The different morphotypes in males of the freshwater prawn Macrobrachium tenellum ( Smith, 1871) (Decapoda: Caridea: Palaemonidae) in Mexico

We analyzed the occurrence of morphotypes in the males of Macrobrachium tenellum (Smith, 1871), a species of potential use in farming, using biometric data and multivariate statistical analysis. Specimens were collected in the Ameca River, Mexico and grown for four months in two rectangular concrete ponds 50 m(2) at an initial density of 10 individuals m(-2). A biometric analysis was done on all male specimens, identified by the presence of the appendix masculina on the second pair of pleopods. We measured eight dimensions in each of the measured male specimens. Color and spination of the right second cheliped were also determined. We performed a statistical analysis of the data using multivariate analysis, which resulted in the identification of five morphotypes: dark-brown claw (DBrC), brown claw (BrC), cinnamon claw (CC), translucent claw (TC), and small male (SM). The mean of groups of almost all variables showed statistically significant differences except for the ratio Lcl:Lpo. There was no significant difference between groups BrC and DBrC, and spine angles were not significant between groups CC versus TC and BrC. A detailed description of the main macroscopic characteristics that differed between morphotypes is provided, which will allow their identification in future work. Our results will also help in studying social interactions between the male morphotypes.