Reproduction of the Cape Horned Lizard, Phrynosoma coronatum (Squamata: Phrynosomatidae) from Baja California Sur, Mexico

Abstract

Species of Phrynosoma (formerly P. coronatum) range west of the Sierra Nevada from Shasta County, California, south through southern California and Baja California (Grismer 2002). Montanucci (2004) and Leache et al. (2009) considered Phrynosoma from the southern tip of Baja California as P. coronatum. Goldberg (1983) reported on reproduction in Phrynosoma blainvillii (as P. coronatum) from southern California. To my knowledge, there is no information on reproduction of P. coronatum from the Cape Region of Baja California Sur, Mexico. The purpose of this note is to report the results of a histological examination of P. coronatum gonads from the Cape Region of Baja California Sur to ascertain whether geographic variation in reproduction exists between northern and southern species of Phrynosoma (formerly P. coronatum, sensu Montanucci 2004, Leache et al. 2009). A sample of fourteen P. coronatum consisting of seven adult males (mean SVL 5 76.9 mm 6 9.1 SD, range: 61–90 mm), five females (mean SVL 5 79.2 mm 6 14.0 SD, range: 67–103 mm), one presumed neonate (SVL 5 27 mm) and one presumed young of the year (SVL 5 36 mm) was examined from the herpetology collection of the Natural History Museum of Los Angeles County (LACM), Los Angeles, California, U.S.A. (Appendix). Phrynosoma coronatum were collected 1964, 1967 and 1968. For histological examination, the left testis was removed from males and the left ovary was removed from females. Enlarged follicles (. 5 mm length) were counted. Tissues were embedded in paraffin and cut into sections of 5 mm. Slides were stained with Harris hematoxylin followed by eosin counterstain (Presnell and Schreibman 1997). Slides of testes were examined to determine the stage of the spermatogenic cycle. Slides of ovaries were examined for the presence of yolk deposition. An unpaired t-test was utilized to compare P. coronatum male and female mean body sizes (SVL) using Instat (vers. 3.0b, Graphpad Software, San Diego, CA). Histology slides were deposited in LACM. There was no significant size difference (mean SVL) between males and females of P. coronatum (unpaired t test, t 5 0.35, df 5 10, P 5 0.73). The only stage present in the testicular cycle was spermiogenesis (sperm formation) in which the lumina of the seminiferous tubules were lined by clusters of sperm and/or metamorphosing spermatids. This condition was noted in the following monthly samples: (July, n 5 1; August, n 5 6). The testes were previously removed leaving the epididymides in one August male (LACM 109380). Tubules of the epididymis were filled with sperm so it was assumed the missing seminiferous tubules were undergoing spermiogenesis. The smallest spermiogenic male (LACM 19904) measured 61 mm SVL and was from August. Monthly stages in the ovarian cycle are in Table 1. Three stages were noted: (1) quiescent, no yolk deposition; (2) early yolk deposition, basophilic yolk granules in the ooplasm; (3) enlarged ovarian follicles . 5 mm. One female from July (LACM 101500) Bull. Southern California Acad. Sci. 110(2), 2011, pp. 56–58 E Southern California Academy of Sciences, 2011