Morphology of a Novel Reproductive Strategy in the Pelvic-Brooding Ricefish Oryzias eversi Herder et al. 2012...

We examined reproductive features of a pelvic brooder, the oviparous teleost Oryzias eversi. Eggs possess two types of filaments that form on the surface of the chorion during oogenesis: long attachment filaments at a restricted area around the vegetal pole, and sparse, short filaments around the animal pole (micropyle). Females spawned eggs through the genital pore when mating with the male. After spawning, females carried a cluster of fertilized eggs suspended from the genital pore by a bundle of long attachment filaments. Fertilized eggs were protected by the pair of long pelvic fins and held in an abdominal concavity posterior to those fins until hatching, about 12 days post-oviposition. During the period that females carried the fertilized egg cluster, the growth of oocytes slowed, and ovulation of a new batch of eggs did not occur. Thus, reproductive cycles in the female of O. eversi appear to depend upon the presence of hanging embryos.