Reproduction of the yellow-backed spiny lizard, Sceloporus uniformis (Squamata: Phrynosomatidae) from California

The reproductive cycle of Sceloporus uniformis was studied by a histological examination of gonads collected from five California counties: Inyo, Kern, Los Angeles, Riverside and San Bernardino. Males followed a testicular cycle in which sperm production (spermiogenesis) started in March and was completed by August. The smallesr reproductively active male measured 79 mm SVL. Females were reproductively active from March into July. Mean clutch size (n 5 21) was 6.48 6 2.2 SD, range 5 3–10. The smallest reproductively active female (enlarged follicles .5 mm) measured 78 mm SVL. Histological evidence is presented (oviductal eggs and concomitant yolk deposition) that multiple clutches are produced by some females of S. uniformis. The yellow-backed spiny lizard, Sceloporus uniformis Phelan and Brattstrom, 1955, occurs primarily in the Mojave and Great Basin Deserts of California, Nevada, Utah, and northwestern Arizona, as well as the Central Valley of California from near sea level to around 1,520 m (Conrad 2009). Schulte et al. (2006) elevated the subspecies Sceloporus magister uniformis to Sceloporus uniformis. Previous information on its reproductive cycle are one or more clutches of 4–19 eggs deposited from May to August (Conrad 2009). In Nye County, Nevada, a mean of 7.0 eggs was produced (Tanner and Krogh 1973). In southern Utah (Washington County), reproduction occurs from May to July with two clutches averaging 6.2, range 2–9 eggs (Tinkle 1976). Five adult S. uniformis females from the Providence Mountains, San Bernardino County, California collected between May 22 and June 11 contained enlarged ovarian follicles (Johnson et al. 1949). The purpose of this paper is to provide additional information on the reproductive cycle of S. uniformis from a histological examination of gonads. Categorization of the reproductive cycle including period of sperm production, timing of yolk deposition and number and sizes of clutches produced provides important information in formulating conservation policies for lizard populations (Gibbons 1994). Due to the difficulty in obtaining collecting permits for large collections of monthly lizard samples, utiliization of museum collections for obtaining reproductive data has become increasingly important. A sample of 239 S. uniformis consisting of 105 adult males (mean SVL 5 100.8 mm 6 9.6 SD, range: 78–124 mm), 51 adult females (mean SVL 5 91.5 mm 6 7.6 SD, range: 77– 108 mm), 75 juveniles (mean SVL 5 56.3 mm 6 10.6 SD, range: 37–56 mm) and eight neonates (mean SVL 5 32.1 mm 6 4.0 SD, range: 24–34 mm) collected 1921 to 1980 was examined from the herpetology collection of the Natural History Museum of Los Angeles County (LACM), Los Angeles, California, USA (appendix). The left gonad was removed and embedded in paraffin. Histological sections were cut at 5mm and stained by hematoxylin followed by eosin counterstain (Presnell and Schreibman 1997). Enlarged follicles . 5 mm length and oviductal eggs were counted. Histology slides were deposited in LACM. The snout-vent length (SVL) of each specimen was measured from the tip of the snout to the posterior margin of the vent. An unpaired Bull. Southern California Acad. Sci. 111(1), 2012, pp. 25–28 E Southern California Academy of Sciences, 2012