ABSTRACT
In echinoderms, sexuality includes gonochorism, parthenogenesis, protandric and protogynic sequential hermaphroditism, which implies the presence and operation of diverse mechanisms of sex determination. The single sex determination mechanism may be in operation in a vast majority of echinoderms. Sex ratios represent the cumulative end product of sex determination and differentiation processes. Despite the availability of actively regenerating tissues/organs, echinoderm cytologists have usually selected the early embryos for karyotyping. Chromosomes of echinoderms are relatively short and tightly clustered. The identified differences in chromosome size may have to be designated as heteromorphism rather than heterogamety. Searches for heterogametic chromosomes in ophiuroids Ophiodaphne formatum, O. scripta, Ophiosphaera insignis and Astroclamys bruneus may prove rewarding, as the 'mini-males' are reported to cling to the female. The polar body is released after the completion of fertilization process. Hence, the eggs are readily amenable to ploidy induction using a shock to retain the body to produce triploid in fishes.
