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 stimula ted in vitro polysaccharide synthesis in albumen gland explants in Helisoma duryi. This activity is heat- and protease-resistant. Dorsal body tissue e xtracts and dorsal body-conditioned medium were passed through solid-phase extraction cartridges, then eluted with increasing concentrations of methan ol (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 d orsal body tissue extracts and the conditioned medium. In addition, another bioactive factor in the conditioned medium eluted with 70% methanol. The e ndocrine dorsal bodies in the freshwater snail H. duryi were maintained in vitro, and following incubation, the culture medium was collected and teste d 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. Identific ation of released ecdysteroids by HPLC/RIA revealed a number of immunoreact ive fractions, which were tested for bioactivity. To test for possible phys iological functions of ecdysteroids in Helisoma duryi, 20-hydroxyecdysone ( a potent ecdysteroid in arthropods) was injected into non-egg laying (virgi n) snails. Injections of ecdysteroid induced low egg-laying activity and th e 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 snail s.