ABSTRACT
This chapter presents information on genes encoding vertebrate-type steroid hormone receptors in mollusks. It discusses the molluscan tissues of steroid-producing cells, enzymes to synthesize or metabolize steroids, and functional receptors for steroids. The aromatase-like activity has been measured and reported in several gastropod species. However, this activity does not necessarily confirm the existence of vertebrate-type aromatase in gastropods. The physiological regulatory system of reproduction appears to differ between gastropod mollusks and vertebrates. Morphogenetic factors might be involved in the formation of the curved penis and vas deferens. In addition, other factors, such as various neuropeptides induced in the head ganglia due to exposure to organotins, might be associated with the retinoid X receptor (RXR) gene-mediated development of imposex, if these factors are induced downstream of the RXR cascade.
