Study of asymmetrical meristic characters of head in Caucasian pit viper, Gloydius halys caucasicus of Golestan and Mazandaran Provinces

Bilateral symmetry is one of the characters of many metazoans. This feature is sometimes was not seen for a number of characters in animals such as reptiles. Asymmetry is both in internal and external characters. Evaluation of head scales in Caucasian pit viper Gloydius halys caucasicus (Viperidae: Crotalinae) was studied. This venomous snake is distributed in sea shore areas and between the Elburz Mountains and the Caspian Sea. For this purpose it was studied 12 meristic characters in 54 specimens of Caucasian pit viper (20 males, 21 females, 11 juveniles and 2 unknown) from Golestan and Mazandaran provinces. Scale counting was done under stereomicroscope by niddle. The results showed that Temp (21 specimens), CG (17 specimens), supralabials (16 specimens), infralabials (13 specimens), A.ch.ifl (12 specimens), Po.ch.a (2 specimens), Po.ch.b (3 specimens), Loreals (3 specimens), Circumocular scales (2 specimens) and Preocular scales (2 specimens) were asymmetrical in right and left sides. The results shows that must be note both sides of head region of snakes in scale counting because of symmetry or asymmetry.