THE SOUTHWESTERN NATURALIST 51(2):163–171 JUNE 2006 REPRODUCTIVE, FAT, AND LIVER CYCLES OF MALE AND FEMALE ROSE-BELLIED LIZARDS, SCELOPORUS VARIABILIS, FROM COASTAL AREAS OF SOUTHERN VERACRUZ, MEXICO AURELIO RAMI ´ REZ-BAUTISTA,* RODOLFO GARCI ´ A-COLLAZO, AND LOUIS J. GUILLETTE,JR. Centro de Investigaciones Biolo ´gicas, Universidad Auto ´noma del Estado de Hidalgo A.P. 1-69 Plaza Jua ´rez, C.P. 42001, Pachuca, Hidalgo, Me ´xico (AR-B) Zoologı ´a, FES-Iztacala, UNAM, Tlalnepantla, Edo. de Me ´xico, C.P. 54090, A.P. 314, Me ´xico (RG -C) Department of Zoology, 223 Bartram Hall, University of Florida, Gainesville, FL 32611 (LJG) *Correspondent: aurelior@uaeh.edu.mx or raurelio@servidor.unam.mx ABSTRACT We studied the reproductive cycles of 350 male and female Sceloporus variabilis from coastal areas of the Gulf of Mexico, Mexico, that exhibited continuous reproduction. Males reached sexual maturity at 45 mm snout–vent length (SVL), whereas females reached sexual ma- turity at 44 mm SVL. Testicular mass varied among months. Testes began to increase in size during April, with maximum sizes reached from May to July. Maximal testicular growth was positively correlated with increasing temperature and photoperiod, but not with precipitation. Females con- tained vitellogenic follicles and oviductal eggs throughout the year, although maximal egg pro- duction occurred from June to January. Forty-two females (40%) had vitellogenic follicles and oviductal eggs simultaneously. Mean clutch size, based on vitellogenic follicles, was similar (mean 5 3.7 6 0.17 SE) to that observed by counting oviductal eggs (mean 5 3.7 6 0.10 SE). Females with a SVL $ 51.5 mm 6 0.91 SE had at least 2 clutches. Clutch size was correlated with female SVL. Differences in reproduction found in this study compared with other populations of the same species might be explained by environmental differences at the study sites. RESUMEN Estudiamos los ciclos reproductivos de 350 machos y hembras de Sceloporus variabilis de las a ´reas costeras del Golfo de Me ´xico, Me ´xico, que exhibieron reproduccio ´ n continua. Los machos alcanzaron la madurez sexual a los 45 mm de longitud hocico-cloaca (LHC), mientras que las hembras alcanzaron la madurez sexual a los 44 mm. La masa testicular vario ´ entre los meses. Los testı ´culos comenzaron a incrementar en taman ˜ o durante abril, con un taman ˜ o ma ´ximo alcanzado de mayo a julio. El ma ´ximo crecimiento testicular estuvo correlacionado positivamente con el incremento en temperatura y fotoperiodo, pero no con la precipitacio ´ n. Las hembras presentaron folı ´culos viteloge ´nicos y huevos oviductales a lo largo del an ˜o, aunque la ma ´xima produccio ´n de huevos ocurrio ´ de junio a enero. Cuarenta y dos hembras (40%) presentaron folı ´culos viteloge ´nicos y huevos oviductales simulta ´neamente. La media del taman ˜o de la puesta, basada en los folı ´culos viteloge ´nicos, fue similar (media 5 3.7 6 0.17 EE) a la observada por el conteo de los huevos oviductales (media 5 3.7 6 0.10 EE). Las hembras con una LHC $ 51.5 mm 6 0.91 EE tuvieron por lo menos dos puestas. El taman ˜o de la puesta estuvo correlacionado con la LHC de la hembra. Las diferencias encontradas en la reproduccio ´n en este estudio, com- parado con otras poblaciones de la misma especie, pueden ser explicadas por las diferencias ambientales de los sitios de estudio. Reproduction in many lizard species from tropical, seasonal environments is usually cycli- cal, with courtship, mating, and copulation oc- curring at the beginning of the rainy season, and incubation during the rainy season (Ra- mı ´rez-Bautista and Vitt, 1997, 1998). However, reproduction in lizard species from tropical re- gions, such as rainforests, is acyclical, with re- productive activity of males (sperm produc- tion) and females (egg production) occurring throughout the year (Ramı ´rez-Bautista and Gonzalez-Romero, 1991; Benabib, 1994). Liz- ard species inhabiting aseasonal tropical re- gions are expected to have a longer reproduc- tive season than do temperate or seasonal trop- ical lizards (Benabib, 1994; Ramı ´rez-Bautista