Répercussion de la durée d'éclairement journalier sur l'évolution des cellules nourricières et de la lignée mâle dans l'ovotestis d'Helix aspersa

Abstract

Summary. The effect of lighting duration on the evolution of nurse cells and male line in the Helix aspersa ovotestis.Adult snails (Helix aspersa) were bred under two photoperiods i.e. long-day : 18 h (JL), short-day : 8 h (JC) immediately after a 4 month hibernation. In these conditions only the long-day snails began to lay eggs from the 10th week of experiment, whereas the others did not.To explain these differences, the structure and functioning of the hermaphroditic glands were investigated in both groups, 6 and 10 weeks later, using electron microscopic and quantitative biochemical methods.At 6 weeks, compared to short-day cycles (JC1, long-days (JL) highly increased spermatogonial multiplication measured by 3 H thymidine incorporation and on the other hand shortened the duration of spermatogenesis. Ultrastructural observations showed that modifications of the nurse cells were strongly correlated with the evolution of the male line.At 10 weeks, the rates of spermatogonial multiplication were rather similar in all snails.In spite of the absence of anomalies in the male cells, no reproduction occurred among the short-day animals ; this is probably due to a low concentration of sperm, suggesting an insufficient stimulation by the neuroendocrine controlling centers.Introduction.

Influence of photoperiod on differentiation of male cells in Helix aspersa. An autoradiographic study

“…In contrast, within 39 days, labeled spermatids and spermatozoa were still absent in short-day animals. Thus, it is evident that the delay observed in the spermatogenic process of pulmonates maintained under short-day is not only due to less spermatogonial proliferation, as reported previously (Sokolove et a/., 1983; Gomot and Griffond, 1987), but also to a lengthening of the late spermatogenesis affecting the second meiotic division. Indeed, there does not appear to be a blockade at this level of spermatogenesis similar to that occurring at low temperatures (Gomot et al, 1986), since spermatozoa are formed some weeks later (Gomot and Griffond, 1987).…”

“…Thus, it is evident that the delay observed in the spermatogenic process of pulmonates maintained under short-day is not only due to less spermatogonial proliferation, as reported previously (Sokolove et a/., 1983; Gomot and Griffond, 1987), but also to a lengthening of the late spermatogenesis affecting the second meiotic division. Indeed, there does not appear to be a blockade at this level of spermatogenesis similar to that occurring at low temperatures (Gomot et al, 1986), since spermatozoa are formed some weeks later (Gomot and Griffond, 1987). However, our observations and previous data (Gomot et al, 1986) do suggest that, in the course of spermatogenesis, the step from secondary spermatocyte to spermatid is the most sensitive to environmental factors.…”

“…Long-day snails ( (Enee et al, 1982 ;Laurent et al, 1984 ;Gomot and Gomot, 1985), affecting both ovopository activity (Bohlken and Joosse, 1982 ;Enee et al, 1982;Joosse, 1984;Bohlken et al, 1986) and spermatogenesis (Henderson and Pelluet, 1960 ;Sokolove and McCrone, 1978 ; McCrone and Sokolove, 1979Sokolove, , 1986McCrone etal., 1981 ;Melrose etal., 1983 ;Sokolove et al, 1983Sokolove et al, , 1984Gomot and Gomot, 1985 ;Gomot and Griffond, 1987). However, in Cepaea nemoralis neither gametogenesis nor reproductive capacity appears to be influenced by photoperiod (Hunter and Stone, 1986).…”

“…Lengthy photophases have been demonstrated to favor the development of male gametogenesis in the slugs, Deroceras reticulatum (Henderson and Pelluet, 1960) and Limax maximus (Sokolove and McCrone, 1978; Sokolove, 1979), as well as in the snail, Helix aspersa (Gomot and Gomot, 1985;Gomot and Griffond, 1987 Radioactive labeling. -Twenty-four hours later, all the snails were injected in the general body cavity with 0.2 ml of tritiated thymidine (= 5 pCi/g wet weight).…”

“…While in long-day snails labeled spermatozoa were identifiable 28 days after ( 3 H)-thymidine injection, in short-day snails neither labeled spermatozoa nor spermatids were present in the gonads of animals killed as late as 39 days post-injection. These data strongly suggest that the photoperiod, besides acting on spermatogonial proliferation (Sokolove etal., 1983 ;Gomot and Griffond, 1987), has an important effect on the second meiotic division. In the course of spermatogenesis in Helix aspersa, the step from secondary spermatocyte to spermatid is probably the most sensitive to environmental factors.…”