Red-spotted Grouper Epinephelus Akaara Research Articles

Evaluate of Wheat Gluten as a Protein Alternative for Fish Meal and Soy Protein Concentrate in Red Spotted Grouper Epinephelus akaara.

The aim of this study was to evaluate the effects of wheat gluten as a substitute for fish meal (FM) and soy protein concentrate (SPC) in the low-fishmeal-based extruded diet in red spotted grouper Epinephelus akaara. Eight isonitrogenous (441-456 g kg-1) and isocaloric (21.5-22.0 MJ kg-1) diets were produced, including the control diet (R0), three diets with 33.3, 66.7, and 100% FM being replaced by a mixture of wheat gluten, wheat, and taurine (GWT) (RF1, RF2, RF3), three diets with 33.3, 66.7, and 100% SPC replaced by GWT (RS2, RS2, RS3) and one diet with 50% FM and 50% SPC replaced by GWT (RFS). Results showed that feed intake (FI), weight gain (WG), protein retention efficiency, and liver superoxide dismutase activity increased linearly, while feed conversion ratio (FCR) decreased linearly with the decrease of dietary FM. Additionally, FI, WG, and FCR significantly increased with decreasing dietary SPC. Overall, 100% FM or 61.2% SPC can be safely replaced by wheat gluten in the red-spotted grouper diet containing 20.0% FM and 21.4% SPC.

Comparison of Biochemical Composition and Non-Volatile Taste Active Compounds of Back and Abdominal Muscles in Three Marine Perciform Fishes, Chromileptes altivelis, Epinephelus akaara and Acanthopagrus schlegelii.

Humpback grouper Chromileptes altivelis (HG), red-spotted grouper Epinephelus akaara (RG) and black seabream Acanthopagrus schlegelii (BS) are three popular perciform fishes with an increasingly important farming industry. The prices of BS are much lower than other grouper species; however, the differences in the nutritive values of these three perciform fishes with commercial specifications have not been reported. In this study, the biochemical composition and non-volatile taste active compounds of adult HG, RG and BS were investigated. Moisture contents in BS were significantly higher than in HG and RG (p < 0.05), and relatively lower crude protein contents in BS were observed. Lipid contents of back muscle were lower than that of abdomen muscle in the three fish species. C22:6n-3 (DHA) was the major poly-unsaturated fatty acid (PUFA) in HG and BS, while the main PUFA in RG was C18:2n-6. The total healthy omega-3 fatty acid (Σn-3) profiles in HG were the highest (24.08–24.59%), followed by RG (18.24–19.06%) and BS (13.63–15.91%) (p < 0.05). Glycine was the most abundant free amino acid (FAA) in HG and RG, while lysine was the major FAA in BS. Equivalent umami concentration (EUC) values in BS were the highest, followed by HG and RG (p < 0.05). Lactic acid and PO43− were the major organic acids and inorganic ions, respectively. In conclusion, HG and RG provided more protein and healthy omega-3 fatty acids than BS, while BS had a stronger umami taste according to the EUC values.

Age, growth, mortality, and yield‐per‐recruit of red spotted grouper Epinephelus akaara in the central Seto Inland Sea, Japan

The red spotted grouper Epinephelus akaara is important for commercial and recreational fishing in the coastal waters of East Asia. In Japan, approximately 850,000 juveniles are released annually for stock enhancement, and the catch in several release areas has increased. Life-history traits are important for fisheries management and stocking programmers. The age, growth, and mortality of fish collected from the central Seto Inland Sea from June 2012 to November 2014 were examined using 1022 sectioned sagittal otoliths, and the yield-per-recruit (YPR) was calculated. The opaque zones in the otoliths were confirmed to be annuli, formed mainly between June and July. The oldest fish was 16 years old. The percentage of those between two and five years was approximately 80%, whereas that of more than ten years was only 0.6%. The five parameters von Bertalanffy growth equation was calculated as: TLt = 390 {1 − 0.23[(t − 3.78)2 + 1]−1}{1 − exp [−0.34 (t + 0.28)]}, where TLt is the total length (mm) at t (year). The total, natural, and fishing mortality rates were calculated to be 0.80, 0.24–0.31 and 0.49–0.56 year−1, respectively. The YPR analysis indicated that the current fishing mortality rate (Fcurrent) was higher than F0.1 and Fmax, and that increasing the age at first capture is more effective than decreasing F for increasing the YPR. These results provide important information for fisheries management and the stocking of E. akaara.

Changes in expression of reproduction-related hormones in the brain and pituitary during early ovarian differentiation and development in the red spotted grouper Epinephelus akaara, with emphasis on FSHβ and LHβ

The brain-pituitary-gonadal (BPG) axis, an important endocrine system, is closely related to gonadal development in teleosts. This study aimed to investigate the regulation of reproduction-related hormones in the BPG axis during early ovarian differentiation and development from 30 to 160 days post hatching (dph) in the red spotted grouper. The immune signals of FSHβ and LHβ were detected by immunohistochemistry. kiss1, kiss2, gpr54, gnrh1, fshβ, and lhβ gene expression was analyzed using qRT-PCR. 17β-estradiol (E2) levels were analyzed by ELISA. The immune signals of FSHβ and LHβ were detected in the central, ventral, or marginal part of the proximal pars distalis area at 55, 80, 100, 120, and 160 dph, along with a few signals detected in the external border of the pars intermedia area at 55, 120, and 160 dph. As a result of histological observation, we determined that ovarian differentiation began at 80 dph and finished at 120 dph. At 30 dph before ovarian differentiation, only the FSHβ signal was detected but with weak reaction, suggesting the earlier appearance of FSHβ than LHβ after hatching. Comparison of the signal intensity and gene expression of FSHβ and LHβ indicated that LH had stronger signals and higher transcript levels at 80 dph while E2 levels also increased, suggesting that LH may play a more active role in the onset of ovarian differentiation. gnrh1 and the kisspeptin genes showed no clear changes, but gpr54 (kisspeptin receptor) significantly increased during the ovarian differentiation phase. These results suggest that the kisspeptin receptor GPR54 may be involved in ovarian differentiation in the red spotted grouper.

Spawning period and reliability of sexual distinction based on visual gonad observation of red spotted grouper Epinephelus akaara in the central Seto Inland Sea, Japan

Spawning period and reliability of sexual distinction based on visual gonad observation of red spotted grouper Epinephelus akaara in the central Seto Inland Sea, Japan

Effects of fresh and low-salinity water immersion on the removal of the monogenean parasite Benedenia epinepheli and survival of its host, red-spotted grouper Epinephelus akaara

Effects of fresh and low-salinity water immersion on the removal of the monogenean parasite Benedenia epinepheli and survival of its host, red-spotted grouper Epinephelus akaara

Swim bladder inflation as a possible cause of saddleback-like syndrome malformation in hatchery-reared red spotted grouper Epinephelus akaara

Saddleback-like syndrome is one of the most frequently observed malformations in hatchery-reared red spotted grouper Epinephelus akaara. Saddleback-like syndrome is characterized by a V-shaped dorsal-profile depression behind the head region accompanied by deformities or misalignments of the first to fourth neural spines on the vertebral column and the first to fourth pterygiophores of the dorsal fin. Abnormal swim bladder inflation in several finfish species leads to malformations, particularly of the vertebral column. The present study examined the influence of swim bladder inflation on saddleback-like syndrome in hatchery-reared red spotted grouper. The incidence of saddleback-like syndrome increased as swim bladder inflation rate increased. Additionally, the incidence of saddleback-like syndrome among juveniles with inflated swim bladders was significantly higher than that among juveniles with uninflated swim bladders. The larval swim bladder is located just below the first to fifth vertebrae and the first to fifth dorsal spines, where saddleback-like syndrome occurs. Our results suggest that an inflated swim bladder increases the risk of saddleback-like syndrome in hatchery-reared red spotted grouper.

Induction of Primary Male in Juvenile Red Spotted Grouper Epinephelus akaara by Immersion of 17α-Methyltestosterone

We investigated the androgenic effects of 17α- methyltestosterone (MT) on gonadal sex reversal in juvenile red spotted grouper Epinephelus akaara. The fish were immersed in 17α-MT at 1 and 5 mg/L. Treatment method of 17α-MT was once weekly for 4 and 8 weeks. Fish were sampled at 12 months after end of the treatment period in order to histological analysis. At the initiation of an experiment (70 day after hatching), juvenile red spotted grouper have the paired primordial gonads with somatic cells bellow kidney in the posterior portion of the body cavity. Formation of ovarian cavity indicates that the ovarian differentiation beginning at 70 DAH in red spotted grouper. At 12 months after end of the treatment period, control group, 17α-MT 1 mg/L treatment group for 4 and 8 weeks, and 17α-MT 5 mg/L treatment group for 4 weeks were all female. However, sex-changed males without ovarian cavity were observed in the 17α-MT 5 mg/L treatment group for 8 weeks. In grouper, we firstly reported that the red spotted grouper be able to induce the primary males by hormone treatment prior to gonadal sex differentiation.

Cloning and immune characterization of the c-type lysozyme gene in red-spotted grouper, Epinephelus akaara

Lysozyme is an important component of the innate immune response against pathogen infection. The gene coding for c-type lysozyme in red-spotted grouper Epinephelus akaara was cloned and designated EaClys. The complete cDNA contains a 432 bp open reading frame encoding a protein of 144 amino acids displaying 65–91% similarity with the amino acid sequences of human, mouse, chicken, and fish counterparts. Recombinant EaClys (rEaClys) was expressed in Escherichia coli, displayed antibacterial activity against Gram-positive and Gram-negative bacteria, and possessed bactericidal activity against Vibrio alginolyticus. EaClys mRNA was constitutively expressed in all tested E. akaara tissues, and its expression increased after pathogen challenge. Most notably, challenges with LPS, SGIV or V. alginolyticus upregulated EaClys mRNA expression in the head, kidney, and blood. Its expression peaked between 16 and 24 h after challenge before dropping back to the baseline level. By using recombinant cytokines as signaling pathway mimetics and blocking antibodies and chemical inhibitors as pathway inhibitors, we show that LPS-induced lysozyme release from macrophages is promoted by cytokines TNF-α and IL-1β, and dependent on NF-κB pathway activation. These data suggest that EaClys is a constitutive and inducible acute-phase protein that is involved in the innate immune defense of E. akaara, and provide new clues about the molecular mechanisms that regulate innate immune responses in fish.

Establishment, Characterization, and Virus Susceptibility of a New Marine Cell Line from Red Spotted Grouper (Epinephelus akaara)

A marine fish cell line from the snout of red spotted grouper Epinephelus akaara, a protogynous hermaphrodite, was established, characterized, and subcultured with more than 60 passages. The grouper snout cell line (GSC) cells multiplied well in Dulbecco's modified Eagle's medium (DMEM) medium supplemented with 10% fetal bovine serum. The optimal growth temperature was 25 degrees C, and morphologically the cells were fibroblastic. Chromosome analysis revealed that the GSC cell line has a normal diploid karyotype with 2n = 8st + 40t. A virus titration study indicated that the cells were susceptible to turbot Scophthalmus Maximus rhabdovirus (SMRV) (10(8.5) TCID(50) ml(-1)), while the viral titer of frog Rana grylio virus 9807 (RGV(9807)) reached 10(3.5) TCID(50) ml(-1). The infection was confirmed by cytopathic effect (CPE), immunofluorescence, and electron microscopy experiments, which detected the viral particles in the cytoplasm of virus-infected cells, respectively. Further, significant fluorescent signals were observed when the GSC cells were transfected with pEGFP vector DNA, indicating their potential utility for transgenic and genetic manipulation studies.

Occurrence of a Monogenean Gill Parasite Pseudorhabdosynochus epinepheli on Red Spotted Grouper Epinephelus akaara and Its Experimental Treatment by Hydrogen Peroxide Bathing

Since 1997, infection of a monogenean gill parasite Pseudorhabdosynochus epinepheli has been occurring in red spotted grouper Epinephelus akaara at the Kagawa Prefectural Sea-Farming Center, Japan. The efficacy of hydrogen peroxide (H2O2) bathing was examined in vivo. Bathing in a 700 ppm H2O2 solution for 45 min at 10 or 15°C, or for 15 min at 20 or 25°C, with infected fish of 230-2100 g in body weight, resulted in 100% mortality of P. epinepheli on the gills. Mortality occurred in fish (550-1730 g) bathed for 30 min or longer at 25°C, but not in fish bathed for at least 60 min at 10, 15 or 20°C. Results indicate that chemotherapy with H2O2 has a high potential as an effective treatment for P. epinepheli infection in red spotted grouper.

キジハタ増殖魚礁の開発と漁港への応用

キジハタ増殖魚礁の開発と漁港への応用

Differential expression of thyroid-stimulating hormone β subunit in gonads during sex reversal of orange-spotted and red-spotted groupers

We have cloned and characterized the full-length cDNA encoding thyroid-stimulating hormone β-subunit (TSHβ) from orange-spotted grouper Epinephelus coioides. It contains 913 nucleotides with an open reading frame encoding 146 amino acids with a 20 amino acid signal peptide. The grouper mature TSHβ has 75, 70, 61, 59, 41, 42 and 40% identities to that of rainbow trout, Atlantic salmon, zebrafish, European eel, chicken, mouse and human, respectively. RT-PCR analysis indicated that the TSHβ mRNA was expressed abundantly not only in pituitary but also in gonads. A more interesting finding is to reveal the differential TSHβ expressions between the ovaries and the transitional gonads or testes in natural individuals of orange-spotted grouper and red-spotted grouper Epinephelus akaara, and in artificial sex reversal individuals of red-spotted grouper induced by MT feeding. In situ hybridization localization provided direct evidence that the TSHβ was transcribed in the germ cells. In the growing oocytes, the TSHβ transcripts were concentrated on the ooplasm periphery. In testicular tissues, the intensively expressed TSHβ cells were found to be spermatogonia and spermatocytes in the spermatogenic cysts. This is the first report of a TSHβ expressed in the gonads of any vertebrates in addition to the expected expression in the pituitary, and it expresses more transcripts in the gonads during sex reversal or testis than in the ovaries both in E. coioides and E. akaara. Importantly, the TSHβ identification in germ cells allows us to further investigate the functional roles and the molecular mechanisms in gametogenesis of groupers, especially in sex reversal and in spermatogenesis.

Influence of feeding regime on fatty acid composition in young red-spotted grouper Epinephelus akaara

ABSTRACT: Young red-spotted grouper Epinephelus akaara with an average total length of 3.4 cm were divided into five groups in floating net-cages, and reared under satiated conditions with different feeding frequencies (0.5, 1, 2, 4 and 8 times per day) for 40 days. Total food intake increased with feeding frequency. Feeding four times per day resulted in the highest growth and food conversion efficiency. Total lipid accumulation in the muscle, liver and intraperitoneal fat body (IPF) increased with feeding frequency. Red-spotted grouper were found to contain a high proportion of docosahexaenoic acid (DHA) in the muscle. Fish fed 0.5 times per day were characterized as having a high proportion of DHA in triglycerides (TG) in muscle (80%), liver (69%) and IPF (18%). Increasing saturated fatty acids and a relative reduction of DHA were observed in the muscle TG as the feeding frequency increased. Frequent feeding accelerated the accumulation of eicosapentaenoic acid and saturated acids in the liver and IPF. Low saturated acids and a subsidiary proportional increase in DHA were the result of the low lipid reserves. A possible role for DHA and saturated acids are discussed with regard to lipid reserves.

ホタテガイ貝殻を利用した人工魚礁へのキジハタ幼魚の放流実験

キジハタ放流魚の保護育成機能を持つ魚礁を開発するため,ホタテガイ貝殻を利用した実験魚礁を用いて放流実験を行った。岡山県白石島沖に2種類の実験魚礁を3基ずつ沈設し,キジハタ幼魚を1,000尾ずつ放流した。潜水観察と実験魚礁の一部引き揚げにより,滞留尾数や再捕魚の胃内容物等を1年間調査した。2種類の実験魚礁はキジハタを一定期間滞留させるとともに餌料生物の培養機能を有していた。このうちキジハタの潜入可能な空間を増やした実験魚礁の滞留尾数が多く,放流魚の保護育成に適していると判断された。

Susceptibility of Various Marine Fish Species to Viral Hemorrhagic Septicemia Virus Isolated from Japanese Flounder

Susceptibilities of six species of marine fish to a flounder isolate KRRV-9601 (a European genotype) of VHSV were examined by intraperitoneal injection. Mortalities were induced in Japanese flounder Paralichthys olivaceus (100%), black sea bream Acanthopagrus schlegeli (90%), red spotted grouper Epinephelus akaara (70%) and rockfish Sebastes schlegeli (10%), but not in marbled sole Pleuronectes yokohamae and red sea bream Pagrus major. VHSV was recovered from dead and moribund fish and the surviving red spotted grouper at 60th day after the virus injection. The neutralizing antibody against VHSV was detected in the sera of surviving rockfish, but not in other surviving fishes. Histopathological features in the affected fish for each species were generally similar to each other, although the severity of hemorrhage varied among fish species.

Evidence of sex reversal towards both directions in reared red spotted grouper Epinephelus akaara

Evidence of sex reversal towards both directions in reared red spotted grouper Epinephelus akaara

Behaviour and Habitat of the Red Spotted Grouper Epinephelus akaara by Underwater Observation at Tajima Coast of Hyogo prefecture in Japan Sea

Behaviour and Habitat of the Red Spotted Grouper Epinephelus akaara by Underwater Observation at Tajima Coast of Hyogo prefecture in Japan Sea

Morphological and Genetic Differences between Japanese and Korean Red Spotted Grouper Epinephelus akaara

Morphological and Genetic Differences between Japanese and Korean Red Spotted Grouper Epinephelus akaara

キジハタ仔魚の摂餌日周期性の検討ならびに日間摂餌量の推定

This paper describes the diurnal rhythm of feeding activity and daily ration estimated by a new approach for reared larval red spotted grouper Epinephelus akaara. The larva fed only during the daytime, and the number of food organisms in the gut increased at dawn and dusk, however, the number remained at a moderate level during the middle of the day. This phenomenon became more evident as larval growth proceeded. The larvae of TL 3.9 and 9.9 mm fed on 193 rotifers and 293 Artemia nauplii per day, respectively. The daily food uptake was estimated to be 30.1% of the wet body weight in the 3.9 mm larva and 28.2% in the 9.9 mm larva. The growth rate of this species was relatively higher compared with those estimated in marine fish species, although the food uptake was relatively low.