Study of genitalia morphometric variability of the two Species Helix aperta and Helix aspersa (gasteropoda, pulmonata)

Our research aims for, firstly, the study of genitalia morphometric variability of the two species Helix aperta and Helix aspersa, and the relation of this variability with individual’s weight and shell size. Secondly, differences in dimensions of the genital organs between the two studied species were investigated. This study showed, first, the existence of an important dimensional variability of genital organs in both studied species, then, a positive correlation between organs’ measurements and those of weight and shell. Finally, two genital organs, that are flagellum and proximal duct of bursa copulatrix, proved to be interesting to discriminate between the two species Helix aperta and Helix aspersa, because both organs are greater in Helix aspersa.Key-words: Genitalia, Helix aperta, Helix aspersa, morphometric variability, positive correlation, weight, shell size, discriminating characters

Influence of season, temperature, and photoperiod on growth of the land snail Helix aperta

Growth strategies are often plastic and influenced by environmental conditions. Terrestrial gastropods are particularly affected by seasonal and climatic variables, and growth rate and size at maturity are key traits in their life history. Therefore, we investigated juvenile growth of Helix aperta snails under four combinations of temperature and photoperiod using two sets of young snails, born in the laboratory from adults collected in either the autumn (aestivating snails) or spring (active snails). Parental snails were collected from Bakaro (Northeastern Algeria). Higher temperature increased adult size and reduced the time to first reproduction. Long day photoperiod also increased the final body weight, but had no effect on the length of the growth period. The season of birth had significant effects on length of the growth period and weight of hatchlings, whereas this weight difference disappeared by adulthood. The Spring snails took less time to develop and reached similar adult body weight as the Autumn snails. These differences may be owing to differences in egg size or quality between the snails from different seasons. More rapid growth in Spring snails results in larger snails entering aestivation, a period with size-related mortality in this species

Intra-specific morphological variation of the spermatheca in the simultaneously hermaphroditic land snail Helix aperta

In the majority of internally fertilizing animals, females are equipped with sperm storage organs where they store the sperm received during copulation. In many simultaneously hermaphroditic pulmonates, these organs consist of complex spermathecae that show inter- and intra-specific variation in their structure. This variability is theoretically predicted by postcopulatory sexual selection in the context of sperm competition and cryptic female choice. In this study, the variation in the structure of the spermatheca was investigated in the land snail Helix aperta from four natural populations near Bejaia in northern Algeria. The populations were different in local snail density, probably also reflecting the intensity of sperm competition. We tested whether the spermatheca showed differences that are predicted by sperm competition theory. In addition, we tested whether the spermathecal structure depends on the shell size and/or is correlated with other reproductive organs that are thought to be affected by sexual selection. We found that the fertilization pouch of H. aperta consists of a simple fertilization chamber and 3–9 spermathecal tubules. The four populations did not differ significantly in the mean number of these tubules. However, significant differences were found in the length of the main tubule, the length of the fertilization chamber, and the average length of lateral tubules. In addition, strong associations were detected between the lengths of these structures and the local snail density, while no effect of shell size or reproductive organs was found. Our results indicate that the intensity of sperm competition may not affect the total number of spermathecal tubules, but may increase their lengths. This increase in spermathecal length may reflect an improved sperm storage capacity that is probably beneficial in situations of high sperm competitions intensity