Gg Smith

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.

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.

An activity test to evaluate larval competency in spiny lobsters ( Jasus edwardsii ) from wild and captive ovigerous broodstock held under different environmental conditions

Abstract A short-term activity test was developed to ascertain the physiological condition of newly hatched phyllosoma larvae of the spiny lobster Jasus edwardsii at hatch. Results of the activity test were compared with growth and survival of larvae cultured at 18 °C for up to 42 days and phyllosoma fatty acid profiles at hatch. The stresses used in the activity test comprised combinations of temperature (18, 23 and 28 °C) and salinity (10‰, 15‰, 35‰, 55‰ and 60‰) applied to larvae for a 1-h period. Larvae exposed to the activity test were sourced from ovigerous captive and wild-caught broodstock held at 21, 17 °C or ambient temperature (9.5–13.5 °C) during embryonic development. Phyllosoma originating from the 21 and 17 °C embryonic development temperatures were smaller in body length during culture compared to larvae from ambient incubated wild-caught broodstock, while better larval survival was achieved in larvae from ambient incubated broodstock. A strong correlation was obtained between larval activity at 23 °C at 10‰ and survival of both unfed larvae cultured for 14 days (Stage I; r =0.8720, P =0.0000), and fed larvae cultured for 42 days (Stage IV; r=0.9054, P =0.0000). Elevated incubation temperature reduced the duration to hatch resulting in the quantitative sparing of a number of fatty acids. There was no correlation between activity test results and the presence of any individual or fatty acids groups. The results of this study demonstrate that it is possible to determine larval physiological condition using an activity test comprising temperature and salinity stresses, while additionally, it was noted that larval competency is compromised when elevated temperatures are used during embryonic development to reduce the duration to hatch.

Artemia prey size and mode of presentation: Effects on the survival and growth of phyllosoma larvae of southern rock lobster (Jasus edwardsii)

Performance of phyllosoma of thesouthern rock lobster (Jasus edwardsii)was examined after feeding Artemia-baseddiets. Survival and growth of newly-hatchedlarvae cultured to Stage III were lower(p < 0.05) when fed 0.8 mm Artemia than1.5 mm or 2.5 mm Artemia alone or 1.5 mmArtemia in combination with pieces ofmussel (Mytilus edulis planulatus) gonad.This could not be attributed to deficiencies inthe composition of fatty acids but appeared tobe due to the inability of larvae to capturesufficient appropriate-sized, enrichedArtemia for their nutritional requirements.There was an indication that survival andgrowth were higher between Stages III and Vwhen fed 2.5 mm Artemia than 1.5 mmArtemia alone or in combination with musselpieces. However, Stage VI larvae grew to asimilar size at Stage VIII when fed 1.5 mm or2.5 mm Artemia. Unexpectedly, larvae fedthe combination of 1.5 mm Artemia plusmussel supplement had lower survival than foundpreviously, and generally lower than when fed≥ 1.5 mm Artemia alone. This was despitean apparent nutritional profile (lipid contentand fatty acid composition) of mussel more akinto that of newly-hatched phyllosoma thanenriched Artemia. On the other hand,survival and growth to Stage VIII were higherwhen larvae were fed alginate pelletscontaining Artemia than when fed 1.5 mmor 2.5 mm Artemia alone.

The effect of embryo incubation temperature on indicators of larval viability in Stage I phyllosoma of the spiny lobster, Jasus edwardsii

Abstract The effect of embryo incubation temperature on larval viability, as measured by biological and biochemical parameters, on newly hatched Jasus edwardsii phyllosoma larvae, was examined. Ovigerous lobsters collected from the wild shortly after egg extrusion were held until hatch in warm (18 °C), ambient (11.7 °C, range 9.5–13 °C) and cold (10.5 °C) water. The duration of embryonic development until hatch was directly related to incubation temperature. The use of all three temperature regimes (warm, ambient and cold) extended the period that phyllosoma hatched to 87 days compared to 30 days under the ambient regime alone. Embryonic development in warm water produced Stage I phyllosoma that were significantly smaller with reduced levels of eicosapentanoic acid (20:5n−3) and sterols compared to the other treatments. Ascorbic acid reserves were highest in cold incubated larvae. The results suggest a detrimental effect of warm incubation temperature during embryonic development on Stage I phyllosoma.

In silico prediction of the G-protein coupled receptors expressed during the metamorphic molt of Sagmariasus verreauxi (Crustacea: Decapoda) by mining transcriptomic data: RNA-seq to repertoire

Against a backdrop of food insecurity, the farming of decapod crustaceans is a rapidly expanding and globally significant source of food protein. Sagmariasus verreauxi spiny lobster, the subject of this study, are decapods of underdeveloped aquaculture potential. Crustacean neuropeptide G-protein coupled receptors (GPCRs) mediate endocrine pathways that are integral to animal fecundity, growth and survival. The potential use of novel biotechnologies to enhance GPCR-mediated physiology may assist in improving the health and productivity of farmed decapod populations. This study catalogues the GPCRs expressed in the early developmental stages, as well as adult tissues, with a view to illuminating key neuropeptide receptors. De novo assembled contiguous sequences generated from transcriptomic reads of metamorphic and post metamorphic S. verreauxi were filtered for seven transmembrane domains, and used as a reference for iterative re-mapping. Subsequent putative GPCR open reading frames (ORFs) were BLAST annotated, categorised, and compared to published orthologues based on phylogenetic analysis. A total of 85 GPCRs were digitally predicted, that represented each of the four arthropod subfamilies. They generally displayed low-level and non-differential metamorphic expression with few exceptions that we examined using RT-PCR and qPCR. Two putative CHH-like neuropeptide receptors were annotated. Three dimensional structural modelling suggests that these receptors exhibit a conserved extracellular ligand binding pocket, providing support to the notion that these receptors co-evolved with their ligands across Decapoda. This perhaps narrows the search for means to increase productivity of farmed decapod populations.

Sexual maturation in captive spiny lobsters, Jasus edwardsii, and the relationship of fecundity and larval quality with maternal size

Summary Reproductive and somatic parameters of southern rock lobsters, Jasus edwardsii, held captive since puerulus and wild-caught adults were examined in terms of size at onset of maturity (SOM) and fecundity, culminating in an examination of how adult size may relate to larval competency. The SOM was much smaller in captive animals (62.5 mm carapace length, CL) compared to historical fishery data and indicated that precocious maturation may be induced in captivity. During this study, the fecundity was assessed as the number of viable phyllosoma at hatch, which was ~45% of egg estimates from the historical fishery data, suggesting either declining egg numbers in wild stocks over time or that major egg loss occurs during embryonic development. The association between SOM and sexual dimorphism was examined for several morphometric parameters. In females, the SOM was concomitant with increases to the width of the 1st and 2nd abdominal segments above 62.5 mm CL, while 2nd and 3rd leg length increased disproportionately in males compared to females above 77.5 mm CL. There were significant correlations between viable fecundity and female size (r = 0.92), phyllosoma size (r = 0.74) and larval viability as quantified by stress indices (r = −0.56) and LD-50 (r = 0.56), indicating that larger females produce larger, more viable larvae. These physiological traits in larval, juvenile and adult animals may have an impact on fishery and aquaculture production.

Effect of physical disturbance on reproductive performance in the spiny lobster, Jasus edwardsii

Abstract A study was conducted to examine the effects of physical disturbance on Jasus edwardsii spiny lobster broodstock during ovarian recrudescence through to larval hatch. Undisturbed brood‐stock were held in relative isolation and subjected to minimal human disturbance, which contrasted with weekly air exposure and handling of the disturbed animals. Broodstock behavioural response, phyllosoma number, competency, and survival in culture were examined. A higher proportion of broodstock from the undisturbed treatment were active during daylight hours compared with those in the disturbed treatment. All ovigerous females in the undisturbed group produced phyllosoma larvae compared with 72.7% of animals in the disturbed treatment. Individual undisturbed females produced greater numbers of phyllosoma larvae, which in turn performed better in larval competency tests, were larger at hatch, and survived better in culture than those from disturbed females. This study demonstrated that physical disturbance altered reproductive performance and larval competency of J. edwardsii. Protocols are suggested to minimise disturbance associated with handling in crustacean broodstock.

Developmental and gut-related changes to microbiomes of the cultured juvenile spiny lobster Panulirus ornatus

ABSTRACT With recent technologies making it possible for commercial scale closed life‐cycle aquaculture production of spiny lobster (Panulirus ornatus) comes a strong impetus to further understand aspects of lobster health. The gut microbiome plays a crucial role in host health, affecting growth, digestion, immune responses and pathogen resistance. Herein we characterise and compare gut microbiomes across different developmental stages (6‐7 days post‐emergence [dpe], 52 dpe and 13 months post‐emergence [mpe]) and gut regions (foregut, midgut and hindgut) of cultured P. ornatus juveniles. Gut samples were analysed using 16S rRNA next‐generation sequencing. Core gut microbiomes of P. ornatus comprised the phyla Tenericutes and Proteobacteria. Within class Gammaproteobacteria, families Pseudoalteromonadaceae and Vibrionaceae were dominant members across the majority of the gut microbiomes. Characterisation of bacterial communities from 13 mpe lobsters indicated that the hindgut microbiome was more diverse and compositionally dissimilar to the foregut and midgut. The bacterial composition of the hindgut was more similar among younger juveniles (6‐7 dpe and 52 dpe) compared to 13 mpe lobsters. This is the first study to explore gut microbiomes of spiny lobster juveniles. We demonstrate that the composition of the gut microbiome was shaped by gut region, whereas the structure of the hindgut microbiome was influenced by developmental stage. &NA; Graphical Abstract Figure. This is the first study to explore gut microbiomes of ornate spiny lobster juveniles and demonstrates that the gut‐associated bacteria are influenced by gut region and developmental stage.

Temperature dependent growth, feeding, nutritional condition and aerobic metabolism of juvenile spiny lobster, Sagmariasus verreauxi

We examined the effects of temperature on the growth, feeding, nutritional condition and aerobic metabolism of juvenile spiny lobster, Sagmariasus verreauxi, in order to determine if temperature acclimated aerobic scope correlates with optimum for growth and to establish the thermal tolerance window for this emerging aquaculture species. Juvenile lobsters (initial weight=10.95±0.47g) were reared (n=7) at temperatures from 11.0 to 28.5°C for 145days. All lobsters survived from 14.5 to 25.0°C while survival was reduced at 11.0°C (86%) and all lobsters died at 28.5°C. Lobster specific growth rate and specific feed consumption displayed a unimodal response with temperature, peaking at 21.5°C. Lobster standard, routine and maximum metabolic rates, and aerobic scope all increased exponentially up to maximum non-lethal temperature. Optimum temperature for growth did not correspond to that for maximum aerobic scope suggesting that aerobic scope is not an effective predictor of the thermal optimum of spiny lobsters. Plateauing of specific feed consumption beyond 21.5°C suggests that temperature dependent growth of lobsters is limited by capacity to ingest or digest sufficient food to meet increasing maintenance metabolic demands at high temperatures. The nutritional condition of lobsters was not influenced by temperature and feed conversion ratio was improved at lower temperatures. These findings add to a growing body of evidence questioning the generality of aerobic scope to describe the physiological thermal boundaries of aquatic ectotherms and suggest that feed intake plays a crucial role in regulating performance at thermal extremes.