Comparative Study on Morphometric of Two Small Portunid Crabs, Charybdis affinis Dana, 1852 and C. anisodon (De Haan, 1850) Collected from Trawling Boat at Ang Sila fishing Port, Chonburi Province

Abstract

Small portunid crabs are small crabs belong to one genus of family Portunidae.   These small crabs are important economic crabs in Chonburi province.  This study aimed to compare morphometric of two small portunid crabs collected from trawling boat at Ang-Sila fishing port, Chonburi province.  From the study, the sex ratio between male and female of Charybdis affinis Dana, 1852 was 1.28:1.00.  The average carapace width and carapace length of male C.affinis were 44.51 ± 3.92 and 29.09 ± 2.60 mm (n = 64) respectively.  The average carapace width and carapace length of female crabs were 42.04 ± 4.10 and 26.63 ± 2.46 mm. respectively (n = 50).  For C. anisodon (De Haan, 1850), the sex ratio between male and female crabs was 1.71:100.  The average carapace width and carapace length of male C.anisodon were 43.10 ± 4.97 and 25.10 ± 3.08 mm. respectively  (n = 41).  The average carapace width and carapace length of female C. anisodon were 40.40 ± 4.22 and 23.63 ± 2.56 mm. respectively (n = 24).   The relationship of width-length of the carapace is a linear regression whereas the relationship of width-weight of carapace is an exponential equation.  There was a difference in the ratio of carapace width and carapace length between the two portunid crabs. The ratio of carapace width and carapace length were 1.53:100 and1.58:1.00 in male and female crabs of C. affinis, respectively.  Whereas the ratio of carapace width and carapace length were 1.72:1.00 and 1.64:1.00 in male and female crabs of C. anisodon, respectively. Keywords: morphology, Charybdis affinis, Charybdis anisodon, Ang Sila, Chonburi