Histological observations on the reproductive organs of harbor porpoises Phocoena phocoena incidentally caught in a set net installed off Usujiri, southern Hokkaido

Abstract

A histological examination of two harbor porpoises Phocoena phocoena caught in a set net established off Usujiri, Hokkaido was conducted in order to further understand the reproductive biology of the species. In the male, a unilateral testis comprised a testicular lobe and rete testis, seminiferous tubules of the former being composed mostly of Sertoli (sustentacular) cells and a few primodial germ cells, whereas the latter contained numerous anastomosing tubules consisting of columnar epithelia. In the female, the smooth-surfaced ovary consisted mostly of primodial and secondary follicles and a few atretic follicles, although more developed Graafian follicles were not found. A highly intricate oviduct (fallopian tube) was constructed from simple high columnar cells, but did not contain AF-positive substance. Both individuals examined were considered to be infants owing to their very immature gonads.