Gastropod shells can be a limiting factor in allowing hermit crab populations to
increase. The impact of this factor on population size of the land crab Coenobita scaevola
(Forskäl, 1775) was examined. Extensive and intensive works were conducted on a sandy
beach of Wadi El-Gemal island and the protected area coast (35°04'0"E, 24°42'0"N).
Activity, spatial and temporal distribution, food foraging, and impact of human tourism
activities for this hermit crab were discussed. A total of 365 crab individuals were collected
from the sandy beach of Wadi El-Gemal island during August 2007 to July 2008, among
these 137 were used for frequency measurements of occupied shells by the land hermit crabs.
The hermit crabs were found occupying seventeen species of gastropod shells. A significant
regression and correlation were recorded between the shell aperture and chelae. However, our
data showing no significant regression values between total body weight of crabs and for
each of the shell weight and internal volume. From the other angle, the correlation
relationship recorded high significant value for the same relationships. This may reflect that
some smaller crabs tend to occupy larger shells than the preferred ones. Moreover, the shell
species occupation as a function of chelar hermit crabs size. While the negative results
between body weight of crab and both shell internal volume and weight it may be due to the
variations behavior of some land hermit crab individuals within population. It is logical that
fit the size of chelae with aperture of shell to achieve protection from predators while some
members of the population that occupied shell is greater than the size of his body to the
unavailability of appropriate shells.