Abstract
Reproductive organs and germ cells of hagfishes were mainly studied in three species of hagfish: Myxine glutinosa, Eptatretus stoutii and Eptatretus burgeri. Especially noteworthy is the scanty number of eggs and the small amount of sperm in all of them. A yearly synchronous reproductive cycle was only found in the Japanese hagfish E. burgeri. A certain percentage of hagfish is sexually sterile and a functional hermaphroditism in 0.1% (or even less) in E. burgeri and in E. stoutii is presumed. There is no copulatory organ in any species of hagfish and the mode of fertilization is still not clear. Investigation on the adenohypophysial region in M. glutinosa has revealed the presence of agranular cells with unclear function. Only in E. burgeri some influence of the adenohypophysis on the gonads was revealed. The GnRH-like system of myxinoids is considered as a possible homologue of the caudal neuromodula-tory GnRH system of higher vertebrates. In M. glutinosa, E. stoutii and E. burgeri indications for the production of steroids by the gonads have been brought forth.
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