Ultrastructural study of vitellogenesis and oogenesis of Crepidostomum metoecus (Digenea, Allocreadiidae), intestinal parasite of Salmo trutta (Pisces, Teleostei)

Crepidostomum metoecus（Digenea、Allocreadiidae）、Salmo trutta（双鱼座、Teleostei）肠道寄生虫的卵黄发生和卵子发生的超微结构研究