Variability of Egg Envelopes in Korean Spined Loaches (Cobitidae)

Fifteen Korean cobitid species were investigated by the light and electron microscope to clarify the structure on the egg envelope of the oocyte. The egg envelope (zona radiata) consists of two layers: 1) zona radiata externa which is the site for attachment of various adhesive materials, and 2) zona radiata interna which consists of heterogeneous electron-dense multi layers. The external appearances of the egg envelope could be classified into seven types as follow: 1) granule (Cobitis sinensis, C. lutheri, C. tetralineata and Iksookimia yongdokensis), 2) villi (C. pacifica, I. koreensis, I. pumila, I. hugowolfeldi and Niwaella multifasciata), 3) papilla (I. longicorpa), 4 grapevine (I. choii), 5) hillock (Kichulchoia brevifasciata), 6) sawtooth-like form (Koreocobitis naktongensis) and 7) unadorned form (Misgurnus anguillicaudatus, M. mizolepsis).