长江中游长吻鮠、蛇鮈寄生粘孢子虫感染率的季节动态

1.寄生长吻鮠上的粘孢子虫有3种:巨囊两极虫和四极虫一种,寄生在胆囊中,碘泡虫一种寄生在肾脏中;寄生蛇鮈上的粘孢子虫有2种:湖北碘泡虫,寄生在脑、鳃、肾、体腔、肠,主要寄生在脑,楚克拉虫一种,寄生在胆囊中。2.粘孢子虫对长吻鮠、蛇鮈的感染率存在明显的季节变化;对长吻鮠的感染率最高值出现在6月(95%),最低值出现在2月(43%),年平均值为65%;湖北碘泡虫对蛇鮈的总感染率最高值出现在12—2月(63—67%),其次在8月(58%),春秋两季感染率较低(36—44%),年平均值为51%。3.总感染率(IR)与鱼体全长(TL)的关系:长吻鮠IR=0.956-0.009TL;蛇鮈IR=-2.0678+0.3838(TL)-0.0136(TL)2,8厘米以下的蛇鮈未发现感染。4.粘孢子虫的感染率与长吻鮠、蛇鮈的性别无关。5.感染粘孢子虫的长吻鮠,肥满度下降不大(0.04),感染粘孢子虫的蛇鮈,肥满度下降0.12,体重平均下降12.4%。6.长吻鮠中寄生粘孢子虫的总感染率(IR)与长江中游水温(T℃)呈显著正相关,二者关系可用下式描述:IR=0.3129+0.0192(T℃)。蛇鮈寄生粘孢子虫的总感染率(IR)与水温(T℃)之间的关系呈一反抛物线型、两者关系可用下式描述 IR=1.1228-0.073777T+0.001795T2  

SEASONAL DYNAMICS OF MYXOSPORIDIANS IN LEIOC ASSIS LONGIROSTRIS AND SAUROGOBIO DABRYI IN MIDDLE REACHES OF THE CHANGJIANG RIVER

Fish for the examination of Myxosporidian were collected from June 1984 to April 1985 in Tuanfeng (30°20′N, 111°5′E), Hubei province. About 20 fish of each species were collected bimonthly, thus, a total of 107 Leiocassis longirostris and 230 Saurogobio dabryi were examined. The results are summarized as follows:1. Generally, there are three species of myxosporidian in Leiocassis longirostris. Myxidium macrocapsulare and Chloromyxum sp. were found in gallbladder, having the infection rates of 55% and 17% respectively. Myxobolus sp. was found in kidney, with 22% infection. In Saurogobio dabryi, two species of myxosporidian are present. Myxobolus hupeiensis may infect brain, gill, kidney, body cavity and intestine, but occurs mainly in brain, where it forms white cysts and has 53% infection. Zschokkella sp. was found in gallbladder only, with 4% infection. 2. Infection rate of myxosporidian in Leiocassis longirostris and Saurogobio dabryi shows an obvious seasonal variation. In Leiocassis longirostris, the infection curve has only a single peak, with the maximum value (95%) in 3une and the minimum (43%) in February. The annual mean value is 65%. In Saurogobio dabryi, peaks of the infection curve are double, with the higher one (63--67%) appearing from December to February and the lower (58%) in August. Infection rate in spring and autumn are rather low (36--44%) and the annual mean value is 51%.3. The relationships between infection rate (IR) and total length of fish(TL) are expressed as follows:For L. longirostris:IR=0.956—0.009TL For S. dabryi:IR=-2.0678+0.3838(TL)-0.0136(TL)2 S. dabryi less than 8 cm are free from being infection4. The relation between infection rate of myxosporidian and different sex of both fishes was found to be inconspicuous, as indicated by x2-test.5. The reduction of weight and plumpness of L. longirostris after being infected by myxosporidian is not conspicuous, with plumpness reduced only 0.04 in average. However S. dabryi infected myxosporidian reduces 0.12 in plumpness and 12.4% in weight.6. Positive relationship between infection rate (IR) of myxosporidian in L. longirostris and water temperature (T) of the Changjiang River was observed and may be described as IR=0.3129-0.019T°(C). In S. dabryi relationship between these two factors may be described as IR=1.1228-0.073777 T+0.001795 T2.