保安湖乌鳢渔获群体结构及生长特性

依据１９９２年和１９９３年４－５月收集的标本，分析保安湖乌鳢渔获体系结构和生长特征。年龄由Ⅰ－Ⅶ龄构成，Ⅰ－Ⅺ龄分别占渔获总尾数的１２．３７％，２４．７４％、４１．２４％和１７．５３％。Ⅴ－Ⅶ龄极少公占４．１２％。优势体长为３１－４２ｃｍ；优势体重为３５０－９５０ｇ。体长与体重关系为Ｗ＝０．００７９９１Ｌ＾３．１６０２。ＶｏｎＢｅｒｔａｌａｎｆｆｔｙ生长方程为Ｌｔ＝７７．３（１－ｅ＾－０．１９８８     

New invasive predator reduces the abundance of native prey in a cold-temperate marine fouling community

1. Invasive species threaten the conservation of marine environments, and urgent management strategies are needed to prevent their introduction, establishment and spread. Specifically, marine invasive predators destabilize ecological interactions and alter community structure and function. However, most of the evidence showing the effect of these predators is restricted to a few species and regions, while for others the information remains scarce.
2. This study experimentally evaluated the ecological effects of the sea slug Pleurobranchaea maculata, a recently introduced invasive predator, on the fouling communities of a cold-temperate port in the South-western Atlantic.
3. The results show that increasing predation pressure reduces significantly the abundance of sea anemones, which are among the preferred prey items.
4. This study reveals new evidence to help better understand the effects of P. maculata on the biological communities of a recently invaded region. Furthermore, it provides the first experimental evidence supporting the hypothesis that marine invasive predators can induce a significant decrease in the abundance of native species in benthic communities of cold-temperate marine environments in the South-western Atlantic.

     

Effect of calcium and magnesium hardness on acute copper toxicity to Indian major carp, Labeo rohita (Hamilton) and catfish, Channa punctatus (Bloch)

Four experiments were conducted to evaluate the effects of calcium and magnesium hardness on the acute toxicity of copper sulphate to Indian major carp, rohu (Labeo rohita, Hamilton) fingerlings and juvenile catfish (Channa punctatus, Bloch) in medium alkalinity experiments. A preliminary bioassay determined the 96 h LC₅₀ of copper sulphate to be 0.56 mg L^?1 for L. rohita fingerlings and 11.78 mg L^?1 for juvenile C. punctatus placed in water with calcium hardness and total alkalinity set at 100 mg L^?1 CaCO₃. In the first experiment, rohu were exposed to 0.56 mg L^?1 copper sulphate in environments where calcium hardness was varied from 50 to 350 mg L^?1 CaCO₃ and total alkalinity was 100 mg L^?1 CaCO₃. As calcium hardness increased, copper‐induced rohu mortalities decreased significantly from 90% at 50 mg L^?1 CaCO₃ to 7% at 350 mg L^?1 CaCO₃. In the second experiment, rohu were exposed to 0.56 mg L^?1 copper sulphate in environments where magnesium hardness was varied from 50 to 350 mg L^?1 CaCO₃ with total alkalinity set at 100 mg L^?1 CaCO₃. Hundred percent mortality was observed in magnesium‐based hardness treatments. In the third experiment, catfish were exposed to 11.78 mg L^?1 copper sulphate in environments where calcium hardness was varied from 50 to 400 mg L^?1 and total alkalinity was 100 mg L^?1 CaCO₃. As calcium hardness increased, copper‐induced catfish mortalities decreased significantly from 90% at 50 mg L^?1 CaCO₃ to 4% at 400 mg L^?1 CaCO₃. In the fourth experiment, catfish were exposed to 11.78 mg L^?1 copper sulphate in environments where magnesium hardness was varied from 50 to 400 mg L^?1 CaCO₃, with total alkalinity set at 100 mg L^?1 CaCO₃. In this case, 100% mortality was also observed in magnesium‐based treatments. Mortality rates in magnesium hardness treatments were consistent with those in the second experiment. These data suggest a calcium‐specific mechanism with respect to acute copper toxicity both in rohu and catfish.     

3种鳢属鱼类ITS序列及系统进化分析

[目的]阐明乌鳢、斑鳢、月鳢核基因序列(ITS)的遗传变异情况,并用ITS序列研究鳢属系统进化关系.[方法]利用PCR扩增3种鳢的ITS,经克隆、拼接得到ITS全长后进行分析.[结果]乌鳢、斑鳢和月鳢ITS全序列长度为902、927、902或903bp.3种鳢ITS的G+C含量较高,约占72％.3种鳢之间核苷酸差异明显大于种内,明显的差异性ITS片段可以鉴别3种鳢.采用NJ和ML方法建立的进化树都表明乌鳢和斑鳢的遗传距离最近,而乌鳢和月鳢遗传距离最远.[结论]该研究为鳢属的分类鉴定、系统进化关系以及种间杂交提供基础资料.     

乌鳢早期鳞被的形成及鳞片形态特征

乌鳢最初出现鳞片时的全长为１９．３￣２０．６ｍｍ，日龄２０￣２２ｄ；鳞被复盖完毕时全长２９．９￣３４．１ｍｍ，日龄３５￣３９ｄ。鳞被发育过程中出现４个起始中心，第１中心为头顶部，主要中心为体侧前部，２个次要中心为鳃盖处和胸部。仔鱼体长２０ｍｍ左右鳞片上开始出现环片，全长２７ｍｍ左右出现鳞沟。仔鱼全长和鳞径、环片数之间，日龄和环片数之间均呈显著的直线相关关系。     

乌鳢仔鱼摄食和消化器官的发育及其选食行为

研究日龄１～２０ｄ，全长３．９～２１．０ｍｍ的乌鳢仔鱼摄食和消化器官的发育特征，仔鱼的食物组成及其选食行为。仔鱼全长５．５ｍｍ时出现颌齿和咽齿，７．５ｍｍ时出现犁齿和副蝶（骨）齿，９．４ｍｍ时出现腭齿；全长８．３３ｍｍ左右，分化出胃、肠。仔鱼孵出后第３ｄ开口摄食。仔鱼主要摄食浮游动物，主要食物随仔鱼摄食器官和消化器官的发育而变化。摄食初期（４ｄ龄）主要为小型枝角类和轮虫，但仅显示出对小型枝角类正的选择性。之后，胃肠内的食物类群增多，由选食枝角类变为选食桡足类。研究结果表明乌鳢仔鱼对食物选择性的这一变化是仔鱼本身摄食和消化器官的发育状态以及各类食物生物的相对密度等诸因素决定的。     

乌鳢嗅觉器官发育的组织学研究

采用组织学方法对乌鳢仔鱼(全长14～31mm)和咸鱼(全长370mm)嗅觉器官的发育进行了研究。结果表明：乌鳢嗅觉器官由头部左右两侧的嗅囊构成,每个嗅囊有前后2个鼻孔。随其发育,仔鱼前鼻孔隆起于外表面。发育为管状延伸物而与外界相通。嗅板在嗅囊内发育时不形成中心脊,其排列方式为纵向平行的D型。从仔鱼发育至咸鱼,乌鳢嗅觉上皮的厚度变化较小,而初级嗅板的数量和隆起高度显著增大。嗅觉上皮主要由感受细胞、支持细胞、纤毛细胞和基细胞组成。     

月鳢消化系统形态及组织学的研究

对月鳢(Channaasiatica)消化系统的形态及组织学进行了研究。结果为:①肠道呈3次盘旋,肠长与体长之比为0 42±0 02;②随着发育和生长,消化道的粘膜层厚度及粘膜皱褶高度增大、粘膜皱褶及杯状细胞增多;③食道、胃、前肠、中肠和后肠的组织结构区别明显,且食道与胃在组织结构上具有一定的连续性和过渡性;④胰腺在肝脏中呈弥散性分布;⑤月鳢消化道的形态和结构与其食性高度相关。探讨了月鳢消化道形态结构与食性的关系,认为月鳢消化道具有典型的肉食性特征。     

WD无敌消毒液治疗月鳢烂尾病的初步试验

本文首次对月鳢Ｃｈａｎｎａａｓｉａｔｉｃａ（Ｌｉｎｎａｅｕｓ）烂尾病的症状进行了描述,并首次以ＷＤ无敌消毒液对该病进行治疗。据初步试验结果,每天泼洒一次ＷＤ无敌消毒液（５ｍＬ／ｍ３）,连续３ｄ,部分病情较轻的病鱼可以痊愈,病情严重者则死亡。试验结束时,试验组无患病鱼,成活率极为显著的高于对照组;而对照组仍有１２．７３％的鱼患病,患病率与试验前无显著差异。表明ＷＤ无敌消毒液对治疗月鳢烂尾病有显著的疗效。     

WD无敌消毒液对月鳢鱼苗急性毒性试验的初步探讨

初步测得WD无敌消毒液对全长7．0mm和19．3mm月鳢鱼苗的安全浓度分别为11mL／m^2和34．2mL/m^3。对月鳢而言。WD无敌消毒液是一种安全的外用药,但用0．1％WD无敌消毒对幼苗进行浸泡消毒时,浸泡时间建议在90s以内为宜。