Analysis of morphometry and dimorphism in Enhydrus sulcatus (Wiedeman, 1821) (Coleoptera: Gyrinidae)

Thiago Marinho Alvarenga, Fernanda Fonseca e Silva, Marconi Souza Silva

Abstract


Enhydrus sulcatus (Wiedeman, 1821) (Coleoptera: Gyrinidae) were found swimming in circles on the surface of streams shaded by forests in preserved sites. The sexual dimorphism was evaluated in that species through the quantification of differences occurring among the length of the first pair of legs, width of the mesonotum, total lengthand body mass of 112 individuals, 71 being females and 41 males. There was significant difference among the width of the mesonotum (KW-H(1.112) = 32.80; p < 0.05), total length (KW-H (1.112) = 38.00; p < 0.05), length of the first leg (KW-H(1.112) = 47.58; p <0.05) and body weight (KW-H (1.82) = 23.86; p < 0.05) of male and female E. sulcatus.The length of the first leg relates positively and significantly with the width of the mesonotum (r2 = 0.40; p < 0.05), with the total weight (r2 = 0.36; p < 0.05) and with the total body length of individuals E. sulcatus (r2 = 0.33; p < 0.05). The total length of individuals of E.sulcatus relates positively and significantly with width of the mesonotum (r2 = 0.65; p <0.05). In this study a clear sexual dimorphism was shown in Enhydrus sulcatus and was present in various other body structures besides the tarsal dilations.

Key words: sexual dimorphism, Gyrinidae, Enhydrus sulcatus, measured morphometrics.


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