ABSTRACT
Sexual reproduction is characterized by the presence of sex, gametogenesis, meiosis and fertilization of gametes arising from usually two conspecific individuals. It generates offspring with different mix of alleles than their parents. It also includes parthenogenics, in which females are always present and males do appear but sporadically by a not yet known cytological mechanism. In molluscs, parthenogenesis is limited to a few species and arises more due to parasitic elimination of males in populations. Self-fertilization is not uncommon among molluscan hermaphrodites but it includes gametegenesis and fertilizaton, of course, all within a single individual.
