Reproduction in the Baja California Collared Lizard, Crotaphytus vestigium (Squamata: Crotaphytidae)

Abstract

Crotaphytus vestigium, a rock-dwelling species of the peninsular ranges of Baja California, occurs along the northern slope of the San Jacinto Mountains, Riverside County, California, south to the southern margin of the volcanic Magdalena Plain in Baja California Sur (McGuire 1996). Published information on the reproduction of C. vestigium consists of brief accounts by Lemm (2006), Ivanyi, (2009) and field observations by McGuire (1996), Grismer (2002) and Stebbins (2003). The purpose of this paper is to examine the reproductive biology of C. vestigium from a histological analysis of gonadal material from museum specimens, an often used method, see for example, Goldberg (1974). Information on the reproductive cycle such as timing of spermiogenesis, number of egg clutches produced and period of vitellogenesis may not only be helpful in determining phylogenetic affinities, but also provides essential life history data for implementing conservation management strategies of lizard species. We examined 61 C. vestigium consisting of 33 males (mean snout-vent length, SVL 5 96.5 mm 6 12.3 SD, range: 72–116 mm and 28 females (mean SVL 5 80.4 mm 6 8.6 SD, range: 54–93 mm) from Imperial, Riverside and San Diego Counties, California and Baja California and Baja California Sur, Mexico. Specimens were examined from the herpetology collections of the Natural History Museum of Los Angeles County (LACM), Museum of Vertebrate Zoology (MVZ), and San Diego Society of Natural History (SDSNH) (Appendix I). Lizards were collected 1934–1997. Histology slides were deposited at LACM, MVZ and SDSNH. The left testis was removed from males and the left ovary was removed from females for histological examination (Presnell and Schreibman 1997). Enlarged ovarian follicles (. 5 mm) and/or oviductal eggs were counted. Tissues were embedded in paraffin, sectioned at 5 mm and stained with hematoxylin followed by eosin counterstain. Ovary slides were examined for yolk deposition or corpora lutea. Testis slides were examined to ascertain the stage of the testicular cycle present. Mean SVL of male and female C. vestigium were compared using an unpaired t-test (Instat vers. 3.0b, Graphpad Software, San Diego, CA). The mean male SVL of C. vestigium significantly exceeded that of females (unpaired t test, t 5 5.82, df 5 59, P , 0.0001). Monthly stages in the testicular cycle of C. vestigium were shown in Table 1. Three stages were present: (1) Regression, the germinal epithelium was reduced to 1–3 cell layers in thickness and consists of spermatogonia and Sertoli cells; (2) Recrudescence, a proliferation of germ cells for the next period of sperm formation was underway. In early recrudescence, primary spermatocytes predominate, Bull. Southern California Acad. Sci. 109(3), 2010, pp. 153–156 E Southern California Academy of Sciences, 2010