The occurrence of cyclic morphological alternation in male crayfish of the family Cambaridae following molting is widely acknowledged. However, there remains a contentious issue within the genus Cambaroides: Some previous studies have proposed that male Cambaroides exhibit a pair of non-corneous Form II gonopods during the non-breeding season, while others argue that these species lack Form II in adult males. This study examined the color and shape of the corneous tips on the gonopod to determine its form. Additionally, morphometric methods were utilized to distinguish between Form II adults and juveniles. The results of the study confirm the presence of Form II adults in Cambaroides dauricus and Cambaroides similis. The Form I gonopod is characterized by four golden-colored corneous terminal elements, whereas the Form II gonopod features blunt, non-corneous terminal elements, on which the color is the same as that of the surrounding surface. Furthermore, cyclic dimorphism on the gonopod of C. dauricus was observed seasonally, and distinct morphological differences in the chela were noted between Form I and Form II adults.
Cyclic dimorphism, Cornification, Life history, East Asian freshwater crayfish, Juvenile, Adult
