I S S N 2 3 47-6 8 9 3 Volume 11 Number1 Journal of Advances in Biology 2155 | Page January 2018 https://cirworld.com/ Testosterone Level, Testicular Histology And Reproductive Events Of Caucasian Pit Viper, Gloydius Halys Caucasicus (Serpentes: Viperidae) Arefeh Salehi 1 , Fatemeh Todehdehghan* 2 Delaram EslimiEsfahani 3 , 1.Animal Science Dept., Faculty of Biological Sciences, University of Kharazmi, Tehran, Iran code 15719, Email: Arefeh Salehi <arefehsalehi92@gmail.com 2*. Venomous Animals and Antivenin production Dept., Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran. Email:f.todehdehghan@rvsri.ac.ir, Corresponding author: Phon: 09125604072 3. Faculty of Biological Sciences, Kharazmi (Tarbiat Moalem) University, Tehran, Iran. Email: eslimi@khu.ac.ir ABSTRACT The steroid hormones regulate the reproductive physiology of animals and may influence by habitat and seasonal conditions. In this study, body weight and length, testosterone concentration and testicular histology were measured in Caucasian pit viper from Lar region, Tehran province, during summer and autumn seasons in year 2014. Serum samples were collected from 24 anesthetized snakes and testicles were removed and fixed for histological study. Enzyme immunoassay (ELISA) was conducted on serum samples to determine concentrations of testosterone (T) and standard histological procedure was performed on gonads. Results indicated that body weights and lengths in summer and fall seasons were respectively 49.88±9.6 gr, 50.25±7.4 cm and 42.75±4.5gr, 43.25±2.3 cm, serum testosterone level in summer, 29.3± 5.12 ng/ml was more than fall, 13.75±2.80 ng/ml at P≤0.05.The numbers of spermatogonias, spermatocytes and spermatids in summer were more than fall and statistically different at P≤0.05. The leydig cells number and diameter in fall were more than summer but differences were not significant.There were significant differences between seminiferous tubules diameter, germinal epithelial height and tunica albuginea thickness in summer as compared to fall at P≤0.05. The data suggest male Caucasian pit-viper of Lar region of Tehran displaying estival spermatogenesis and some relationship was revealed between T level and snake's body weight, and high level of T coincide with the mating period. KEYWORDS: Testosterone, Testis histology, Snake, Body weight, Reproduction event 1. INTRODUCTION The timing of reproductive events and testicular functions of animals regulated by endogenous factors, seasonal variations and (Jallageas et al., 1978; Maurel and Boissin, 1981; Saboureau and Boissin, 1978) and varying in different species.There are correlation between reproductive activities ie. spermatogenesis, vitellogenesis, mating, breeding season and gonadal cycle and hormonal concentration. These interrelations are little known for snakes.Reports show reproduction, in the European Viperidaeis mainly in spring, follows a period of hibernation of varying length according to the species and their geographical distribution (Prestt, 1971; Niison, 1980).The timing of the sexual cycle is partially dependent on annual period of inactivity.The V. aspis has two mating periods in flat country, but only one in mountains where hibernation is longer. North American pitvipers have been characterizedas exhibiting two major types of mating seasons, with courtship,copulation, and male–male combat restricted to either: (i) latesummer/fall, or (ii) late summer/fall and spring (Schuett, 1992;Aldridge and Duvall, 2002; Schuett et al., 2002, 2006). A mating season restricted to spring is reported in the taxon, Crotalus ruber (Aldridge and Duvall, 2002). Theannual cycle of plasma testosterone of North American pit-vipers exhibits either a unimodal or bimodal patterns, and is associated with and considered a robust predictor of the mating season (Aldridge and Duvall, 2002; Schuett et al., 2002, 2005).These unimodal and bimodal patterns of sex steroidsecretion, secondary sex characteristics (e.g., the kidney sexual segment, SSK), and reproductive behavior,persist despite a conserved sequence of spermatogenesis, whichpeaks during the late summer/fall in all North American pit-vipers(the aestival, or Type I pattern; Saint Girons, 1982; Schuett, 1992; Aldridge and Duvall, 2002).Although the mating patterns of pit vipers are complex andmay vary within family,genus, and even species (Aldridge and Duvall, 2002). In many studies the gonadal cycles have still been used to describe the mating systems of many pit viper species (Agkistrodon piscivorus: Johnson et al., 1982; C. atrox: Tinkle, 1962; C. helleri: Aldridge, 2002; C. horridus: Gibbons, 1972: C. lepidus: Goldberg, 2000a; C. mitchellii: Goldberg, 2000b; Crotalus molossus: Goldberg, 1999a; C. oreganus: Aldridge, 2002; C. ruber: Goldberg, 1999b; C. scutulatus: Goldberg and Rosen, 2000; C. viridis: Aldridge, 1979; C.willardi: Holycross and Goldberg, 2001). Although four types of male reproduction in snakes is defined by Saint Girons (1982), the distinctly seasonal (displaying estival spermatogenesis) to aseasonal (displaying continuous spermatogenesis), and exceptions certainly exist. Snakes display considerable variability in reproductive traits among species ( Hartmann ,et al., 2004) exhibiting a wide range of mating systems and male and male reproductive behaviors (Tourmente, et al., 2009).Anatomical and physiological indicators of the mating season in male pit- vipers have been identified, as patterns of annual testosterone (T) and kidney sexual segment (SSK) hypertrophy (Aldridge and Duvall, 2002; Schuett et al., 2002, 2005).In the Trapelus lessonae from the Western plateau of Iran, Central Zagros, three spermatogenesis phases are reported;active phase, in months where spermatogenesis occurs and primary and secondary spermatocytes and also spermatozoa can be seen in luminal seminiferous or lumen epididymis, the resting phase, in which, spermatocytes and