South American Journal of Herpetology, 1(2), 2006, 143-148 © 2006 Brazilian Society of Herpetology SEASONAL CHANGES IN TESTICULAR ACTIVITY OF THE PROTECTED CITES I BOA CONSTRICTOR OCCIDENTALIS (SERPENTES: BOIDAE): AN HISTOLOGICAL STUDY NORA R. IBARGÜENGOYTÍA 1,3 , M. BERTONA 2 AND M. CHIARAVIGLIO 2 1 Departmento de Zoología, Centro Regional Universitario Bariloche. Universidad Nacional del Comahue. Unidad Postal Universidad del Comahue, Bariloche, 8400, Río Negro, Argentina. Consejo Nacional de Investigaciones científicas y técnicas. (CONICET). Tel. 54-2944-524021/423374. Fax: 54-2944-422111. E-Mail: norai@bariloche.com.ar 2 Departamento de Diversidad Animal y Ecología; Facultad de Ciencias Exactas, Físicas y Naturales; Universidad Nacional de Córdoba; Vélez Sársfield 299; Córdoba 5000; Argentina. E-Mail: mchiara@eco.unc.edu.ar 3 Corresponding author. ABSTRACT: The general features of testes change with reproductive maturity and in many species of reptiles show a seasonal pattern reflected in macroscopic and microscopic gonadal changes. In previous studies the sexual maturity and reproductive cycle of Boa constrictor occidentalis (Boidae, Appendix I of CITES, 1997) have been determined by testes and epididymis macroscopic differences using ultrasound scanning on live individuals. In this study, the gametogenic activity is studied histologically and the correspondence with previous studies analysed. Our results corroborate the age classification based on morphological features and support the reproductive cycle described for B. c. occidentalis based on live individuals. KEY WORDS: Reproduction, Boidae, Boa constrictor occidentalis INTRODUCTION In snakes, testes are paired enlarged organs com- posed by convoluted seminiferous tubules surrounded by fibrous connective tissue, which constitutes the al- buginea tunic (Fox, 1976). In relation to the histologi- cal architecture of the seminiferous elements, the germ epithelium is arranged in seminiferous tubules inter- spersed with interstitial cells, blood and lymphatic ves- sels. Each seminiferous tubule includes an outer base- ment membrane, Sertoli cells, and a syncitium of ger- minal elements (Fox, 1976). The germ tissue has dif- ferent cellular types: spermatogonia in the epithelium boundary, spermatocytes and spermatids in the se- quence of the cellular differentiation, and spermatozoa in the lumen. In this epithelium, sexual cells are associ- ated with the Sertoli cells forming the tubules (Patt and Patt, 1969, Guibé, 1970). The histological analysis of the gametogenic activity provides a more accurate determination of adulthood and may be used to con- firm or reject macroscopic observations and gonado- somatic indices (Hernandez-Gallegos et al., 2002). In this study the testicular dynamic of the Argentine boa constrictor (Boa constrictor occidentalis) is analy- sed histologically. This boid is a large (up to 4 m), heavy-bodied, vi- viparous, constricting snake. It is one of the four spe- cies of the family Boidae found in the subtropical re- gion of western and mid-western of Argentina (Cei, 1993). The Argentine territory has the world’s largest and southernmost population of the Argentine boa con- strictor. This subspecies is found in the semiarid plains of the phytogeographic provinces of Monte, Espinal, and Chaco, Argentina (Di Fonzo de Ábalos and Buch- er, 1981, 1983). In the province of Córdoba, it is dis- tributed to the north and west (Di Fonzo de Ábalos and Bucher, 1981; 1983, Chiaraviglio et al., 1998). An- nual average temperatures range from 18 to 23°C and rainfall from 300 to 550 mm with distinct wet (Octo- ber to March) and dry (April to September) seasons (Capitanelli, 1979). The Argentine boa constrictor shows morpholog- ical differences in testes and epididymis used to de- termine sexual maturity and reproductive activity (Chiaraviglio et al., 2003). Male boas were classi- fied as adult if they had large, turgid testes, and/or opaque, thickened vas deferens. In addition, males and females were classified into four life stages re- lated to body coloration, snout-vent length (SVL) and reproductive condition: (1) newborn juveniles (< 101 cm SVL) with a pinkish coloration; (2) larger juveniles with the same coloration as adults (females 101-163 cm SVL, males 101-148 cm SVL); (3) adult boas (females 164-223 cm, males 149-223 cm); and (4) only by the largest females (> 223 cm; Chiaraviglio et al., 2003).