BIOMETRICAL AND HISTOLOGICAL ASPECTS OF THE REPRODUCTIVE CYCLE OF THE OVARIES OF ASTERIAS RUBENS (ECHINODERMATA)

¹ Laboratory of Chemical Animal Physiology and Section Comparative Endocrinology of the Zoological Laboratory, State University of Utrecht, The Netherlands

The reproductive cycle of the ovaries of the starfish Asterias rubens has been studied by histological and biometrical methods and can be divided into 4 stages, based on semi-quantitative and biometrical data. On the basis of biometrical data and their statistical analyses, each stage can be subdivided into two substages.

Frequency distributions of oocyte diameters present a characteristic for each (sub)stage. McCall units were calculated from the frequency distribution of oocyte diameters of stage 3. This stage is the reference for each other stage or substage and can be used as reference for any other group of animals of the species under examination. McCall transformations allow for the comparison of frequency distributions. It is concluded that the oocyte diameter is a reliable parameter for delineating the reproductive cycle and oogenesis of Asterias rubens, but a detailed description of the annual reproductive cycle required the analysis of a complex of variables, including the correlations among them.

From the stages' frequency distributions, the theoretical and proportional duration of each stage and of the period of spawning was derived. Minor, not significant variations have been found from year to year in the duration of the stages and in the beginning and conclusion of each period.