Body growth pattern of an isolated land crab species (Johngarthia planata) (Decapoda, Gercarcinidae) from the eastern tropical Pacific: an ecological approach

This study examines the sexual differences in relative growth and morphometrical traits of the land crab Johngarthia planata (Stimpson, 1860). Individuals came from Clipperton, where an expedition was conducted in April 2015. A total of 275 individuals were captured manually, sexed and measured in seven dimensions from the carapace and chelae. Measurements were fitted to a power function to analyse the degree of allometry in growth. Results indicated that males had larger body and chelae sizes than females. For both sexes growth was negatively allometric for the carapace and positively allometric for the chelae. We hypothesize that stronger bodies in males confer advantages during intraspecific combats and their enlarged chelae are associated to their sexual behaviour. For each sex, measurements of both right and left chelae showed a homochelic condition. We suggest that these symmetrical features provide stability and balance to their body when feeding, fighting or excavating their burrows.