Analysis of the Central Nervous System Transcriptome of the Eastern Rock Lobster Sagmariasus verreauxi Reveals Its Putative Neuropeptidome

Neuropeptides have been discovered in many arthropod species including crustaceans. The nature of their biological function is well studied and varies from behavior modulation to physiological regulation of complex biochemical processes such as metabolism, molt and reproduction. Due to their key role in these fundamental processes, neuropeptides are often targeted for modulating these processes to align with market demands in commercially important species. We generated a comprehensive transcriptome of the eyestalk and brain of one of the few commercially important spiny lobster species in the southern Hemisphere, the Eastern rock lobster Sagmariasus verreauxi and mined it for novel neuropeptide and protein hormone-encoding transcripts. We then characterized the predicted mature hormones to verify their validity based on conserved motifs and features known from previously reported hormones. Overall, 37 transcripts which are predicted to encode mature full-length/partial peptides/proteins were identified, representing 21 peptide/protein families/subfamilies. All transcripts had high similarity to hormones that were previously characterized in other decapod crustacean species or, where absent in crustaceans, in other arthropod species. These included, in addition to other proteins previously described in crustaceans, prohormone-3 and prohormone-4 which were previously identified only in insects. A homolog of the crustacean female sex hormone (CFSH), recently found to be female-specific in brachyuran crabs was found to have the same levels of expression in both male and female eyestalks, suggesting that the CFSH female specificity is not conserved throughout decapod crustaceans. Digital gene expression showed that 24 out of the 37 transcripts presented in this study have significant changes in expression between eyestalk and brain. In some cases a trend of difference between males and females could be seen. Taken together, this study provides a comprehensive neuropeptidome of a commercially important crustacean species with novel peptides and protein hormones identified for the first time in decapods

Chemicals released by male sea cucumber mediate aggregation and spawning behaviours

The importance of chemical communication in reproduction has been demonstrated in many marine broadcast spawners. However, little is known about the use of chemical communication by echinoderms, the nature of the compounds involved and their mechanism(s) of action. Here, the hypothesis that the sea cucumber Holothuria arguinensis uses chemical communication for aggregation and spawning was tested. Water conditioned by males, but not females, attracted both males and females; gonad homogenates and coelomic fluid had no effect on attraction. Male spawning water, but not female spawning water, stimulated males and females to release their gametes; the spermatozoa alone did not induce spawning. H. arguinensis male spawning water also induced spawning in the phylogenetically related H. mammata. This indicates that males release pheromones together with their gametes that induce spawning in conspecifics and possibly sympatric species. Finally, the male pheromone seems to be a mixture with at least one labile compound (biological activity is lost after four hours at ambient temperature) possibly including phosphatidylcholines. The identification of pheromones in sea cucumbers offers a new ecological perspective and may have practical applications for their aquaculture.FCT - Foundation for Science and Technology [UID/Multi/04326/2013, SFRH/BD/90761/2012]info:eu-repo/semantics/publishedVersio

Marine Fish Culture

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Atlantic salmon aquaculture

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Induced ovulation and larval rearing of four species of Australian marine fish

This thesis developed techniques for the large-scale breeding of marine fish in New South Wales. It provides the first published account of the hormone induction and larval rearing to metamorphosis of Australian bass Macquarie novemaculeata (Percichthyidae), snapper Pagrus auratus (Sparidae), mulloway Argyrosomus hololepidotus (Sciaenidae) and sand whiting Sillago ciliate (Silliganidae) in Australia. Wild-caught broodstock were induced to spawn using hormones (hCG, LHRHa, Ovaprim) and either spawned naturally or were stripped. Pagrus auratus and S. ciliate were found to be multiple spawners with asynchronous ovaries. Conversely, M. novemaculeata and A. hololepidotus were found to be highly fecund single spawners having group synchronous ovaries. All four species were successfully induced to ovulate after periods in captivity ranging from one to five years. Species specific differences in hormone induction were determined, particularly in relation to the overripening of eggs and the optimum time between treatment and stripping. Commercial scale batches of larvae were reared in 2000 L conical tanks and replicated experiments were conducted in aquaria ranging in size from 2 to 70 L. Larval development for all four species was described and egg size, time to hatch, size at hatch, yolk size, oil globule size, and beginning of exogenous feeding were compared among species. First feeding larvae were reared on rotifers Brachionus plicatilis and then brine shrimp Artemia sp. Survival, growth and weaning of larvae at metamorphosis were compared. Factors affecting larval survival, particularly those influencing initial swim bladder development were tested in replicated laboratory experiments. The timing of swim bladder inflation was found to coincide with the start of exogenous feeding but feeding was not required for initial swim bladder inflation. Larvae that failed to inflate their swim bladder grew poorly and were susceptible to stress induced mortality. Light intensity, was shown to be an important factor influencing swim bladder inflation in cultured larvae. The effect of light intensity on inflation in M. novemaculeata and S. ciliate was quantified. Exposure to continuous light (100-200 Lux) inhibited inflation in M. novemaculeata. In contrast, S. ciliate were shown to have a diel pattern of nocturnal inflation and required higher light intensities to feed (1000 Lux). Manipulative experiments with S. ciliate larvae showed that they responded to darkness by inflating their swim bladders. Other abiotic factors such as surface access, low salinity and high aeration were shown to reduce inflation in larvae. Initial swim bladder inflation strategies are discussed and recommendations made regarding the importance of maximising inflation. The results of the study were used to assess the relative difficulty of intensive commercial production of each species for aquaculture

Induced ovulation and larval rearing of four species of Australian marine fish

No description availabl