Characteristics of aggressive behaviors of five species of the genus Ilyoplax (Brachyura, Dotillidae) in East Asia

Abstract

Aggressive behaviors are described for five species of the genus Ilyoplax (Dotillidae), I. pusilla (De Haan, 1835), I. formosensis (Rathbun, 1921), I. ningpoen-sis Shen, 1940, I. deschampsi (Rathbun, 1913), and I. tansuiensis Sakai, 1939, and the male/female ratios are compared relative to the sex ratio of the population. Aggressive behaviors were similar in all species. The main types of aggressive behaviors, includ-ing aggressive dash, aggressive wave, and wrestling, were common to the five spe-cies. The mutual aggression of wrestling was confined to male crabs in all five spe-cies. The frequencies of aggressive behaviors were higher in male crabs than in female crabs, suggesting male-biased aggressiveness. This may be reflected in the male-biased carapace and chela size dimorphisms observed in I. pusilla.