Stages of rock bream oplegnathus fasciatus (Temminck et Schlegel 1844): embryonic development

The embryonic development of rock bream, Oplegnathus fasciatus, was studied from fertilization until hatching. The hatching occurred approximately at 25 h after fertilization at 23.5 ± 0.5 °C. The embryogenesis is divided into seven stages: Zygote period, Cleavage period, Morula period, Blastula period, Gastrula period, Segmentation period and Hatching period. The first cleavage furrow of rock bream fertilized eggs is vertically oriented, as is usual until horizontal cleavage occurs at the fifth cleavage. The blastocoel is observed between the blastoderm and I‐YSL at blastula period. At 90%‐epiboly stage, the earliest somitic furrow appears in the middle of embryo. The myotomes develop from somites at 15 h 30 min post fertilization. The Kupffer's vesicle consisting of ventrally I‐YSL and dorsally columnar cells appears with the completion of epiboly. It degenerates gradually with the penetration of some eosinophilic granules and disappears completely at 20 h 30 min after fertilization. The digestive tract, a straight tubule, is differentiated into foregut, midgut and hindgut. The epithelium of midgut and hindgut are the monolayer cubic and columnar cells respectively. The staging series provides a preliminary baseline reference for future studies on embryos of the rock bream.     

条石鲷早期发育阶段的生长模式

为研究条石鲷在早期发育阶段的生长特性和重要功能器官的异速生长规律,测定了条石鲷仔稚幼鱼(0~50日龄)全长和体质量随日龄的生长变化。通过统计学方法分析发现,全长、体质量随日龄的变化均符合Cubic函数关系式,其变化曲线呈S型。全长、体质量随日龄的变化可分为3个阶段,不同阶段的全长、体质量生长率具有显著性差异(P<0.05)。运用SPSS 13.0和OriginPro 7.5软件分析了条石鲷仔稚幼鱼头长、头高、体高、眼径、口裂、吻长、腹长、尾鳍长等外部形态参数与全长的变化关系,发现各功能器官的生长均呈现出异速生长的特点,但生长的拐点却各不相同。研究表明,在条石鲷的早期发育过程中,有关运动、摄食、消化等的重要器官(眼、口、腹部、尾鳍等)具有优先发育的特征,且发育的时段各有差异,故在其苗种的培育过程中,应根据其生长、生态规律为其创造最佳的环境条件,以提高苗种的存活率。     

饲养密度对条石鲷生长的影响

通过模拟工厂化养殖模式,采用单因素实验方法进行各体长阶段的密度梯度饲养试验。经过为期60的饲养管理后,对条石鲷的增长率及饵料系数进行比较分析,结果表明：适宜条石鲷工厂化养殖的各体长阶段放养密度：体长在10-13cm,养殖密度为80ind／m3;体长在14-16cm,养殖密度为52ind／m3;体长在17～20em,养殖密度为36ind／m3;体长在21—24cm,养殖密度为24ind／m3。     

Effects of water temperature on mortality in Megalocytivirus‐infected rock bream Oplegnathus fasciatus (Temminck et Schlegel) and development of protective immunity

Rock bream iridovirus (RBIV) causes huge losses, especially in rock bream Oplegnathus fasciatus. Rock bream injected with RBIV and held at 29, 26, 23 or 20 °C had 100% mortality. Conversely, all infected fish held at 17 °C survived even after the temperature was progressively increased to 26 °C at 100 dpi. Rock bream exposed to virus and held for 2, 4 and 7 days at 23/26 °C before the temperature was reduced to 17 °C had mortality rates of 26.6/73.2%, 66.6/100% and 93.4/100%, respectively, through 100 dpi. When surviving fish had the water temperature increased from 17 to 26 °C at 100 dpi, they did not exhibit signs of disease and had low virus copy numbers (below 10³). To investigate the development of a protective immune, rock bream were infected with RBIV and held at 23 °C before shifting the water temperature to 17 °C at 4 dpi. All injected fish survived until 120 dpi. While 100% of the previously unexposed fish died, 80.2% of the previously infected fish survived. When the survivors were rechallenged again at 160 dpi, no further mortality occurred. The high survival rate of fish following rechallenge with RBIV indicates that protective immunity was established in the surviving rock bream.     

条石鲷苗种繁育技术

条石鲷（Oplegnathus fasciatus）属于鲈形目（Perciformes）,石鲷科（Oplegnathidae）,俗称石鲷、石加拉,肉食性,栖于岩礁及珊瑚礁地形海域,以小型贝类、甲壳类为食,齿板锐利,可轻易咬碎贝类、甲壳类的坚硬外壳,所以英文称为刀颔鱼。分布在我国福建、广东、浙江等海水较深的清水、太平洋和印度洋沿岸,     

Expression and serological application of a capsid protein of an iridovirus isolated from rock bream, Oplegnathus fasciatus (Temminck & Schlegel)

Iridoviruses infect a wide variety of wild and cultured fish. Those iridoviruses belonging to the genus Ranavirus, in the Iridoviridae family, cause systemic disease in infected animals with a high morbidity and mortality. This paper reports the cloning, sequencing, and expression of the rock bream iridovirus (RBIV) major capsid protein (MCP) in an Escherichia coli expression system for subsequent immunological studies. The completeness of the expressed protein was confirmed by peptide mass fingerprinting (PMF) analysis using MALDI-TOF MS. The recombinant MCP (rMCP)-specific mouse polyclonal antibody reacted with the viral 52 kDa protein, indicating that this rMCP induces an immunological response. Fish antibodies induced against iridovirus infection were also detected using ELISA when rMCP was used as an antigen. As a result, it was found that many cultured rock bream (92.5%) were naturally infected with iridovirus and that the rMCP might be useful for serological tests.     

Viral nervous necrosis in hatchery-reared larvae and juveniles of Japanese parrotfish, Oplegnathus fasciatus (Temminck & Schlegel)

Abstract. Mass mortalities of hatchery-reared Japanese parrotfish larvae and juveniles, Oplegnathus fasciatus (Temminck & Schlegel), have occurred in Nagasaki Prefecture. Light and electron microscopic examinations showed that the only consistent histopathological feature was extensive nervous necrosis in the spinal cord, spinal ganglia and brain. Numerous non-enveloped virus particles, icosahedral in morphology and measuring about 34 nm in diameter, were found in the cytoplasm of affected neurones and glial cells. Such nervous necrosis is believed to be the major cause of the mass mortalities of hatchery-reared Japanese parrotfish larvae and juveniles.     

Optimal Stocking Density with the Provision of Self‐feeders for Striped Knifejaw,Oplegnathus fasciatus (Temminck and Schlegel 1844)

To determine the optimal stocking density, three densities of 5 (SD₅), 10 (SD₁₀), and 15 kg/m³ (SD₁₅) were used to culture striped knifejaw, Oplegnathus fasciatus, for 10 wk. A total of 10, 20, or 30 juveniles with mean weights of approximately 96 g were stocked into one of nine 300‐L tanks (with an initial water volume of 200 L) and fed with commercial feed via self‐feeders. The fish were sampled at 4 and 8 wk, and the stocking density was maintained by adjusting the water volume of the tanks. The final body weights in SD₁₀ and SD₁₅ were 183.8 and 178.9 g, respectively, which were significantly higher than 161.7 g in SD₅ (P< 0.05). However, there was no significant difference between the SD₁₀ and SD₁₅ (P > 0.05). A similar trend was observed in the specific growth rate among the treatments. Feed efficiency and the lipid retention efficiency were both significantly higher in SD₁₀ than that in SD₅. The plasma levels of cortisol, glucose, and total protein were similar among the treatments. These results clearly suggest that densities of 10 and 15 kg/m³ can be used to improve the growth performance of striped knifejaw, O. fasciatus, when fed with a self‐feeder.     

Characterization of a megalocytivirus from cultured rock bream,Oplegnathus fasciatus (Temminck & Schlege), in China

Megalocytivirus belongs to the Iridoviridae family and is known to affect finfish. Megalocytivirus epizootics have been reported to occur in several cultured fish species in China; however, no megalocytivirus associated with rock bream, Oplegnathus fasciatus (Temminck & Schlege), has been documented. In this study, we characterized for the first time a megalocytivirus, rock bream iridovirus (RBIV)‐C1, detected in cultured rock bream in a fish farm in China that had been inflicted with a high‐mortality disease outbreak. Sequence analysis of three conserved genes showed that RBIV‐C1 shares over 90% overall identities with a number of known megalocytiviruses. Electron microscopic examination revealed RBIV‐C1 as hexagonal particles similar to those reported for megalocytiviruses. In vivo infection study indicated that, following inoculation into rock bream, RBIV‐C1 induced 100% mortality and upregulated the expression of Mx, IL‐1β and IL‐8. The infected fish exhibited pathological signs similar to those observed in naturally diseased fish. Furthermore, studies in a turbot (Scophthalmus maximus L.) model indicated that RBIV‐C1 induced acute infection in turbot that led to 100% mortality. These results indicate that RBIV‐C1 is highly virulent to rock bream as well as turbot and that RBIV‐C1 is closely related to a number of previously reported megalocytivirus and likely a genetic variant of the latter.     

Ontogeny of immune system organs in northern bluefin tuna (Thunnus orientalis, Temminck and Schlegel 1844)

Serial sections, prepared from 0.5 to 30 days posthatch (dph) larval and juvenile Thunnus orientalis (Temminck & Schlegel 1844), were stained with haematoxylin and eosin and examined by light microscopy for immune organ development. The early kidney was present at 0.5 dph, undifferentiated stem cells began to appear at 2 dph, and by 7 dph occasional small lymphocytes were present. The thymus was first obvious at 5 dph, located above the fourth branchial arch, small lymphocytes appeared at 7 dph, and by 15 dph an outer thymocytic zone and an inner epithelioid zone were visible. The progenitor spleen was present at 2 dph, located close to the gut, and by 12 dph it consisted of a mass of sinusoids filled with red blood cells, and remained mainly erythroid throughout the period studied. These results suggest that development of immune organs in this species is precocious relative to other marine teleosts.     

Dietary eicosapentaenoic acid requirement of juvenile rock bream,Oplegnathus fasciatus

A feeding trial was conducted to evaluate the optimum dietary level of eicosapentaenoic acid (EPA, 20:5n‐3) based on growth and non‐specific immune responses in juvenile rock bream. A basal diet without EPA supplementation was used as a control, and six other diets were prepared by supplementing with 4, 8, 12, 16, 20 or 40 g of EPA per kg diet. The actual EPA concentrations of the diets were 0.5, 4.3, 8.5, 13.0, 16.8, 21.0 and 41.2 g of EPA per kg diet, and the diets were abbreviated as EPA_0.5, EPA_4.3, EPA_8.5, EPA_13.0, EPA_16.8, EPA_21.0 and EPA_41.2, respectively. Triplicate groups of fish averaging 1.06 ± 0.01 g (mean ± SD) were fed one of the seven experimental diets at the apparent satiation for 8 weeks. At the end of the feeding trial, weight gain, specific growth rate and feed efficiency of fish fed EPA_16.8, EPA_21.0 and EPA_41.2 diets were significantly higher than those of fish fed EPA_0.5, EPA_4.3, EPA_8.5 and EPA_13.0 diets (p < .05). Superoxide dismutase activity of fish fed EPA_16.8, EPA_21.0 and EPA_41.2 diets were significantly higher than those of fish fed EPA_0.5, EPA_4.3 and EPA_8.5 diets. Fish fed EPA_21.0 and EPA_41.2 diets showed significantly higher lysozyme activity than did fish fed EPA_0.5, EPA_4.3, EPA_8.5 and EPA_13.0 diets. The broken‐line analysis of weight gain indicated that the optimum dietary EPA level was 16.7 g/kg diet. These results suggested that the optimum dietary EPA level in juvenile rock bream could be greater than 16.7 g/kg diet but less than or equal to 16.8 g/kg diet based on the broken‐line analysis and the ANOVA test of weight gain.     

南海区养殖条石鲷的胚胎发育

在较高温度下对南海区养殖条石鲷(Oplegnathus fasciatus)的受精卵进行观察,详尽记录和描述了发育时序和各发育时期的形态特征.条石鲷受精卵的卵径为0.860±0.023 mm,油球径为0.191±0.009 mm.在孵化水温为25.64±0.77 ℃、盐度30～32的条件下,受精卵历时22 h 30 min孵化出膜.初孵仔鱼(孵化后10～15 min)体长为1.836±0.078 mm.根据受精卵的发育过程,将其分为卵裂期、囊胚期、原肠期、胚孔关闭期、克氏泡期、尾芽期、心跳期、孵化前期和孵化期等9个时相.其中卵裂期、囊胚期和原肠期分别历时3 h、3 h和4 h 45 min.对比不同温度下条石鲷的胚胎发育,认为原肠期、尾芽期至孵化期这2个时期的发育速率受温度的影响最大.     

红鳍东方鲀Fugu rubripes(Temminck et Schlegel)与牙鲆Paralichthys olivaceus(Temminck et Schlegel)的混养越冬技术

红鳍东方Tun与牙鲆是我国重要的养殖经济鱼类和出口创汇品种。在我国北方，这两种于通常是单独越冬。本文作者采用混养越冬技术，不仅降低了越冬成本，提高了水体利用率，而且使牙鲆在河Tun的影响下，明显增重和有效地预防了疾病。     

养殖条石鲷消化道形态构造及组织学观察

应用解剖学和光学显微镜检术研究了养殖条石鲷（Oplegnathus fasciatus）消化道的形态学和组织学特性。条石鲷消化道包括口咽腔、食道、胃、幽门盲囊和肠。条石鲷口咽腔较大,颌齿愈合成鹦鹉喙嘴状,舌半椭圆形。食道较短,显微组织可分为4层：粘膜层、粘膜下层、肌肉层和浆膜层,上皮含有极少量杯状细胞和黏液分泌细胞。胃膨大,呈V形,和食道一样分为4层,粘膜层表皮下含有发达的胃腺。小肠组织分为3层：粘膜层、肌肉层和浆膜层。直肠组织结构类似于小肠。小肠和直肠上皮中均分布有较多的杯状细胞。文章对养殖条石鲷消化道的形态学和组织学特征与其食性的适应关系作了探讨。     

温度、盐度对条石鲷胚胎发育影响及初孵仔鱼饥饿耐受力

研究了盐度、温度对条石鲷胚胎发育的影响和初孵仔鱼对饥饿的耐受力。结果表明,胚胎发育的适宜盐度范围为20～35,最适盐度范围为25～30,孵化率都在89%以上,盐度低于20或高于35,孵化率都降低。盐度对孵化时间有一定影响,盐度高于35或者低于15条件下孵化时间都延长。胚胎发育的适宜温度范围为21～27℃,孵化率都在77%以上,最适温度范围为23～25℃,孵化率达89%以上,低于19℃或者高于27℃时孵化率降低且初孵仔鱼畸形率升高。胚胎孵化时间与温度成负相关关系,胚胎发育速率与温度成正相关关系。条石鲷胚胎发育的生物学零度（阈温度）为10.06℃,有效积温值为405.3℃·h。对胚胎发育的Q10值进行了计算。饥饿条件下,条石鲷初孵仔鱼8日龄全部死亡,半数死亡时间出现在第6天,饥饿对初孵仔鱼生长具有明显的抑制作用。     

条石鲷的耗氧率与窒息点研究

2008年4～8月,采用Winkler法研究了70日龄（平均全长37.68mm,平均体重1.07g）和105日龄（平均全长65.71mm,平均体重5.58g）的条石鲷在不同温度（15、20和25℃）、不同盐度（20、25和30）下的耗氧率、窒息点及耗氧率昼夜变化。结果表明,105日龄组的相对耗氧率明显低于70日龄组,但个体耗氧量明显高于70日龄组;耗氧率随幼鱼体重的增加而相对减少。盐度一定时,温度升高,相对耗氧率和个体耗氧量都随之增大。盐度对70日龄幼鱼组的耗氧率影响显著（P〈0.05）,对105日龄幼鱼组影响不显著（P〉0.05）。盐度25左右、温度20～25℃时是条石鲷苗种培育和生长的最适盐度和最适温度。条石鲷在温度15～25℃、盐度20～30下的窒息点为1.6021～2.9538mgO2/L,窒息点随着个体的增大而降低;温度、盐度对条石鲷窒息点的影响均不显著（P〉0.05）。条石鲷耗氧率的昼夜变化明显,白天的耗氧率平均为0.9459mgO2/g.h,夜间平均为0.2727mgO2/g.h,白天的耗氧率是夜间的3～5倍,条石鲷白天代谢旺盛并持续到夜间22∶00左右。