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Betta splendens , also known as the Siamese fighting fish, is an anabantoid native to Southeast Asia and is among the top ten freshwater ornamental fish species imported into the USA for the aquarium trade. Although B. splendens is a staple in the ornamental aquaculture industry, larval production continues to rely heavily on the use of Artemia spp. nauplii. Digestive physiology data can be used to minimize the use of costly live feeds during larval production by indicating when larvae can digest complex feeds like microdiets (MDs). A 30-day trial was conducted to determine the timing of the maturation of the digestive tract. Standard microplate assays were conducted to quantify pepsin, trypsin, and lipase activities and histology was used to describe digestive tract morphology. Pepsin activity and the development of gastric glands indicated the presence of a functional stomach between 15 and 18 DPH (days post-hatch). Next, a 42-day dietetics trial was conducted to determine which of three commercially available MDs best promoted growth and survival in larval B. splendens compared to an Artemia spp. reference diet. Survival was statistically similar for larvae fed Gemma Micro compared to the Artemia spp. reference diet and all MD treatments yielded significantly higher growth compared with the reference diet. Finally, a 25-day weaning trial was conducted where MD was introduced at three timepoints surrounding the development of the digestive tract. Larvae were subjected to one of five treatments: Artemia spp. reference diet, MD from first-feeding, or MD introduction at 12, 15, or 18 DPH. MD introduction at 15 and 18 DPH yielded similar survival and growth compared to the Artemia spp. reference diet. MD from first-feeding yielded statistically lower survival and growth compared to all other treatments. These results suggest that B. splendens can transition to a MD as early as 15 DPH without reducing growth or survival. • A series of trials were conducted to develop efficient feeding protocols for larval B. splendens. • B. splendens can utilize microdiet from first feeding. • Feeding B. splendens microdiet at 15 days post hatch yielded the highest survival. [ABSTRACT FROM AUTHOR]

The Artemia nauplii intake by painted river prawn Macrobrachium carcinus was determined for larvae in stages III, IV, IX, X and XI of development, under laboratory conditions, aiming at optimizing feed management. The daily intake rate was determined for three supply densities of newly hatched Artemia nauplii (AN) (2, 4, 8 AN mL − 1 ), which were counted and placed in 10 Petri dishes of 20 mL (repetitions), kept on black background. One larva of each developmental stage was added to each plate. After 24 h, the remaining intact nauplii were counted. In general, the larvae average intake increased significantly ( p < 0.05) as nauplii density increased. Larvae in stage XI consumed significantly less nauplii ( p < 0.05), independent of density. The percentage of intake of Artemia , regardless of nauplii density was lower in stage XI (36.8%), indicating lowest nauplii capture efficiency. Larvae in the initial developmental stages seem to have greater need for live food, unlike the final stages, which seem to necessitate addition of inert food to the diet. While the live food supplied at insufficient density can lead to larval malnutrition, resulting in reduced growth rate and cannibalism. The AN excess can result in problems with water quality and an increase in cost of production. Results obtained provide guidance for development of a dietary protocol technically and economically more efficient. [ABSTRACT FROM AUTHOR]

The clam, Panopea globosa , is one of two geoduck species intensively exploited in Mexico because of its high demand and commercial export value to Asian countries. Current efforts to develop successful seed production technology involve appropriate methods for improving the survival of larval and metamorphic stages. Several organic and inorganic chemicals have been successfully used to induce, synchronize or accelerate the settlement and/or metamorphosis of different molluscan species. In the present study the effect of 5 chemicals (serotonin, GABA, L -DOPA, epinephrine and KCl) on the metamorphosis of P. globosa larvae was tested at 3 different concentrations (10 − 6 , 10 − 5 and 10 − 4 M, or 1, 10 and 20 mM in the case of KCl), with 3 different exposure periods (1.5, 6 and 24 h). Percent metamorphosis and survival were evaluated after 30 h. In each case, 3 metamorphic phases were documented (initial, intermediate and completed). Survival approached 100% after exposure to the different treatments, except with L -DOPA, where 80% of P. globosa larvae died after 24 h exposure at the highest concentration (10 − 4 M). The compounds GABA, L -DOPA and KCl failed to induce larval metamorphosis when compared to their respective controls. Serotonin rapidly triggered the initiation of metamorphosis, and the highest percent of metamorphosed larvae (87% ± 6.7 standard error) was observed in the combination of 6 h exposure and 10 − 6 M concentration. Epinephrine effects were slower than those of serotonin, yet the former also induced a high percent metamorphosis (> 75%) after 6 to 24 h exposure to a concentration of 10 − 4 M or 10 − 6 M. It is concluded that both serotonin and epinephrine can be potentially used to accelerate and synchronize the process of metamorphosis of P. globosa larvae. [ABSTRACT FROM AUTHOR]

Abstract: The objectives of the study were to examine if early cod larvae could incorporate long-chain highly unsaturated fatty acids like docosahexaenoic acid (22:6 n−3, DHA) from dietary phospholipids (PL) more efficiently than from dietary triacylglycerides (TAG), and to investigate if because of this, PL from copepods is a better DHA source than PL from rotifers for larval cod. Two diets of Brachionus plicatilis Nevada were compared in one first feeding experiment. Their lipid composition was similar, but %DHA of PL fatty acids was different; 2.1% for Brachionus-Low and 9.4% for Brachionus-High. A second experiment compared the Brachionus-High diet (9.4% DHA in PL) and cultivated nauplii of Acartia tonsa that contained 30% DHA of PL-fatty acids. The total lipid per fry dry weight (DW) and the lipid class composition were similar for all larval groups at 17days post-hatching (dph). The %DHA of total fatty acids in PL of newly hatched larvae (2dph) was 26%, and the values for fed groups varied from 17 to 30% DHA of PL fatty acids. The dominant fatty acids in the PL of larvae and PL of the diets were well correlated (r2 =0.84, p<0.05), specifically for %DHA (r2 =0.90). The %DHA in larval PL was also significantly positively correlated to larval DW at 17dph, whereas the relationship to survival was positive, but not significantly correlated across the three diets. We conclude that cod larvae exhibited a low capacity for de novo PL synthesis based on dietary TAG, the normal pathway of adult fish and humans. The 17dph cod larvae instead synthesised their PL through re-acylation of digested dietary PL. It then follows that only a dietary PL composition close to the PL composition of larval cod, like in PL of many copepods, can secure high DHA incorporation in larval PL, and ultimately high larval growth and survival. We suggest that the DHA requirement of cod larvae cannot be easily met with B. plicatilis Nevada and call for new approaches of larval feeding. [Copyright &y& Elsevier]

Tropical commercial sea cucumber Stichopus horrens is extensively distributed throughout the tropical Indo-Pacific region, and wild stocks are severely depleted over the past decade. This study firstly presented preliminary results on the spawning, the development of larvae and the growth of the juvenile of S. horrens in Xisha Islands. It was proved that S. horrens followed a predictable lunar spawning periodicity and might reproduce throughout the year in Xisha Islands. Dry stimulation was a simple and efficient way to induce S. horrens to spawn. The mean quantity of spawned eggs was 1.37×106 (s.e.=2.09×106, n=8), and the mean egg diameter was 114μm (s.e.=2.8μm, n=8). S. horrens developed from fertilized eggs to pentactula larval after 19–27days at 25–27°C. From oosperm to settled juvenile, the survival rate of S. horrens was 1.0%–6.83% when enough live microalgae were supplied. The mean growth rate of juveniles was 0.4mm per day and the survival rate was about 23.3%–50.5% during 80days culture after settlement. Then some juveniles of S. horrens were further cultivated in tanks and majority were released in the wild. Ongoing observations showed good survival and growth of juvenile in the wild. The study indicates S. horrens are amenable to culture using standard techniques which may also be applied on the culture of other tropical species. They exhibit a relatively quick growth both in indoor and wild culture. Furthermore, the test results support possible aquaculture and stock restoration using hatchery produced stocks. [ABSTRACT FROM AUTHOR]

Abstract: Responses of mussel (Mytilus coruscus) larvae to neuroactive compounds, ions and organic solvents were investigated through a series of bioassays. In the 24-h exposure assays, epinephrine, dopamine, serotonin, actylcholine and γ-aminobutyric acid induced larval metamorphosis at 10−6 to 10−4 M concentrations. In addition, epinephrine and dopamine, an epinephrine precursor, both exhibited inductive activity, indicating that the epinephrine biosynthesis pathway may play an important role in the process of larval metamorphosis in this species. The ions, NH4 + at 10−3 M induced 8% metamorphosis, excess K+ at 5×10−2 M induced 20% metamorphosis, and Ca2+ did not induce larval metamorphosis in all concentrations tested. Ethanol and methanol both induced metamorphosis in the 24-h exposure assays. Effects of exposure time on larval metamorphosis were further investigated for epinephrine, NH4 + and ethanol. Experiments revealed that efficacy of these chemicals varied with exposure time. Epinephrine at 10−4 M induced a maximum of 31% larval metamorphosis after 1h exposure. NH4 + at 10−2 M induced a maximum of 43% larval metamorphosis after 3h exposure. Ethanol at 0.5M yielded a maximum of 35% metamorphosis after 24h exposure. Thus, the above compounds were shown to be effective inducers of larval metamorphosis, and may be used to improve M. coruscus larval production for the Chinese aquaculture industry. The findings provide new insights on the biochemical mechanism controlling larval metamorphosis in this species. [Copyright &y& Elsevier]

Abstract: Mollusc aquaculture is an important commodity for France with Pacific oysters, flat oysters and the great scallop being the three main species. Pacific oyster larvae production is currently successful, however larval production of flat oyster and scallops regularly face problems remedied by antibiotics. Using a bioassay technique, four potential probiotic strains (Alteromonas macleodii 0444, Neptunomonas sp. 0536, Phaeobacter gallaeciensis, Pseudoaltermonas sp. D41) were tested upon the larvae of the three mollusc species when challenged with pathogens. Pacific oysters and flat oysters were challenged individually with the pathogens Vibrio coralliilyticus and V. pectenicida, while scallops were challenged with V. coralliilyticus and V. splendidus. Survival of the larvae was measured in challenged larvae given the probiotics and those without probiotic. In scallop larvae, protection against V. coralliilyticus and V. splendidus was provided by prior administration of P. gallaeciensis (29% and 53% better than the respective pathogen controls), A. macleodii 0444 (30%, 36%) and Neptunomonas sp. 0536 (36%, 55%). Significant protection with Pseudoalteromonas sp. D41 was only provided against V. splendidus (35%). In flat oyster larvae, protection against V. coralliilyticus and V. pectenicida was provided by P. gallaeciensis. (73%, 69%) and A. macleodii 0444 (45%, 53%). Neptunomonas sp. 0536 provided significant protection only against V. pectenicida (48% higher). Use of Pseudoalteromonas sp. D41 did not offer significant protection for flat oyster larvae against either pathogen. Experiments with Pacific oysters suggested that Pseudoalteromonas sp. D41 and P. gallaeciensis could be effective against challenge by V. coralliilyticus (50% and 40% improved survival respectively) but not against V. pectenicida. The results indicate that P. gallaeciensis, A. macleodii 0444, Neptunomonas sp. 0536 and Pseudoalteromonas sp. D41 could be useful in mollusc larviculture. [Copyright &y& Elsevier]

Abstract: In this study, thirty-five strains of Vibrio ichthyoenteri, which is a causative agent of bacterial enteritis, were isolated from diseased larval olive flounder (Paralichthys olivaceus) (n =35) taken from a hatchery located in Jeju Island. The minimum inhibitory concentration (MIC) of nine antimicrobials was determined for each strain using the Etest or the CLSI broth microdilution method. The MIC distributions were used to generate epidemiological cut off values using normalized resistance interpretation (NRI). The wild type cut off values (COwt) for OTC, ERY, FLU, NA, OXA and CFX were ≤2.0, 16.0, 1.5, 3.0, 0.5 and 0.5mg/L, respectively. Using these COwt values, only isolates from 2007 were treated as non wild-type (NWT) for FLU, NA, OXA and CFX. Most isolates retrieved in 2009 were categorized as wild type (WT) for tetracycline and erythromycin. However, NRI analysis could not be applied to three of the antimicrobials (ampicillin, amoxicillin and trimethoprim/sulfamethoxazole); thus, visual examinations were conducted to determine COwt. We used a limit of 2mg/L for both ampicillin and amoxicillin, and most strains were classified as NWT for the antibiotics, indicating that beta-lactam antibiotics are not very efficient for the treatment of this disease. Based on the MIC values, V. ichthyoenteri seemed to be sensitive to trimethoprim/sulfamethoxazole. The results of this study showed that the NRI-derived COwt values for the six agents (tetracycline, erythromycin, FLU, NA, OXA and CFX) can be used as provisional epidemiological cut off values. [Copyright &y& Elsevier]

Abstract: This study investigates the efficacy of using different quality parameters to predict hatching percentage of fertilized eggs and early larval survival in a newly farmed species Polyprion oxygeneios (called ‘hapuku’ and ‘groper’ in New Zealand). Blastomere morphology was assessed for individual fertilized eggs, which were then incubated and monitored until hatch. Additionally, blastomere morphology, percentage of floating eggs, fertilization percentage and egg and lipid vesicle diameter were measured for multiple batches incubated during two consecutive captive hapuku spawning seasons in 2008 and 2009. The blastomere morphology score of individual fertilized eggs was significantly correlated with the percentage of individual fertilized eggs that hatched (R²=0.89, p <0.001). Furthermore, blastomere morphology score showed a significant correlation with the combined hatching percentage data from egg batches incubated in 2008 and 2009 (R²=0.32, p <0.001) and was also significantly correlated with larval survival to the post-yolk sac stage (R²=0.34, p =0.005). The percentage of floating eggs and fertilization percentage also significantly correlated with hatching success (R²=0.18 and 0.21 respectively, p<0.05) and with larval survival (R²=0.22 and 0.16 respectively, p <0.05). By comparison, egg diameter and lipid vesicle diameter showed no correlation with percentage hatch or with larval survival. We conclude that of all the egg quality parameters tested, the blastomere morphology score is the most useful and is an effective tool for assessing the quality of egg batches during hapuku hatchery management. [Copyright &y& Elsevier]

Abstract: Biofilms is an important mediator of larval settlement and metamorphosis for the pearl oyster Pinctada fucata, which is an important aquaculture species in South China. However, the role of biofilms in larval settlement and metamorphosis in this species remains unclear. This paper presents the first laboratory study investigating larval settlement and metamorphosis of P. fucata in response to natural biofilms of different ages and biofilm-conditioned seawater. Natural biofilms from 1 to 9day-old except 6-day-old significantly induced larval settlement, while there was no obvious positive correlation between microbial abundance of the biofilms and percentages of larval settlement and metamorphosis. These results indicate that the inductive effect may be closely associated with biofilms community structure and extracellular products in the biofilms rather than microbial abundance. No inductive effects were observed when larvae were exposed to biofilm-conditioned seawater. Thus, the inductive cues from the natural biofilms seem to result from its surface-associated characteristic rather than waterborne. In addition, this study also provides valuable information for studies of mechanism of larval settlement and metamorphosis in this species, which is useful information for the hatchery industry of this pearl oyster. [Copyright &y& Elsevier]

Abstract: Although the swimming crab Portunus trituberculatus females can spawn up to 5 times during a reproductive season, only larvae hatched from the first brood are normally used for larval culture in commercial hatcheries. With the increasing price of swimming crab broodstock and decreasing availability of wild stock, there are increasing interests in the possible utilization of the second brood for larval culture. However, to date, no detailed study has been conducted to assess the reproductive performance and offspring quality from the second brood of female P. trituberculatus. The present study was conducted to compare reproductive performance and offspring quality of the first (1st) and the second brood (2nd) produced by female P. trituberculatus during a reproductive season. No significant differences in several important reproductive parameters, including percentage of females spawned, percentage of berried females successfully hatched, egg production per female and fecundity per unit body weight, was found between the first and the second brood. However, the first brood had significantly higher individual egg wet weight (1st=40.54µg; 2nd=31.40µg), egg dry weight (1st=13.51µg; 2nd=10.55µg) and hatchability (1st=78.41%; 2nd=66.04%), and significantly higher survival (1st=88.31%; 2nd=65.38%) and faster development (1st=3.82days; 2nd=4.34days) from zoea I to zoea II and showed better starvation resistance in newly hatched larvae (1st=5.03days; 2nd=2.98days) than the second brood (P <0.05). Furthermore, the newly hatched zoea I from the first brood also had significantly higher total lipids, 16:1n−7, 18:1n−9, threonine (Thr) and arginine (Arg) contents, but lower levels of 18:0 and histidine (His) (P <0.05) as compared to those of the second brood. These biochemical differences are likely linked to different larval quality of the first and the second brood. [Copyright &y& Elsevier]

Abstract: Larvae of the scallops Nodipecten subnodosus and Argopecten ventricosus were reared at a hatchery under five seawater sources: (1) filtered seawater, as the control group; (2) pasteurized seawater; (3) seawater taken from a well; (4) synthetic seawater, and (5) seawater containing a commercial probiotic (Epicin). The quality of each seawater source was measured in terms of counts of Vibrio pathogenic bacteria, levels of nitrites, nitrates, and ammonium, and content of suspended and organic matter. Overall response of larvae under each treatment was measured in terms of growth, survival, biochemical composition, and recruitment rate of spat. Differences in all these parameters, as a function of the seawater source, were analyzed with one-way ANOVA. Larvae survived more, grew faster and larger, had higher protein levels, and recruited more in filtered seawater (in N. subnodosus) and pasteurized seawater (in A. ventricosus), but significant differences between treatments were slight. In A. ventricosus cultures, filtered seawater favored significantly higher Vibrio counts than pasteurized seawater, but this result did not affect the response and condition of larvae. The well seawater treatment ranked third in terms of low bacterial counts, high nitrate levels, larvae showing relatively high survival and growth rates, and spat reaching the settlement stage (only in A. ventricosus ). The synthetic seawater and Epicin treatments did not yield satisfactory results for any of the indicators measured. In fact, in the Epicin treatment, larvae survived only the first days of hatchery cultivation and settlement occurred only in A. ventricosus. The results from these first set of trials are useful for planning additional experiments aimed to improve the protocol of seawater use at our research hatchery. [Copyright &y& Elsevier]

Abstract: Inheritance of 27 informative microsatellite loci was examined in 40-h D-shaped larvae of three induced meiogynogenetic diploid families of zhikong scallop (Chlamys farreri) for centromere mapping using half-tetrad analysis. Mendelian inheritance was confirmed for the loci by examining the genotypic segregation in three control crosses. Nine of the 27 microsatellite loci showed the existence of null alleles in control crosses. All gynogenetic offspring only possessed the alleles of the mother, indicating 100% success level for the three families. The second division segregation frequency (y) of the microsatellite loci ranged from 0.05 to 0.78 with a mean of 0.41, suggesting the existence of positive interference after a single chiasma formation in some chromosomes in the scallop. Microsatellite–centromere (M–C) distances ranged from 3 cM to 39 cM under the assumption of complete interference. Information on the positions of centromeres in relation to the microsatellite loci will represent a contribution towards assembly of genetic maps in the commercially important scallop species. [Copyright &y& Elsevier]

Abstract: Populations of the coconut crab, Birgus latro, have been severely depleted on most inhabited islands throughout Indo-Pacific regions because of overharvesting and environmental degradation. To assist in the development of artificial propagation technologies for restocking/stock enhancement of this species, this study was designed to elucidate the effect of rearing temperature on survival and developmental period of zoeae through a laboratory experiment testing six constant temperatures levels (18.9, 21.3, 24.6, 27.0, 29.8, and 32.4 °C). Mortality of all first stage zoeae occurred at 18.9 °C. In contrast, the survival rate to the megalopal stage was significantly higher (85.6 and 82.2%) at 27.0 and 29.8 °C, respectively, than all other treatments. Temperature also had marked effects on larval developmental periods. The number of days from hatching required to reach each larval stage (D) significantly decreased with increasing temperature (T). The mean duration from hatching to the megalopal stage ranged between ~19 and 23 days at appropriate temperatures for larval survival (27.0 and 29.8 °C). [Copyright &y& Elsevier]

Abstract: A growth trial was conducted at 28.8±1.8 °C to investigate the effect of salinity on survival rates, specific growth rates (SGR), food conversion efficiencies (FCE) and energy parameters of Penaeus monodon. Juveniles of P. monodon with average weight 1.20±0.05 g were cultured at salinities of 5, 10, 15, 20, 25, 30 and 35 psu. Results showed that survival rates of P. monodon were not significantly affected by salinity in the range 10–35 psu. However, the lowest and significantly different (p <0.05) survival rate was observed at 5 psu. The highest SGR (3.24±0.25%/d) and FCE (54.90±2.97) were observed at 25 psu. Salinity had a strong influence on various energy parameters, namely energy deposited for growth (G), energy lost for respiration (R), energy lost in feces (F), energy lost in excretion (U) and energy lost in exuviae (E), but had little influence on feeding rate (FR). It indicated that growth rate differences under different salinities were not resulted from differences of FR, but mainly resulted from differences of assimilation efficiency and energy channeled into respiration. The highest net growth efficiency was attained at 25 psu, and a salinity range outside 20–35 psu increased the energy channeled to respiration, excretion and exuviae, which led to significant reduction in growth and feed conversion efficiency. Therefore, the optimum salinity for the culture of P. monodon appeared to be ~25 psu, where the average energy budget was: 1OOC (100% energy consumed in food)=14.51(±1.05)G+66.68(±1.56)R+14.54(±0.72)F+3.33(±0.24)U+0.93(±0.07)E. [Copyright &y& Elsevier]

Abstract: A technique was developed to determine apparent digestibility coefficients (ADCs) of protein in microparticulate and live feeds for marine fish larvae. The technique is analogous to methods used for larger fish and allows for an in vivo measurement of protein digestibility by employing a spectrophotometric protein assay for protein determination and rare earth oxides as inert digestibility markers. Either a microbound microparticulate diet developed in our laboratory or Artemia nauplii were fed to 8-week-old Atlantic cod as a single 30-min feeding and fecal solids collected 6 h later. Protein ADCs for the two diets were significantly different (P =0.016) with determined ranges of 47 to 58% and 76 to 86%, (Artemia and microparticulate diets, respectively). Measured ADCs are presented as a range to account for the possibility of leaching of protein from the microparticulate diet, and the evacuation (loss) of marker from the live prey during the 30-min feeding. It is suggested that this new technique will assist researchers in selecting experimental larval feeds with the most nutritive potential for extended feeding studies. Detection limits for this technique were determined to be 8.6 μg for protein and 0.020 and 0.038 μg for yttrium (Y2O3) and dysprosium (Dy2O3) markers, respectively, in collected fecal solids. [Copyright &y& Elsevier]

Abstract: Three experiments, each of 8-days, were conducted to evaluate the effects of (5) N-acyl homoserine lactone (AHL) either alone or in combination on the development and survival of Macrobrachium rosenbergii larvae. Experiment 1 was carried out as preliminary trial to confirm whether AHL mixture added daily at 1 mg/L concentration could have any negative effect on the larval performance. In experiment 2, it was verified whether the negative effect on the larvae was due to individual AHL or their interactions and experiment 3 was carried out to determine the critical threshold dose of AHL mixture. Results revealed that AHL mixture added daily at 1 mg/L concentration significantly (P <0.01) reduced the development and survival of the larvae. Except for C4-HST, there was no significant effect (P >0.05) of any of the AHL molecules added individually at 1 mg/L concentration on the development and survival of the prawn larvae. The AHL molecule C4-HST significantly (P <0.01) reduced the larval stage index (LSI) and survival of prawn larvae by about 9.1 and 8.7%, respectively. In contrast, the AHL mixture added daily at 1 mg/L concentration significantly (P <0.01) reduced the LSI and survival of the larvae by 12 and 41%, respectively. Thus the poor development and low survival of the larvae is probably due to the interaction of different AHL molecules which could have instigated the production of various virulence factors in micro-organisms associated with the larvae. Using the AHL mixture, the dose response relationship with respect to the performance of the larvae showed that the development of the larvae was already negatively affected by adding the mixture to a final concentration of 0.125 mg/L while at that concentration, the survival was still unaffected. This indicate that the standing microbial communities associated with the prawn larvae can become virulent when a quorum or critical threshold level is reached through the daily addition of the AHL mixture at a concentration of 0.125 mg/L. [Copyright &y& Elsevier]

Abstract: To obtain basic knowledge on the feeding habits of greater amberjack Seriola dumerili larvae during the early phase of seed production, larvae were reared until 15–20 days post hatching. Larvae were fed on rotifers Brachionus plicatilis sp. complex with different body sizes, i.e., super small type, small type, and large type rotifers, and the survival rate, standard body length (SBL) and gut contents of the larvae were examined. There were no significant effects of rotifer size on survival and growth of greater amberjack larvae, except for the smallest SBL of larvae fed with super small type rotifers. The body sizes (lorica length and lorica width) of rotifers ingested by larvae did not change in accordance with the growth in larval body size and mouth size from the onset of feeding to ~7.6 mm SBL, despite the larvae having a chance to prey on larger body size rotifers in the tanks. Counting the number of rotifer eggs in the guts revealed that larvae≥4.5 mm SBL appeared to selectively prey on egg-bearing rotifers, whose body sizes are relatively large among the rotifer populations in the tanks, indicating an ontogenic change in the feeding habit of greater amberjack larvae. [Copyright &y& Elsevier]

Abstract: While literature is relatively abundant on adult shellfish, ecophysiological studies at the larval stage are scarce because of both technical difficulties and inadequate methodology. A tool dedicated to provide basic information for larval ecophysiology was accordingly developed. Two steps were followed: first a flow-through method of Crassostrea gigas larval culture was perfected during a set of experiments in which rearing systems and larval density were assessed. Then a continuous hydrobiological data recorder was adapted with modifications to comply with our experimental aim. SILO (Système d''Instrumentation des Larves en flux Ouvert) allowed the successive acquisition of hydrobiological parameters in ten 150-l larval tanks in which larvae were reared using flow-through techniques under controlled environmental conditions. An automated system enabled alternate measurement of hydrobiological parameters from one larval culture to the next. A chamber system contained several probes for measurement of temperature, salinity, pH and fluorescence. The electronic system allowed real time acquisition, storage and transfer of data. SILO was successful as a larval rearing device, reducing larval disturbance that could result from transfer and handling for measurement. It was also efficient as a tool to provide basic information for larval ecophysiology research. The effect of temperature (17, 22, 25, 27, 32 °C) on growth and ingestion of microalgae was studied to test SILO. Maximum growth occurred at 27 °C (16±2 μm d−1) and 32 °C (15±3 μm d−1) whereas larvae reared at 22 and 25 °C showed lower development (8.6±3.1 and 11.7±2.5 μm d−1, respectively). Moreover, metamorphosis exhibited no significant difference at 27 or 32 °C with 87.5±7.1 and 85.9±9.6% respectively, while at 22 or 25 °C lower metamorphosis was recorded with 55.2±8.3 and 57.6±9.6%, respectively. The lowest temperature (17 °C) strongly inhibited ingestion whereas the highest temperature (32 °C) stimulated maximum feeding activity over the whole larval rearing period. [Copyright &y& Elsevier]

Abstract: Identifying appropriate larval husbandry is a key to improve larval quality and shorten duration of larval stages, and culture costs of ornamental cleaner shrimps Lysmata amboinensis. Several feeding and zootechnical experiments were conducted under laboratory conditions to test the effect of food during the first day posthatch, the effect of feeding with microalgae on larval digestion after 24 h posthatch, the effect of enriched rotifers upon survival and the combined effect of stocking density and food concentration on growth and survival of young larvae. For the first time, oxygen consumption values, trypsin-like activity and metabolite content (protein and triacylglycerols) were determined for L. amboinensis early stage larvae. When starved during the first day of life, L. amboinensis larvae had the same oxygen consumption as fed larvae, indicating that food ingestion is not crucial during that period. Nevertheless, energy reserves such as TAG were significantly lower in 24 h starved larvae when compared with fed larvae indicating facultative primary lecitotrophy. Trypsin-like activity of digestive enzymes (U mg prot−1) was low when compared with other decapod larvae. Larvae fed with Tetraselmis chuii showed a significant increase in enzyme activity after 24 h. Present results showed that enriched rotifers result in higher larval survival during the first days of life when compared with larvae fed with non-enriched rotifers and that survival is not dependent on the relation between larval density and food concentration. In addition, stocking densities of 10 larvae ml−1 showed higher survival compared to that obtained at the stocking density of 20 larvae ml−1. [Copyright &y& Elsevier]