Valdivia I M, Criscione C D, Cárdenas L, Durán C P, Oliva M E
Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Isla Teja, Valdivia, Chile; Programa de Doctorado en Ciencias Aplicadas, Mención en Sistemas Marinos Costeros, Universidad de Antofagasta, Antofagasta, Chile.
Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843, USA.
Int J Parasitol. 2014 Mar;44(3-4):183-8. doi: 10.1016/j.ijpara.2013.10.008. Epub 2014 Jan 18.
Intraspecific variability in parasite life cycle complexity (number of hosts and species of hosts in the life cycle) may have an impact how parasite genetic variation is partitioned among individual parasites, host individuals or host species within a given area. Among digenean trematodes, a three-host life cycle is common. However, a few species are precocious and may reach sexual maturity in what is typically regarded as the second intermediate host. The objective of this study was to determine whether a precocious life cycle predisposes digeneans to possible inbreeding or genetic subdivision among host species. As a study system, we used the digenean Proctoeces cf. lintoni whose metacercariae precociously mature (facultative) without a cyst wall in the gonads of multiple sympatric species of keyhole limpets (Fissurella spp.), typically regarded as the second intermediate hosts. Genotyped parasites were collected from four species of limpets and the clingfish Sicyases sanguineus, the third and final host where sexual maturity occurs. We found very high microsatellite diversity, Hardy-Weinberg equilibrium over all genotyped individuals, and little to no genetic structuring among parasites collected from the different host species. The fact that metacercariae do not encyst in the keyhole limpets, coupled with the high mixing potential of an aquatic environment, likely promote panmixia in local populations of P. cf. lintoni.
寄生虫生命周期复杂性（生命周期中的宿主数量和宿主种类）的种内变异性可能会影响寄生虫遗传变异在给定区域内的个体寄生虫、宿主个体或宿主物种之间的分配方式。在复殖吸虫中，三宿主生命周期很常见。然而，有少数物种发育早熟，可能在通常被视为第二中间宿主的宿主体内达到性成熟。本研究的目的是确定早熟的生命周期是否会使复殖吸虫在宿主物种间易于发生近亲繁殖或遗传细分。作为一个研究系统，我们使用了复殖吸虫Proctoeces cf. lintoni，其尾蚴在多个同域分布的钥孔帽贝（Fissurella spp.）物种的性腺中早熟成熟（兼性），且没有囊壁，钥孔帽贝通常被视为第二中间宿主。对从四种帽贝和粘鱼Sicyases sanguineus（性成熟发生的第三和最终宿主）中收集的寄生虫进行了基因分型。我们发现微卫星多样性非常高，所有基因分型个体都处于哈迪-温伯格平衡状态，并且从不同宿主物种收集的寄生虫之间几乎没有遗传结构。尾蚴不在钥孔帽贝中形成包囊，再加上水生环境的高混合潜力，可能促进了Proctoeces cf. lintoni当地种群的随机交配。
