Respiratory Adaptations of Prenatal Young in the Ovary of two Species of Viviparous Seaperch, Rhacochilus vacca and Embiotoca lateralis

The structure of the ovary and embryos of embiotocids is reviewed in relation to those factors that would affect the exchange of materials between ovarian and embryonic blood streams. Weight, exchange surface areas (particularly of the fins), diffusion distances, and capillary densities were measured for prenatal young and ovaries of two species of Embiotocidae, Rhacochilus vacca and Embiotoca lateralis, during middle and late gestation. Brood size and ovarian fluid volume were also measured. Changes in brood weight and ovarian fluid volumes were interpreted in relation to the load imposed on the ovary by the young. This was expressed as the brood/ovary weight ratio which was found to increase during gestation to a maximum value of eight. Changes in exchange surface areas and diffusion distances of the young and the ovary were determined and evaluated in relation to the metabolic requirements of the brood. Convection of the ovarian fluid must occur as a necessary mechanism for efficient exchange of materi...