Role of major histocompatibility complex II antigen-presentation pathway genes in orange-spotted grouper infected with Cryptocaryon irritans

Cryptocaryon irritans, a pathogen model for fish mucosal immunity, causes skin mucosal and systematic humoral immune response. Where and how MHC II antigen presentation occurs in fish infected with C. irritans remain unknown. In this study, the full-length cDNA of the grouper cysteine protease CTSS was cloned. The expression distributions of six genes (CTSB, CTSL, CTSS, GILT, MHC IIA and MHC IIB) involved in MHC II antigen presentation pathway were tested. These genes were highly expressed in systematic immune tissues and skin and gill mucosal-associated immune tissues. All six genes were upregulated in skin at most time points. Five genes expected CTSS was upregulated in spleen at most time points. CTSB, CTSL and MHC IIA were upregulated in the gill and head kidney at some time points. These results indicate that the presentation of MHC II antigen intensively occurred in local infected skin and gill. Spleen, not head kidney, had the most extensive systematic antigen presentation. In skin, six genes most likely peaked at day 2, earlier than in spleen (5–7 days), marking an earlier skin antibody peak than any recorded in serum previously. This significant and earlier mucosal antigen presentation indicates that specific immune response occurs in local mucosal tissues.     

云纹石斑鱼和赤点石斑鱼杂交子一代线粒体相关基因的母性遗传特征分析

对云纹石斑鱼和赤点石斑鱼及其正反杂交子代的3种线粒体基因(COⅠ、16S rDNA、Cyt b)和核基因Tmo-4c4进行序列分析,其中16S rDNA序列中有明显的插入缺失位点,而其他3个基因序列无插入缺失变异。在12个分析样本中,COⅠ同源序列(387 bp)中共检测到41个核苷酸多态性位点,16S rDNA(529 bp)中有21个核苷酸多态位点,Cyt b(383bp)中有49个核苷酸多态位点。Tmo-4c4(467 bp)有8个核苷酸多态位点。序列差异分析和遗传距离比较结果显示,正反杂交子一代的3个线粒体基因序列与母本基因序列的同源性都为100%,与父本的基因序列同源性分别为COⅠ:90%和89.4%;16S rDNA:96%和96%;Cyt b:87%和87.2%。核基因Tmo-4c4正反交子一代与母本的序列同源性为98.9%~99.6%之间,与父本的同源性为98.7%~99.4%之间,没有明显的遗传差异。以上结果表明了云纹石斑鱼和赤点石斑鱼杂交子一代在3种线粒体基因上严格按照母性遗传的规律,而核基因Tmo-4c4没有明显的遗传偏向性。     

Temporal genetic heterogeneity of juvenile orange-spotted grouper (Epinephelus coioides, Pisces: Serranidae)

Juveniles of orange-spotted grouper ( Epinephelus coioides ), a tropical serranid species, are heavily harvested for aquaculture seeds from nursing grounds in several Southeast Asian countries. Because juveniles of similar sizes are present in a nursery area throughout the year, we aimed to determine whether more than one genetically distinct population contributes to juvenile aggregations. We examined the temporal genetic heterogeneity of juvenile aggregations collected at four different times of the year at a nursery area in coastal waters of the Andaman Sea in Trang province, Thailand. Also, we examined the differences between these temporal samples and an outgroup collected from the Gulf of Thailand (Chantaburi). The genetic variation at six polymorphic microsatellite loci within each sample was moderate, with observed heterozygosities across all loci ranging from 0.551 to 0.629 and number of alleles per locus ranging from 7.0 to 8.33. Results indicated substantial genetic differences between the two geographically distant samples, Trang and Chantaburi (F_st=0.040–0.050, P <0.005), and between the July sample and the remaining samples from Trang (F_st=0.096–0.106, P <0.005). The observed temporal genetic heterogeneity of E. coioides juveniles may reflect high variability in the reproductive success of each spawning event and the existence of spatially isolated groups of spawners.     

石斑鱼一氧化氮合酶cDNA的分子克隆及序列分析

一氧化氮合酶(nitricoxidesynthase,NOS)专一性催化L-精氨酸转化为L-瓜氨酸和一氧化氮(nitricoxide,NO),产物NO是一种重要的生物信使分子,对其功能和代谢的研究越来越受人们的重视[1]。国际上,鱼类NOS的研究还刚起步,已有研究者在鱼类中检测到NOS的存在[2-5]。虹鳟[6]、金鱼[4]、大西洋鲑[7]和沟鲶[8]的诱导型NOS(iNOS)和神经型NOS(nNOS)的部分序列已鉴定。国内对哺乳动物的NOS也进行了研究[9-11],尚未见关于鱼类NOS方面的研究报道。JOURNALOFFISHERIESOFCHINA　　　　　　　　　　　Vol.27,No.4　斜带石斑鱼(Epin…     

17α-甲基睾酮对赤点石斑鱼性逆转的影响

赤点石斑鱼Epinephelus akaara(Temminck et Schlegel)是我国名贵海产经济鱼类。近几年来,因盲目钩捕,在东南沿海资源日益减少。因此,国内外一些学者对赤点石斑鱼性腺发育进行周年研究,并开展了人工繁殖和育苗试验。然而,由于此鱼雌雄同体,雌性先熟,在六龄鱼才转变为雄鱼。由此常见因缺少雄鱼无法开展人工繁殖。所以,作者在非繁殖季节,试图用外源性雄激素拌入饵料中,喂低龄和高龄赤点石斑鱼,目的在于诱发其性逆转,现已取得显著的效果,这对于解决雄鱼困难,提供科学依据。     

What causes cannibalization‐associated suffocation in cultured brown‐marbled grouper,Epinephelus fuscoguttatus (Forsskål, 1775)?

During culture of grouper, cannibalism is a frequent phenomenon that usually causes economic loss. Grouper culture often requires grading to prevent size‐dependent cannibalism. In comparison with orange‐spotted (Epinephelus coioides) and giant grouper (E. lanceolatus), failure to swallow prey during cannibalism is frequently observed in brown‐marbled grouper (E. fuscoguttatus). The cannibal cannot engulf the entire prey and the two fish ultimately end up dying together. Herein, we attempted to compare morphometric differences among orange‐spotted, giant and brown‐marbled grouper. We established a cannibal–prey total length (TL) relationship for brown‐marbled grouper: TL_prey=0.71 TL_cannibal−1.75. According to the equation, a difference of approximately 50% in TL is a threshold to use for grading the grouper. This value is much larger than that used (30%) in orange‐spotted and giant grouper, and this size difference results in a higher incidence of failed cannibalism attempts in brown‐marbled grouper. It is our belief that the standard grading method will fail to produce as good an effect in brown‐marbled grouper as is seen in orange‐spotted and giant grouper. Therefore, in addition to grading, other manipulations such as satiation feeding, nutritional supplementation and optimal stocking densities should be applied to reduce cannibalism of brown‐marbled grouper.     

赤点石斑鱼仔稚幼鱼的形态发育和生长

通过赤点石斑鱼各个发育期的仔稚幼鱼连续取样,系统地观察了仔稚幼鱼各个发育期的形态变化及生长特征,并进行描图。赤点石斑鱼初孵仔鱼全长1．35－1．45mm。稚鱼第6－7d长出特别伸长的背鳍第2鳍棘和腹鳍棘,其长度与全长之比在第16－18d,全长11mm左右时达到最大值,接近50%,这一形态特点是石斑鱼属仔稚鱼期特有的。以后随着个体的生长和其他鳍棘的伸长,这一比例逐渐减小,直至小于其他鳍棘,这是稚鱼完成变态成为鱼种的重要标志。最早完成变态的稚鱼须在孵化后第35 d,全长30mm以上,但到第45d时,全长24mm的个体也可以完成变态。即使在相同的环境条件下,仔稚幼鱼的个体大小差异也很大,且越到后期差异越大。     

Pyridoxine deficiency of grouper, <Emphasis Type="Italic">Epinephelus coioides</Emphasis>: physiological and biochemical alteration

Pyridoxine is essential for animals. The purpose of this study was to investigate the pyridoxine deficiency symptoms and the fit dose of pyridoxine to keep normal physiological function in grouper, Epinephelus coioides. Graded levels of pyridoxine (0, 1, 2, 4, 8, 16, 32 mg pyridoxine kg⁻¹ diet) were fed to grouper juveniles (14.83±0.31 g) for 8 weeks, and then some physiological and biochemical parameters were measured. Pyridoxine deficiency symptoms such as anorexia, poor survival, convulsion, helically swimming and hyperirritability were observed in fish fed the pyridoxine-deficient diet, and these fish also showed low whole blood haemoglobin level, liver glutamic-pyruvic transaminase (GPT) and superoxide dismutase (SOD) activities. Slight symptoms of pyridoxine deficiency also appeared among fish fed the diet with very low dose (1 mg pyridoxine kg⁻¹ diet) of pyridoxine in 6 weeks. Broken-line regression analysis showed that the optimal pyridoxine levels for these fish to keep normal survival, whole blood haemoglobin level, liver GPT and SOD activities were approximately 1.75, 1.87, 2.22 and 2.05 mg kg⁻¹, respectively.     

Effect of dietary lipid level on growth performance,feed utilization and body composition of grouper <Emphasis Type="Italic">Epinephelus coioides</Emphasis> juveniles fed isonitrogenous diets in floating netcages

An experiment was conducted to determine the effect of dietary lipid levels on growth performance and body composition of grouper Epinephelus coioides juveniles cultured in floating netcages (1.5 m × 1 m × 1.5 m). Six isonitrogenous diets (53% dietary protein) with increasing dietary lipid concentration (5.16, 7.38, 9.73, 12.36, 14.13, 16.04% of dry material, DM) were fed to satiation to triplicate groups of 20 fish (mean weight: 10.9 ± 0.1 g) for 56 days. Dietary energy levels were 300, 322, 340, 371, 382, 400 kcal/100 g DM, respectively. Fish fed the 9L diet had the highest weight gain (WG) and specific growth rate (SGR), but they were not significantly different from that of fish fed the 7L or 12L diet (p > 0.05). FI varied inversely with dietary lipid levels. The poorest FCR and the lowest PER were observed in fish fed the 5L diet but these parameters showed no significant differences (p > 0.05) for fish fed the dietary lipid level ranging from 9 to 16%. Nitrogen intake decreased with dietary lipid levels. Fish fed the 7L diet showed the highest N gain, which was not markedly different from that of fish fed the 9L and 12L diets (p > 0.05). N retention was significantly lower in fish fed the 5L diet than in the other groups. Lipid intake and lipid gain increased with dietary lipid levels. Lipid retention (%) of the 7L diet was lowest but showed no significant differences among other treatments (p > 0.05). Proximate composition of fish body was significantly affected by dietary lipid level (p < 0.05). Body lipid content increased in direct proportion to dietary lipid levels. In contrast, moisture content of whole-body was correlated negatively to dietary lipid level. Dietary lipid content had no significant effect on protein content in whole-body and white muscle (p > 0.05). Condition factor (CF), hepatosomatic index (HSI) and viscerosomatic index (VSI) increased with increasing dietary lipid level. Based on second-order polynomial regression analysis of WG against dietary lipid level, a breakpoint of 10.0% was indicated to be the optimal dietary lipid concentration for maximum growth for grouper Epinephelus coioides juveniles cultured in floating netcages.     

Apparent digestibility of selected ingredients in diets for juvenile grouper, Epinephelus coioides (Hamilton)

Apparent digestibility coefficients (ADCs) for dry matter (ADC_dm) and crude protein (ADC_cp) of selected feed ingredients were determined in vivo for grouper using passive faeces collection (Guelph System). A reference diet (RF) and test diets (consisted of 70% RF and 30% test ingredient) with 1% Cr₂O₃ as an inert indicator were used. An RF contained 45% protein, 10% fat and 15.7 kJ g^?1 metabolizable energy. Three isonitrogenous and isocaloric diets, each contained a test ingredient (white fish meal, white cowpea meal and ipil‐ipil leaf meal), were used in a growth study based on ADC_cp of feed ingredients. An RF without Cr₂O₃ was a control. The ADC values of experimental diets were also determined. In grouper, the ADC_dm of white cowpea meal, defatted soybean meal, wheat flour and shrimp meal (74–76%) were significantly lower than that of squid meal (99%), but comparable with those of the fish meals (84–89%). No significant difference was observed between the ADC_dm of ipil‐ipil leaf meal, rice bran and wheat flour (56–73%). The ADC_cp of white cowpea meal and defatted soybean meal were similar to those of the fish meals, squid meal and shrimp meal (94–99%). The ADC_cp of wheat flour was comparable with that of ipil‐ipil leaf meal (79–83%). Rice bran had the lowest ADC_cp value of 43%. Based on specific growth rate (SGR), the growth of fish fed white cowpea meal‐based diets was similar to that of the control fish (3.2–3.3% day^?1). Also, no significant difference was observed between the ADC_dm (68–72%) and ADC_cp (88–91%) of white cowpea meal‐based diet and the control diet. The results suggest that ADC values can be used as indicators to determine the nutritional value of feed ingredients. White cowpea meal can be incorporated as a protein source in practical diet for grouper at 20.5% of the diet with no adverse effect on growth.