Sex Difference in the Cloacal Gland in the Hagfish,Eptatretus burgeri,and its Possible Significance in Reproduction

The cloacal gland of the hagfish, Eptatretus burgeri, was studied histologically in four seasons. Before the breeding season (spring and summer) the male cloacal gland was larger than the female cloacal gland. The gland was largest in the males with a more mature testis. After the breeding season (autumn and winter) there was no sex difference in the size of the cloacal gland. The cloacal gland consists of mucus and thread cells, as do the lateral slime glands. The sperm may be entangled within slime in the cloacal gland and be shed outside as a slimy sperm mass. Such a slimy sperm mass may play an important role in reproduction of the hagfish.