Academic literature on the topic 'Hormosira banksii Development'

Hormosira banksii is distributed throughout southern Australasia, but dispersal of propagules is thought to be limited. In the present study, the hypothesis that outbreeding depression occurs in H. banksii was tested by assessing fertilisation success and early development of embryos in crosses between populations at local to regional spatial scales. Hierarchical experiments were conducted at three spatial scales with nesting present within each scale: small scale (within a rocky shore population), intermediate scale (regions separated by 70 km) and large scale (450-km separation between two states: Victoria and Tasmania). In each experiment, eggs and sperm were crossed within and between each population located in the spatial scale of interest. There were no consistent patterns of variable fertilisation success and subsequent development within a population or at different spatial scales. It was concluded that outbreeding depression is not detected in analyses of fertilisation success or early development processes in H. banksii. The results suggest one of the following to be likely: (1) H. banksii is capable of longer distance dispersal than previously considered, thus maintaining gene flow between distant populations, (2) gene flow is restricted by limited dispersal, but populations have not been isolated for a sufficient length of time to cause genetic divergence or (3) outbreeding depression is manifested as effects on later life-history stages.

Adhesives from marine organisms are often the source of inspiration for the development of glues able to create durable bonds in wet environments. In this work, we investigated the adhesive secretions produced by germlings of two large seaweed species from the South Pacific, Durvillaea antarctica , also named ‘the strongest kelp in the word’, and its close relative Hormosira banksii . The comparative analysis was based on optical and scanning electron microscopy imaging as well as Fourier transform infrared (FTIR) spectroscopy and principal component analysis (PCA). For both species, the egg surface presents peripheral vesicles which are released soon after fertilization to discharge a primary adhesive. This is characterized by peaks representative of carbohydrate molecules. A secondary protein-based adhesive is then secreted in the early developmental stages of the germlings. Energy dispersive X-ray, FTIR and PCA indicate that D. antarctica secretions also contain sulfated moieties, and become cross-linked with time, both conferring strong adhesive and cohesive properties. On the other hand, H. banksii secretions are complemented by the putative adhesive phlorotannins, and are characterized by a simple mechanism in which all constituents are released with the same rate and with no apparent cross-linking. It is also noted that the release of adhesive materials appears to be faster and more copious in D. antarctica than in H. banksii . Overall, this study highlights that both quantity and quality of the adhesives matter in explaining the superior attachment ability of D. antarctica .

Bioadhesives produced by marine macroalgae represent a potential source of inspiration for the development of water-resistant adhesives. Assessing their adhesion strength, however, remains difficult owing to low volumes of adhesive material produced, low solubility and rapid curing time. These difficulties can be circumvented by testing the adhesion strength of macroalgae propagules attached to a substrate. In this paper, we present a simple, novel flow channel used to test the adhesion strength of the germlings of the fucalean alga Hormosira banksii to four substrates of biomedical relevance (PMMA, agar, gelatin and gelatin + lipid). The adhesion strength of H. banksii germlings was found to increase in a time-dependent manner, with minimal adhesion success after a settlement period of 6 h and maximum adhesion strength achieved 24 h after initial settlement. Adhesion success increased most dramatically between 6 and 12 h settlement time, while no additional increase in adhesion strength was recorded for settlement times over 24 h. No significant difference in adhesion strength to the various substrates was observed. Computational fluid dynamics (CFD) was used to estimate the influence of fluid velocity and germling density on drag force acting on the settled organisms. CFD modelling showed that, on average, the drag force decreased with increasing germling number, suggesting that germlings would benefit from gregarious settlement behaviour. Collectively, our results contribute to a better understanding of the mechanisms allowing benthic marine organisms to thrive in hydrodynamically stressful environments and provide useful insights for further investigations.

University of Technology, Sydney. Dept. of Environmental Sciences.
A wealth of information exists for chlorophyll a fluorescence applications in ecophysiology. However, the use of chlorophyll a fluorescence in marine ecotoxicology has been limited and this is especially true of macroalgal ecotoxicology. The primary objective of this thesis was to develop and describe a bioassay protocol that uses improvements on past macroalgal assay techniques to allow the photosynthetic capacity of Hormosira banksii gametes to be assessed using chlorophyll a fluorescence measurements. Two protocols (using H. banksii eggs or sperm) have been developed that allow for rapid assessment of toxic impact (less than 8 h) on macroalgal gametes. This rapid time-to-result allows for timely management decisions to be made. This is significant since past macroalgal bioassays have necessitated up to a 48 h delay before results are available to decision makers. In addition to this much improved rapidity of result, comparison between a germination based endpoint and the fluorescence endpoint has shown the fluorescence measure to be more sensitive to some classes of toxicant, more precise (in terms of Coefficient of Variation), and can also offer information on mechanistic pathways of toxicants. In order to validate 'real-world' use of the new fluorescence protocol, the sperm fluorescence bioassay was effectively applied to the assessment of interactive effects displayed by mixtures of anti-foulant compounds. Furthermore, a level of eco-relevance was demonstrated for the chlorophyll a fluorescence endpoint %PSII Inhibition. This is significant in that eco-relevance has not previously been experimentally demonstrated for a chlorophyll a fluorescence endpoint in ecotoxicology and the demonstrated link to higher level effects may have favourable implications as to future acceptance of fluorescence data into water quality guidelines. Essentially, this work describes the development of, and also the successful application of, a novel, fluorescence macroalgae bioassay that not only has advantages over currently employed methods, but also offers a powerful tool in both the rapid assessment of toxic impact on near-shore macroalgal communities, and as an effective toxicity screening tool.