倪氏复口吸虫在稀有鮈鲫体内的移行及对其耳石微结构的影响

MIGRATION OF DIPLOSTOMUM NIEDASHUI CERCARIAE IN THE RARE MINNOW GOBIOCYPRIS RARUS WITH OBSERVATION ON THE PARASITE-INDUCED OTOLITH CHECKS

倪氏复口吸虫是我国淡水鱼类的一种常见的危害严重的寄生虫。利用稀有鲫作为寄主 ,研究了倪氏复口吸虫在其体内的移行途径 ,并观察了复口吸虫的感染是否在寄主耳石上留下标记轮。倪氏复口吸虫尾蚴从稀有鲫体表的各个部位侵入 ,但主要集中在头部 ,侵入体内的尾蚴通过肌肉和结缔组织直接进入眼球。感染倪氏复口吸虫的稀有鲫耳石表面微结构发生变化 ,部分鱼耳石上出现明显的标记轮。

The penetration and migration of the eyefluke Diplostomum niedashui,a common parasite of freshwater fish in China were investigated using the rare minnow Gobiocypris rarus as the second intermediate host. The first intermediate host,Lymnaea stagnalis was collected from a fish farm in Wuhan,Hubei province of China,and the snails shedding cercariae were maintained in the laboratory. The cercariae of D. niedashui were identified according to the original description,and used to infect the rare minnow. Infected fish were either fixed in Bouin's solution and then sectioned before being stained in H-E,or observed live under microscope. Otoliths of some infected fish were dissected out for the examination of checks. The penetration of cercariae was observed on the whole body surface of the fish,while most cercariae were found on the head region of the fish, suggesting that the head region is the main site for the penetration. Although the penetrated cercariae were observed in the notochord,no meta-cercariae were found in the optic nerve,nor to migrate to the brain and to the eye through the nervous system. The metacercariae were found frequently in muscles and connective tissues of the fish and found moving directly into the lens through the muscle and connective tissue of the fish. The examination of otolith microstructure revealed some differences between the infected and un-infected fish,and checks on the otolith were found when the infection occurred,indicating that the parasite infection may induce the formation of checks on otoliths.