Internal fertilization in Lepidogalaxias salamandroides Mees (Pisces: Lepidogalaxiidae)

The gonads of Lepidogalaxias salamandroides are structurally distinctive. A duct, the surface of which is ciliated, is located on the ventral surface of each ovary and may be a modification of the ovarian tunica. The testes are small and the majority of the testicular structure functions as a sperm storage area. Secondary requisite sex characters are present in the male and the function of a modified scale sheath in copulation is unique among teleosts. Fertilization is internal and a viscous mucus mass secreted during copulation may serve as a copulatory plug. It is postulated that internal fertilization within this species has arisen as a response to sperm competition.