L'escargot ou les difficultés de l'hermaphrodisme

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Abstract
The article summarizes the research carried out in Besançon on the stylommatophoran snail Helix aspersa, a pulmonate gastropod mollusc. The influence that external factors like photoperiod and temperature have on growth and reproduction was studied in this animal. The obtained results made possible a great development of snail breeding. The potentialities of the hermaphroditism emerge from the observations made on the ovotestis: differentiation and development of the different cell types, presence of fibronectin, richness in neuropeptides, existence of male and female steroids, vitellogenesis processes. In vivo experiments as well as in vitro cultures demonstrated the involvement of the cerebral complex in the control of reproduction. The dorsal bodies (DB)—(it consists of scattered cells)—stimulate the growth of the oocytes. The DB are under an inhibitory nervous control of the cerebral green cells (CGC); the FMRF-amide might be involved in this process. A map of the neurons of the cerebral complex has been prepared. It shows the presence and the diversity of neuropeptides. Attention was focused on met-enkephalin and somatostatin. This later peptide seems to be involved in the shell growth. The active molecule, which was isolated from hemolymph and digestive gland is structurally quite similar to vertebrate somatostatin. The results are compared with those obtained in other molluscs, especially in basommatophora. They reveal that the biological phenomena observed in the snail model are included in the fundamental processes, known in other invertebrates or vertebrates.

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