rio Teles Pires and rio Jamanxim, rio Tapajós basin, and rio Jari, clearwater tributaries of the lower portion of the Brazilian Amazon.

Three new species of chigger mites are described from two species of iguana endemic to the Galápagos Islands. Odontacarus cruzi sp. nov. and Schoengastia galapa sp. nov. are found on the marine iguana, Amblyrhynchus cristatus Bell, and Eutrombicula pachytrichia sp. nov. is found on the Santa Fe land iguana, Conolophus pallidus Heller. All these mite species were collected, identified, and named by P.H. Vercammen-Grandjean, but remained undescribed until the present.

The oldest known specimen of Galapagos marine iguana (Amblyrhynchus cristatus), now in the University Museum, Oxford, was originally thought to have come from Mexico. A plausible history of its origin with sealers in the Galapagos Islands about 1824 and transportation to and across Mexico is advanced. The naturalists David Douglas and John Scouler, on James (Santiago) Island in January 1825, encountered and attempted unsuccessfully to preserve specimens of the land iguana (Conolophus subcristatus) but only a Scouler specimen of marine iguana made it back to England, and it has since disappeared. Published and previously unpublished journal entries from the voyage of HMS Blonde, which had shore parties at Albemarle (Isabela) and Narborough (Fernandina) islands in March 1825, establish that the specimens on which the original description of Amblyrhynchus (later Conolophus) subcristatus J. E. Gray, 1831 , was based originated in the voyage of the Blonde. Banks Bay, Albemarle Island, is here designated as the type locality for Conolophus subcristatus. Specimens of the marine iguana were also brought back by the Blonde. The published accounts of Scouler and the voyage of the Blonde established the Galapagos as the true home of the marine iguana well before the return of Charles Darwin and HMS Beagle in 1836.

The ability to recognize and respond to the alarm calls of heterospecifics has previously been described only in species with vocal communication. Here we provide evidence that a non-vocal reptile, the Galápagos marine iguana ( Amblyrhynchus cristatus ), can eavesdrop on the alarm call of the Galápagos mockingbird ( Nesomimus parvulus ) and respond with anti-predator behaviour. Eavesdropping on complex heterospecific communications demonstrates a remarkable degree of auditory discrimination in a non-vocal species.

Squamates are ideal subjects for investigating relationships between diet and dental patterns because they exhibit wide dietary diversity, marked variation in dental shape, and are taxonomically abundant. Despite this, well-established links between diet and dental morphology are primarily qualitative in nature, with specific patterns of squamate dental complexity remaining largely unknown. Here, we use quantitative methods and a broad taxonomic dataset to quantify key patterns in squamate dental morphology, including re-examining the relationship between dentition and diet, testing for differences in complexity between dentigerous elements, and exploring the effect of ontogenetic dietary shifts in dental complexity in two iguanid genera. Our findings support previous research by demonstrating that species consuming more plant material possess more complex teeth. We did not find significant complexity differences between the left and right dentigerous elements nor the upper and lower jaws, with the exception of Amblyrhynchus cristatus, the marine iguana, which possesses significantly more complex dentary teeth than premaxillary and maxillary teeth. We find discordant patterns when testing for dental complexity changes through ontogeny. Amblyrhynchus, which is primarily herbivorous throughout its lifetime, increases dental complexity through ontogeny, whereas Ctenosaura, which is generally insectivorous as juveniles and herbivorous as adults, decreases dental complexity. Although preliminary, this research documents and quantifies novel patterns of squamate dental complexity and exhibits the possibilities for further research on the diversity of squamate dental morphology.

Les requins de récif sont particulièrement impactés par les activités humaines et ont observé un fort déclin de leurs populations au niveau mondial. Un tel déclin présente le risque d’entrainer une perturbation profonde des écosystèmes de récifs coralliens, où les requins de récifs jouent un important rôle fonctionnel. Il est donc urgent de prendre des mesures efficaces et appropriées pour la conservation des requins de récif. Les Aires Marines Protégées (AMPs) représentent un des outils les plus employés pour la protection des écosystèmes marins. Malheureusement, les AMPs actuelles sont souvent inefficaces pour la protection des espèces mobiles telles que les requins de récif. Ce travail de thèse vise à étudier les déplacements et l’utilisation de l’espace d’une espèce commune de requin de récif en Nouvelle-Calédonie afin d’améliorer la protection de cette espèce. Dans ce but, 147 requins gris, Carcharhinus amblyrhynchos, ont été marqués et leurs déplacements ont été suivis sur trois années au sein d’un réseau de 73 récepteurs acoustiques déployés au travers de l’archipel. Le requin gris représente un bon modèle pour évaluer l’apport de l’étude de l’utilisation de l’espace pour la conservation des requins de récif. En effet, c’est une des espèces de requin de récif les plus communes dans la région Indo-Pacifique et de forts déclins de ses populations ont été documentés au travers de son aire de répartition. En Nouvelle-Calédonie, des déclins d’abondance de plus de 90% ont notamment été observés chez cette espèce dans les régions les plus anthropisées de l’archipel. De plus, les AMPs locales ne sont pas capables de protéger cette espèce. La présence d’un fort gradient de proximité à l’Homme au sein de ce réseau a permis dans un premier temps d’évaluer l’impact anthropique sur l’utilisation de l’espace par le requin gris. Les données de télémétrie acoustique ont notamment permis de mettre en évidence une augmentation du domaine vital des individus à proximité des implantations humaines. Les liens de causalité entre déclin des populations et altération de l’utilisation de l’espace sont cependant difficiles à établir. En effet, cette augmentation du domaine vital à proximité de l’Homme peut à la fois être un facteur du déclin des populations et en être une conséquence. Une plus faible densité des populations peut en effet pousser les individus à accroitre leur surface d’évolution pour la recherche de partenaires sexuels. Les données de taille de domaine vital ont ensuite été utilisées pour renseigner sur la capacité des AMPs à protéger le requin gris. Les résultats concordent avec le constat de l’inefficacité des AMPs locales pour protéger cette espèce, en soulignant leur taille trop limitée pour couvrir le domaine vital des individus et en particulier des mâles adultes. Ces résultats valident cependant les récents efforts du Gouvernement de la Nouvelle-Calédonie à mettre en place des AMPs géantes au sein de la Zone Economique Exclusive du territoire. La comparaison des résultats avec la taille des AMPs à l’échelle de l’Indo-Pacifique confirme également les récents efforts entrepris à cette échelle. Ces travaux permettent de fournir des informations concrètes sur la taille minimale d’une AMP nécessaire à la protection du requin gris. L’étude des déplacements à grande échelle a également permis de documenter pour la première fois chez le requin gris l’existence de migrations saisonnières. Sept mâles adultes ont ainsi été observés à entreprendre une migration aller-retour le long de la côte ouest de l’île principale, jusqu’à plus de 300 km de leur région de marquage, et ce sur plusieurs années consécutives. Le fait que seuls des mâles adultes aient été observés à migrer et le timing de ces migrations suggèrent que ce comportement est lié à la reproduction. Ces résultats ont d’importantes implications pour la gestion de la protection de cette espèce, notamment localement pour l’identification de zones privilégiées de reproduction
Reef sharks, like most shark species and other marine predators, are strongly impacted by human activities and are experiencing sharp population decline worldwide. Such decline poses great risk of causing a profound disruption of coral reef ecosystems where reef sharks play a key functional role. Effective and appropriate reef shark conservation measures are therefore urgently needed. Marine Protected Areas (MPAs) are one of the most widely used tools for the protection of marine ecosystems. Unfortunately, current MPAs are often ineffective for the protection of mobile species such as reef sharks. This PhD aims at studying the movements and space use of a common reef shark species in New Caledonia in order to improve the protection of this species. To achieve this goal, 147 grey reef sharks, Carcharhinus amblyrhynchos, were tagged with acoustic transmitters and their movements were monitored over three years within a network of 73 acoustic receivers deployed throughout the archipelago. The grey reef shark is a good model to evaluate how information on movement and space use may improve shark conservation. Indeed, it is one of the most common reef shark species in the Indo-Pacific and drastic population declines have been documented throughout their geographical range. In New Caledonia, grey reef shark abundance has dropped by over 90% in the most anthropized regions of the archipelago. In addition, local MPAs are not able to protect this species. The presence of a strong gradient of human proximity in New Caledonia, including highly impacted reefs near the capital Nouméa and wilderness reefs in the remote parts of the archipelago, made it possible to assess the impact of human activities on various aspects of grey reef sharks’ space use. Acoustic telemetry data revealed an increase in grey shark home range in the vicinity of human settlements. However, the causal links between population decline and changes in space use are difficult to establish. This increase in shark space use at human proximity can constitute a driver of population decline, via a reduction in fitness, as well as a consequence of it. A lower population density may indeed drive individuals to expand their movements in the pursuit of mates. The shark home range dataset was then used to inform MPAs’ ability to protect the species. Results are consistent with the reported inability of local MPAs to protect this species, emphasising MPA size are too small to cover shark home ranges, especially for adult males. However, these results validate the recent efforts of the Government of New Caledonia to establish very large MPAs within its Economic Exclusive Zone. Comparison of these results with the size of MPAs in the Indo-Pacific also confirms the recent efforts undertaken at this scale. This work provides concrete information on the minimum size of an MPA necessary for the protection of the grey reef shark. The analysis of large-scale movements also made it possible to document for the first time the existence of seasonal migrations in the grey reef shark. Seven adult males were observed to undertake a round-trip migration along the west coast of the main island, up to more than 300 km from their tagging area, and over several consecutive years. The fact that only adult males have been observed to migrate and the timing of these migrations suggest that this behaviour is related to reproduction. These results have important implications for the management of this species, particularly at the local scale for the identification of preferential breeding areas

Chapter 1 DNA barcoding based on the mitochondrial cytochrome c oxidase subunit I (COI) gene sequence is emerging as a useful tool for identifying unknown, whole or partial organisms to species level. However, the application of only a single mitochondrial marker for robust species identification has also come under some criticism due to the possibility of erroneous identifications resulting from species hybridizations and/or the potential presence of nuclear-mitochondrial psuedogenes. The addition of a complementary nuclear DNA barcode has therefore been widely recommended to overcome these potential COI gene limitations, especially in wildlife law enforcement applications where greater confidence in the identifications is essential. In this study, we examined the comparative nucleotide sequence divergence and utility of the mitochondrial COI gene (N=182 animals) and nuclear ribosomal internal transcribed spacer 2 (ITS2) locus (N=190 animals) in the 8 known and 1 proposed cryptic species of globally widespread, hammerhead sharks (family Sphyrnidae). Since hammerhead sharks are under intense fishing pressure for their valuable fins with some species potentially set to receive CITES listing, tools for monitoring their fishery landings and tracking trade in their body parts is necessary to achieve effective management and conservation outcomes. Our results demonstrate that both COI and ITS2 loci function robustly as stand-alone barcodes for hammerhead shark species identification. Phylogenetic analyses of both loci independently and together accurately place each hammerhead species together in reciprocally monophyletic groups with strong bootstrap support. The two barcodes differed notably in levels of intraspecific divergence, with average intraspecific K2P distance an order of magnitude lower in the ITS2 (0.297% for COI and 0.0967% for ITS2). The COI barcode also showed phylogeographic separation in Sphyrna zygaena, S. lewini and S. tiburo, potentially providing a useful option for assigning unknown specimens (e.g. market fins) to a broad geographic origin. We suggest that COI supplemented by ITS2 DNA barcoding can be used in an integrated and robust approach for species assignment of unknown hammerhead sharks and their body parts in fisheries and international trade. Chapter 2 The gray reef shark (Carcharhinus amblyrhynchos) is an Indo-Pacific, coral reef associated species that likely plays an important role as apex predator in maintaining the integrity of coral reef ecosystems. Populations of this shark have declined substantially in some parts of its range due to over-fishing, with recent estimates suggesting a 17% decline per year on the Great Barrier Reef (GBR). Currently, there is no information on the population structure or genetic status of gray reef sharks to aid in their management and conservation. We assessed the genetic population structure and genetic diversity of this species by using complete mitochondrial control region sequences and 15 nuclear microsatellite markers. Gray reef shark samples (n=305) were obtained from 10 locations across the species’ known longitudinal Indo-Pacific range: western Indian Ocean (Madagascar), eastern Indian Ocean (Cocos [Keeling] Islands, Andaman Sea, Indonesia, and western Australia), central Pacific (Hawaii, Palmyra Atoll, and Fanning Atoll), and southwestern Pacific (eastern Australia – Great Barrier Reef). The mitochondrial and nuclear marker data were concordant in most cases with population-based analysis showing significant overall structure (FST = 0.27906 (pST = 0.071 ± 0.02), and significant pairwise genetic differentiation between nearly all of the putative populations sampled (i.e., 9 of the 10 for mitochondrial and 8 of the 10 for nuclear markers). Individual-based analysis of microsatellite genotypes identified at least 5 populations. The concordant mitochondrial and nuclear marker results are consistent with a scenario of very low to no appreciable connectivity (gene flow) among most of the sampled locations, suggesting that natural repopulation of overfished regions by sharks from distant reefs is unlikely. The results also indicate that conservation of genetic diversity in gray reef sharks will require management measures on relatively local scales. Our findings of extensive genetic structuring suggests that a high level of genetic isolation is also likely to be the case in unsampled populations of this species.

Reef sharks (fam. Carcharhinidae) are high-order predators, found throughout the Indo- Pacific. I examined the abundance, growth, reproduction and demography of two species of reef carcharhinid; the grey reef shark (Carcharhinus amblyrhynchos) and the whitetip reef shark (Triaenodon obesus), and investigated the genetic stock structure of T. obesus across the Indo-Pacific. Underwater visual census protocols were successfully developed, and provided realtime, fisheries-independent estimates of reef carcharhinid abundances. Visual censusing of a minimally-exploited reef system ascertained that reef crest was the preferred habitat of T. obesus and C. amblyrhynchos, while the blacktip reef shark (C. melanopterus) was more abundant in reef flat and lagoon habitats. Reef carcharhinid densities were low, and even in the most abundant habitat, did not exceed 3.5 sharks hectare-1. Visual censuses across reef systems in the Indian and Pacific Oceans found consistently low numbers of reef sharks, with most regions having less than 0.5 sharks hectare-1. Closer investigation of the Great Barrier Reef (Australia) revealed a significant effect of fishing management on reef shark abundance. All levels of fishing pressure impacted upon reef carcharhinid abundance, with reductions on fished reefs of up to 80% and 97% for T. obesus and C. amblyrhynchos, respectively. This suggests that reef shark populations are particularly vulnerable to population depletion. The inability of marine protected areas to provide refuge for reef carcharhinids was highlighted and discussed. Age and growth characteristics of T. obesus and C. amblyrhynchos populations from the Great Barrier Reef were examined through vertebral thin sections. Both shark species grew slowly, with longevities of 19 years. Females out-lived males in both species. Both sexes of C. amblyrhynchos grew at similar rates, while sexually-dimorphic growth rates were observed in older T. obesus. Age estimates were preliminarily validated through oxytetracyclined recaptures of C. amblyrhynchos, while characterisation of the vertebral edge provided strong evidence that T. obesus also lays annual growth bands. Females matured 1-2 years later than males, at 8 and 11 years for T. obesus and C. amblyrhynchos, respectively. Mean litter sizes were comparable with smaller (<1 m) carcharhinids. Litter sizes initially increased with female body size in C. amblyrhynchos, reaching 3-4 pups per breeding for most of their reproductive life. Litter sizes ranged between 1-4 pups per breeding in T. obesus, with a mean of 2 pups per breeding, irrespective of female somatic size. Breeding occurs biennially in both species, with an offspring sex ratio of 1:1. For the longevities recorded, maximum reproductive output was estimated at 12 pups per female for both species. Population dynamics of the two species were analysed using age-based (Leslie) matrices. Using two methods of mortality estimation, annual decline rates of 6.3-8.8% year-1 and 10.3-15.2% year-1 were found for T. obesus and C. amblyrhynchos, respectively. This suggests that reef carcharhinids are overfished on the Great Barrier Reef. Based on current (albeit exploited) demographic parameters, the natural rates of population growth were estimated at 3.4-5.7% year-1 for T. obesus, and 0.8–3.5% year-1 for C. amblyrhynchos. Elasticity analyses and reproductive values showed that juvenile survival is the most important component of each species lifespan. However, catch analyses revealed that a high proportion of juveniles are taken in both species (especially C. amblyrhynchos). At the current rates of decline, abundances of T. obesus and C. amblyrhynchos are forecast to decline to 16-27% and 4-12% of current levels on fished reefs in the next 20 years, respectively. Development of an in-situ underwater biopsy probe enabled non-lethal, minimally invasive, collection of reef carcharhinid tissues. High levels of genetic differentiation were found in T. obesus across the Indo-Pacific, as well as between two contiguous sites on the Great Barrier Reef. Genetic separation did not correlate with geographic separation, suggesting that T. obesus has a high degree of site fidelity on coral reefs, even when migrations are possible. On an evolutionary scale, it was found that the Indian Ocean was invaded first by T. obesus, with Pacific Ocean invasion occurring simultaneously with a second Indian Ocean invasion. The unique combination of fisheries-independent abundance counts, population dynamics and investigation of genetic stock structure provides a comprehensive overview of the low abundance and slow population dynamics of coral reef carcharhinids. Findings from this PhD provide further evidence of the variety of age and reproductive strategies employed by the family Carcharhinidae, and a scientific basis for future decisions regarding reef carcharhinid management.

This is the species account about the Marine Iguana (Amblyrhynchus cristatus), a chapter in the Reptiles of Ecuador book. This account summarizes novel as well as historical information (recognition, natural history, distribution, conservation, etymology, and relevant literature) about the species and provides maps and images to facilitate identification of this reptile in the field.