Aj Ritar

Biochemical composition during growth and starvation of early larval stages of cultured spiny lobster, Jasus edwardsii , phyllosoma

We examined biochemical changes accompanying feeding and starvation from hatch to Stage VI (day 74 after hatch) in spiny lobster, Jasus edwardsii, phyllosoma larvae. Larval dry weights (dw) increased 17-fold from hatch (80+/-1 microg) to Stage VI (1415+/-44 microg). Larvae starved for 6-11 days at Stages II, IV and VI were 14-40% lighter than their fed counterparts fed enriched Artemia. The increases and losses in total dry weight during feeding and starvation were associated with changes in the content of protein (constituting 31.4-41.7% of dw) and carbohydrate (constituting 2.6-5.3% of dw), while larger changes in lipid content indicated its greater importance as an energy substrate. Lipid content increased from 7.9% of dw at hatch to its highest of 12.5% at Stage IV, but declined by 50% or more during starvation. This suggests that protein, carbohydrate and lipid are all important energy stores, although lipids are catabolized at a greater rate during food deprivation. The principal lipid class was polar lipid (PL; 79-92% of total lipid), followed by sterol (ST; 6-20%), with triacylglycerol and other lipid classes at <2%. PL were catabolized and ST were conserved during starvation. Changes in the fatty acid (FA) profile had mostly occurred before the first moult at day 8 after hatch, with gradual changes thereafter to Stage VI, reflecting their abundance in the Artemia diet. There was some conservation of the major essential FAs, 20:4n-6, 20:5n-3, 22:6n-3, and the FA profile showed large gains in the C(18) polyunsaturated FA, 18:1n-9, 18:2n-6. Ascorbic acid content increased 10-fold from hatch to the end of Stage I (36 and 333 microgg(-1) dw, respectively), while the content at the end of Stage II was higher in fed than that in starved larvae (439 and 174 microgg(-1) dw, respectively). Our study will assist in the development of alternatives to nutritionally incomplete diets, such as live ongrown Artemia, to meet the requirements of phyllosoma in culture.

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.

Effect of consecutive 9- or 12-month photothermal cycles and handling on sex steroid levels, oocyte development, and reproductive performance in female striped trumpeter Latris lineata (Latrididae).

Abstract Duplicate groups of sexually mature striped trumpeter Latris lineata were maintained for two seasons on either a 12-month cycle of ambient temperature (9–18°C) and photoperiod, or a 9-month compressed temperature and photoperiod cycle. One of the duplicates from each cycle was handled frequently (handled) and blood and ovarian samples taken monthly from females until the start of gonadal recrudescence, and then fortnightly until ovulations had ceased. Fish from the other group were not handled (non-handled), except near the end of their spawning seasons to determine which fish had ovulated. Naturally spawned eggs were collected daily from the tanks and hand-stripping was conducted fortnightly in the handled fish during the respective spawning seasons. The 12-month group started spawning in September in both years, whereas the compressed cycle advanced spawning by 1 and 4 months during consecutive seasons, i.e. August 1995 and May 1996. For all handled fish, oocytes developed to late cortical alveoli/early vitellogenic stage, but on average, only 64% of fish continued development through to ovulation. The duration of spawning averaged 45 days for the 9-month and 64 days for the 12-month cycle. The mean volume of eggs produced for each day of production was higher for the handled than the non-handled fish, but there was no difference between cycles (9- and 12-month). Eggs from fish on the 9-month cycle were significantly smaller than from fish on the 12-month cycle. Plasma levels of testosterone (T) and 17β-oestradiol (E 2 ) in fish from both the 9- and 12-month cycles were at or near their lowest levels at first sampling ( −1 , respectively) and remained low except for elevations during the 3–4 month period of oocyte maturation and ovulation, when levels peaked at 1.3 and 6.3 ng ml −1 , respectively.

Mouthpart and foregut ontogeny in phyllosoma larvae of the spiny lobster Jasus edwardsii (Decapoda; Palinuridae)

Mouthpart and foregut structure indicates that Jasus edwardsii phyllosomas ingest soft fleshy foods such as gelatinous zooplankton. Mouthpart morphology changes little during larval development, indicating that ingestive capabilities and external mastication are well developed from an early age. However, the density and complexity of setation and robustness of individual mouthparts increases with age, suggesting a greater capacity to ingest larger prey during development. The foregut consists of a single chamber with a number of well-developed grooves, ridges, and setae but lacking a gastric mill. The primary role of the foregut is mixing, sorting, and filtering particles, preground by the mouthparts. Phyllosomas have been divided into early (stage I-III), mid (IV-V), and late (VI-X) stages based on the development of the filter press and main brushes. Increasing robustness of setation and complexity of the foregut suggest that the texture of prey becomes more muscular (fibrous) with larval development. The results presented here suggest that early-stage phyllosoma would benefit from a diet comprising soft gelatinous items, whereas late-stage phyllosomas are better prepared to deal with larger, fleshy prey. The changes in structural characteristics with age should also serve as a guide in the development of formulated diets.

The experimental culture of phyllosoma larvae of southern rock lobster (Jasus edwardsii) in a flow-through system

A system for the experimental larval rearing of phyllosoma of southern rock lobster (Jasus edwardsii) is described. Sea water filtered to 1 um, heated to 18 degrees C and disinfected with ultraviolet light, passes into circular 35 l vessels via a series of jets to achieve constant circular flow. Water exits through a screened drain fitted to the wall of the vessel and positioned to maintain a volume of 10 l with a turnover of 3-4 times per hour. Phyllosoma were cultured in this system from hatch to Stage XI when fed ongrown Artemia and pieces of mussel (Mytilus edulis). The system may readily and cheaply be replicated for experimental comparisons of several treatments.

Effects of temperature on the embryonic development of the striped trumpeter (Latris lineata Bloch and Schneider, 1801)

Abstract Eggs collected from females of striped trumpeter ( Latris lineata ) that were induced to ovulate with LHRHa were inseminated and incubated at six different temperatures ranging from 8.1 to 18.1°C. Mortality was recorded for four embryonic periods (I: cell cleavage, II: epiboly, III: organogenesis and IV: organogenesis-growth). A power law was used to approximate the relationship between temperature and developmental time to four stages of embryonic development (visible peripheral periblast, yolk plug closure, heart beat and hatching). These models may have application for the ageing of striped trumpeter eggs. The time taken for 50% of embryos to hatch at 8.1, 10.5, 12.3, 14.1 and 16.2°C was 13.0, 8.7, 6.4, 5.1 and 4.1 days, respectively. Embryos incubated at 18.1°C developed abnormally and almost all died during epiboly. Embryonic mortality was high during epiboly at 8.1, 16.2 and 18.1°C and during organogenesis-growth at 8.1°C. Survival to hatch was highest at 10.5, 12.3 and 14.1°C. The standard length and body depth at vent at hatching decreased with increasing temperatures but yolk volume was largest at 12.3°C. The optimal temperature range for the incubation of striped trumpeter eggs was 10.5 to 12.3°C, which is close to the mean sea-surface temperature during the spawning season (11.42–12.66°C) and the ambient temperature experienced by the broodstock at spawning (11°C).

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.

Feeding Artemia and shellfish to phyllosoma larvae of southern rock lobster (Jasus edwardsii)

Newly-hatched phyllosoma larvae from southern rock lobster (Jasus edwardsii) were grown in culture vessels containing 10 l sea water in a flow-through system at 18 degrees C and fed diets of Artemia sp. and shellfish. The survival and growth of larvae to Stage II was higher when fed ongrown (1.5 mm long) Artemia enriched with Isochrysis galbana (Tahitian strain) at 3 ml-1 compared to those fed pieces (0.5-1 mm) of blue mussel (Mytilus edulis planulatus), clam (Katelesia scalarina) or Pacific oyster (Crassostrea gigas) at 0.08 pieces ml-1. There were no differences in survival, size or intermoult interval for newly-hatched larvae grown to Stage III when fed ongrown Artemia only at densities of 1.5, 3 or 6 ml-1 or for Stage III larvae grown to Stage VI when fed ongrown Artemia at densities of 1.5, 3 or 6 ml-1 plus mussel (0.04 pieces ml-1). Stage VI larvae fed ongrown Artemia plus mussel (0.08 pieces ml-1) were larger by instar 10 than larvae fed mussel only (0.08 or 0.16 pieces ml-1). Lower survival became apparent for the mussel-only treatments 205 days after hatch (at Stages IX or X). The pattern of moulting became progressively less synchronised with each successive stage and instar, so that after instar 11 (about Stage IX), it was difficult to discern discrete peaks in the moulting pattern. The first larva reached Stage XI 288 days after hatch. The size of larvae and duration to successive moults, but not survival, were influenced by parent of origin indicating the importance of selection of broodstock in hatchery rearing.

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.

The ontogeny of physiological response to light intensity in early stage spiny lobster (Jasus edwardsii) larvae

Early stage phyllosoma larvae of the spiny rock lobster Jasus edwardsii were examined for swimming speed, feeding, oxygen consumption and nitrogen excretion as instantaneous performance indicators when exposed to different irradiance levels. Swimming speed was measured in recently hatched Stage I larvae while all other parameters were measured in larvae from hatch to mid-Stage V. The swimming speed of recently hatched Stage I phyllosoma increased logarithmically between light intensities of 2.9 x 10(14) and 1.8 x 10(16) quanta s(-1) cm(-2) indicating that, within this range, swimming activity was only suppressed at the lowest irradiance level. Larvae examined under dark (no light) conditions showed lower feed intake, oxygen consumption and nitrogen excretion than larvae under low (7.7 x 10(12) q s(-1) cm(-2)) and high (3.9 x 10(14) q s(-1) cm(-2)) light intensities, and this was a consistent pattern observed throughout development from hatch to Stage V. There was no difference in feeding, oxygen consumption and nitrogen excretion between larvae exposed to low and high light intensities. However, from mid-Stage I to mid-Stage V, the metabolic feeding efficiency (feed intake:oxygen consumption ratio) was consistently higher in larvae exposed to low light intensity than in phyllosoma assessed in the dark and under high irradiance. A light intensity of about 7.7 x 10(12) quanta s(-1) cm(-2) and no higher than 3.9 x 10(14) quanta s(-1) cm(-2) is recommended to stimulate feeding and optimise metabolic feeding efficiency in early larval stages of J. edwardsii.