Staging and the time course of embryonic development in kurosoi,Sebastes schlegeli

Synopsis

Intraovarian development of embryos was observed in 31 female rockfish kurosoi,Sebastes schlegeli, which had been raised in the laboratory. Three of the females had newly fertilized eggs; the others' embryos were at various stages. The developmental series (33 stages) was not very different from that in oviparous fishes. However, several characteristic features were noted: thin egg envelope, narrow perivitelline space, elliptical encapsulated embryo in the late stages and depletion of yolk at parturition. The time course of development up to birth at different temperatures was adjusted to that at 9.8°C using the Arrhenius equation and processed for the relationship between the stage number (X) and stage-to-birth time in days (Y). An equation,$Y = - 0.001425 X^3 + 48.0028,$ was obtained, and the gestation period was calculated to be 48 days at 9.8°C.