成年日本新糠虾血细胞组成、形态及其不同发育阶段的免疫活性酶

采用光镜和电镜的方法,以血细胞所含颗粒与否,颗粒多少和核质比等将成年日本新糠虾血细胞进行分型,并对各型血细胞所占比例进行统计。利用生化分析的方法,对不同发育阶段(新孵后0、10、20和30d)日本新糠虾全组织中磷酸酶(酸性磷酸酶和碱性磷酸酶)、溶菌酶和酚氧化酶的活性进行测定。结果表明,日本新糠虾血细胞可为3种类型,它们分别为透明细胞、半颗粒细胞和颗粒细胞。它们的胞体大小依次增大,核质比依次降低。对此3种类型血细胞比例分别统计后发现,颗粒细胞所占比例最多约为47.53%±0.02,其次是半颗粒细胞约为31.23%±0.01,最少的是透明细胞约为21.24%±0.02。日本新糠虾体内磷酸酶(酸性磷酸酶和碱性磷酸酶)、溶菌酶和酚氧化酶的活性均有随个体发育而呈降低的趋势。3种酶中以溶菌酶的活性最高,平均约为305.20U/mg蛋白,其次是酸性磷酸酶约为0.2365U/mg蛋白,而酚氧化酶和酸性磷酸酶在成体中的活性基本一致,约为0.1295U/mg蛋白。研究表明,日本新糠虾血细胞组成中,以颗粒细胞为主。溶菌酶是其主要的免疫活性物质。日本新糠虾体内磷酸酶(酸性磷酸酶和碱性磷酸酶)、溶菌酶和酚氧化酶活性有随其个体发育而逐渐...     

基于水龄的河道型水库总磷评价标准参考值研究

针对目前河道型水库TP评价标准存在争议的水环境管理实际问题,提出了基于水龄权重的TP评价标准参考值计算方法。以朱沱为控制断面,基于EFDC水动力模型模拟2017年三峡水库水动力过程,计算出三峡水库库区干流主要断面逐日水龄,依据水龄将三峡水库各断面分为河流型水体(朱沱~清溪场)、河流型-过渡型混合型水体(苏家~白帝城)、过渡型水体(巫峡口~木鱼岛)。计算了基于水龄权重的过渡型水体TP评价标准参考值,并据此对2017年三峡水库主要断面水质因子进行评价,结果表明三峡水库泄水期早期(1-2月),白帝城以下断面水质污染指数较高,风险较大。     

铜合金围栏养殖大黄鱼海域水质综合评价与分析

为了评价铜合金围栏养殖大黄鱼(Larimichthys crocea)海域的水质状况,通过大黄鱼养殖期与非养殖期的4次调查,分析评价了调查海域海水中的p H、溶解氧、铜、锌、无机氮、活性磷酸盐等指标的区域分布、季节变化及污染水平,并利用内梅罗指数对调查海域水体进行了质量综合评价。结果表明:调查海域大黄鱼非养殖时间段的海水综合质量整体上属于清洁或者较清洁状态,大黄鱼养殖时间段的海水综合质量下降,分布趋势是以养殖网箱为高值中心,向外缘逐渐下降。     

辽宁地区河蟹暴发性流行病病原研究

从患暴发性流行病的中华绒螯蟹稚蟹体内分离到５株细菌,其中２株经人工感染试验证实为病原菌,又经形态,生理生化特性测试,鉴定为嗜水气单胞菌和副溶血弧菌,生物型２。药敏试验结果表明,前者对氯霉素,庆大霉素,红霉素等敏感;后者对呋喃唑酮,磺胺,链霉素,卡那霉素,磺胺＋ＴＭＰ等敏感。     

Morphological, structural, and functional characterization of the haemocytes of the scallop, Argopecten irradians

Argopecten irradians is one of the most important commercial species of Pectinidae family in China. The internal defense system of mollusks consists of circulating haemocytes. In order to characterize the haemocytes of the scallop A. irradians, light and electron microscopical studies were carried out. Four types of haemocytes were recognized: type I small hyalinocytes (2.38 ± 0.08 μm, 30-35%), type II large hyalinocytes (4.41 ± 0.33 μm, 15-20%), type III small granulocytes (4.15 ± 0.26 μm, 20-25%), and type IV large granulocytes (8.26 ± 0.52 μm, 25-30%). Granulocyte types showed smaller N/C ratios than hyalinocytes. The mean haemocyte concentration was about (3.75 ± 0.65) × 10⁷ cells ml^− 1 of haemolymph. Among haemocytes, 44.7% are granular and 55.3% are agranular. These gave a relatively systematic classification scheme for haemocytes of A. irradians. Three types of granules were identified: type I, with high electron-density; type II, with low electron-density; and type III, with a middle level of electron-density, based on TEM studies. Different haemocyte types were not separated with DDGC of Percoll in this study. Both granulocytes and hyalinocytes showed a phagocytic response to the two strains of bacteria, Escherichia coli and RLOs. The phagocytic ability of granulocyte was significantly higher (41-48%) than that of hyalinocyte (9.2-11.2%).     

虎纹蛙病毒主要衣壳蛋白基因的克隆及其序列

从新分离感染虎纹蛙的病毒培养细胞中提取病毒DNA作模板，用分别对应于蛙病毒－3型（FV3）主要衣壳蛋白（Major Capsid Protein,MCP）基因读码框两侧的寡核苷酸片段作引物进行PCR扩增，得到预期大小基因片段，进一步将此基因片段插入到pGEM-T载体中，进行全长片段的序列测定和分析。结果表明，编码虎纹蛙病毒的MCP基因的读码框核苷酸数为1392bp，编码463个氨基酸；基因的核苷酸序列与其他脊椎动物虹彩病毒的MCP基因序列比较结果显示，该病毒与蛙病毒属的FV3的同源性（98％)明显高于囊肿病毒属的FLDV－1（52％），并且与虹彩病毒科其他成员的MCP基因序列均有所不同，说明该病毒株是虹彩病毒科蛙病毒属的新成员。     

Localization of calcium regulatory hormones in fish

Immunocytochemical localization of hypocalcin, a hypocalcemic factor in the corpuscles of Stannius (CS), in American eels was examined at the light (ABC method) and electron microscopic (protein A-gold technique) levels with the specific antiserum raised against purified rainbow trout hypocalcin. Only type 1 cells in the CS were immunoreactive in the light microscopic immunocytochemistry. At the electron microscopic level, however, hypocalcin immunoreactivity was observed in secretory granules of both type 1 and type 2 cells. Our findings may indicate that type 1 cells are the main source of hypocalcin, but that type 2 cells also produce it, suggesting that the presence of two cell types reflects different physiological conditions of a single cell type, rather than functionally different cell types. In addition, we summarize our recent data on the localization of other calcium regulatory, or putative calcium regulatory, hormones in fish: parathyroid hormone, calcitonin and calcitonin gene-related peptide.     

Apparent digestibility coefficients of European grain legumes in rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus)

Two trials were carried out to evaluate the apparent digestibility coefficients (ADCs) of dry matter (DM), crude protein (CP), lipids, starch and gross energy (GE) of six European varieties of grain legumes, namely chickpea‐type Kabuli (CHK), chickpea‐type Desi (CHD), field pea (FP), faba bean (FB), white lupin (WL) and chickling vetch (CV), in rainbow trout and Nile tilapia juveniles. The ADCs were measured using a reference diet and six experimental diets (700 g/kg of the reference diet and 300 g/kg of each raw grain legume) containing 10 g/kg chromic oxide as inert marker. Additionally, grain legumes were analysed for the organic acids profile. In rainbow trout, FP presented the highest ADCs of DM, CP and GE, whereas chickpeas and FB had the lowest DM, GE and starch ADC values. In Nile tilapia, the lowest values of nutrients (except starch) and energy ADCs were found for FP and CV. Nutrients and energy of chickpeas, WL and FB were better digested by tilapia, whereas FP was better digested by trout. Overall results reveal raw grain legumes as promising feed sources for both fish species.     

池塘养殖牙鲆(Paralichthys olivaceus)无眼侧体色黑化消褪机理

针对池塘养殖牙鲆(Paralichthys olivaceus)无眼侧体色黑化消褪的现象,本研究从形态、血清和mRNA水平上对其生理学机制进行了研究.光镜观察显示,无眼侧消褪区域的黑色素细胞数量显著少于有眼侧和无眼侧黑化区域(P＜0.05),电镜观察发现,无眼侧消褪区域皮肤中黑色素颗粒模糊,黑色素细胞中色素体存在凋亡现象.无眼侧黑化区域消褪过程中,鳞片类型经历了由栉鳞—弱栉鳞—圆鳞转变的过程,栉鳞上硬棘数量也随之减少.无眼侧黑化消褪的牙鲆血清中的黑色素聚集激素(MCH)肽含量显著高于无眼侧正常和无眼侧黑化的牙鲆(P＜0.05),但无眼侧体色黑化的牙鲆血清中的黑色素细胞刺激激素(MSH)肽含量显著高于其他2种类型的牙鲆(P＜0.05).基因表达分析显示,无眼侧黑化消褪鱼垂体MCH mRNA表达水平显著高于无眼侧黑化鱼(P＜0.05),而垂体POMC1 mRNA表达水平显著低于无眼侧黑化鱼(P＜0.05),但都与无眼侧正常鱼无显著差异.研究结果可为阐释池塘养殖牙鲆无眼侧体色黑化调控机制提供理论支持.     

中国罗非鱼主养区无乳链球菌的分子流行特征及其传播方式

为分析2007—2015年中国罗非鱼主养区无乳链球菌(Streptococcus agalactiae)的分子特征和流行情况,分离并收集了248株罗非鱼源无乳链球菌。通过分子血清型、MLST、毒力基因和前噬菌体等分型方法对248株无乳链球菌进行了分子遗传特征分析。结果表明,229株无乳链球菌(92.3%)的分子血清型是Ⅰa型,其余19株均是Ⅰb型(7.7%)。MLST分析结果表明,所有Ⅰa型无乳链球菌都是ST7型,所有Ⅰb型无乳链球菌都是ST261型。毒力基因检测结果发现,229株Ⅰa-ST7型无乳链球菌的毒力基因型相同,即V1型;19株Ⅰb-ST261型无乳链球菌的毒力基因型相同,即V2型。前噬菌体检测结果表明,Ⅰa-ST7型无乳链球菌可分为两种前噬菌体基因型,分别是P1型(36株)和P2型(193株);Ⅰb-ST261型无乳链球菌的10个前噬菌体基因都是阴性,即P3型。根据以上4种分子分型方法可将248株无乳链球菌分为3种基因型,即Ⅰa-ST7-V1-P1型、Ⅰa-ST7-V1-P2型和Ⅰb-ST261-V2-P3型。2010—2011年主要流行菌株由Ⅰa-ST7-V1-P1型转变为Ⅰa-ST7-V1-P2型,其中Ⅰa-ST7-V1-P1型是2011年之前的主要流行菌株,Ⅰa-ST7-V1-P2型在2011年及之后成为主要流行菌株。研究表明,近年来我国罗非鱼源无乳链球菌发生了明显的遗传变异,同时,根据我国罗非鱼主养区无乳链球菌的流行特点,推测我国罗非鱼源无乳链球菌是通过苗种或水体等介质进行传播的,属于输入性传播方式。     

Genetic characterization of Streptococcus phocae strains isolated from Atlantic salmon, Salmo salar L., in Chile

Streptococcus phocae is a beta-haemolytic bacterium frequently involved in disease outbreaks in seals causing pneumonia or respiratory infection. Since 1999, this pathogen has been isolated from diseased Atlantic salmon, Salmo salar , causing serious economic losses in the salmon industry in Chile. In this study, we used different molecular typing methods, such as pulsed-field gel electrophoresis (PFGE), randomly amplified polymorphic DNA (RAPD), enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR), repetitive extragenic palindromic PCR (REP-PCR) and restriction of 16S–23S rDNA intergenic spacer regions to evaluate the genetic diversity in S. phocae . Thirty-four strains isolated in different years were analysed. The S. phocae type strain ATCC 51973^T was included for comparative purposes. The results demonstrated genetic homogeneity within the S. phocae strains isolated in Chile over several years, suggesting the existence of clonal relationships among S. phocae isolated from Atlantic salmon. The type strain ATCC 51973^T presented a different genetic pattern with the PFGE, RAPD, ERIC-PCR and REP-PCR methods. However, the fingerprint patterns of two seal isolates were distinct from those of the type strain.     

Localization of Zn-binding protein in the digestive tract tissue of common carp

ABSTRACT: The concentrations of Zn and sulfhydryl (SH) groups in the digestive tract tissue of common carp and some aquatic animals were studied. It was found that Zn and bound SH groups could be used as indicators for detecting the Zn-binding protein in the digestive tract tissue of common carp. The digestive tract tissue of the fish underwent subcellular fractionation, and it was found that the nuclei/cell debris fraction contained most of the DNA (85%), Na⁺/K⁺-ATPase (82%), organic phosphate (90%) and the Zn-binding protein (79%), but only part of the 5'-nucletidase and alkaline phosphatase (<23%). The nuclei/cell debris fraction of the digestive tract tissue of common carp was treated with either collagenase type I or type IV, and subfractionated by sucrose density centrifugation. It was found that treatment with collagenase type IV could release more than 50% of the Zn-binding protein, Na⁺/K⁺-ATPase and organic phosphate from collagen. Sections of digestive tract tissue of common carp were stained for Zn. It was observed that Zn can be found mainly on the edge of the epithelial layer, and everywhere in the 'membrane-like' portion of the submucosal and muscular layers. It is proposed that most of the Zn-binding protein in the digestive tract tissue of common carp is located on the basolateral plasma membranes of the epithelial cells and on the surrounding muscle cells that are attached to the collagen type IV of basal laminae.     

豹纹鳃棘鲈消化道粘液细胞的类型与分布

应用AB-PAS染色法对工厂化养殖条件下豹纹鳃棘鲈(Plectropomus leopardus)消化道粘液细胞的类型与分布进行了观察研究。结果显示:豹纹鳃棘鲈粘液细胞在消化道各部位均有分布,不同部位的粘液细胞密度和类型均有差异,豹纹鳃棘鲈消化道粘液细胞可分为Ⅰ型、Ⅱ型、Ⅲ型、Ⅳ型。其中,食道粘液细胞以Ⅲ型为主,胃以Ⅰ型为主,幽门盲囊和肠以Ⅲ型为主,直肠以Ⅲ型和Ⅳ型为主;胃部粘液细胞分布密度最大,达(111.37±21.74)cell·mm~(-2),极显著高于消化道其它部分,直肠、幽门盲囊、肠的粘液细胞分布密度分别为(35.09±8.74)、(30.23±5.37)、(28.00±4.67)cell·mm~(-2),相互之间差异不显著,食道的粘液细胞分布密度最低,为(10.83±1.94)cell·mm~(-2),与消化道其它部分相比差异极显著。另外,消化道各段单位面积内粘液细胞的分泌能力顺序为食道直肠肠幽门盲囊胃。通过对消化道各部位粘液细胞的分类对比可以发现,粘液细胞的类型和分布与其所在部位的功能有密切关系。     

Isolation, cloning, sequencing of brain type aromatase and its expression in male and female Wrasse, Pseudolabrus sieboldi

Pseudolabrus sieboldi, wrasse being a diurnal spawner provides a good opportunity to study the endocrine mechanism of estrogen formation in brain and gonads. Moreover, an extremely large amount of E2 was produced in serum and testis of wrasse. It is assumed that the presence of E2 may play a major role in diurnal gametogenesis in male fish. In this study brain type aromatase have been isolated, cloned and sequenced from the brain of wrasse. Further, the expression pattern of brain type aromatase in gonads and adult tissue of male and female fish have been analyzed. In addition, the diurnal expression pattern of brain type aromatase in both male and female fish brain during spawning season have been analyzed. The P450arom (br) was isolated, cloned and sequenced from both male and female bamboleaf wrasse. The P450arom (br) gene (1877 sequenced nucleotide) contains an ORF of 1470 bp, a 5′-UTR of 18 bp and at least 407 bp in 3′-UTR. The amino acid sequence homology in the coding region of wrasse P450arom (br) is high compared to that of medaka, Oryzias latipes (80%), rainbow trout type 2, Oncorhynchu mykiss (78.2%), fugu, Takifugu ribripes (78%) rainbow trout type 1, (76%), goldfish, Carassius auratus (66.8%) and zebrafish, Danio rerio (66.2%). Expression study reveals that P450arom (br) mRNA were most abundant in brains of both male and female fish throughout the day during the spawning season. RT-PCR study revealed that P450arom (br) was expressed in skin, anal fin and tail fin of both male and female wrasse. P450arom (br) was not detected at any time of the spawning day in either ovary or testis of wrasse.     

Effect of hook type and hook setting method on deep-hooking rates when bait fishing for trout in lentic waters

Fishing with circle hooks along with prescribed hook-setting methods can reduce deep-hooking rates in some fisheries, but baited circle hooks have not been evaluated in stillwater trout fisheries. Deep-hooking rates and catch probabilities were compared for cutthroat trout Oncorhynchus clarkii​ (Richardson), rainbow trout Oncorhyncus mykiss (Walbaum), cutthroat × rainbow trout hybrids, and brook trout Salvelinus fontinalis (MItchill) caught using three types of baited hooks (circle, intermediate circle and traditional J) and two hook-setting methods (active and passive) in several lakes containing naturally reared trout. Hook type had a negligible effect on deep-hooking rates, which averaged 20%. Actively setting the hook and fishing with a bobber both reduced deep-hooking rates, regardless of hook type. Larger fish were deeply hooked more frequently regardless of hook type. Catch probabilities were higher when active rather than passive hook-setting was used, particularly in combination with intermediate circle hooks. The present results, which indicate that circle hook use did not reduce deep hooking in lentic settings, contrast earlier studies done in lotic waters. Therefore, before proposing hook-type regulations intended to reduce deep hooking, fisheries managers should consider waterbody type in addition to fishing methods, fish size and species.     

Optimization of the Enzymatic Hydrolysis Assisted by Ultra-high Pressure Processing of Alaska Pollock Frame for Improving Flavour

ABSTRACT

In order to improve the flavor of aquatic enzymatic hydrolysate, this study determined the effect of ultra-high pressure processing (UHP) coupled with enzymatic hydrolysis on the flavor of Alaska pollock frame (APF) hydrolysates. The optimal conditions for UHP enzymatic hydrolysis were as follows: pressure time was 60 min, pH value was 7.5, and pressure was 150 MPa. The content of soluble peptide, total-free amino acid, and delicious amino acid (DAA) content of atmospheric pressure and UHP hydrolysates were 11.37 vs 16.70 mg/mL, 5 528 vs 6 234 mg/100 g, and 2145 vs 2411 mg/100 g, respectively. The major compounds in the enzymatic hydrolysates of UHP included seven types of ketones (18.31%), 8 types of aldehydes (6.35%), 3 types of alcohols (2.61%), one type of ester (0.38%), and one type of furan (7.89%). The results of electronic tongue (e-tongue) demonstrated good agreement with gas chromatography-mass spectrometry (GC-MS) analysis. In conclusion, UHP enzymatic hydrolysis can be a potential tool to improve the flavor compounds of hydrolysates.     

不同营养状况对鲫鱼偏好游泳速度的影响

为考察不同营养状况对鲤科鱼类偏好游泳速度的影响,本研究以鲫鱼(Carassius auratus)为实验对象,(25±1.0)℃条件下设置3个不同营养状况实验组:对照组(禁食48 h)、饱食组(饱食)和饥饿组(饥饿14 d),将单尾实验鱼置于梯度流速选择仪(流速范围为11.86~65.45 cm/s,等距离划分为5个流速区域,从第一到第五流速区域流速连续增加)中拍摄1 h,采用Ethovision XT9软件分析视频资料并计算实验鱼在不同流速区域平均进入频次(F,次)、单次进入停留时间(T,s/次)和平均停留时间百分比(P_t,%)等流速选择行为指标。结果显示,对照组和饱食组的F值随水流速度上升而增加,对照组的T值不同流速区域间无差异(P0.05),而饱食组第三和第四流速区域T值均显著大于其他流速区域(P0.05),因此两实验组第三和第四流速区域的P_t均显著大于其他流速区域,其偏好游泳速度为20.12~41.30 cm/s。饥饿组流速偏好行为出现表型分化,I型实验鱼在第一流速区域P_t和T值显著大于其他流速区域(P0.05),各流速区域的F值均显著小于其他实验组(P0.05),故I型实验鱼的偏好游泳速度为11.86~15.18 cm/s。而II型实验鱼则与对照组相似,在第三和第四流速区域Pt均显著大于其他流速区域(P0.05),故II型实验鱼的偏好游泳速度为20.12~41.30 cm/s。结果表明,饱食不影响鲫鱼的偏好游泳速度,可能是饱食不影响鲫鱼的游泳能力所致,但饱食组在各流速区域间的出入频次减少而停留时间有所增加。饥饿后鲫鱼偏好游泳速度出现表型分化,I型实验鱼的偏好游泳速度降低,而II型实验鱼则无明显变化,I型和II型实验鱼偏好游泳速度的差异可能是由于在饥饿条件下二者能量节约和游泳功能维持的策略不同。     

Effects of differently processed diets on growth,immunity and water quality of the sea cucumber,Apostichopus japonicus (Selenka, 1867)

The type of formulated diet used in aquaculture systems affects the feed efficiency and water quality. In this study, the water quality, growth performance and immunity of the sea cucumber, Apostichopus japonicus (Selenka, 1867), fed diets produced using four different processing methods (extruded pellet diet, cold‐bonded pellet diet, flake diet and mash diet) were quantified for 60 days to identify the optimal feed type for culturing of this species. Sea cucumbers grew faster, the feed conversion ratio was much lower, and immunity indicators were higher when fed the extruded pellet diet compared to the other diets. Sea cucumbers fed the extruded pellet diet had the highest specific growth rate (0.96), whereas A. japonicus fed the cold‐bonded pellet diet had the lowest specific growth rate (0.51). The lysozyme activity of sea cucumbers fed the extruded pellet diet was higher (57.52) than that of A. japonicus fed the cold‐bonded pellet diet (39.22), flake diet (37.32) and mash diet (32.68). When animals were fed the mash diet, the ammonia–nitrogen, nitrite–nitrogen and phosphate productions were higher than in animals fed the other diets. These results indicate that the extruded pellet diet is the optimum feed type for use in the culture of A. japonicus.     

鲤、鲫杂交子代的同工酶分析

利用水平式淀粉凝胶电泳法对乌克兰鳞鲤(♀)×乌龙鲫四倍体(♂)、红鲫(♀)×乌龙鲫四倍体(♂)、红鲫(♀)×乌龙鲫二倍体(♂)、白鲫(♀)×墨龙鲤(♂)4组鲤鱼、鲫鱼杂交子代背侧肌肉组织的天冬氨酸转氨酶、α-甘油醛磷酸脱氢酶、葡萄糖磷酸异构酶、异柠檬酸脱氢酶、乳酸脱氢酶、苹果酸脱氢酶、磷酸葡萄糖变位酶及肌浆蛋白进行电泳分析,并测量了红细胞长径。红细胞测量结果表明,乌克兰鳞鲤(♀)×乌龙鲫四倍体(♂)、红鲫(♀)×乌龙鲫四倍体(♂)、红鲫(♀)×乌龙鲫二倍体(♂)杂交子代为三倍体,白鲫(♀)×墨龙鲤(♂)杂交子代为二倍体。4组杂交子代葡萄糖磷酸异构酶同工酶的基因组成结果显示,父本乌龙鲫四倍体和父本乌龙鲫二倍体均产生二倍体配子,且二倍体配子中1套为鲤鱼染色体组,1套为鲫鱼染色体组。     

Immunocytochemical and ultrastructural identification of adenohypophyseal cells in Ctenopharyngodon idella (Cypriniformes: Cyprinidae) during gonadal differentiation

The adenohypophysis was studied by immunocytochemical and ultrastructural methods in juvenile grass carp (Ctenopharyngodon idella) from natural reproduction in Northern Italian rivers. The adenohypophysis included the rostral pars distalis (RPD), the proximal pars distalis (PPD) and the pars intermedia (PI), all deeply penetrated by branches of the neurohypophysis (Nh). The prolactin (PRL), adrenocorticotropic (ACTH), somatotropic (GH), thyrotropic (TSH), gonadotropic type I (GtH I) and type II (GtH II), somatolactin (SL), melanotropic (MSH) and endorphin (END) cells were identified with antisera raised against piscine and human pituitary hormones. In juveniles of 51–69 mm of total body length (TL) with undifferentiated gonads, the PRL cells, arranged in thick strands, occupied most of the RPD. The ACTH and GH cells organized in cords bordering Nh were, respectively, confined to RPD and PPD. The TSH cells were scattered among ACTH cells in RPD and among GH cells in PPD. Cells simultaneously immunoreactive to anti-follicle stimulating hormone and to anti-croaker gonadotropin were intermingled among GH and TSH cells, which were mostly in the dorsal PPD. The SL cells were detected in PI layers bordering the Nh. The MSH and END cells were intermingled in PI and, unlike what observed in other teleosts, their respective antisera did not cross-react. In individuals of 78–112 mm TL with gonads at the beginning of differentiation, the GtH II cells were detected in PPD; all other cell types increased in number. These results, supported by ultrastructural investigations, suggest that SL and GtH II cells are directly involved in gonadal differentiation in C. idella.