Matthew M. Nelson

Lipids and nutrition of the southern rock lobster, Jasus edwardsii, from hatch to puerulus

We examined the lipid class and fatty-acid composition of the southern rock lobster, Jasus edwardsii, phyllosomas larvae and puerulus stage to improve understanding of their nutrition in relation to aquaculture. Lipid is critical in the nutrition of larval crustaceans, including lobsters. Specimens were from Tasmanian waters, Australia, and North Island, New Zealand, waters. Analyses were by TLC-FID and capillary GC and GC-MS. Phyllosomas larvae and nektonic pueruli were low in storage lipid (triacylglycerol), and phospholipid was the major lipid class. Sterol, mainly cholesterol, was the next most abundant class. The ratio of the essential omega-3 fatty acid eicosapentaenoic acid (EPA) to the omega-6 fatty acid arachidonic acid (AA) was lower in newly hatched phyllosomas (1.2-1.3) than in other phyllosomas (stages III-XI; 2.8-6.7) and pueruli (3.8). Ratios of the omega-3 fatty acid DHA (docosahexaenoic acid) to EPA were also lower in newly hatched phyllosomas (0.5) than in later-stage phyllosomas (1.5-2.1) and pueruli (1.2). We have followed up these compositional data by successfully enriching the live diet (Artemia) of early phyllosomas with AA, EPA and DHA. This dietary manipulation has achieved ratios of these key polyunsaturated fatty acids similar to those of wild phyllosomas. These findings will be of significance to the future of rock-lobster aquaculture.

Marked depletion of polar lipid and non-essential fatty acids following settlement by post-larvae of the spiny lobster Jasus verreauxi.

The development from the non-feeding post-larva (puerulus) to the first instar juvenile of spiny lobsters is highly energetically demanding. These demands may greatly compromise the energy reserves of the lobsters following settlement, leading to reduced growth and survival in the wild, and also in aquaculture. Therefore, the lipid class and fatty acid composition of wild caught pueruli and first instar juveniles of the spiny lobster Jasus verreauxi (H. Milne Edwards, 1851) were analysed by thin layer chromatography-flame ionisation detection and capillary gas chromatography. Pueruli contained substantially more lipid than first instar juveniles (mean difference =3.5 mg, or 41.9%) and most of this difference was due to the presence of greater amounts of polar lipid (mean difference =3.9 mg or 49.2%) in pueruli. First instar juveniles contained significantly more triacylglycerol (mean =0.2 mg), consistent with the polar lipid being converted to a more readily metabolised lipid class in the hepatopancreas. These results indicate that polar lipid is the major energy store during the non-feeding puerulus stage of spiny lobsters from the genus Jasus. Overall, the essential, polyunsaturated linoleic, docosahexaenoic and eicosapentaenoic acids did not show a significant decrease between the two developmental stages, despite the absence of feeding. However, significant reductions in the abundance of both saturated and monounsaturated fatty acids between the two stages were identified (decrease of 811 and 783 microg per individual, respectively). This suggested that selective depletion of non-essential fatty acids may be occurring, with resultant sparing of the essential fatty acids. Supplying diets rich in these depleted fatty acids, and in particular the essential fatty acids, preferably in polar lipid, is likely to result in increased survival and growth of J. verreauxi and other spiny lobsters from first instar juveniles in aquaculture.

Changes in gut content and composition of juvenile Artemia after oil enrichment and during starvation

Some predators, such as spiny lobster phyllosoma larvae, tear Artemia to pieces before ingestion. This results in the loss of gut content, which may partly negate the benefits of enrichment with essential fatty acids (EFA). Therefore, the influence of gut content on the lipid composition of juvenile Artemia (5 day old) was examined by starvation alone or starvation with forced gut evacuation using 20-30 µm plastic beads. Artemia gut content at 3 h and 6 h after the completion of feeding did not contribute significantly to the total lipid or fatty acid profiles of the Artemia. Artemia subjected to starvation alone (without beads) failed to evacuate their gut over the 6 h starvation period suggesting they require the intake of suitable sized particulate matter to undertake gut evacuation. To assess the uptake of EFA in nauplii (day 2) and juveniles, an enrichment diet containing high levels of arachidonic [AA, 20:4(n-6)] and eicosapentaenoic acid [EPA, 20:5(n-3)] was compared to a basal oat-based diet and a commercial oil emulsion high in docosahexaenoic acid [DHA (22:6(n-3)]. Both AA and EPA were increased in juvenile Artemia within a 24 h enrichment period at a rate proportional to their inclusion in the enrichment, while DHA was incorporated to a lesser degree. For all three EFA, the percentage loss during 6h starvation was small, but was greater for DHA than EPA or AA. Juvenile Artemia, a life stage seldom used in feeding regimes, have the ability to assume the AA and EPA profile of their dietary source. The ability to produce a larger food source with a non-traditional fatty acid profile may be valuable for a number of larval crustacean and fish species.

NEITHER MATERNAL SIZE NOR SITE OF SPAWNING INFLUENCES LARVAL COMPETENCY IN WESTERN ROCK LOBSTER PANULIRUS CYGNUS GEORGE

Abstract The size of the western rock lobster broodstock is variable over the range of the Western Australian fishery, due to regional differences in the density and length structure of the stock and the females size at maturity. Management regulations do not currently discriminate in the protection afforded to the broodstock in the different regions. This study has examined whether regional and size differences in early egg diameter, phyllosoma length at hatch and phyllosoma competency, are related to lipid class and fatty acid composition, protein composition and water content in late stage eggs and early stage phyllosoma larvae. A positive relationship, particularly to phyllosoma competency, would have management implications for the protection of broodstock in different parts of the fishery. Females were sampled in three size groups captured in two sampling regions (Abrolhos Islands 60-70 and 80-90 mm CL; coastal 80-90 and > 95 mm CL). Mostly, eggs and larvae from different maternal size classes and regions were not significantly different with respect to lipid class and fatty acid composition, protein composition and water content, and larval competency. The lipid classes of eggs differed significantly (P < 0.02) between the three maternal size-classes; fatty acids differed significantly between both eggs and phyllosoma grouped by maternal catch site and size-class (P = 0.02 and 0.003, respectively); and there was no correlation between biochemical differences and larval competency. These results imply that maternal identity and subsequent diet may have a greater influence on larval competency in P. cygnus than the maternal attributes (size and capture site) that were tested.