Color pattern and body size variation in live Aspidoscelis costatus costatus (Squamata: Teiidae) from a protected enclave in southern Mexico

Coloración en la lagartija Aspidoscelis costatus costatusWhiptail lizards in the sexlineatus species group (genus Aspidoscelis) in North America represent some of the most challenging patterns of variation in the North American herpetofauna. The range of color patterns in these populations is based on individual, ontogenetic, sexual, seasonal, and/or geographic variation. We studied representatives of a population of Western Mexico Whiptail (A. costatus costatus) from a protected private enclave of approximately 0.27 ha in the municipality and city of Ixtapan de la Sal, Estado de México, México. We captured 50 lizards in 2016 and 24 in 2018, most of which we photographed ex situ and a few in situ. These photographs revealed that a variety of age/size related dorsal and ventral patterns were consistently present. Males progressed through five stages of dorsal pattern changes from pale stripes, dark intervening fields, no spots to spots, and diverse pale configurations set in a black ground color. Females in this population showed similar changes but did not lose striping as they grew. Ontogenetic changes in ventral color patterns were also apparent, with males becoming more colorful than females. The adaptive significance of extensive color pattern variation in this urban population of A. c. costatus warrants further study

Massive predation of pine toad, Incilius occidentalis (Anura: Bufonidae)

Depredación masivaMamíferos depredan masivamente anuros cuando éstos se congregan en sitios de reproducción. Se registró depredación masiva de Incilius occidentalis caracterizada por la presencia de múltiples indivi- duos muertos carentes de vísceras y extremidades, pero con la cabeza y las glándulas parótidas presen- tes. La evidencia sugiere que este evento ocurrió por el depredador Procyon lotor

Aspidoscelis costatus costatus (Squamata, Teiidae): high elevation clutch production for a population of whiptail lizards

Artículo del tamaño de nidada en la lagartija Aspidoscelis costatus costatus.Clutch size and number of clutches per reproductive cycle are important life history traits that can be influenced by anatomical, physiological, evolutionary, and ecological factors. This report on the clutch size and number of clutches of an endemic Mexican whiptail lizard, Aspidoscelis costatus costatus (Cope, 1878), is based on a study of population at an unsually high elevation for a member of this genus. The study site is located in Ixtapan de la Sal, southeastern Estado de México, Central Mexico, at 2090 m a.s.l. Lizards were sampled in June 2006, and from May to July 2007, where females of Aspidoscelis costatus costatus were collected by hand along a drift fence. Female reproductive condition was evaluated based on abdominal palpation for presence of developing eggs; clutch size was determined by actual counts of either vitellogenic follicles or oviductal eggs. The smallest reproductive female was 77 mm snout vent length; females produced a minimum of two clutches during the breeding season, the mean clutch size of 6.5 eggs (n = 33) was one of the largest reported for the genus. However, both length and width of its eggs, and the relative clutch mass have not been diminished by development of a large clutch. Additionally, comparisons of clutch size were undertaken within the polytypic A. costatus complex, within the genus Aspidoscelis, and between certain genera of whiptail lizards. This apparently represents the first study of whiptail lizards (genus Aspidoscelis), assessing the aforementioned reproductive characteristics, in a population above 2000 m

Ontogenic development of spermatids during spermiogenesis in the high altitude bunchgrass lizard (Sceloporus bicanthalis)

The body of ultrastructural data on spermatid characters during spermiogenesis continues to grow in reptiles, but is still relatively limited within the squamates. This study focuses on the ontogenic events of spermiogenesis within a viviparous and continually spermatogenic lizard, from high altitude in Mexico. Between the months of June and August, testicular tissues were collected from eight spermatogenically active bunchgrass lizards (Sceloporus bicanthalis) from Nevado de Toluca, México. The testicular tissues were processed for transmission electron microscopy and analyzed to access the ultrastructural differences between spermatid generations during spermiogenesis. Interestingly, few differences exist between S. bicanthalis spermiogenesis when compared with what has been described for other saurian squamates. Degrading and coiling membrane structures similar to myelin figures were visible within the developing acrosome that are likely remnants from Golgi body vesicles. During spermiogenesis, an electron lucent area between the subacrosomal space and the acrosomal medulla was observed, which has been observed in other squamates but not accurately described. Thus, we elect to term this region the acrosomal lucent ridge. This study furthers the existing knowledge of spermatid development in squamates, which could be useful in future work on the reproductive systems in high altitude viviparous lizard species

Reproductive activity in males of Sceloporus variabilis: Little time to rest, long time to breed

Los reptiles presentan una gran variedad de patrones reproductores, que, en el caso de los machos, van desde diferencias en la duración del ciclo reproductor (Huang, 1997; Lozano et al., 2015), la época (primavera y/o verano, época de lluvias y/o sequía) en que se lleva a cabo (Vitt y Goldberg, 1983; Ramírez-Pinilla, 1991; Ferreira et al., 2002; Goldberg, 2008) o si la actividad es continua o estacional (Méndez-de la Cruz et al., 2015). La actividad reproductora continua, es aquélla donde la producción de espermatozoides es constante durante todo el año y aunque suele ser asociada a especies tropicales (Sherbrooke, 1975; Vial y Stewart, 1985; Van Sluys, 1993), se ha registrado en especies de clima templado (Hernández-Gallegos et al., 2002; Lozano et al., 2015). En contraste, la actividad reproductora estacional es aquélla donde los machos llevan a cabo la gametogénesis en periodos específicos del año, generalmente en primavera o verano/otoño, y está típicamente asociada a especies de clima templado (Abu-Zinadah, 2008; Goldberg, 2011; Rheubert et al., 2014). De igual modo, la actividad reproductora estacional también ha sido registrada en especies tropicales (Ochotorena et al., 2005; Granados-González et al., 2017).The reproductive activity of reptiles is typically assessed using monthly sampling. The spermatogenic cycle of Sceloporus variabilis was recently assessed using the aforementioned methodology, and only two spermatogenic phases (recrudescence and maximum activity) were observed. The authors hypothesized that quiescence and regression must occur in a short period (less than a month), which was not visualized by their monthly sampling methods. Thus, the entire spermatogenic cycle displayed by this species may have not been adequately represented. The present study assessed the spermatogenic cycle of S. variabilis in those months where the spermatogenic activity passes from maximum activity (July) to recrudescence (August) using weekly sampling to test the hypothesis that quiescence and regression do indeed occur. The results showed a regression period for 2 weeks, whereas quiescence was not observed. These results lead us to two hypotheses: (a) quiescence occurs in a very short period (days/hours) or (b) does not occur in this species. The data generated in this study suggest that species exhibiting rapid changes in spermatogenic activity need to be assessed at more frequent intervals to accurately depict the spermatogenic stages.CONACY

Amplexo diurno de Rhinella horribilis (Anura: Bufonidae) en una población del Centro de México

Artículo amplexo saposLos eventos reproductivos explosivos son una característica conductual registrada en sapos del género Rhinella, donde la actividad reproductora es observada durante la noche. Aquí se registra el primer caso de un amplexo diurno en R. horribilis en México

Home range of the parthenogenetic lizard Aspidoscelis maslini (FRiTTS, 1969), on a beach strand

Se logró la caracterización del ámbito hogareño de una lagartija microendémica de la Península de Yucatán.he average home range size of A. maslini represents the smallest within the genus Aspidoscelis recorded to date (P ERRY & G ARlANd 2002), including both parthe - nogenetic [616 m 2 in Aspidosceli s unipa - rens (W RiGHT & l OWE , 1965), H ulSE 1981; 45.1 m 2 in A. cozumelus , H ERNáNdEZ -G Al - lEGOS et al. 2015] and gonochoristic species [400 m 2 in Aspidoscelis tigris (B AiRd & G iRARd , 1852), j ORGENSEN & T ANNER 1963; 306 m 2 in Aspidoscelis hyperythrus (C OPE , 1863), R OWlANd 1992]. This result con- trasts with theoretical predictions of broad home ranges for widely foraging species (H ulSE 1981; R OWlANd 1992; V ERWAijEN & V AN d AmmE 2008). Reduced home ranges at coastal habitats in other species of lizards including both sit and wait predators (R O - CHA 1999; k ACOliRiS et al. 2009) and wide foraging species (H iRTH 1963) have been recorded previously

Movimientos y uso de hábitat de la tortuga Kinosternon integrum, especie en riesgo de acuerdo a la Norma Oficial Mexicana NOM-059

El uso de la radio-telemetría es uno de los métodos más utilizados para la localización de los animales en repetidas ocasiones (Aguirre et al., 1984; White y Garrott 1990). El uso de radio-telemetría es clave para analizar diferentes aspectos de la actividad como: uso de hábitat en respuesta a factores ambientales, movimientos, alimentación, reproducción, termorregulación, refugios, entre otros. Kinosternon integrum es la tortuga de agua dulce más ampliamente distribuida en México, es endémica, se encuentra al oeste y centro del país en elevaciones de 0 a 2300 msnm (Iverson, 1998). De acuerdo a la Norma Oficial Mexicana NOM-059, K. integrum está sujeta a protección especial (Pr). De acuerdo a la NOM-059 estas especies son “Aquéllas que podrían llegar a encontrarse amenazadas por factores que inciden negativamente en su viabilidad, por lo que se determina la necesidad de propiciar su recuperación y conservación o la recuperación y conservación de poblaciones de especies asociadas”

Genetic determination and JARID2 over- expression in a thermal incubation experiment in Casque-Headed Lizard

Artículo incubaciónNon-avian reptiles, unlike mammals and birds, have undergone numerous sex determina- tion changes. Casque-Headed Lizards have replaced the ancestral XY system shared across pleurodonts with a new pair of XY chromosomes. However, the evolutionary forces that triggered this transition have remained unclear. An interesting hypothesis suggests that species with intermediate states, with sex chromosomes but also thermal-induced sex reversal at specific incubation temperatures, could be more susceptible to sex determination turnovers. We contrasted genotypic data (presence/absence of the Y chromosome) against the histology of gonads of embryos from stages 35–37 incubated at various temperatures, including typical male-producing (26 ̊C) and female-producing (32 ̊C) temperatures. Our work apparently reports for the first time the histology of gonads, including morphological changes, from stages 35–37 of development in the family Corytophanidae. We also observed that all embryos developed hemipenes, suggesting sex-linked developmental het- erochrony. We observed perfect concordance between genotype and phenotype at all tem- peratures. However, analysis of transcriptomic data from embryos incubated at 26 ̊C and 32 ̊C identified transcript variants of the chromatin modifiers JARID2 and KDM6B that have been linked to temperature-dependent sex determination in other reptiles. Our work tested the validity of a mixed sex determination system in the family Corytophanidae. We found that XY chromosomes are dominant; however, our work supports the hypothesis of a con- served transcriptional response to incubation temperatures across non-avian reptiles that could be a reminiscence of an ancestral sex determination system.This study was supported by grants from PAPIIT-UNAM (No. RA-200516 and No. RA- 200518; https://dgapa.unam.mx/index.php/ impulso-a-la-investigacion/papiit) and CONACyT Basic Science grant (No. 254240; https://conacyt. mx/) awarded to D.C., and UAEMe ́x 4668/2019SF (https://www.uaemex.mx/) to OH-G

Límite de elevación de la salamandra Isthmura bellii (Grey, 1850) en México

Artículo I. belliiEl Tlaconete rojo (Isthmura bellii) es una de las salamandras neotropicales de mayor tamaño con amplia distribución y cuenta con el récord del intervalo de elevación más grande que cualquier otra salamandra. En el presente trabajo registramos una elevación que supera lo reportado