ドヂヨウのPit organ(孔器)の形態學的考察

抄録

Previously (SATO, Japanese Soc. Sci. Fisheries. Vol. 15, No. 6, 1949), the histological structure of the large and small pit organs of a Japanese catfish, Parasilurus asotus L. was described and in the present paper the same problem is taken up with a Cobitoid fish, Misgurnus angnillicaudus. This fish has large pit organs in the epidermis of the head and trunk, but it does not possess anything comparable with the small pit organs of the catfish. The large pit organs are arranged in a definite lines and attain their most luxuriant development on the head as shown in Figs. 1 and 2. These organs, as already mentioned in the catfish, are divided histologically into two types, viz., the “naked” and “sunken type”. The naked type of this organ is found most commonly in the young fish under 10mm. long (Fig. 3 a), but in the adult this type decreases in its number and the other type, namely the sunken type is found more numerous (Fig. 3 b). From these results of observation, it is clear that the large pit organ in the early stage usually projects slightly above the surrounding epidermis, and as development progresses this organ is withdrawn from the surface and come to lie at the bottom of a little pit.