Understanding the limiting factors of the reproduction process in host–affiliate relationships is a high priority. We examined the effects of habitat location on the reproductive process of freshwater pearl mussels Margaritifera laevis (Bivalvia, Unionida) as a parasite using sympatric and allopatric Oncorhynchus masou masou (Actinopterygii, Salmoniformes) as a host fish. Initial infection rates of parasitic larvae (glochidia) and transformation rates to cysts (encysted glochidia) were examined for all parasite-host combinations from three habitat locations (a total of nine combinations) to test the hypothesis that sympatric pairs of mussels and fish result in the highest success rates of glochidia infection and encystment. Measurements of glochidia-infected fish reared in flow-through experimental indoor tanks were taken at the initial infection point as well as at encystment, 2 weeks after the infection. Results disagreed with our hypothesis. Instead, an unexpected heterogeneity in a pathological deformity in gills explained a greater amount of variance in these processes. This deformity was responsible for reducing the initial infection rate and increasing the metamorphosis rates of initially attached glochidia to cysts. The field-measured prevalence of the gill deformity was low in all habitat locations, indicating that the deformity occurred during the acclimation period before infection for relatively small-sized host fish more susceptible to infection. Our results did not show the local adaptation of parasitic freshwater mussels to host fish but shed light on one of the least studied factors, providing an empirical underpinning of the importance of pathologically diversified host conditions in the reproductive processes of unionid mussels.

中文翻译：

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测试附属淡水珍珠贻贝 Margaritifera laevis 对其寄主鱼 Oncorhynchus masou masou 的本地适应性

了解宿主-附属关系中繁殖过程的限制因素是一个高度优先事项。我们使用同域和异域Oncorhynchus masou masou研究了栖息地位置对作为寄生虫的淡水珍珠贻贝Margaritifera laevis（Bivalvia，Unionida）繁殖过程的影响(Actinopterygii, Salmoniformes) 作为寄主鱼。对来自三个栖息地的所有寄生虫 - 宿主组合（总共九种组合）的寄生幼虫（glochidia）的初始感染率和向包囊（有囊的glochidia）的转化率进行了检查，以检验贻贝和鱼类的同域对导致的假设glochidia 感染和包囊的成功率最高。在最初的感染点以及感染后 2 周的包囊处，对在流通实验室内水箱中饲养的被钩端虫感染的鱼进行了测量。结果与我们的假设不一致。相反，鳃病理性畸形的意外异质性解释了这些过程中更大的差异。这种畸形是降低初始感染率和增加最初附着在囊肿上的钩端虫的变态率的原因。现场测量的鳃畸形患病率在所有栖息地位置都较低，表明畸形发生在感染前的适应期，对于更容易感染的相对较小的寄主鱼。我们的结果没有显示寄生淡水贻贝对寄主鱼的局部适应，但揭示了研究最少的因素之一，为病理多样化寄主条件在贻贝繁殖过程中的重要性提供了经验基础。表明畸形发生在感染前的适应期，对于更容易感染的相对较小的寄主鱼。我们的结果没有显示寄生淡水贻贝对寄主鱼的局部适应，但揭示了研究最少的因素之一，为病理多样化寄主条件在贻贝繁殖过程中的重要性提供了经验基础。表明畸形发生在感染前的适应期，对于更容易感染的相对较小的寄主鱼。我们的结果没有显示寄生淡水贻贝对寄主鱼的局部适应，但揭示了研究最少的因素之一，为病理多样化寄主条件在贻贝繁殖过程中的重要性提供了经验基础。