Claw and Walking Leg Morphometric of the Fiddler Crab (Tubuca rhizophorae) Distributed in the Ca Mau and Bac Lieu Provinces, Vietnam

This study investigated variations in claw and walking leg morphometric characteristics of the fiddler crab (Tubuca rhizophorae) - collected from two sites (Dam Doi, Ca Mau, and Dong Hai, Bac Lieu) in the Mekong Delta, Vietnam. An average of 30 samples per month were manually collected at each site. The samples were randomly collected in different sizes. Subsequently, the samples were fixed and stored in 70% ethanol. The claw morphological parameters were measured such as propodus length (PL), manus length (M), pollex length (P), dactyl length (D), and walking leg length (L). The results did not show significant differences in these claw morphological indices between the two sampling points (Dam Doi, Ca Mau, and Dong Hai, Bac Lieu). However, there were significant variations based on sex; males had larger PL, M, P, D, and L values than females. The PL, M, P, D, and L values in male and female individuals were 5.70±0.05 (mean ± standard error of mean) and 5.07±0.06, 2.54±0.03 and 2.26±0.03, 3.16±0.03 and 2.80±0.04, 3.52±0.03 and 3.17±0.03, 14.5±0.11 and 13.2±0.12. The claw morphological ratios (M/PL, P/PL, D/PL) showed that these meristics had no variations by sampling site or sex. The principal component analysis reveals that environmental factors such as temperature, pH, and salinity (30.46°C, 7.79, and 26.02‰ in DDCM and 30.94°C, 7.74, and 32.97‰ in DHBL) contribute to the variations in some morphological traits according to sex, with temperature and salinity showing the most significant multivariate correlation based on the three principal components studied.