Black gill disease of Paciifc white leg shrimp(Litopenaeus vannamei)byAspergillus lfavus

Objective:To study the epidemiology of black gill disease in white leg shrimp which is a major problem being faced by the commercial shrimp farmers who are culturing Litopenaeus vannamei(L.vannamei)in India.Methods:The normal and infected shrimps were collected from shrimp pond and the gill was preserved in appropriate preservative for histopathological examination and scanning electron microscope analysis.Pathogenic fungus was isolated from black gill of L.vannamei in potato dextrose agar medium.Morphological study and fungal strain identification were done by using light microscopy and scanning electron microscope.Fungal DNA was amplified by ITS4 and ITS5 primers and gene sequencing was done by Macrogen Inc.,Korea.Phylogenetic tree was prepared by using MEGA 6 software.Results:Fungal spores and hyphae were observed both in internal and external gill surface of infected shrimps.Fungal spores were round in shape and mature sporangium was observed.The histopathology study showed clearly that infected gill was damaged by the fungi.Scanning electron microscopic study showed adherence of fungi in infected gill.Internal transcribed spacer gene sequencing revealed that it was caused by Aspergillus flavus.Conclusions:The outcome of the present study would help to know the cause of black gill disease and to understand the effect of pathogenic fungi in shrimp culture.This study will initiate researchers for work in field of treatment or prevention of black gill disease in commercial L.vannamei culture.

Toxicological effects of ammonia on gills of Cyprinus carpio var.communis(Linn.)

Objective:To monitor the response of gills of Cyprinus carpio var. communis to LC_(50) levels of ammonia over a period of 96 h by bath exposure, using scanning electron microscopy (SEM). Methods: Cyprinus carpio procured from a local fish farm in Vadalore, Cuddalore District, Tamil Nadu, India were acclimatized under laboratory conditions for 20 d. Fish were placed into experimental tanks with 20 L of water and 22 mg/L ammonia. A total of 10 fish were collected from each experimental tank every 24 h for histopathological studies. Results:Histopathological studies showed these changes in the gills:secondary lamellar fusion, haemorrhage, oedema, epithelial hyperplasia, and chloride cell proliferation. Occasionally, multifocal necrosis of inter-lamellar regions of gill filaments but with no apparent haemorrhage was observed under electron microscopy. Conclusion:The present study shows that histopathological and ultrastructural alterations in gills are useful indicators for ammonia toxicity in Cyprinus carpio.

鲤鳃表面结构扫描电镜研究

鲤的鳃丝表面显示了由三边形—六边形不等的表皮细胞,呈现出各种图案式的结构。

鲈鱼的鳃寄生车轮虫病及扫描电镜观察

报道鲈鱼的鳃寄生车轮虫病及病理组织的扫描电镜观察。病原鉴定为 :直钩车轮虫、杜氏车轮虫、日本车轮虫、劳牧小车轮虫及简单两分虫 5种车轮虫科纤毛虫 ,其中数量上占优势的为直钩车轮虫。扫描电镜观察结果表明 ,鳃寄生车轮虫可对宿主的上皮组织产生明显的机械性损伤并造成鳃丝粘液分泌增多及炎症反应。文中就海水养殖鱼类及野生鱼类由车轮虫寄生造成的危害及防治途径做了探讨。

缺氧和有毒微囊藻胁迫下三角帆蚌鳃和主要消化器官以及晶杆体的扫描电镜观察

为了阐明缺氧和有毒铜绿做囊藻对三角帆蚌鳃和主要消化器官的毒理效应和组织病理,实验利用扫描电镜研究了暴露于缺氧和有毒铜绿做囊藻下三角帆蚌的鳃、胃、肠以及晶杆体等器官组织病理学变化。结果显示,从第7天开始缺氧和有毒藻类复合胁迫组三角帆蚌的鳃丝及柱状细胞出现大量坏死和脱落,胃肠腔面纤毛脱落、上史细胞破裂坏死,晶杆体在第5天已经完全消失;第7天单独缺氧组和单独有毒藻类组的鳃和消化道出现少量的病变,单独缺氧组晶杆体在第7天完全消失,单独有毒藻类组晶杆体则一直存在。胁迫消失后,3个实验暴露组的晶杆体都未恢复正常对照组水平,因此缺氧和有毒铜绿做囊藻对三角帆蚌鳃和消化系统产生不可恢复性损伤,双重胁迫组影响最为严重,缺氧胁迫组相对有毒铜绿做囊藻胁迫组影响更为显著。本研究为三角帆蚌在缺氧和有毒藻类胁迫下的生理适应机制提供了组织病理学上的参考,并为其作为富营养化水体治理工具种的可行性提供了理论依据。

泥鳅鳃表面形态结构扫描电镜研究

本文应用扫描电镜对泥鳅鳃表面形态结构进行了详细的观察和研究，结果表明：泥鳅鳃的鳃引鳃耙、鳃丝及鳃小片的上皮细胞表面各具不同的形态特征。鳃弓、鳃耙及鳃丝上皮细胞表面都有环形隆嵴、断续的短纹或点纹及小孔，而鳃小片的表面结构与其明显不同。这些结构特点与其鳃的功能机理是密切相关的。

龙骨蛏蚌消化管、外套膜和鳃的扫描电镜观察

利用扫描电镜首次对龙骨蛏蚌的消化管、外套膜和鳃进行了观察研究,消化管包括唇瓣、食道、胃、盘旋肠、直肠以及肛门。消化管各段内表面均具有纤毛,纤毛密集细长;盘旋肠和直肠内表面还具有微绒毛;在食道、胃和盘旋肠内表面可见分泌细胞;分泌细胞夹杂在纤毛柱状细胞之间,呈棒状突起。外套膜内表皮呈不规则的板块状结构,具沟和嵴,沟嵴上分布有纤毛和微绒毛,纤毛柱状细胞间夹杂较多的分泌细胞;外表皮表面相对平滑,无明显的沟嵴,表面仅分布有微绒毛,未见大量分泌细胞和球状颗粒。鳃表面布满纤毛,每条鳃丝由前纤毛、前侧纤毛和侧纤毛组成,这些结构在食物的选择与运输方面具有重要的意义。该研究对进一步了解龙骨蛏蚌的摄食机制提供理论依据。