Effect of rearing density on the blood and tissues of mullet (Mugil cephalus L.)

This study evaluated the biological effects of high stocking density on mullet (Mugil cephalus). Fifty fish, caught from Faro lake, were divided into two groups, a low-density control group (n = 15), stocked at 3.4 kg/m³ in an 800 l tank and a high-density experimental group (n = 35), stocked at 8.4 kg/m³ an 800 l tank. The ammonia concentration in the control group tank reached 0.3 mg/l after 2 days while that in the experimental tank reached 5 mg/l. Haematological parameters and serum protein profiles were determined following blood sampling. An Unpaired T-test showed significant differences between the two groups on Red Blood Cell Count, Haematocrit, Haemoglobin, White Blood Cell Count, Mean Corpuscular Haemoglobin, Mean Corpuscular Haemoglobin Concentration, total proteins, albumin and α-globulins. In the experimental group, the disappearance of prealbumin and the γ-globulin fraction was particularly evident. Histopathological changes indicated that mucosal electrolytic failure was the main function compromised. This could eventually lead to death. The findings suggest that mullet is sensitive to stocking density linked to ammonia toxicosis.     

鲻鱼甲状腺免疫组织化学与超微结构

用组织学、免疫组织化学和电镜技术对鲻鱼甲状腺的分布与形态结构进行研究。结果表明，鲻鱼甲状腺滤泡分散地分布在第1对至第3对鲻弓的入鳃动脉之间；构成同一滤泡的单层上皮细胞呈扁平形和立方形两种形态，反映出同一滤泡中上皮细胞生理活动的不同步，且发现不同发育时期的鲻鱼这两种形态细胞的比例有显著差异。用特异性甲状腺球蛋白(TG)抗体对甲状腺滤泡的免疫染色反应显示，阳性物质分布在滤泡上皮细胞的脑膜及围绕滤泡腔的周边与中央胶质，幼年与成年鲻鱼甲状腺滤泡的免疫阳性反应部位有所不同。两种不同活动状态的细胞，扁平形细胞和立方形细胞，在核与胞质的超微结构上有显著不同。扁平形细胞的核为扁平形或椭圆形，核内常染色质十分丰富，核膜光滑，核周腔和核孔没有扩张，胞质中各种细胞器发育较差；立方形细胞的核膜高度凹陷，将核分为2叶至3叶，核周腔和核孔扩张，胞质中各种细胞器发育良好，出现长棒形和哑铃形线粒体，且数量明显多于扁平形细胞，多层粗面内质网呈板层状排列，还有发育好的高尔基复合体。另外，我们还观察到一种介于扁平形细胞和立方形细胞之间的中间型细胞，其胞质和核的发育明显好于扁平形细胞，但比立方形细胞差。上述结果可为了解鲻鱼甲状腺滤泡细胞分泌活动的机制提供基础资料[动物学报49(2)：230—237，2003]。     

Coexistence of Mugil cephalus and M. curema in a coastal lagoon in the Gulf of Mexico

Mugil cephalus and M. curema coexist in Tamiahua Lagoon, with no difference in diet or digestive system, but with a separation of 3 months in reproductive timing.     

Cloning,expression and enantioselective hydrolytic catalysis of a microsomal epoxide hydrolase from a marine fish, <Emphasis Type="Italic">Mugil cephalus</Emphasis>

The cDNA of a marine fish microsomal epoxide hydrolase (mEH) gene from Mugil cephalus was cloned by rapid amplification of cDNA ends (RACE) techniques. The homology model for the mEH of M. cephalus showed a characteristic structure of α/β-hydrolase-fold main domain with a lid domain over the active site. The characteristic catalytic triad, consisting of Asp(238), His(444), and Glu(417), was highly conserved. The cloned mEH gene was expressed in Escherichia coli and the recombinant mEH exhibited (R)-preferred hydrolysis activity toward racemic styrene oxide. We obtained enantiopure (S)-styrene oxide with a high enantiopurity of more than 99% enantiomeric excess and yield of 15.4% by batch kinetic resolution of 20 mM racemic styrene oxide.     

Ceratomyxa sparusaurati N. Sp. (Myxosporea: Bivalvulida), a New Parasite from Cultured Gilthead Seabream (Sparus aurata L.) (Teleostei: Sparidae): Light and Electron Microscopic Description

ABSTRACT. A new Myxosporea, Ceratomyxa sparusaurati n. sp., was found in the gall bladder and bile of cultured gilthead sea bream ( Sparus aurata L.) from different Spanish fish farms. It is clearly different from all the previously reported Ceratomyxa from sparids, and it is distinguished from other members of the genus by the shape and size of the spores. Prevalence of infection was 2.15% in an Atlantic farm, 48.7% in a Mediterranean farm and 28.6% in the facilities of the Instituto de Acuicultura de Torre de la Sal. The cell-in-a-cell pattern was found through all the sporogenesis and the general ultrastructure resembled other Myxosporea. Primary cells with two developing spores, harbored other secondary cells. Disporous sporoblasts contained numerous membrane-bound inclusions, a few lipid droplets and polysaccharides as evidenced by cytochemistry. In mature spores, binucleate sporoplasmic cells contained abundant Thièry-negative sporoplasmosomes.