SPERMATOGENESIS IS EXTRAORDINARILY ACCELERATED IN METAMORPHOSIS-ARRESTED LARVAE OF A SALAMANDER, HYNOBIUS-RETARDATUS

Laboratory experiments were conducted to induce neoteny in Hynobius re tardatus, which had been reported to propagate in larval forms like ax olotl. A large number of newly hatched larvae were reared in an aqueou s solution of thiourea (TU) and sodium perchlorate (SPC) in order to a rrest the metamorphosis. Gonadal development in the metamophosis-arres ted larvae was compared with that in normally metamorphosing and metam orphosed controls. Metamorphosis-arrested male larvae produced morphol ogically mature spermatozoa approximately 4 months after hatching, whe n the gonads in the controls began to differentiate into testes, or to show the premeiotic proliferation of germ cells. Possible endocrine c ontrols of these phenomena are discussed.