Some Ecological Factors Influencing Egg Hatching, Incubation Period, Food Consumption and Aestivation of Monacha cartusiana Snails Under Laboratory Conditions

Abstract

This study was conducted on the land snail Monacha cartusiana to determine the influence of four different degrees of temperature (18, 20, 22 and 24 0 C) treated with four levels of soil moisture (25,50,75 and 100% field capacity) on egg hatching and developmental period and to define the activity of snails during aestivation and food consumption under the effect of seven temperature degree ranges (5,10,15, 20, 25,30 and 35 0 C) under laboratory conditions. The present data revealed that the optimum temperature (22 0 C) for the highest percent of egg hatching was (78 and 76%) treated with 75 and 100% of soil field capacity and the shortest incubation and hatching period were 4.6 and 0.8 days at 24 0 C with 75% soil moisture and at 20 0 C with 50% soil moisture, respectively. Food intake by M. cartusiana on cabbage leaves was directly related to temperature and the land snail sizes. Feeding was maximal at 20 and 35 0 C for juveniles (8-9, 10-11mm) and at 5 and 35 0 C for all sizes of adults. All juveniles sizes showed higher food intake rate (general mean,31.14mg) than the adult sizes (general mean,30.20mg), as it increased by increasing only the shell size of all juveniles indicated by the general mean which could be arranged in an ascending order as follows, 29.03, 31.04 and 33.37 mg for the size of (8-9), (9-10) and (10-11 mm), respectively, during three days. When the aestivated snails were exposed to serial levels of temperature degrees (starting from 10 to 40 0 C,15 to 40 0 C, 20 to 40 0 C, 25 to 40 0 C and 30 to 40 0 C), were more active (19.2, 50, 17.2, and 3.6%) at temperature 25 0 C and became less active with increasing temperature (0.4, 6.4, 7.6, 5.6 and 4%) at 40 0 C. By the end of the experiment, all the aestivated snails become epiphragmed and only died when exposed suddenly to a lower temperature, while it still alive when exposed to higher temperature.