Rantanen J T, Valtonen E T, Holopainen I J
University of Jyväskylä, Finland.
Dis Aquat Organ. 1998 Jul 30;33(3):201-8. doi: 10.3354/dao033201.
The host-parasite relationship between digeneans and a semelparous population of the mollusc. Pisidium amnicum Müller in a small river in eastern Finland was studied during 1992/1993. The parasite prevalence of the population was high. The total prevalence was 45.6% in 1992 (n = 790) and 47.5% in 1993 (n = 160). The dominant digenean, Bunodera luciopercae (34.2% in 1992, 35.0% in 1993), had highest prevalences in July/August and in winter. Two other species, Palaeorchis crassus (7.8% in 1992, 7.5% in 1993) and Phyllodistomum elongatum (4.7% and 5.0%), were rare during the winter. The prevalence of B. luciopercae increased as clams aged, while the other species were most common in middle-sized clams. Apparently B. luciopercae rediae dominate over P. elongatum, which has only sporocyst stages, while P. crassus, which has large rediae, is more deleterious to the clam and induces host mortality. Double infections were significantly less common (1.2%) than might be expected by chance. All parasites castrated their hosts; no clam containing both parasites and embryos was found. Semelparity of the population is apparently caused by parasitic castration.
1992年至1993年期间，对芬兰东部一条小河中复殖吸虫与一次性繁殖的软体动物——淡水豆蚬（Pisidium amnicum Müller）之间的宿主 - 寄生虫关系进行了研究。该种群的寄生虫感染率很高。1992年的总感染率为45.6%（n = 790），1993年为47.5%（n = 160）。优势复殖吸虫——鲈豆蚴（Bunodera luciopercae，1992年为34.2%，1993年为35.0%）在7月/8月和冬季的感染率最高。另外两种吸虫，厚古睾吸虫（Palaeorchis crassus，1992年为7.8%，1993年为7.5%）和长叶叶形吸虫（Phyllodistomum elongatum，分别为4.7%和5.0%）在冬季较为罕见。鲈豆蚴的感染率随蛤蜊年龄增长而增加，而其他物种在中等大小的蛤蜊中最为常见。显然，鲈豆蚴的雷蚴比仅具有孢蚴阶段的长叶叶形吸虫更具优势，而具有大型雷蚴的厚古睾吸虫对蛤蜊的危害更大，并会导致宿主死亡。双重感染的情况明显比随机预期的要少得多（1.2%）。所有寄生虫都会使宿主绝育；未发现同时含有寄生虫和胚胎的蛤蜊。该种群的一次性繁殖显然是由寄生虫阉割引起的。
