Inter-populational variations in body color related to growth stage and sex in Gaetice depressus (De Haan, 1835) (Decapoda, Brachyura, Varunidae)

Abstract

The relative frequencies of color morphs in two populations of Gaetice depressus (De Haan, 1835) differed between size classes and sexes, the proportion of dark-colored crabs being greater in a habitat of dark colored cobbles, less where cobbles were light, indicating a conformance of G. depressus carapace color with background color. This difference between the two populations was apparent from the onset of the benthic stage. Field experiments demonstrated that a change in color proportion was greater on a dark-colored background compared to a light-colored background. However, a tethering experiment revealed no difference in the survival rate of young crabs of either color on either site, indicating that while body color difference between populations is attributable to the color pattern at settlement, the darkening of individual crabs on a dark-colored background was not due to different survival rates for individuals of different color patterns. As with carapace color in relation to body size, the proportion of dark-colored crabs was found to increase with increasing body size. Field and laboratory experiments demonstrated that light-colored crabs became darker with time, whereas dark-colored crabs exhibited little temporal change in body color. The proportion of dark-colored crabs was higher in females than in males, temporal color changes observed in the field also demonstrating that females became darker compared to males, irrespective of background color.