Taskinen J
Department of Biological and Environmental Sciences, University of Jyväskylä, Finland.
J Parasitol. 1998 Apr;84(2):345-9.
The numbers of cercariae that trematodes produce have been previously investigated in the laboratory but not in the field. I studied cercarial production of the bucephalid trematode Rhipidocotyle fennica in the freshwater unionid clam Anodonta piscinalis kept under natural conditions. Naturally infected clams (n=180) were collected and marked in early June 1996. Every 14 days, starting from the collection date and ending in October, these clams were taken to the laboratory where they were monitored for the emergence of trematode cercariae. Between monitoring dates, the clams were returned to the collection site. From a random subsample of infected clams (n=12), the number of cercariae produced was counted during every monitoring. Cercarial production started in late July. The proportion of infected clams releasing cercariae increased from late July to late August. The mean daily production also increased during that period from 140 to 10,400 cercariae, decreasing thereafter. The mean annual production was 290,000+/-26,000 (160,000-440,000) cercariae. Daily production in late August and early September was positively correlated with annual production. Two of the 12 clams appeared to be infected with both R. fennica and Rhipidocotyle campanula. The average annual productions of R. fennica and R. campanula cercariae in double infections were 181,000+/-58,000 and 73,000+/-29,000, respectively.
吸虫产生尾蚴的数量此前已在实验室中进行过研究，但尚未在野外进行过研究。我研究了淡水珠蚌（Anodonta piscinalis）体内的头槽吸虫（Rhipidocotyle fennica）在自然条件下的尾蚴产生情况。1996年6月初收集并标记了自然感染的蚌（n = 180）。从收集日期开始，每隔14天，直至10月，将这些蚌带到实验室，监测吸虫尾蚴的逸出情况。在监测日期之间，蚌被放回收集地点。从受感染蚌的随机子样本（n = 12）中，在每次监测期间统计产生的尾蚴数量。尾蚴产生始于7月下旬。释放尾蚴的受感染蚌的比例从7月下旬到8月下旬有所增加。在此期间，日均产量也从140尾蚴增加到10400尾蚴，此后下降。年平均产量为290,000±26,000（160,000 - 440,000）尾蚴。8月下旬和9月初的日产量与年产量呈正相关。12只蚌中有两只似乎同时感染了芬兰头槽吸虫（R. fennica）和钟形头槽吸虫（Rhipidocotyle campanula）。双重感染中，芬兰头槽吸虫和钟形头槽吸虫尾蚴的年平均产量分别为181,000±58,000和73,000±29,000。
