Jokela J, Lively C M, Taskinen J, Peters A D
Experimental Ecology, ETH-Zürich, ETH-Zentrum NW, CH-8092 Zürich, Switzerland email:
Department of Biology, Indiana University, Bloomington, IN 47405, USA, , , , , , IN.
Oecologia. 1999 May;119(3):320-325. doi: 10.1007/s004420050792.
The level of host exploitation is expected, under theory, to be selected to maximise (subject to constraints) the lifetime reproductive success of the parasite. Here we studied the effect of two castrating trematode species on their intermediate snail host, Potamopyrgus antipodarum. One of the trematode species, Microphallus sp., encysts in the snail host and the encysted larvae "hatch" following ingestion of infected snails by birds. The other species, Notocotylus gippyensis, by contrast, releases swimming larvae; ingestion of the snail host is not required for, and does not aid, transmission to the final host. We isolated field-collected snails for 3 months in the laboratory, and followed the survival of infected and uninfected snails under two conditions: not fed and fed ad libitum. Mortality of the infected hosts was higher than mortality of the uninfected ones, but the response to starvation treatment was parasite species specific. N. gippyensis induced significantly higher mortality in starved snails than did Microphallus. Based on these results, we suggest that host exploitation by different species of trematodes may depend on the type of transmission. Encysting in the snail host may select for a reduced rate of host exploitation so as to increase the probability of transmission to the final host.
根据理论，宿主被利用的程度预计会被选择到最大化（在一定限制条件下）寄生虫的终生繁殖成功率。在此，我们研究了两种阉割性吸虫对它们的中间宿主蜗牛——新西兰泥蜗（Potamopyrgus antipodarum）的影响。其中一种吸虫，微小阴茎吸虫（Microphallus sp.），在蜗牛宿主体内形成包囊，并且被包囊的幼虫在鸟类摄食受感染的蜗牛后“孵化”。相比之下，另一种吸虫，吉普斯兰诺托吸虫（Notocotylus gippyensis），释放游动的幼虫；向终末宿主的传播不需要摄食蜗牛宿主，且摄食蜗牛宿主对传播也没有帮助。我们在实验室中将野外采集的蜗牛隔离3个月，并在两种条件下跟踪受感染和未受感染蜗牛的存活情况：不喂食和随意喂食。受感染宿主的死亡率高于未受感染宿主，但对饥饿处理的反应具有寄生虫物种特异性。吉普斯兰诺托吸虫在饥饿的蜗牛中诱导的死亡率显著高于微小阴茎吸虫。基于这些结果，我们认为不同种类吸虫对宿主的利用可能取决于传播类型。在蜗牛宿主体内形成包囊可能会选择降低宿主被利用的速率，以便增加传播到终末宿主的概率。
