Sexual Dimorphism and Reproductive Status of the Red Swamp CrayfishProcambarus clarkii

摘要

The red swamp crayfish Procambarus clarkii is native to northeasternMexico and the south-central USA, and it has expanded its distribution worldwide andnegatively impacted the ecosystems in the invaded regions. The dynamics of the P.clarkii populations have been studied as the basis for the development ofeffective control measures against this invasive alien species. Adult males of P.clarkii exhibit a cyclical dimorphism between two sexual morphotypes;reproductive form I has large chelae and non-reproductive form II has small chelae.However, whether P. clarkii females have two sexual morphotypes andexhibit form alternation has not been resolved, and little is known about the degree ofintra-sexual dimorphism of the chelae, even among males. We employed allometric growthanalysis on the chelae dimensions of P. clarkii females and males thatwere collected from a small pond in Yokohama, Japan. Our analysis demonstrated theexistence of form I, which has larger chelae, and form II, which has smaller chelae, inP. clarkii females and highlighted the intra- and inter-sexualdimorphisms in the chelae of this species. The reproductive cycle of the population wassuccessfully traced by the reproductive status of P. clarkii based on theoccurrence patterns of each sexual morphotype; the form I crayfish occurred throughout thesampling period from April to December, while the occurrences of form I females and maleswere highly correlated, peaking in October. Our results suggested that alternation ofsexual forms occurs in P. clarkii females. The ability to discriminatebetween the sexual morphotypes based on chelae allometric growth would allow us toevaluate the female reproductive status more easily and precisely in invasive P.clarkii populations.