aestivation; epiphragm; shell aperture;
pp. 165 -

Aestivation is the state of dormancy that occurs in snails when the weather condition is harsh, either dry season or warm season. During this period, the giant African land snails form epiphragm, sealing the aperture of the shell which serves as water preservative strategies, preventing mechanical damage of the inner soft tissues. A study on the formation and mineral composition of the epiphragm in three species of giant African land snails namely: Achatina achatina, Achatina fulica and Archachatina marginata was carried out. Twenty matured snails were used for this experiment. They were induced into aestivation by withdrawing food and water. The snail weight, shell length, aperture length, and epiphragm weight were measured during aestivation as well as duration of epiphragm formation. The ionic concentration (calcium, iron and phosphorus) of the epiphragm was also analyzed. The morphometric analysis showed that A. marginata formed the heaviest epiphragm while the least was formed by A. fulica during aestivation. Analysis of the ions revealed that calcium was the most abundant ion in the epiphragm of the snails. Comparison of mean values reveals that A. achatina has the highest ionic composition in the epiphragm when compared to other species. Regression analysis (r2) revealed that a positive relationship existed between the aperture length and days for epiphragm formation (+0.62) on one hand and between weight of epiphragm formed and the days of its formation on the other hand (+0.77).

Формирование и состав эпифрагмы у трёх гигантских африканских улиток (Archachatina marginata, Achatina fulica и Achatina achatina)