Gills Of Shrimp Research Articles

Comparison of detoxification capacity between broodstock and hybrid offspring in the gills of juvenile shrimp ( Macrobrachium nipponense ): Response to chronic ammonia stress

Ammonia nitrogen is an important source of water pollution that severely limits the development of aquaculture. Macrobrachium nipponense is widely cultivated due to its delicious meat, strong reproductive ability and short reproductive cycle, but the problems caused by germplasm degradation are becoming increasingly concerning. Hybridization is an efficient means to solve this problem. In this study, the parental population, Dianshan Lake (DS) and the hybrid population, DS ♀ × CD (Changjiang, CJ ♂ × Dongting, DT ♀ [SCD]) were exposed to 0, 1 or 10 mg/L total ammonia nitrogen (TAN) for 28 days. Our results indicated that the number of gill-positive cells and the apoptosis rate of the two groups showed an upward trend with the ammonia nitrogen concentration increased. The ammonia metabolism-related substance levels and the detoxifying enzyme activities in the gills of shrimp in the SCD group exposed to 10 mg/L of TAN were significantly higher than shrimp in the DS group (p < 0.05). As the TAN concentration increased, the respiratory-related genes displayed a downward trend and the nitrogen metabolism-related genes presented an upward trend. Our results suggest that the SCD population had a stronger detoxifying capacity and a greater stress resistance ability than the DS population when subjected to the same concentration of ammonia nitrogen stress.

Salinity-dependent modulation by protein kinases and the FXYD2 peptide of gill (Na+, K+)-ATPase activity in the freshwater shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae)

The geographical distribution of aquatic crustaceans is determined by ambient factors like salinity that modulate their biochemistry, physiology, behavior, reproduction, development and growth. We investigated the effects of exogenous pig FXYD2 peptide and endogenous protein kinases A and C on gill (Na+, K+)-ATPase activity, and characterized enzyme kinetic properties in a freshwater population of Macrobrachium amazonicum in fresh water (<0.5 ‰ salinity) or acclimated to 21 ‰S. Stimulation by FXYD2 peptide and inhibition by endogenous kinase phosphorylation are salinity-dependent. While without effect in shrimps in fresh water, the FXYD2 peptide stimulated activity in salinity-acclimated shrimps by ≈50 %. PKA-mediated phosphorylation inhibited gill (Na+, K+)-ATPase activity by 85 % in acclimated shrimps while PKC phosphorylation markedly inhibited enzyme activity in freshwater- and salinity-acclimated shrimps. The (Na+, K+)-ATPase in salinity-acclimated shrimp gills hydrolyzed ATP at a Vmax of 54.9 ± 1.8 nmol min−1 mg−1 protein, corresponding to ≈60 % that of freshwater shrimps. Mg2+ affinity increased with salinity acclimation while K+ affinity decreased. (Ca2+, Mg2+)-ATPase activity increased while V(H+)- and Na+- or K+-stimulated activities decreased on salinity acclimation. The 120-kDa immunoreactive band expressed in salinity-acclimated shrimps suggests nonspecific α-subunit phosphorylation by PKA and/or PKC. These alterations in (Na+, K+)-ATPase kinetics in salinity-acclimated M. amazonicum may result from regulatory mechanisms mediated by phosphorylation via protein kinases A and C and the FXYD2 peptide rather than through the expression of a different α-subunit isoform. This is the first demonstration of gill (Na+, K+)-ATPase regulation by protein kinases in freshwater shrimps during salinity challenge.

Investigating water quality and disease in white leg shrimp (Penaeus vannamei) culture applying Nanobubble technology

This study evaluates the variation of water quality, microbiology, gill morphology and shrimp growth of the intensive white leg shrimp (Penaeus vannamei) applying Nanobubble technology. The experiment consisted of 9 commercial concrete tanks with a volume of 25-35 m3divided into 3 treatments of oxygen Nanobubble (O2-NB), ozone Nanobubble (O3-NB), and control (CTRL), 3 tanks for each treatment. O2-NB and O3-NB were provided to the tanks for 1 hour/day during the culture period from stocking to harvest. Shrimps were stocked at a density of 300 shrimp/m3 and applied with the same care and environmental management protocol such as feeding, water change, aeration, siphon, and microbiological treatment. The results showed that the pH, DO, and ORP parameters are affected by the O2-NB and O3-NB treatments. The average concentration of total Vibrioin the water of the O2-NB group was 1.41 times higher than that of the control group, and 1.51 times higher than that of the O3-NB group. The gill tissue of the shrimp was affected and changed to different degrees but did not reduce the survival rate of the shrimp in the experimental treatments. The harvest weight of shrimp of the control, O2-NB, and O3-NB treatments were 11.50±2.29, 11.48±2.66, and 13.87±1.65 g/shrimp, respectively. Research results exhibited that O3-NB treatment increased DO, reduced total Vibrio in water and increased growth rate compare to the control and O2-NB treatments. Reducing Nanobubble generator running time should be considered to minimise the impact on shrimp gills.

Chemoprotection mediated by açaí berry (Euterpe oleracea) in white shrimp Litopenaeus vannamei exposed to the cyanotoxin saxitoxin analyzed by in vivo assays and docking modeling.

Saxitoxin (STX) is a neurotoxic cyanotoxin that also generate reactive oxygen species, leading to a situation of oxidative stress and altered metabolism. The Amazonian fruit açaí Euterpe oleracea possesses a high concentration of antioxidant molecules, a fact that prompted us to evaluate its chemoprotection activity against STX toxicity (obtained from samples of Trichodesmium sp. collected in the environment) in the shrimp Litopenaeus vannamei. For 30 days, shrimps were maintained in 16 aquaria containing 10 shrimps (15% salinity, pH 8.0, 24°C, 12C/12D photoperiod) and fed twice daily with a diet supplemented with lyophilized açaí pulp (10%), in addition to the control diet. After, shrimps (7.21±0.04g) were exposed to the toxin added to the feed for 96h. Four treatments were defined: CTR (control diet), T (lyophilized powder ofTrichodesmium sp. 0.8μg/g), A (10% of açaí) and the combination T+A. HPLC analysis showed predominance of gonyautoxin-1 concentrations (GTX-1) and gonyautoxin-4 concentrations (GTX-4). The results of molecular docking simulations indicated that all variants of STX, including GTX-1, can be a substrate of isoform mu of the glutathione-S-transferase (GST) enzyme since these molecules obtained similar values of estimated Free Energy of Binding (FEB), as well as similar final positions on the binding site. GSH levels were reduced in muscle tissues of shrimp in the T, A, and T+A treatments. Increased GST activity was observed in shrimp hepatopancreas of the T treatment and the gills of the A and T+A treatments. A decrease of protein sulfhydryl groups (P-SH) was observed in gills of shrimps from T+A treatment. A reduction in malondialdehyde (MDA) levels was registered in the hepatopancreas of the T+A treatment in respect to the Control, T, and A treatments. The use of açaí supplements in L. vannamei feed was able to partially mitigate the toxic effects caused by Trichodesmium sp. extracts, and points to mu GST isoform as a key enzyme for saxitoxin detoxification in L. vannamei, an issue that deserves further investigation.

Evaluation of immune stimulatory products for whiteleg shrimp (Penaeus vannamei) by a metabolomics approach

The use of probiotics, prebiotics and dietary fiber has become a common practice in shrimp aquaculture as alternatives to antibiotic treatment. However, not much is known about the metabolic mechanisms underlying the effects of probiotics and immunostimulant used in shrimp aquaculture. In this study, a gas chromatography−mass spectrometry (GC−MS) based metabolomics approach was used to characterize metabolite profiles of haemolymph and gills of whiteleg shrimp (Penaeus vannamei) exposed to four treatments (cellulose fiber, probiotics with Vibrio alginolyticus, a combination of cellulose fiber and V. alginolyticus and a control treatment). The cellulose fiber was administrated as a feed additive (100 mg⋅Kg−1 feed), while the probiotics was applied in the water (105 UFC⋅mL−1 culture water). The results showed significant differences in haemolymph metabolite profiles of immune stimulated treatments compared to the control and among treatments. The combination of cellulose fiber and probiotics resulted in greater differences in metabolic profiles, suggesting a better immune stimulation with this approach. The changes in haemolymph metabolome of treated shrimp reflected several biochemical pathway modifications, including changes in amino acid and fatty acid metabolism, disturbances in energy metabolism and antimicrobial activity and stress responses. For gill tissues, significant differences were only found in lactic acid between the probiotic group and the control. Among the altered metabolites, the increases of itaconic acid in haemolymph, and lactic acid in both haemolymph and gill tissues of immune-stimulated suggest the potential use of these metabolites as biomarkers for health assessment in aquaculture.

Identification and functional characterization of a systemic RNA interference defective 1 gene in Litopenaeus vannamei

RNA interference (RNAi) is a conservative and important functional pathway in eukaryocyte. It regulates the expression of genes that are engaged in a variety of cellular physiological functions. Among the functions of RNAi, its antiviral function have attracted many attentions.The RNAi pathway molecules are able to recognize virus-related dsRNA and degrade it, therefore killing the virus. More importantly, RNAi could mediate systemic antiviral responses, transmit from cell to cell, and systemic RNA interference defective 1 (SID1) was thought to play an important role in this process. In the present study, a SID1 gene (LvSID1) of Litopenaeus vannamei was cloned. LvSID1 could locate to both plasma membrane and endoplasmic reticulum. Result of real-time RT-PCR assay showed that it was highly expressed in shrimp gills. Besides, it was shown that over-expressed LvSID1 in Sf9 cells could significant enchane RNAi efficiency. It was found that the expression of LvSID1was regulated by white spot syndrome virus (WSSV), and knockdown expression of LvSID1 increased the cumulative mortality of WSSV infection shrimp. These results suggested that LvSID1 likely to played a role in L. vannamei systemic RNAi, and was involved in WSSV resistence.

Systemic gene silencing from oral uptake of dsRNA in Litopenaeus vannamei requires both clathrin-mediated endocytosis and LvSID-1

RNA interference (RNAi) is a powerful technique that has been widely applied to inhibit both DNA and RNA viruses in shrimp. To accomplish RNAi in shrimp, dsRNA is often delivered by direct injection or feeding, although the latter method has a much lower efficacy. Therefore, understanding the molecular mechanisms underlying the cellular uptake of dsRNA after oral feeding may help in improving the potency of fed RNAi in shrimp. Chlorpromazine was used to block clathrin-mediated endocytosis before feeding a formulated food containing dsRNA specific to shrimp the Rab7 transcript for 6 days. Suppression of Rab7 expression was seen only in the hepatopancreas and gill tissues of the shrimp fed without drug, and suppression was lost when shrimp were pre-treated with chlorpromazine. The results indicate that clathrin-mediated endocytosis participates in dsRNA uptake from the diet into shrimp hepatopancreas. Up-regulation of LvSID-1 was also observed in the gill of Rab7-silenced shrimp fed with the dsRab7 diet, indicating that the RNAi signal derived from feeding was systemically spread by the hemolymph, possibly in the form of long dsRNA. Moreover, induction of LvSID-1 expression before ingestion of dsSTAT improved suppression levels of STAT mRNA in gill tissues, showing that the fed RNAi signal was taken up into gill cells via the LvSID-1 protein. This study reports for the first time on the involvement of both clathrin-mediated endocytosis and LvSID-1 in systemic gene silencing after oral uptake of dsRNA in shrimp, which could help in improving the potency of antiviral strategies in shrimp by fed with RNAi in the future.

Behavioural and biochemical responses in adult Pacific white shrimp,Litopenaeus vannamei, exposed to the essential oil ofCymbopogon citratus

This study evaluated the effects of continuous exposure to the essential oil of Cymbopogon citratus (EOC) on behavioural and biochemical parameters in shrimp Litopenaeus vannamei. Adult shrimp were randomly placed in aquaria and divided into the following groups: control (pure seawater), ethanol (360 μl L−1 of ethanol) and 5 or 10 μl L−1 EOC for 6 h. Shrimp movements were recorded using a camera for 5 min at the following timepoints: 0, 1, 2, 4 and 6 h of exposure. Light sedation and behavioural changes were observed in shrimp in the 10 μl L−1 EOC group. The total antioxidant capacity against peroxyl radicals (ACAP) in the gills and hepatopancreas of shrimp exposed to 10 µl L−1 EOC was higher than control, whereas, in the muscle, it was lower in those exposed to 5 µl L−1 EOC. In the gills and hepatopancreas, reduced glutathione (GSH) was increased in the control group. Sulphhydryl groups associated with protein (P-SH) were decreased in the gills of shrimp exposed to 10 μl L−1 EOC. Thiobarbituric acid reactive substance levels, indicative of lipid peroxidation, were higher in the gills and hepatopancreas of shrimp exposed to ethanol, which indicates ROS formation. It is concluded that EOC reduced the swimming behaviour of L. vannamei and improved their tolerance with up to 6 h of exposure.

Co-Infection of Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV) and White Spot Syndrome Virus (WSSV) in the Wild Crustaceans of Andaman and Nicobar Archipelago, India.

The present study was intended to screen the wild crustaceans for co-infection with Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV) and White Spot Syndrome Virus (WSSV) in Andaman and Nicobar Archipelago, India. We screened a total of 607 shrimp and 110 crab samples using a specific polymerase chain reaction, and out of them, 82 shrimps (13.5%) and 5 (4.5%) crabs were found positive for co-infection of IHHNV and WSSV. A higher rate of co-infection was observed in Penaeus monodon and Scylla serrata than other shrimp and crab species. The nucleotide sequences of IHHNV and WSSV obtained from crab in this present study exhibited very high sequence identity with their counterparts retrieved from various countries. Histopathological analysis of the infected shrimp gill sections further confirmed the eosinophilic intra-nuclear cowdry type A inclusion bodies and basophilic intra-nuclear inclusion bodies characteristics of IHHNV and WSSV infections, respectively. The present study serves as the first report on co-infection of WSSV and IHHNV in Andaman and Nicobar Archipelago, India and accentuates the critical need for continuous monitoring of wild crustaceans and appropriate biosecurity measures for brackishwater aquaculture.

Responses of energy homeostasis and lipid metabolism in Penaeus vannamei exposed to ammonia stress

Ammonia accumulates in the process of shrimp culture and has a strong toxic effect on shrimp survival, physiological metabolism and immune function. Shrimp can adapt to ammonia stress by regulating lipid metabolism. In the present study, to explore the regulatory mechanism of lipid metabolism in ammonia tolerance of Penaeus vannamei (3.08 ± 0.40 g) based on the energy supply, a 96-h ammonia stress experiment was conducted, and energy homeostasis and lipid metabolism responses in the hepatopancreas, muscle and gills of shrimp were observed at total ammonia concentrations of 0 (control group), 6.42, 32.11, and 64.22 mg/L. The cumulative mortality of shrimp increased significantly with increasing ammonia stress concentration. Exposure to ammonia stress significantly decreased the content of adenosine triphosphate (ATP) and the adenylate energy charge (AEC) in the hepatopancreas, muscle and gills, whereas the relative expression of the AMPK, TOR, and SREBP genes was significantly upregulated. The activities of fatty acid synthase (FAS), acetyl-coenzyme A carboxylase (ACC), and carnitine palmitoyltransferase I (CPT-1) and the peroxisome proliferator-activated receptor-α (PPAR-α) level in the hepatopancreas were significantly increased, whereas the opposite was observed in the muscle and gills. In general, the triglyceride (TG) content of the hepatopancreas increased significantly with increasing ammonia concentration. The results indicated that ammonia stress reduced cellular energy levels in the hepatopancreas, muscle and gills of P. vannamei, thereby inducing the activation of the AMPK signaling pathway in these tissues and resulting in increased levels of lipid decomposition and energy supply in the hepatopancreas. However, the activation of the AMPK pathway did not improve the levels of lipid decomposition or energy supply in the shrimp muscle and gills.

Prevalence of Black Gill (Hyalophysa lynni) in White Shrimp Litopenaeus setiferus and Brown Shrimp Farfantepenaeus aztecus along the Texas Gulf Coast

AbstractShrimp black gill is an emerging disease caused by a parasitic ciliate, Hyalophysa lynni, that attacks gill tissue in white shrimp Litopenaeus setiferus and brown shrimp Farfantepenaeus aztecus and induces an immune response that produces melanized tissue in shrimp gills. This immune response causes necrosis and damage in shrimp gill tissue, which limits shrimp metabolic capability and can lead to high predation mortality among infected individuals. Shrimp black gill was first observed in the southeast Atlantic shrimp fishery in the United States, and this ciliate has been increasing in prevalence in shrimp populations of this region since 2000. The Gulf of Mexico, with its lucrative shrimp fishery and extended warmwater conditions during the year, is a potential region for H. lynni spread. White and brown shrimp were sampled from seven major bays along the Gulf coast of Texas from March to November 2019 and underwent PCR analysis to detect H. lynni presence in gill tissue. From March to November, 65% of the collected shrimp samples tested positive for H. lynni. Samples from all seven bays tested positive for H. lynni, with the upper‐coast bays having a significantly higher disease prevalence than lower‐coast bays. Both white and brown shrimp samples tested positive for H. lynni; however, white shrimp samples had a significantly higher disease prevalence. Overall, disease prevalence showed a temporal pattern of low prevalence in the spring, peaking during the late fall. Generalized additive mixed models detected a high water temperature and a salinity level of 30‰ or less as significant contributors to high disease prevalence. This study validates the commonality of H. lynni presence in the western Gulf of Mexico, serves as a baseline for future shrimp black gill sampling efforts in this region, and contributes to the understanding and management of potential disease threats to the Texas shrimp fishery.

EFEKTIVITAS VARIASI UMPAN PADA FLY TRAP DALAM PENGENDALIAN KEPADATAN LALAT

Flies are the main vector of gastrointestinal infections, so it must control them. Flytraps are one of the fly control methods that are considered the few risk to environmental health. This study aims to determine the effectiveness of flytraps decoy variations in chikens farm. The study used a completely randomized design (CRD), during February-April 2019. Two types of bait (shrimp and fish gills) were used from traditional market waste and placed in the flytrap (size 50cm x 50cm x 50cm). All trapped flies were counted using a tally counter two times (every 60 minutes). Experiments were carried out with five replication for each type of bait. The results showed that the total number of flies caught using fish gill bait was more (363) than shrimp (317). In the first 60 minutes, shrimp bait attracts as many as 22.8 flies (SD = 1.3) and 40.6 fish (SD = 3.6) in the second 60 minutes. Gill bait of fish attracted 25.4 individuals (SD = 0.9), and 47.2 individuals (SD = 2.6). The time variable shows the effect on the number of flies caught; it's related to decomposition time. The characteristics of fish gills high in water, protein, and blood are thought to cause interest in flies. The use of flytraps with fish gill bait is more effective than shrimp bait to apply it.

Iron deposits turn blue shrimp gills to orange

In the grow-out ponds of the blue shrimp (Litopenaeus stylirostris) farms of New Caledonia, animals with orange gills (OG) have been observed over the last ten years, with up to 70% of the shrimp in a given pond being affected. During the processing and marketing of the product, this coloring leads to reduced quality and selling prices, resulting in lower income for the producers concerned. Individual observations and transfer experiments led us to conclude that gill coloration intensity varies according to the intermolt stages, ranging from white in the postmolt stage to a deep orange in the premolt stage, which then disappeared after molting. Histological, biochemical studies and a semi-quantitative analysis by scanning electronic microscopy (SEM + EDX) showed that the coloration is due to layers of iron which settle on the gill tissue surface in a heterogeneous way. Because Cr and Co showed an increase in their concentrations on the whole orange gills but not at their surface, it is possible that elements were mobilized and transported (translocated) from the exoskeleton to the tissue. Animals kept out of contact with sediment show a decrease in OG intensity, suggesting a link with the sediment biogeochemistry. In grow-out ponds, orange gills first appeared in shrimp populations between 10 and 13 weeks after stocking and reached a maximum after 15 weeks. These findings are discussed with a view to identifying the environmental processes that lead to metal accumulation on gills.

Diagenetic Processes in Aquaculture Ponds Showing Metal Accumulation on Shrimp Gills

The gill is the organ by which many toxic metals are taken up by crustaceans. Iron is known to precipitate at its surface, a phenomenon recently observed in some tropical aquaculture ponds. The present study uses a field approach to understand better the environmental conditions and ecological processes involved in this deposit. Because shrimp are exposed to reduced products originating from organic waste accumulated in the sediment, spatial variation in pH, redox potential and concentrations of dissolved metals in pore water were investigated in these ponds. Total organic carbon, acid volatile sulfide and pyrite were also analyzed in the solid phase. Fe2+ in pore waters showed high spatial variability between ponds and within the same pond with concentrations up to 1,193 μmol l–1. Behaviors of Fe2+, Mn2+ and Co2+ in pore water were similar. Four geochemical environments were identified, based on their physico-chemical characteristics. Highest concentrations for Fe2+, Mn2+ and Co2+ in sediment pore water occurred in slightly acidic and suboxic conditions. When the sediment became anoxic, the H2S produced reacted with Fe2+ and/or Co2+ to form acid volatile sulfide and pyrite. When pH increased, the concentration of free H2S rose up to 736 μmol l–1. With neutral and suboxic conditions, dissolved metal concentrations could be controlled by their precipitation as oxides and hydroxides. The production of pyrite suggested the existence of a possible process of sediment acidification between two crop periods through the production of sulfuric acid. This acidification could increase with pond age and be the cause of the accumulation of reduced metal after 30 years of aquaculture activity.

Metabolic responses of whiteleg shrimp to white spot syndrome virus (WSSV)

Outbreaks of white spot syndrome virus (WSSV) have caused serious damage to penaeid shrimp aquaculture worldwide. Despite great efforts to characterize the virus, the conditions that lead to infection and the infection mechanisms, there is still a lack of understanding regarding these complex virus-host interactions, which is needed to develop consistent and effective treatment methods for WSSV. In this study, we used a gas chromatography − mass spectrometry (GC−MS)-based metabolomics approach to compare the metabolite profiles of gills, haemolymph and hepatopancreas from whiteleg shrimp (Penaeus vannamei) exposed to WSSV and corresponding controls. The results revealed clear discriminations between metabolite profiles of WSSV-challenged shrimp and controlled shrimp in each tissue. The responses of shrimp gills to WSSV infection were characterized by increases of many fatty acids and amino acids in WSSV-challenged shrimp compared to the controls. Changes in haemolymph metabolite profiles include the increased levels of itaconic acid, energy-related metabolites, metabolites in glutathione cycle and decrease of amino acids. The WSSV challenge led to the decreases of several fatty acids and amino acids and increases of other amino acids, lactic acid and other organic compounds (levulinic acid, malonic acid and putrescine) in hepatopancreas. These alterations of shrimp metabolites suggest several immune responses of shrimp to WSSV in a tissue-specific manner, including upregulation of osmoregulation, antimicrobial activity, metabolic rate, gluconeogenesis, glutathione pathway in control of oxidative stress and shift from aerobic to anaerobic metabolism in shrimp which indicates the Warburg effect. The findings from this study provide a better understanding of molecular process of shrimp response against WSSV invasion which may be useful for development of disease management strategies.

Clinical signs of naturally white spot syndrome virus (WSSV)-infected kuruma shrimp Marsupenaeus japonicas, based on their physiological and behavioural states

White spot syndrome virus (WSSV) proliferates rapidly and causes a high fatality rate in shrimp. Additionally, there is a lack of effective prevention and treatment methods for this disease. Although WSSV pathology is well-studied by molecular biology techniques, little research has have focused on the clinical signs of this disease based on individual shrimp performances. In this study, we recorded the clinical signs of diseased shrimp by observing their physiological and behavioural states. The physiological state of shrimp, including their heart rate (HR), heart rate variability (HRV), and ventilatory rate (VR), was recorded with a high-speed camera, which was used for crustacean disease diagnosis for the first time. The behavioural state of the shrimp consisted of their behaviour in the pond before sampling and the action demonstrated by the shrimp while falling into the water. Quantitative of WSSV in the shrimp was performed after measuring their physiological and behavioural characteristics. The virus was detected in both shrimp with and without white spots. The amount of virus in shrimp with or without white spots in the sand was relatively low and that of shrimp with white spots swimming in the water was high. The HR and VR both first increased and then decreased as the amount of virus increased gradually. There was a significant negative correlation between HRV and virus quantity in diseased shrimp. The swimming ability of shrimp with high virus quantities was weaker than that of shrimp with low virus quantities. Based on the data, we infer that the burrowing behaviour of shrimp is a disease resistance strategy; the slow swimming or knocking at the wall are symptoms of shrimp suffering from severe infection stage; WSSV destroys the heart, gill and muscle tissue of shrimp, causing damage to their basic motor function. Using the HRV index, we uncovered a fast and effective method with which to determine the virus quantity in diseased shrimp. On the basis of the above symptoms, WSSV is demonstrated as a shrimp disease not only related to the immune system, but also to the motor nervous system and respiratory circulatory systems.

Host specificity and microhabitat preference of symbiotic copepods (Cyclopoida: Clausiididae) associated with ghost shrimps (Decapoda: Callichiridae, Callianideidae).

We examined the host specificity of two ectosymbiotic Clausidium Kossman, 1874 copepods (Cyclopoida: Clausiididae) on two co‐occurrence species of host ghost shrimps. Our results revealed that both species of symbiotic copepod demonstrated extremely high host specificity. Moreover, within a single host shrimp species, each symbiont species displayed strong spatial patterns in microhabitat selection on their hosts’ bodies. Clausidium persiaensis Sepahvand & Kihara, 2017, was only found on the host Callianidea typa Milne Edwards, 1837 and almost exclusively within the host shrimp gill chamber, while C. iranensis Sepahvand, Kihara, & Boxshall, 2019 was only found on the host Neocallichirus jousseaumei (Nobili, 1904) and showed extremely strong preferences for the chelae and anterior walking legs. We also found that while the number of symbionts tends to increase with the host size, the two host species differed in the degree of symbiont infestation, with large C. typa hosting approximately 7× as many symbionts as the similarly sized N. jousseaumeia. The mechanisms resulting in the observed differences in infestation levels and microhabitat preferences of clausidium copepods among their hosts, including differences in physiology, burrowing pattern, and host grooming behavior should be further investigated.

Corrigendum: Muricauda alvinocaridis sp. nov., isolated from shrimp gill from the Okinawa Trough.

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Biological observations on the Bengal guitarfish Rhinobatos annandalei Norman, 1926 from the Eastern Arabian Sea, India

Biological data for the little known Bengal guitarfish Rhinobatos annandalei Norman, 1926 (Rhinopristiformes: Rhinobatidae) are presented based on specimens collected from bycatch of commercial shrimp trawlers, gill netters and bag or dol netters operating in the Arabian Sea at depths of 2-70 m off the north-west coast of India. Five hundred ninety-three specimens measuring 30.0 to 95.0 cm total length (TL) and weighing between 64.0 to 3300 g total weight (TW) were collected for the study. The length-weight relationships (LWR) were significantly different between the sexes (p&lt;0.001) and for the combined sexes was derived as TW= 0.000604 TL3.408256 (r2= 0.997). The co-efficients ‘a’, ‘b’ of the LWR were estimated as 0.000621, 3.410115 (r2= 0.999) for females and 0.000766, 3.333872 (r2= 0.999) for males. The length at maturity (TL50) for females and males was estimated to be 61.0 and 63.3 cm TL, respectively. In a single female, the number of embryos ranged from 2 to 11 and the size at birth was estimated between 25.0 to 30.0 cm TL. The overall sex ratio favoured females at the rate of 1.6:1. An analysis of the stomach contents (%IRI) revealed that R. annandalei mainly fed on Solenocera spp. (18.7% IRI), along with P. sculptilis (0.5% IRI), P. stylifera (0.4% IRI), Loligo spp. (0.4% IRI) and sciaenids (0.3% IRI). Since, the species is poorly studied and assessed as ‘Data Deficient’ in the IUCN red list criterion, it is anticipated that the biological results from the present study, will update information on the species thereby enabling more effective management decisions.

Survey of survival rate and histological alterations of gills and hepatopancreas of the Litopenaeus vannamei juveniles caused by exposure of Margalefidinium / Cochlodinium polykrikoides isolated from the Persian Gulf

Harmful algal blooms (HABs) have had harmful effects on the health of a wide range of organisms and are becoming a noteworthy risk to fisheries, human health and wildlife around the globe. Although the lethal influences of dinoflagellate Margalefidinium / Cochlodinium polykrikoides have been well-documented for finfish, the impacts on decapod crustacean species, especially, Litopenaeus vannamei are poorly understood. Here, we examined the exposure of L. vannamei juveniles with different M. polykrikoides densities (T1: 1 × 103, T2: 2 × 103, T3: 3 × 103, T4: 9 × 103 and T5: 30 × 103 cells ml−1), in order to observe possible histological alterations in gills and hepatopancreas. After 96 h exposure, shrimp exhibited increased mortality and survival rate of juveniles in control group were meaningfully (P < 0.05) higher than treatments exposed to 9 × 103 and 30 × 103 cells ml−1 of M. polykrikoides. The lowest survival observed in treatments T4 (95.56%) and T5 (82.20 %), respectively. The juveniles exposed to high densities of M. polykrikoides had flaccid bodies and gills were yellow in color with some black spots (melanization) in pereiopods. At the end of the experiment, shrimps’ hepatopancreas and gills exhibited various histological alterations. The irregular appearance of the tubular structure of the hepatopancreas, R- and B-cells reduction, separation of epithelium and myoepithelial layer, ruptured epithelial cells and degeneration of tubules were detected in the hepatopancreas of shrimps exposed to 30 × 103 cells ml−1. In gills of shrimp exposed to 30 × 103 cells ml−1, alterations in epithelial structure, increases in the number of intercellular hemocytes, and changes in tissue structure were observed. Finally, findings suggest that M. polykrikoides blooms can lead to significant impacts on survival and major histological alterations in gills and hepatopancreas organs when the density of M. polykrikoides was over 9 × 103 cells ml−1.