Fermer J, Culloty S C, Kelly T C, O'Riordan R M
Department of Zoology, Ecology and Plant Science, University College Cork, Distillery Fields, North Mall, Cork, Ireland.
J Helminthol. 2010 Dec;84(4):362-8. doi: 10.1017/S0022149X09990708. Epub 2010 Feb 1.
In order to study seasonal patterns of Meiogymnophallus minutus infections in its intermediate hosts, bivalve samples were collected monthly between April 2008 and March 2009 from a high intertidal flat at Courtmacsherry Bay, Ireland. Infection rates in the first intermediate host Scrobicularia plana did not fluctuate significantly with season. Completely developed M. minutus cercariae appeared in daughter sporocysts from June and prevailed from July to October, indicating that transmission of M. minutus from its first to its second intermediate host is confined to this period of the year. All analysed individuals of the second intermediate host Cerastoderma edule were found to be infected with metacercariae. Infection levels significantly increased in September, suggesting recent cercarial invasions. Throughout the year, the majority of metacercariae were hyperinfected by the pathogenic microsporidian Unikaryon legeri. Spreading of hyperinfections was confined to spring and summer. Newly settled metacercariae were not affected by hyperparasitism and presumably retained their infectivity for half a year. Our findings suggest that the spreading of hyperinfections is correlated with higher water temperatures and that the entire metacercarial population has to rebuild every year as a consequence of hyperparasite-induced mortality.
为了研究微小美叶裸吸虫在其中间宿主中的感染季节模式，于2008年4月至2009年3月期间每月从爱尔兰考特马谢里湾的一个高潮间带滩涂采集双壳贝类样本。第一中间宿主扁平河蚬的感染率并未随季节发生显著波动。完全发育的微小美叶裸吸虫尾蚴于6月出现在子胞蚴中，并在7月至10月占主导地位，这表明微小美叶裸吸虫从其第一中间宿主传播至第二中间宿主仅限于一年中的这段时期。所有被分析的第二中间宿主欧洲厚蟹个体均被发现感染了囊蚴。9月感染水平显著增加，表明近期有尾蚴入侵。全年中，大多数囊蚴都被致病性微孢子虫勒热单孢子虫高度感染。高度感染的传播仅限于春季和夏季。新定居的囊蚴未受到超寄生的影响，并且大概在半年内保持其感染力。我们的研究结果表明，高度感染的传播与较高水温相关，并且由于超寄生虫引起的死亡率，整个囊蚴种群每年都必须重新建立。
