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

Advances in the culture of striped trumpeter larvae: A review

Striped trumpeter, Latris lineata, was chosen as the best new candidate for sea cage culture in Tasmania in the late 1980s. It has a complex and extended post-larval or ‘paperfish’ stage lasting up to 9 months and has historically proven difficult to culture. Excellent progress has been made in understanding and controlling reproduction and broodstock are spawned year-round through photothermal control. Problems with early larval rearing have been overcome and egg incubation and early larval rearing protocols have been established. A mortality peak associated with first feeding has been reduced using better live feed production techniques and improved water quality. Using antibiotics showed that high bacterial loads were an important factor in larval mortality. A new water filtration and ozonation system has removed the need for antibiotics. Larval nutrition research focused on the link between potential deficiencies or imbalances in the three essential PUFA in live feeds: docosahexaenoic acid, eicosapentaenoic acid and arachidonic acid. Novel experimental emulsions were applied with dose response experimental designs to identify the dietary requirement for selected PUFA and vitamins. Despite the advances in live feed enrichments, the live feeds, particularly Artemia, were found to have sub-optimal lipid profiles. Copepods were cultured, as a supplement to traditional live feeds, and improved larval rearing success. Costs to scale-up production and to control extensive cultures presently restrict the usefulness of copepods. Important breakthroughs have occurred in health with the detection and control of nodavirus, myxozoan and bacterial disease. Ozone disinfection of eggs and sterilisation of hatchery seawater have been important control measures. Another bottleneck to production has been mortality of larvae from notochord flexion to metamorphosis. System changes to reduce nocturnal movements and a better understanding of optimal live feed densities, and weaning onto formulated diets, have improved survival and growth. High rates of jaw malformation remain a challenge and no definitive cause has been established. Reduced rates of malformations have been associated with one or a combination of high feed rates, lower larval densities and temperatures, and reductions in ‘walling’ behaviour. Future research is aimed at finding ways to reduce malformations, develop probiotics and early weaning strategies, control parasites and scale-up production to assess performance of juveniles in sea cages

Jaw malformation in striped trumpeter Latris lineata larvae linked to walling behaviour and tank colour

Jaw malformations are a recurrent obstacle in the hatchery production of high quality juveniles of many marine finfish species. Whilst nutrition and temperature are often cited as the most likely causes, this study investigated manipulation of the physical culture environment and larval behaviour to reduce jaw malformations. The onset of jaw malformation after metamorphosis in striped trumpeter, Latris lineata, follows changes in larval behaviour from an even distribution throughout the water column to close association with the tank walls, often with vigorous swimming into the walls known as ‘walling’ behaviour. Larvae were reared through metamorphosis, 16 to 44 days post-hatching (dph), in twenty four 300-l hemispherical tanks with six different wall colours, black, blue, green, marble (a black, grey and white mottled pattern), red and white. Walling behaviour and jaw malformation were assessed. The highest proportion of severely malformed jaws at 44 dph occurred in red tanks, followed by green, white, blue, black and marble. More fish walled in coloured tanks (25-44%) than in black and marble tanks (9.6 and 3.4%, respectively). The proportion of fish with jaw malformations at 44 dph was positively correlated with fish walling behaviour. Both black and marble tanks had more than 50% of fish with normal jaws at 44 dph, and close to 80% with no or very minor malformations. Growth and survival to 44 dph were highest in the black (15.7 ± 1.3 mm fork length, 7.9 ± 0.9 mg dry weight, 71 ± 6%) and marble (15.6 ± 1.2 mm, 7.6 ± 0.5 mg, 58 ± 17%) tanks, compared with the lowest values in red tanks (14.2 ± 1.1 mm, 6.4 ± 0.4 mg, 11 ± 6%). Potential mechanisms for the influence of walling behaviour on jaw malformation are mechanical damage and poor nutrition, via reduced feed intake and increased energy expenditure. The study highlights the often overlooked importance of hard-surface interactions in the growth and survival of some cultured marine fish and demonstrates a cheap and effective technique for assessing tank background colour as a means of reducing malformations in cultured fish