Odonus Research Articles

Fatty Acid Profile and Mineral Composition of Red-Toothed Triggerfish (Odonus niger) Landed in Karnataka, Southeastern Arabian Sea.

The seasonal and sex-wise variations in fatty acid and mineral composition in the tissue of Odonus niger collected from the Karnataka coast, southeastern Arabian Sea, were evaluated for the first time. The fatty acid profile was assessed using gas chromatography, nutritional indices were employed to evaluate lipid quality, and standard methods were utilized to estimate mineral composition and heavy metals. Palmitic acid (20.2-45.9%), oleic acid (10.0-19.2%), and docosahexaenoic acid (10.9-36.7%) were found in the highest proportions. The amount of ω3 fatty acids was significantly higher than ω6 fatty acids indicating the healthiest food fish and a promising source for nutrient supplementation. The P/S (PUFA/SFA) and ω3/ω6 ratios of the species were greater than those recommended by the UK Dept. of Health. Index of atherogenicity (IA) and thrombogenicity (IT) was low, and hypocholesterolemic to the hypercholesterolemic ratio (HH), unsaturation index (UI), health-promoting index (HPI), fish lipid quality (FLQ), and polyene index (PI) were high. The relationship between the quantities of macronutrients and trace elements was calculated as K > P > Na > Mg > Ca and B > Fe > Zn > Ga > Al respectively. Heavy metals like Be, Bi, Co, and Hg were found below the detection level. Benefit-risk ratio value indicates that the species is safe for consumption.

Antidiabetic effect and haematological changes in alloxan induced diabetic rats treated with trash fish, Odonus niger liver oil in comparision with cod liver oil

Antidiabetic effect and haematological changes in alloxan induced diabetic rats treated with trash fish, Odonus niger liver oil in comparision with cod liver oil

Report of the Red-Toothed Triggerfish Odonus niger (Rüppell, 1836) from the North-East Region of the Arabian Gulf

Report of the Red-Toothed Triggerfish Odonus niger (Rüppell, 1836) from the North-East Region of the Arabian Gulf

Biochemical composition, protein quality and amino acid profile of red‐toothed triggerfish (Odonus niger), an underutilised fish

SummaryThe present study aims to assess the seasonal and sex‐wise variations in proximate composition, amino acid profile and protein quality of Odonus niger, which will be the first report for this species. High‐protein (15.15%–20.05%) and low‐fat contents (0.46%–1.94%) were observed for the species studied. The highest protein was observed in September and December for male and female fishes respectively. The total essential amino acid (TEAA) content was 58.65–77.41 mg g−1 (males) and 60.25–77.38 mg g−1 (females) and leucine was the predominant EAA in both the sexes. The EAA index and biological value ranged between 17.50–22.56 and 7.38–12.89 for males and 18.02–22.48 and 7.94–12.80 for female fishes respectively. In male, TEAA followed Sept>Jan > Dec > Aug > Oct > Nov and in female it was Oct > Sept>Dec > Nov > Aug > Jan. The chemical score for histidine and threonine was more than the FAO recommended values. Overall, the nutritional quality of this unconventional species proved very good and comparable with other commercially important lean fishes.

ANTIOXIDANT PROPERTIES OF TRASH FISH Odonus niger LIVER OIL IN COMPARISON WITH COD LIVER OIL

The present study was undertaken to compare the in vitro antioxidant properties of marine trash fish Odonus niger liver oil and commercially available cod liver oil. For this O. niger fishes were collected and the oil was extracted from the liver mass by following Bligh and Dyer method and it was purified. Further the antioxidant potential of various concentrations (12.5 to 200µg/ml) of the extracted oil was performed through different standard antioxidant assays, simultaneously the same concentrations of commercial cod liver oil were also performed. The antioxidant potential of both oils was compared with appropriate standards like ascorbic acid, gallic acid and quercetin in the respective assays. The different assays performed were hydroxyl radical scavenging activity (23.24%), total antioxidant activity (43.06%), DPPH radical scavenging activity (60.06%), reducing power effect (68.22%), lipid peroxidation inhibitory activity (53.10%) and ferrous ions chelating activity (75%) respectively for O. niger at the highest concentration of 200μg/ml. All the above activities showed that O. niger liver oil possessed better antioxidant potential, especially at higher concentration (200 µg/ml) than the tested commercial cod liver oil.

First record of patchy coral reef off Terekhol, North Goa, India

This study reports the first time record of the patchy coral reef (~ 2 km2) of Terekhol in North Goa, the western coast of India during January – February 2020. There were more than 07 genera/species of hard corals in the reef and is dominated by a reef building Turbinaria mesenterina (Dendrophylliidae), which is considered as a sediment tolerant coral species. A total of 25 fish species were counted and the major species recorded were Chromis viridis, Chromis sp., Dascyllus sp., Abudefduf saxatilis, Abudefduf bengalensis, Acanthurus blochii, Acanthurus nigroris, Acanthurus sp., and Odonus niger that contributed 80 % of the total fish community. The documentation and record of the reef area could give identity to the ecosystem in the spatial platform and the conservation efforts can be planned for the reef by limiting the anthropogenic activities in and around the ecosystem.

First report on the diet and reproductive biology of red-toothed triggerfishOdonus niger(Ruppell, 1836) from the south-eastern Arabian Sea

AbstractThe feeding habits and reproductive biology of red-toothed triggerfishOdonus niger(Ruppell, 1836) was analysed from 449 specimens collected from the Karnataka coast of the south-eastern Arabian Sea. Of the total stomachs examined, only 54 (12%) were empty and 395 contained food remains. The diet comprised crustacean remains (48.0%), zooplankton (21.4%), algae (16.5%), fish remains (6.1%) and cephalopod remains (5.3%) along with partially digested matter (2.3%) and detritus (0.4%). The species was found to be a generalist feeder and an omnivore. The overall sex ratio between males and females (1: 0.44) was significantly (P< 0.05) different. Histological examination of the ovaries indicated asynchronous ovarian development in females, with males maturing earlier than females. The gonadosomatic index (GSI) patterns of males and females, and the presence of ripe ovaries and spermatozoids suggested that April–May is the peak spawning period. The absolute and relative fecundity estimates ranged from 16,464–312,420 eggs and 251–2812 eggs g−1respectively. Fecundity was positively correlated with total length and body weight. The biological information on diet composition and reproductive traits provided for the first time in this study can facilitate conservation, management and sustainable exploitation of this species in the study area.

Morphometry, length-weight relationship and relative condition factor of red-toothed trigger fish, Odonus niger

Aim: The study aimed to investigate the morphometric and meristic measurements, length-weight relationship and relative condition factor of Odonus niger landed along coastal Karnataka. Methodology: The morphometric and meristic measurements, length-weight relationship and relative condition factor (Kn) of O. niger was studied for a period of eight months from August 2019 to March 2020. The different morphometric characters were subjected to statistical analysis. The length-weight relationship was analyzed for both the sexes (female and male) and combined data. Monthly relative condition factor was analyzed for both the sexes and for different size group. Results: A comparison of different morphometric measurements exhibited good extent of correlation indicating good extent of interdependence of these characters. Four out of eight morphometric characters are environmentally controlled and suggested wide range of zoogeographical distribution of O. niger. The length-weight relationship is indicated as W = 0.046 L2.565, W = 0.044 L2.589 and W = 0.047 L2.561 with coefficient of determination (r2) of 0.910, 0.913 and 0.910 for male, female and combined sexes, respectively. The 'b' values of both the sexes (male and female) exhibited negative allometric growth (p<0.05) and appeared to be leaner. There was no significant (p<0.05) variation for relative condition factor (Kn) among the months and size groups. However, little higher values were observed during November and February. Interpretation: The study fills the knowledge gap and support for developing a suitable management system for this fish species.

Molecular characterization of a novel β-defensin isoform from the red-toothed trigger fish, Odonus niger (Ruppel, 1836)

BackgroundThe concern regarding a post-antibiotic era with increasing drug resistance by pathogens imposes the need to discover alternatives for existing antibiotics. Antimicrobial peptides (AMPs) with their versatile therapeutic properties are a group of promising molecules with curative potentials. These evolutionarily conserved molecules play important roles in the innate immune system of several organisms. The β-defensins are a group of cysteine rich cationic antimicrobial peptides that play an important role in the innate immune system by their antimicrobial activity against the invading pathogens. The present study deals with a novel β-defensin isoform from the red-toothed trigger fish, Odonus niger. Total RNA was isolated from the gills, cDNA was synthesized and the β-defensin isoform obtained by polymerase chain reaction was cloned and subjected to structural and functional characterization in silico. ResultsA β-defensin isoform could be detected from the gill mRNA of red-toothed trigger fish, Odonus niger. The cDNA encoded a 63 amino acid peptide, β-defensin, with a 20 amino acid signal sequence followed by 43 amino acid cationic mature peptide (On-Def) having a molecular weight of 5.214 kDa and theoretical pI of 8.89. On-Def possessed six highly conserved cysteine residues forming disulfide bonds between C1–C5, C2–C4, and C3–C6, typical of β-defensins. An anionic pro-region was observed prior to the β-defensin domain within the mature peptide. Clustal alignment and phylogenetic analyses revealed On-Def as a group 2 β-defensin. Furthermore, it shared some structural similarities and functional motifs with β-defensins from other organisms. On-Def was predicted to be non-hemolytic with anti-bacterial, anti-viral, anti-fungal, anti-cancer, and immunomodulatory potential. ConclusionOn-Def is the first report of a β-defensin from the red-toothed trigger fish, Odonus niger. The antimicrobial profile showed the potential for further studies as a suitable candidate for antimicrobial peptide therapeutics.

Acute toxicity and clotting times of anticoagulant rodenticides to red-toothed (Odonus niger) and black (Melichthys niger) triggerfish, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides).

Acute toxicity and clotting times of anticoagulant rodenticides to red-toothed (Odonus niger) and black (Melichthys niger) triggerfish, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides).

Fish fin physique factor in food preferences

Some fish are built for power, scything sleekly through the water, powered by their tails, while others simply potter around rippling their fins. But, the members of one superfamily, comprising triggerfish and filefish (known collectively as the Balistoidea), are able to switch effortlessly between the distinctive styles: rippling the dorsal and anal fins – located above and below the base of their tails – at low speeds, and switching to beating the tail powerfully to and fro when they shift up the gears for a high-speed swim. Yet, each species performs the switch from low to high speed in subtly different ways. Intrigued by the fishes’ elaborate family tree and distinctive appearance, Andrew George and Mark Westneat from the University of Chicago, USA, wondered which aspects of their fin physique determine when they transition from one swimming mode to the other.Selecting members of the superfamily spanning the entire dynasty, from the orange-spotted filefish (Oxymonacanthus longirostris) to the orange-lined triggerfish (Balistapus undulatus), George filmed and observed the fish as they swam, gradually increasing the flow speed from 5 to 60 cm s−1, until the fish could no longer keep swimming against the water. During that time, he recorded the speed at which the animals stepped up a gear and began to beat their tail fin back and forth. ‘The most difficult part was controlling for variation in the fish's behaviour’, says George, adding how every single filefish initially tried to avoid swimming, by gripping the grill at the front of the tank with their jaws. In addition, George carefully photographed and measured the area and shape of the animals’ body and fins before painstakingly analysing the relationships between each fish's build and swimming performance.Impressively, the fastest fish for its size was the tiny (9 cm long) red-toothed triggerfish (Odonus niger) – which clocked up a speedy 55 cm s−1 – while the more sluggish bristle-tail filefish (Acreichthys tomentosus) and larger whitespotted filefish (Cantherhines macrocerus) trailed in at the more sedate speeds of 30 and 40 cm s−1, respectively. Comparing the swimming styles of the fishes, it was clear that the filefish rarely used their tailfins, preferring to use their dorsal and anal fins up to 94% of the time, while some triggerfish beat their tails almost 60% of the time. And when George compared the shape of the fishes’ fins with their swim speeds, it was clear that those with the triangular fins were able to power swimming at higher speeds than those with rectangular fins.However, the duo was surprised when they realised that the fish with rectangular anal and dorsal fins hit similar top swimming speeds (35–42 cm s−1) to the more powerful-looking fish with triangular anal and dorsal fins before they added in their tail fins. In contrast, the fish with short rounded anal and dorsal fins turned on their tail beat over a wide range of speeds, from the slowest at 21 cm s−1 up to 34 cm s−1. And when they analysed the fishes’ swimming styles relative to their fin sizes, it was clear that those with long chunky anal and dorsal fins rarely use their tail fins, while those with small stubby anal and dorsal fins use their tail fins a significant proportion of the time.But what does this all mean for the fishes’ lifestyles? ‘The ecological pattern that popped out most clearly was that species with similar fin and body shapes tend to eat similar food’, says George, pointing out that fishes with the highest swim speeds tend to consume plankton in fast-flowing water, while slower anal and dorsal fin-propelled fishes recruit their tail fin for a sudden burst of speed when dining on fast-moving fish and octopus snacks.

English

Rhizoctonia solani is the causative agent of rice sheath blight, which has become a major problem in rice production. Seaweed provides a rich source of structurally diverse and biologically active secondary metabolite and is proved to be better in decreasing foliar fungal diseases which ultimately increase its fertility and help in the growth of plants. The use of natural products is the ultimate way of combating this disease. In this context, five different seaweeds such as Sargassum wightii, Dictyota bartyrensiana, Ulva reticulate, Gelidiella acerosa and Odonus niger were used together with the fish powder extract in the control of sheath blight disease in rice were studied. Evaluation of marine products against R. solani was carried out by paper disc assay; agar well method and mycelial dry weight. Among the five marine extracts tested, extracts of S. wightii [brown seaweed algae] at a high concentration (20%) was found to be the best in the reduction of spore germination (19.60%). The leaf extracts of S. wightii [brown seaweed algae] at highest concentration of 20% showed a maximum reduction in both paper disc method and agar well method with 44.65 and 45.90% zone of inhibition, respectively. The antifungal compounds were identified through gas chromatography mass spectroscopy. The results revealed that, 18 compounds were present in S. wightii and among that n-hexadecanoic acid which was closely related to 9, 12-octadecadienoic acid may be responsible for the inhibition of the growth of R. solani. The present study revealed that the efficacy of seaweed extracts against fungal pathogens may be due to higher levels and early accumulation of phenolics and phytoalexins, and the pot study proved that R. solani can be controlled by the application of marine products which may be further used for field study. Key words: Seaweeds, Rhizoctonia solani, antifungal compounds, rice.

Hypoxia tolerance in coral-reef triggerfishes (Balistidae)

Despite high rates of photosynthetic oxygen production during the day, the warm waters of coral reefs are susceptible to hypoxia at night due to elevated respiration rates at higher temperatures that also reduce the solubility of oxygen. Hypoxia may be a challenge for coral-reef fish that hide in the reef to avoid predators at night. Triggerfishes (Balistidae) are found in a variety of reef habitats, but they also are known to find refuge in reef crevices and holes at night, which may expose them to hypoxic conditions. The critical oxygen tension (P crit) was determined as the point below which oxygen uptake could not be maintained to support standard metabolic rate (SMR) for five species of triggerfish. The triggerfishes exhibited similar levels of hypoxia tolerance as other coral-reef and coastal marine fishes that encounter low oxygen levels in their environment. Two species, Rhinecanthus rectangulus and R. aculeatus, had the lowest P crit (~ 3.0 kPa O2), comparable to the most hypoxia-tolerant obligate coral-dwelling gobies, while Odonus niger and Sufflamen bursa were moderately tolerant to hypoxia (P crit ~ 4.5 kPa), and Xanthichthys auromarginatus was intermediate (P crit ~ 3.7 kPa). These differences in P crit were not due to differences in oxygen demand, as all the species had a similar SMR once mass differences were taken into account. The results suggest that triggerfish species are adapted for different levels of hypoxia exposure during nocturnal sheltering within the reef.

Optimization and partial purification of a protease produced by selected bacterial strains grown on trash fish meal substrate and its antagonistic property against bacterial pathogens

Optimization and partial purification of a protease produced by selected bacterial strains grown on trash fish meal substrate and its antagonistic property against bacterial pathogens

High gene flow in reef fishes and its implications for ad-hoc no-take marine reserves

Integration of genetic connectivity information in effective marine reserve (MR) design is important in sustaining marine biodiversity. Here, genetic connectivity based on mitochondrial DNA (mtDNA) of three reef fish species, namely Epinephelus merra (n = 67; 32 from Bolinao, 14 from Alaminos, and 21 from Masinloc), Parupeneus multifasciatus (n = 23; 12 from Bolinao and 11 from Masinloc), and Odonus niger (n = 35; 21 from Mabini and 14 from Tingloy), sampled across western Luzon, Philippines, was inferred by assessing their genetic diversity, population genetic structure, and historical demography. The results show high haplotype and nucleotide diversity in the three species. Tests for population structure indicate high gene flow and no spatial genetic structuring for the three species. Mismatch analyses suggest unimodal distribution for E. merra and P. multifasciatus, but bimodal distribution for O. niger. Even with differences in mismatch distributions, all the three species exhibit low raggedness index indicating demographic population expansion. The bimodal distribution of O. niger could be attributed to the mixing of two isolated populations. High gene flow between sampling locations implies genetic exchanges and connectivity between many small MRs and fishing grounds in western Luzon, Philippines, at a scale similar to our study. This research is among the first few to elucidate the high genetic connectivity of reef fish communities across the Philippines (here western Luzon), but it also calls for more support (i.e. government and academia) for genetic research that aims to (1) understand the maintenance of megadiversity of the country and (2) search for effective biodiversity conservation options for the coral reefs.

Skin, bone and muscle collagen extraction from the trash fish, leather jacket (Odonus niger) and their characterization

Acid soluble (ASC) and pepsin soluble (PSC) collagens were extracted from the skin, bone and muscle of a trash fish, leather jacket (Odonus niger) by three different extraction methods. Method I gave 46-50% yield for ASC, Method II gave 49-58% yield for both ASC and PSC and Method III gave 64-71% yield for PSC. The addition of pepsin had increased the yield by 30-45%. The yields of collagen from skin and bone were higher than muscle. SDS-PAGE pattern revealed that skin and bone collagen as Type I collagen with a typical (α1)2α2 chains and muscle collagen as Type V collagen with a typical α1α3α2 chains. Td values of bone and muscle collagen were high (30-32°C) compared to skin collagen (27-28°C). The higher imino acids (190 residues/1,000 residues) were found responsible for the higher Td values. The trash fish, leather jacket can therefore be exploited effectively for collagen as it has got good thermal properties for pharmaceutical and biomedical applications.

Mating Systems, Maternal and Biparental Care in Triggerfish (Balistidae)

Groups of the triggerfish Pseudobalistes fuscus and Odonus niger were studied from the underwater laboratory Neritica in Eilat, Gulf of Akaba, in the Red Sea. Mating and the roles of the sexes during broodcare seem to depend strongly on territory size, probably determined by shelter site and food availability, and territorial control- and defendability. The discussion considers why evolution has favoured maternal broodcare in the one case and biparental in the other.

Comparative study on the liver fatty acid profiles of the red toothed trigger fish ( Odonus niger ) from southwest coast of India

In order to find an alternative source for the highly unsaturated fatty acids oil with lower cost, a marine trash fish Odonus niger has been analysed and characterised. The body weight and the corresponding liver weight of the fish were studied and the results showed that for one gram increase in the size of the animal, the liver weight can increase to 0.04 g. The oil yielding capacity of the liver was assessed by four different methods namely Soxhlet, Bligh and Dyer, Direct steaming and Solar extraction. The percentage of oil yield was high in Soxhlet method (67.7%), but it was 54.3% in Bligh and Dyer method, 42.5% in direct steaming method and minimum of 32.0% in solar extraction method. The solidification point of all the extracted oils remained at 29 ± 0.5 o C. The specific gravity (0.95 to 0.96) and refractive index (1.42µ to 1.48µ) of the oil extracted by the four different methods were not varied significantly. The cholesterol contents of the oil extracted by Bligh and Dyer and direct steaming extraction methods were at the highest level (1991.00 and 2059.00mg 100ml -1 ) but it was 50% less in other methods. The percentages of PUFA in the total fatty acid of the oils were 13.78, 20.46, 19.07 and 22.54% (by weight) in solar extraction, direct steaming, Soxhlet and Bligh and Dyer methods, respectively. Thus the physico-chemical properties of liver oil of O. niger were found to be influenced by the extraction adopted methods. Also it is clear that Bligh & Dyer method is the suitable method for the extraction of liver oil from marine fishes without much loss of nutrients.

English

  To investigate the maximum accumulation of highly unsaturated fatty acids (HUFA) inArtemia franciscana nauplii through bioencapsulation process, five different concentrations (0 - 4%) of emulsified Odonus niger liver oil were prepared. The prepared emulsions were used to enrich A. franciscana at different time intervals of 6, 12, 18 and 24 h. After the enrichment period, the fatty acid composition of the nauplii were analysed and estimated individually along with freshly hatched A. franciscana andO. niger liver oil. The HUFA content such as linoleic (18: 2n-6), linolenic (18: 3n-3), arachidonic (20: 4n-3 + n-6), eicosapentaenoic (20: 5-n3) and docosahexaenoic (22: 6n-3) acids were 12.87, 0.21, 2.66, 2.86 and 2.30% dry weight (DW), respectively, inO. niger liver oil, and 8.60, 17.20, 1.80, 2.40 and 0.1% DW, respectively, in freshly hatched A. franciscana. During 6 – 24 h of enrichment period, all the above HUFA increased considerably from 8.76 to 10.84, 17.24 to 23.84, 1.16 to 3.98, 2.45 to 5.88 and 0.30 to 2.69% DW, respectively. The increase in the level of individual HUFA ofA. franciscana enriched with various concentrations of emulsified liver oil at different time durations showed a positive linear relationship and the correlation coefficient obtained were statistically significant (P< 0.05).   Key words: Artemia franciscana, HUFA, linoleic, linolenic, eicosapentaenoic, docosahexaenoic.

Delivery of HUFA, probionts and biomedicine through bioencapsulated Artemia as a means to enhance the growth and survival and reduce the pathogenesity in shrimp Penaeus monodon postlarvae

One of the major problems in the shrimp culture industry is the difficulty in producing high-quality shrimp larvae. In larviculture, quality feeds containing a high content of highly unsaturated fatty acids (HUFA) and ingredients that stimulate stress and disease resistance are essential to produce healthy shrimp larvae. In the present study, Penaeus monodon postlarvae (PL15) were fed for 25 days on an unenriched Artemia diet (control; A) or on a diet of Artemia enriched with either HUFA-rich liver oil of the trash fish Odonus niger (B), probionts [Lactobacillus acidophilus (C1) or yeast-Saccharomyces cerevisiae (C2)] or biomedicinal herbal products (D) that have anti-stress, growth-promoting and anti-microbial characteristics. P. monodon postlarvae fed unenriched Artemia exhibited the lowest weight gain (227.9 ± 8.30 mg) and specific growth rate (9.95 ± 0.05%), while those fed the HUFA-enriched Artemia (B) exhibited the highest weight gain and specific growth rate (362.34 ± 12.56 mg and 11.77 ± 0.08%, respectively). At the end of the 25-day rearing experiment, the shrimp postlarvae (PL40) were subjected to a salinity stress study. At both low and high (0 and 50‰) salinities, the group fed the control diet (A) experienced the highest cumulative mortality indices (CMI) 935.7 ± 2.1 and 1270.7 ± 3.1, respectively. Those fed diet D showed the lowest stress-induced mortality, and CMI were reduced by 31.1 and 32.3% under conditions of low and high salinity stress, respectively. A 10-day disease challenge test was conducted with the P. monodon postlarvae (PL40–PL50) by inoculating the shrimp with the pathogen Vibrio harveyi at the rate of 105–107 CFU/ml in all rearing tanks. P. monodon postlarvae fed probiont-encapsulated Artemia diets (C1 and C2) exhibited the highest survival (94.3 and 82.3%, respectively) and lowest pathogen load (V. harveyi) in hepatopancreas (5.2 × 102 ± 9.0 × 10 and 4.6 × 102 ± 9.0 × 10 CFU g−1, respectively) and muscle (2.0 × 102 ± 6 × 10 and 1.7 × 102 ± 8.6 × 10 CFU g−1, respectively) tissues. The shrimp that were fed the unenriched Artemia (Control; A) showed the lowest survival (26.33%) and highest bacterial load in the hepatopancreas (1.0 × 105 ± 5 × 103 CFU g−1) and muscle (3.6 × 104 ± 6 × 102 CFU g−1). The shrimp fed the herbal product (D)-enriched Artemia also exhibited enhanced survival and reduced V. harveyi load in the tissues tested compared to the control diet (A) group. The results are discussed in terms of developing a quality larval feed to produce healthy shrimp larvae.