Comments on the Reproductive Mode of the False Cat Shark Pseudotriakis microdon

Abstract

Fifteen specimens of the false cat shark, Pseudotriakis microdon, were collected at depths between 530-990 m around the Okinawa Islands, Japan, and from the Three Kings Ridge off New Zealand. Reproductive systems of immature and mature males and females are described. Three gravid females were captured each with two embryos. The ratio of embryonic males to females was 1:1. The ovary contained numerous ova 2-10 mm in diameter. Yolk material was observed in the uteri and weighed 730-1010 g. The stomachs of two embryos contained yolk material and egg capsules indicating oophagous behavior. Embryos appear to transfer yolk from ingested egg fragments to the external yolk sac for storage. The mode of embryonic nutrition of the false cat shark appears to differ from previously described modes in elasmobranchs and appears to represent a modified form of oophagy in which the yolk reserves of the external yolk sac are replenished and used subsequently in the last stages of gestation. This is the first fully documented report of oophagy in a nonlamniform shark.