Partial characterization of the secretory material from the dorsal bodies in the snail Helisoma duryi (Mollusca: Pulmonata), and its effects on reproduction

Both dorsal body tissue extracts and dorsal body-conditioned medium stimulated in vitro polysaccharide synthesis in albumen gland explants in Helisoma duryi. This activity is heat- and protease-resistant. Dorsal body tissue extracts and dorsal body-conditioned medium were passed through solid-phase extraction cartridges, then eluted with increasing concentrations of methanol (20%, 70%, and 100%) and the various eluates tested for their biological activity. An active factor was found in the 100% methanol wash from both dorsal body tissue extracts and the conditioned medium. In addition, another bioactive factor in the conditioned medium eluted with 70% methanol. The endocrine dorsal bodies in the freshwater snail H. duryi were maintained in vitro, and following incubation, the culture medium was collected and tested for the presence of ecdysteroids. Radioimmunoassay of the culture medium demonstrated the presence of ecdysteroid-like immunoreactivity, suggesting the dorsal bodies are capable of secreting ecdysteroids in vitro. Identification of released ecdysteroids by HPLC/RIA revealed a number of immunoreactive fractions, which were tested for bioactivity. To test for possible physiological functions of ecdysteroids in Helisoma duryi, 20-hydroxyecdysone (a potent ecdysteroid in arthropods) was injected into non-egg laying (virgin) snails. Injections of ecdysteroid induced low egg-laying activity and the maturation of oocytes in the ovotestis. Incubation of albumen glands with ecdysteroid stimulated polysaccharide synthesis. The results are discussed in relation to the possible function(s) of ecdysteroids in pulmonate snails.