Epinephelus Malabaricus Research Articles

The transcriptional landscape underlying larval development and metamorphosis in the Malabar grouper (Epinephelus malabaricus).

Most teleost fishes exhibit a biphasic life history with a larval oceanic phase that is transformed into morphologically and physiologically different demersal, benthic, or pelagic juveniles. This process of transformation is characterized by a myriad of hormone-induced changes, during the often abrupt transition between larval and juvenile phases called metamorphosis. Thyroid hormones (TH) are known to be instrumental in triggering and coordinating this transformation but other hormonal systems such as corticoids, might be also involved as it is the case in amphibians. In order to investigate the potential involvement of these two hormonal pathways in marine fish post-embryonic development, we used the Malabar grouper (Epinephelus malabaricus) as a model system. We assembled a chromosome-scale genome sequence and conducted a transcriptomic analysis of nine larval developmental stages. We studied the expression patterns of genes involved in TH and corticoid pathways, as well as four biological processes known to be regulated by TH in other teleost species: ossification, pigmentation, visual perception, and metabolism. Surprisingly, we observed an activation of many of the same pathways involved in metamorphosis also at an early stage of the larval development, suggesting an additional implication of these pathways in the formation of early larval features. Overall, our data brings new evidence to the controversial interplay between corticoids and thyroid hormones during metamorphosis as well as, surprisingly, during the early larval development. Further experiments will be needed to investigate the precise role of both pathways during these two distinct periods and whether an early activation of both corticoid and TH pathways occurs in other teleost species.

The transcriptional landscape underlying larval development and metamorphosis in the Malabar grouper (Epinephelus malabaricus)

Most teleost fishes exhibit a biphasic life history with a larval oceanic phase that is transformed into morphologically and physiologically different demersal, benthic, or pelagic juveniles. This process of transformation is characterized by a myriad of hormone-induced changes, during the often abrupt transition between larval and juvenile phases called metamorphosis. Thyroid hormones (TH) are known to be instrumental in triggering and coordinating this transformation but other hormonal systems such as corticoids, might be also involved as it is the case in amphibians. In order to investigate the potential involvement of these two hormonal pathways in marine fish post-embryonic development, we used the Malabar grouper (Epinephelus malabaricus) as a model system. We assembled a chromosome-scale genome sequence and conducted a transcriptomic analysis of nine larval developmental stages. We studied the expression patterns of genes involved in TH and corticoid pathways, as well as four biological processes known to be regulated by TH in other teleost species: ossification, pigmentation, visual perception, and metabolism. Surprisingly, we observed an activation of many of the same pathways involved in metamorphosis also at an early stage of the larval development, suggesting an additional implication of these pathways in the formation of early larval features. Overall, our data brings new evidence to the controversial interplay between corticoids and thyroid hormones during metamorphosis as well as, surprisingly, during the early larval development. Further experiments will be needed to investigate the precise role of both pathways during these two distinct periods and whether an early activation of both corticoid and TH pathways occurs in other teleost species.

Effect of Physical Factors on Milt Quality of Malabar Grouper, Epinephelus Malabaricus in Summer and Winter Season

A study was conducted to test the effect of physical factors such as temperature, salinity, and pH on spermatozoa motility of Malabar grouper (Epinephelus malabaricus). Mature and healthy male fishes were collected from the Red Sea during the summer and winter seasons for milt collection. Milt quality was assessed for colour, volume, sperm cell concentration, motility, and viability. Sperm motility was tested under different water temperatures, salinity, and pH media. A significant difference (P < 0.01) in sperm cell concentration (density), sperm motility (%), and viability (%) was observed between the summer and winter seasons. Changes in water temperature, pH, and salinity influenced sperm motility (%) and motility duration (min). Low pH and salinity caused adverse effects on spermatozoa motility. The results of the study are useful for the germplasm conservation of Malabar grouper, E.malabaricus.

Molecular characterization of the SP3a gene, a negative regulator of viral infection in the orange-spotted grouper, Epinephelus coioides

SP3 (specificity protein 3) is a transcription factor characterized by three conserved Cys2His2 zinc finger motifs that exert a transregulatory effect by binding to GC boxes, either upregulating or downregulating multiple genes or by co-regulating gene expression in coordination with other proteins. SP3 potentially regulates a series of processes, such as the cell cycle, growth, metabolic pathways, and apoptosis, and plays an important role in antiviral effect. The function of sp3 in fish is poorly understood. In this study, the Sp3a open reading frame was cloned from the orange-spotted grouper, Epinephelus coioides. The full-length open reading frame of Sp3a was 2034 bp, encoding 677 amino acids, with a predicted molecular weight of 72.34 kDa and an isoelectric point of 5.05. Phylogenetically, Sp3a in Epinephelus coioides was the most closely related to Sp3a in the Malabar grouper, Epinephelus malabaricus. RT-qPCR revealed ubiquitous expression of Sp3a in all examined grouper tissues, with no significant differences in expression levels among tissues. A eukaryotic expression vector, pEGFP-Sp3a, was constructed and transfected into grouper spleen (GS) cells. Subcellular localization of Sp3a was observed using an inverted fluorescence microscope. When Spa3 was overexpressed in GS cells, the expression of orange-spotted grouper nerve necrosis virus (RGNNV) genes (CP and RdRp) decreased significantly, indicating that Sp3a significantly inhibited RGNNV replication. siRNA inhibition of Sp3a accelerated the intracellular replication of RGNNV, implying the antiviral effect of Sp3a. Conclusively, our findings contribute to further research on the antiviral capabilities of Sp3a in grouper and other fish. Therefore, our research has potential implications on the development of the aquaculture industry.

Functional characterization of Malabar grouper (Epinephelus malabaricus) interferon regulatory factor 9 involved in antiviral response

IRF9 is a crucial component in the JAK-STAT pathway. IRF9 interacts with STAT1 and STAT2 to form IFN-I-stimulated gene factor 3 (ISGF3) in response to type I IFN stimulation, which promotes ISG transcription. However, the mechanism by which IFN signaling regulates Malabar grouper (Epinephelus malabaricus) IRF9 is still elusive. Here, we explored the nd tissue-specific mRNA distribution of the MgIRF9 gene, as well as its antiviral function in E. malabaricus. MgIRF9 encodes a protein of 438 amino acids with an open reading frame of 1317 base pairs. MgIRF9 mRNA was detected in all tissues of a healthy M. grouper, with the highest concentrations in the muscle, gills, and brain. It was significantly up-regulated by nervous necrosis virus infection and poly (I:C) stimulation. The gel mobility shift test demonstrated a high-affinity association between MgIRF9 and the promoter of zfIFN in vitro. In GK cells, grouper recombinant IFN-treated samples showed a significant response in ISGs and exhibited antiviral function. Subsequently, overexpression of MgIRF9 resulted in a considerable increase in IFN and ISGs mRNA expression (ADAR1, ADAR1-Like, and ADAR2). Co-immunoprecipitation studies demonstrated that MgIRF9 and STAT2 can interact in vivo. According to the findings, M. grouper IRF9 may play a role in how IFN signaling induces ISG gene expression in grouper species.

Activation of the growth–IGF-1 axis, but not appetite, is related to high growth performance in juveniles of the Malabar grouper, Epinephelus malabaricus, under isosmotic condition

Salinity, a determining factor in aquatic environments, influences fish growth. Here, we evaluated the effect of salinity on osmoregulation and growth performance in juveniles of the Malabar grouper, Epinephelus malabaricus, a species of high commercial value in Asian markets; we also identified the salinity that maximized this species' growth rate. Fish were reared at 26 °C and under a 14:10 h photoperiod with a salinity of 5 psu, 11 psu, 22 psu, or 34 psu for 8 weeks. Change in salinity had minimal impact on the plasma Na+ and glucose concentrations, although the Na+/K+-ATPase (nkaα and nkaβ) transcript levels in the gills were significantly lower among fish reared at 11 psu salinity. Concomitantly, oxygen consumption was low in fish reared at 11 psu salinity. The feed conversion ratio (FCR) was lower in fish reared at 5 psu and 11 psu salinities than at 22 psu and 34 psu salinities. However, the specific growth rate (SGR) was higher in fish reared at 11 psu salinity. These results suggest that rearing fish at 11 psu salinity would decrease energy consumption for respiration and improve food-conversion efficiency. Among fish reared at 11 psu salinity, the transcript levels of growth hormone (gh) in the pituitary, as well as its receptor (ghr) and insulin-like growth factor I (igf-1) in the liver, were upregulated; these findings suggested stimulation of the growth axis at low salinity. In contrast, there were minimal differences in the transcript levels of neuropeptide Y (npy) and pro-opiomelanocortin (pomc) in the brains of fish reared at any salinity, suggesting that salinity does not affect appetite. Therefore, growth performance is higher in fish reared at 11 psu salinity because of activation of the GH-IGF system, but not appetite, in Malabar grouper juveniles.

DETERMINED BIOCHEMICAL CONTENT IN Epinephelus malabaricus AND Lutjanus argentimaculatus ARE ECONOMICALLY IMPORTANT FINFISHES IN NAGAPATTINAM COAST, SOUTH INDIA

The finfishes Epinephelus malabaricus and Lutjanus argentimaculatus are cost-effectively imperative, so selected for divergent sizes, proximate compositions like crude protein, carbohydrate, lipids, ash and gross energy in relation to dissimilar seasons, size and sex groups with the vision of assessing the nutritive values and their % contributions, Indeterminates (IM), females (F), males (M) are selected for these studies. In the current studies results are showed different parameters; in E. malabaricus the utmost crude protein amount was observed (20-30 cm; 73.86%) post-monsoon from IM followed by same season in IM showed (10-20 cm; 73.85%), crude carbohydrate uppermost content was noticed in post-monsoon from F (50-60 cm; 72.15%) followed by same post-monsoon in M showed (50-60 cm; 71.31%). superior amount of lipid content maximum amount was observed in F (40-50 cm; 7.75%) in post-monsoon followed by same season in F (50-60 cm; 7.11%), the highest ash content was obtained from IM (20-30 cm; 8.12%) observed in post-monsoon followed by same season in IM (10-20 cm; 8.11%), highest cross energy was noticed in post-monsoon of F (50-60 cm; 18.39%) followed by same season in M showed (50-60 cm; 18.35%). In L. argentimaculatus premier amount of crude protein in IM was observed (10-25 cm; 75.05%) in summer followed by same season in IM showed (25-40 cm; 75.02%), crude carbohydrate high content was noticed from M & F (70-85 cm; 4.75%) in summer, followed by in F showed (70-85 cm; 4.45%) in monsoon and post-monsoon. Uppermost lipid content was observed from F in summer (55-70 cm; 7.21% & 70-85 cm; 7.20%) followed by post-monsoon in F was obtained (70-85 cm; 6.98%), utmost ash content was expressed in IM (10-25 cm; 7.25%) pre-monsoon followed by same season IM (25-40 cm; 7.05%), highest energy content was noticed in summer in F (70-85 cm; 18.34 MJ/kg) followed by same season M showed (70-85 cm; 18.04 MJ/kg), based on different parameters it concluded that selected finfishes are potentially functional for the human societies.

Marine habitats and related fishery resources in Ly Son and adjacent waters in the Northern part of Quang Ngai province

The study assessed the distribution of key marine habitats and related fishery resources and spawning and nursery grounds of target species in the waters of Ly Son islands and adjacent locations of Tra Bong and Sa Ky estuaries using data from analysis of the Sentinel-2 satellite image and ground-truthing. There were about 1,787 ha of coral reefs, 117.3 ha of seagrass beds, and 309 ha of nipa palm (Nypa fruticans) distributed in this area, in which the water surrounding Ly Son marine protected area (MPA) supported more than 1,706 ha of coral reefs and 116 ha of seagrass beds. The area also supported 12 nursery grounds of 10 target resources, including giant trevally, mangrove-red snapper, orange-spotted spinefoot, orange-spotted grouper, malabar grouper, barramundi related to nipa palms in Tra Bong and Sa Ky estuaries. In contrast, sea cucumbers, turbo snails, top shells, and giant clams were associated with coral reefs in Ly Son MPA. Related fishery resources, spawning, and nursery grounds of target species involved 8 consultations of local experienced fishermen and a field investigation of the presence of spawning and nursery grounds from November 2019 to September 2020. A total of 1,278 tonnes of commercial resources were harvested in the coral reefs and some 4.647 thousand juveniles of fish and crabs were collected from the adjacent estuaries, in which some essential species of reef fishes indicate linkages between juveniles collected from the nipa palm and seagrass beds in Tra Bong and Sa Ky estuaries and adults fished in the coral reefs in Ly Son MPA. So, conservation and management of exploitation of fish juveniles related to the nipa palm and seagrass beds in Tra Bong and Sa Ky estuaries are considered important solutions for the maintenance of the linkages of fish resources associated with critical marine habitats and fisheries in the waters of Ly Son MPA and adjacent locations in the future.

Effects of selected light wavelengths on the transcript levels of photoreceptors and growth-related hormones and peptides in the Malabar grouper Epinephelus malabaricus

Fish growth is influenced by environmental cues, including light conditions. The duration of exposure (photoperiod), the intensity of exposure (illumination), and quality (light spectrum) play crucial roles in maximizing growth. This study aimed to clarify how selected light wavelengths are perceived and transduced as an internal signal to stimulate growth of the Malabar grouper Epinephelus malabaricus, an important aquaculture species in Asian countries. Four opsins (RH1, RH2, SWS2, and LWS) were selected from the database of photoreceptors of groupers, and reverse-transcription polymerase chain reaction revealed that these opsins were expressed in the eyes and brain. When fish were reared under conditions of long-day (light:dark = 14:10) with red (peak at 632 nm), green (519 nm), and blue (465 nm) LED and natural light, the specific growth rate was higher (P < 0.05) in fish exposed to blue LED light than to red LED light. Rearing fish under shorter light wavelengths (blue or green) resulted in high transcript levels (P < 0.05) of RH1 and RH2 in the eyes (retina) and of RH1 and SWS2 in the brain (diencephalon), suggesting that certain light wavelengths activate photoreceptors in light perceptive organs. The transcript levels of growth hormone (GH) and insulin-like growth factor (IGF-I) increased significantly (P < 0.05) in the pituitary and liver of fish reared under blue LED light, respectively. Moreover, similar increases (P < 0.05) in the transcripts of neuropeptide Y (NPY) and pro-opiomelanocortin were observed in the brain of fish reared under blue LED light. We concluded that blue light perceived by visual opsins in the eyes and brain activates the growth of the endocrine axis and its interaction with NPY. Consequently, rearing the Malabar grouper under specific light wavelengths helps maximize their growth.

Composition of peroximate and types of amino acids analysis of cost-effectively essential finfishes – Lutjanus argentimaculatus, Epinephelus malabaricus in Nagapattinam Coast of Tamil Nadu, South India

The current study was undertaken to investigate the composition of peroximate in relation to the types of season, sex, and group sizes in edible tissues of the finfishes of Lutjanus argentimaculatus and Epinephelus malabaricus in Nagapattinam coast of Tamil Nadu, South India. L. argentimaculatus, indeterminates are 10-40 cm, male and females are 40-85 cm, in E. malabaricus the indeterminates are 10-30 cm, male and females are 30-60 cm. Variations in proximate composition noticed between L. argentimaculatus and E. malabaricus. In L. argentimaculatus indeterminates showed moisture content ranged between 75.31 and 81.75%, both the size groups of indeterminates (10-25 and 25-40 cm) exhibited elevated values during pre-monsoon (81.75 followed by 80.34%) and small values during summer (10-25 and 25-40 cm; 78.44 followed by 78.15%). Variations in proximate composition noticed in E. malabaricus are depicted, the moisture content ranged between 72.65 and 79.95%. The male size groups (30-40 cm and indeterminates 20-30 cm) exhibited superior values during summer (79.95 followed by 78.95%) and small values during pre-monsoon and monsoon (50-60 cm; 72.75 followed by 72.65%).

Biodegradation of the pyrethroid pesticide cyfluthrin by the halophilic bacterium Photobacterium ganghwense isolated from coral reef ecosystem

A halophilic bacterial strain T14 isolated from the mucus of coral Acropora sp. was found to be highly effective in degrading the pyrethroid pesticide, cyfluthrin. T14 was identified as Photobacterium ganghwense (GenBank Accession No. MT360254) based on phenotypic and biochemical characteristics as well as by 16S rRNA gene sequence analysis. The pyrethroid degrading efficiency of P. ganghwense T14 strain was examined under different culture conditions. It was observed that P. ganghwense T14 was able to utilise cyfluthrin as a sole carbon source and was found to grow on mineral medium with pesticide concentrations ranging from 10 to 100 mg l-1. Optimal temperature and pH conditions for efficient cyfluthrin degradation by P. ganghwense T14 were determined as 30° C and 8 respectively. Degradation of cyfluthrin by P. ganghwense T14 was quantitated by gas chromatography-tandem mass spectrometry (GC-MS/MS). Mineral medium supplemented with 100 mg l-1 cyfluthrin and inoculated with P. ganghwense T14 (106 cells ml-1) recorded 92.13% pesticide decomposition within 120 h. Cytotoxicity assay on a fish cell line EM4SpEx derived from the grouper Epinephelus malabaricus, revealed a drastic reduction in cyfluthrin toxicity as evidenced by reduction in the intensity of cell destruction as well as morphological changes when exposed to P. ganghwense T14 treated filtrate, in comparison with that of parent cyfluthrin filtrate. Results of the study clearly indicated potential bioremediative use of P. ganghwense T14 in cyfluthrin contaminated sites.

Epizootics of epizootic ulcerative syndrome among estuarine fishes of Kerala, India, under post-flood conditions.

Epizootic ulcerative syndrome (EUS), primarily caused by the water mold Aphanomyces invadans, is an OIE-notifiable disease, having potential impacts on fisheries. We report EUS epizootics among estuarine fishes of Kerala, India, during 2018, under post-flood conditions 3 decades after its primary outbreak. Six fish species (Mugil cephalus, Platycephalus sp., Scatophagus argus, Arius sp., Planiliza macrolepis and Epinephelus malabaricus) were infected, including the first confirmed natural case in E. malabaricus and P. macrolepis. Salinity, surface temperature, dissolved oxygen and pH of resident water during the epizootic were <2 ppt, 25°C, 4.1 ppm and 7.0. The presence of zoonotic bacterial pathogens (Aeromonas veronii, Shewanella putrefaciens, Vibrio vulnificus and V. parahaemolyticus) in tissues of affected fish indicates that EUS-infected fish may pose a public health hazard if not handled properly. Lack of clinical evidence in the region during the last 3 decades, a high number of affected fishes, including 2 new fish species, the severity of skin lesions and very low water salinity (<2 ppt) during the outbreak in contrast to historical water salinity records suggest relatively recent invasion by A. invadans. Phylogenetic analysis based on the internal transcribed spacer region of the rRNA gene showed that the same clone of pathogen has spread across different continents regardless of fish species and ecotypes (fresh/estuarine environments). Altogether, the present study provides baseline data which can be applied in EUS management strategies within brackish-water ecosystems. We recommend strict surveillance and development of sound biosecurity measures against the disease.

Length-Weight Relationships for Eight Caught Marine Fish Using Midwater Trawler in Chabahar Fishing Grounds, Sistan and Bluchestan (The Sea of Oman)

The present research provides length-weight relationship (LWR) of eight fish species included Pomadasys stridens (ForsskA¥l, 1775), Epinephelus areolatus (ForsskA¥l, 1775), Pristipomoides multidens (Day, 1871), Pomadasys maculatus (Bloch, 1793), Johnius borneensis (Bleeker, 1851), Diagrmma pictum (Thunberg, 1792), Epinephelus malabaricus (Bloch & Schneider, 1801) and Epinephelus coioides (Hamilton, 1822) from Chabahr fishing grounds (latitude 25° 11’ to 25° 12’ N; longitude 60° 04’ to 60° 13’ E) in the Sea of Oman. All fish specimens were caught using midwater trawl net, with 65 mm mesh size in the cod-end, from April to May 2016 during the spring season. The LWRs for fish species were W = 0.0127L2.874 for P. stridens, W = 0.0153L2.971 for E. areolatus, W = 0.0227L2.873 for P. multidens, W = 0.0534L2.689 for P. maculatus, W = 0.0023L3.157 for J. borneensis, W = 0.0164L2.807 for D. pictum, W = 0.0487L3.287 for E. malabaricus, and W = 0.0487L3.287 for E. coioides, respectively.

Investigation on the validity of 3D micro-CT imaging in the fish brain

BackgroundMicro-computed tomography (CT) is a non-invasive technique that is used to obtain three-dimensional (3D) images of tissue structure in small animals. Compared with extensive mammal studies, few 3D imaging studies of fish have been conducted using micro-CT. An optimized method for imaging fish tissue structure is necessary, because they have adapted to diverse environments via functional and structural specialization. New methodBrains of three species with different sizes and habitats were fixed in 4% paraformaldehyde and immersed in non-ionic iodinated contrast agent (Iopamiron). We examined the relationship between Iopamiron concentration and immersion time to determine universally optimal conditions for use in fish. ResultsWe reconstructed 3D images of whole fish brains from cross-sections of brains from the Malabar grouper (Epinephelus malabaricus), bastard halibut (Paralichthys olivaceus), and threespot wrasse (Halichoeres trimaculatus). Developmental changes in brain structure were observed in the bastard halibut. Most brain regions of the threespot wrasse were distinguishable, although inner regions of the brain were less visible. Comparison with existing methodsHistological techniques are typically used to observe fish brain structure, despite its drawbacks in terms of tissue sample preparation (shrinkage and distortion) and image capture (3D image constriction). The technique examined in the present study solves these problems and allows for the simultaneous handling of multiple specimens. ConclusionMicro-CT imaging is suitable for observing the surfaces and inner structures of fish of various species.

The complete mitochondrial genome of the breed Ningbo brown-marbled grouper (Epinephelus fuscoguttatus)

We used NGS technologies to resequence the complete mitochondrial genome of (Epinephelus fuscoguttatus). The complete mitochondrial genome of the breed Ningbo brown-marbled grouper is a 16,373 bp circular molecule, which contains 37 typical mitochondrial genes (13 protein-coding genes, two rRNAs, and 22 tRNAs) and a D-loop. Its gene arrangement pattern is the same as the accession no. KP013758. Comparing to accession no. KP013758 sequence, the D-loop region is much shorter. ATG is the most common start codon, and TAA is the most common stop codons; the 12S rRNA and 16S rRNA are located between the tRNAPhe and tRNALeu genes and are separated by the tRNAVal gene. Phylogenetic trees indicated E. fuscoguttatus has close relative with Epinephelus coioides and Epinephelus malabaricus.

Fishery and population dynamics of Epinephelus malabaricus (Bloch &amp; Schneider, 1801) off Tuticorin, southeast coast of India

Fishery, population characteristics and stock estimates of grouper with special reference to Epinephelus malabaricus from Tuticorin were carried out during 2015-2017. Among the groupers, E. malabaricus was the dominant resource contributing 42.2%, with an annual average production of 420t along this region. The asymptotic length (L∞), growth coefficient (K) and arbitrary origin of growth (t0) were estimated at 99.75 cm, 0.53 y-1 and 0.18 respectively. The mortality parameters, the instantaneous total mortality rate (Z), fishing mortality (F) and natural mortality rates (M) were estimated at 1.14 y-1, 0.62 y-1 and 0.52 y-1 respectively. The recruitment season was during April to August. The length structured virtual population (VPA) analysis revealed a heavy fishing pressure on length group between 40 and 55cm and there is no sign of recruitment over-fishing in this region. The estimated maximum sustainable yield (MSY) and annual catch were 384 t and 420 t respectively. E. malabaricus was optimally exploited as the exploitation ratio (E) was 0.54 but the study infers that further increase in effort may have a detrimental effect on the stock of this species. The results of this study will serve as baseline information for formulating future management measures for the resource along the coast.

Daily expression of a clock gene in the brain and pituitary of the Malabar grouper (Epinephelus malabaricus)

Recent studies have revealed that, in addition to regulating the circadian system, clock genes such as cryptochrome (Cry) genes are involved in seasonal and lunar rhythmicity in fish. This study clarified the transcriptional characteristics of a Cry subtype (mgCry2) in the brain of the Malabar grouper, Epinephelus malabaricus, which is an important aquaculture species that spawns around the new moon. The cDNA sequence of mgCry2 showed high identity (97–99%) with fish Cry2 and had an open reading frame encoding a protein with 170 amino acids. Phylogenetic analyses revealed that mgCRY2 had high identity with CRY in other fish species. Real-time quantitative polymerase chain reaction (qPCR) showed the widespread distribution of mgCry2 in neural (brain, pituitary, and retina) and peripheral (heart, liver, kidney, spleen, gill, intestine, and ovary) tissues. When immature Malabar groupers were reared under a light-dark cycle (LD = 12:12) and the amounts of mgCry2 mRNA in the telencephalon and diencephalon were measured at 4-h intervals, the levels increased during photophase and decreased during scotophase. Day–night variation in mgCry2 mRNA abundance was also observed in the pituitary. These daily profiles suggest that mgCry2 is a light-responsive gene in neural tissues. In situ hybridization analyses showed that mgCry2 was strongly transcribed in the nucleus lateralis tuberis of the ventral hypothalamus, peripheral area of the proximal pars distalis, and the pars intermedia of the pituitary. We conclude that clock genes expressed in the pituitary and diencephalon play a role in entraining the endocrine network of the Malabar grouper to periodic changes in external cues.

EmPis-1L, an Effective Antimicrobial Peptide Against the Antibiotic-Resistant VBNC State Cells of Pathogenic Bacteria.

The antibiotic-resistant viable but non-culturable (VBNC) pathogenic bacteria are considered as a new threat to public health. Antimicrobial peptides (AMPs), possessing bactericidal effects in a rapid membrane attacking mode, are supposed to be effective against bacteria entering the VBNC state. In the current study, the activity of grouper AMP piscidin killing the VBNC state cells of pathogenic bacteria Escherichia coli O157, Staphylococcus aureus, and Vibrio parahaemolyticus OS4 was studied. After entering the VBNC state, cells of E. coli O157, S. aureus, and V. parahaemolyticus OS4 developed resistance to the antibiotics Ampicillin and Kanamycin. Rather than truncated form of Malabar grouper piscidin 1 (EmPis-1S), full-length Malabar grouper piscidin 1 (EmPis-1L) showed strong activity to kill the above VBNC bacteria. The VBNC state cells (1 × 105CFU/mL) of the three species of bacteria could be totally lysed by 10μmol/L of EmPis-1L in 1h. The VBNC state cells of S. aureus were most susceptible to EmPis-1L, which killed the cells by 100% in 30min at the low concentration of 2.0μmol/L. In addition, EmPis-1L at the concentration of no more than 10μmol/L showed no observed toxicity to human lung carcinoma epithelial cells (A549) and mouse neuroblastoma cells (N2a). Accordingly, EmPis-1L could be a promisingly safe and efficient agent for eliminating the traditional antibiotic-resistant VBNC state cells of pathogenic bacteria, E. coli, S. aureus, and V. parahaemolyticus.

Differences in trophic resources and niches of two juvenile predatory species in three Pangani estuarine zones, Tanzania: stomach contents and stable isotope approaches

BackgroundEstuaries are primary habitats that serve as feeding and nursery grounds for most juvenile marine fish. However, estuaries have been used as fishing grounds by the artisanal fishers in Tanzania. The slow-growing predatory fish at juvenile and sub-adult stages are among the most frequently caught species that functionally enhance multiple linkages of energy pathways within the food web. Stomach contents and stable isotopes (δ13C and δ15N) were used to describe the nutritional sources and trophic niches between the co-existing benthic, predatory species, Carangoides chrysophrys and Epinephelus malabaricus in the Pangani estuary, Tanzania.ResultsThe findings indicated significant inter-specific variations in dietary composition (PERMANOVA, p = 0.001, pseudo-F = 15.81). The prey-specific index of relative importance (%PSIRI) indicated that juvenile shrimps (%PSIRI = 51.4) and Teleostei (%PSIRI = 26.5) were the main diets of C. chrysophrys while brachyura (%PSIRI = 38.8), juvenile shrimps (%PSIRI = 25.6) and Teleostei (%PSIRI = 23.3) were important diets of E. malabaricus. The isotope mixing models indicated that the predatory fish species accumulate nutrients derived from similar autotrophic sources, microphytobenthos, seagrass and macro-algae via consumption of small fish, including clupeids and mugilids. Yet, they significantly showed different isotopic niche width with varying degree of niche overlap across the longitudinal estuary gradient. This situation was justified by the presence of basal food sources among the estuarine zones that isotopically were different.ConclusionThe reliance of both predators on clupeids and mugilid preys that are trophically linked with estuarine and marine basal food sources, is an indication of low estuarine food webs’ connectivity to the fresh water related food web. This situation is most likely threatening the stability of the estuarine food web structure. Management strategies and plans in place should be cautiously implemented to ensure the balanced anthropogenic freshwater use in the catchment and fishing activities, for the maintenance of the Pangani estuarine ecosystem health.

Effects of replacing fish meal with soybean meal, with or without dietary arginine, on growth performance, immune indices and intestinal morphology of grouper, Epinephelus malabaricus

A 10-week feeding experiment was conducted to evaluate the effects of replacing fish meal with soybean meal (SBM), with or without dietary arginine (Arg), on growth performance, immune indices and intestinal morphology of grouper, Epinephelus malabaricus. Nine experimental diets were formulated to contain 20%, 30% and 40% fish meal protein (FMP) replaced using SBM and 0, 0.5% and 1% dietary Arg supplementation. The results showed that weight gain (WG) of fish was significantly affected by the interaction of substitution level and Arg supplemental level. The maximum WG occurred at the 30% FMP substitution level and the 0.5% Arg supplemental level. The immune assay showed that the interaction between the two levels significantly influenced the production of serum nitric oxide but did not affect serum IgG concentration and alkaline phosphatase activity or the liver IGF-1 gene expression. Significant interaction effects between the two levels were observed in muscle layer thickness (tML) and fold height (hF) in the proximal and mid-intestine. High SBM level in diets reduced the tML and hF in the entire intestine. The results suggested that the interaction of 30% FMP substitution level and Arg supplemental level of 0.5% most benefitted growth performance, immune indices and intestinal structure of grouper.