Abstract

The life cycle of the nematode Cosmocerca ornata (Dujardin, 1845)—a parasite of amphibians—was studied for the first time. The experimental infection of yearlings of the marsh frog Pelophylax ridibundus infected by larvae of C. ornata was performed. The development stages of parasites in the host were studied. It has been revealed that amphibians are infected with infectious larvae (J3) of nematodes in the surface-water layer by the penetration of parasites through eyes onto the conjunctiva under the lower eyelid, where the larvae undergo the third and fourth molting. Then the parasites migrate into the oropharyngeal cavity and through the digestive tract to the place of constant localization: the posterior part of the intestine. Morphological descriptions and original drawings of J3 and J4 juveniles, molting juveniles, and adults of C. ornata are given. The development stages of the juveniles are diagnosed by the body size, location of the genital primordium, and forming copulative structure. The sex of the nematodes can be identified at the third molt stage. Mature nematodes differ from juveniles by the presence of copulative organs: the vulva in adult females and spicules in adult males. The time of the development stages of C. ornata and the total life span of the parasite in the host is determined. The effect of ambient temperature on the period of development of nematodes in amphibians is established.

中文翻译：

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Cosmocerca ornata（线虫科：Cosmocercidae）的生命周期，一种两栖动物的寄生虫

摘要

首次研究了线虫Cosmocerca ornata (Dujardin, 1845)——一种两栖动物的寄生虫——的生命周期。C. ornata幼虫感染沼蛙Pelophylaxridibundus一岁幼仔的实验感染进行了。研究了寄主体内寄生虫的发育阶段。已经发现，两栖动物通过寄生虫通过眼睛渗透到下眼睑下的结膜上而感染了地表水层中线虫的传染性幼虫（J3），幼虫在那里经历第三和第四次蜕皮。然后寄生虫迁移到口咽腔并通过消化道到达持续定位的地方：肠道的后部。C. ornata的 J3 和 J4 幼鱼、蜕皮幼鱼和成虫的形态描述和原图给出。幼鱼的发育阶段通过体型、生殖原基的位置和交配结构的形成来诊断。线虫的性别可以在第三次蜕皮阶段确定。成熟线虫与幼虫的区别在于交配器官的存在：成年雌性的外阴和成年雄性的针状体。C. ornata发育阶段的时间和寄生虫在宿主中的总寿命是确定的。确定了环境温度对两栖动物线虫发育时期的影响。