Maternal body volume constrains water uptake by lizard eggs in utero

1. Flexible shelled eggs of squamate reptiles normally take up substantial amounts of water, and swell accordingly, during development. However, most water uptake occurs after oviposition, beginning immediately or soon after oviposition, and water uptake is severely restricted in eggs that are retained in utero past the normal time of oviposition.
2. These observations suggest that some aspect of retention in the oviductal environment limits the amount of water eggs can absorb prior to oviposition.
3. This paper presents evidence, from two species of Sceloporus lizard, supporting the hypothesis that limited space within the mother's body cavity physically constrains the ability of eggs to expand, and thereby their ability to absorb water. When adjusted for maternal body size, the water content of a female's clutch of eggs is negatively correlated with the dry mass of her clutch (the space available in the body cavity is finite, and thus a greater dry mass content leaves less volume for water).
4. If such a constraint on water uptake is widespread, it can have important implications for our understanding of the evolution of viviparity, the costs of reproduction, and the determinants of reproductive output in squamate reptiles.     

Locomotor performance of hatchling fence lizards (Sceloporus occidentalis): Quantitative genetics and morphometric correlates

Summary We examined heritabilities and correlations among measures of locomotor performance (speed, stamina) and among possible morphometric determinants of performance (hindlimb span, tail length) in families of hatchling lizards (Sceloporus occidentalis). We were particularly interested in determining whether these traits were heritable and thus might potentially respond genetically to selection. Moreover, we wished to determine whether speed and stamina are negatively genetically correlated, as suggested bya priori physiological and empirical considerations. All four traits appeared to be significantly heritable. Broadsense heritabilities were 0.33–0.36 for speed, 0.35–0.36 for stamina, 0.45–0.51 for hindlimb span, and 0.46–0.47 for tail length. Contrary to expectations, speed and stamina were not negatively genetically correlated. Hindlimb span and tail length, however, were negatively genetically correlated (but not phenotypically correlated). Hindlimb span and stamina were positively phenotypically correlated. Thus, for example, selection for longer hindlimb span could potentially result in shorter tails, contrary to evolutionary predictions based only on phenotypic correlations.     

Activity metabolism of lizards after thermal acclimation

1. 1. I tested the hypothesis that thermal acclimation necessarily exerts the same effect on resting metabolism and on aerobic and anaerobic activity metabolism in Anolis carolinensis and Sceloporus jarrovi, diurnally active iguanid lizards that exhibit reduced winter activity but not prolonged dormancy and that are often active on warm winter days.

2. 2. Cold acclimation reduced the total metabolic scope for activity in these lizards by 33–40%. The benefits of winter activity must outweigh the increased risk of predation that presumably accompanies this reduction in capacity for intense, short term muscular exercise.

3. 3. Acclimation did not influence resting metabolism, aerobic activity metabolism, and anaerobic activity metabolism in parallel ways.

Reproductive cycle of the oviparous lizard Sceloporus jalapae,from Zapotitlán Salinas,Puebla, Mexico

Reproductive patterns vary widely among species and populations of squamates. In general, patterns can be divided into cyclic and acyclic. Cyclic patterns are common in tropical and temperate species of seasonal environments, while acyclic ones are characteristic of tropical species that inhabit less variable environments. We studied the reproductive cycle of Sceloporus jalapae, one of the smallest species of Sceloporus, in an arid environment at Zapotitlán Salinas, Puebla, Mexico. Both sexes mature in the first year following hatching and exhibit a seasonal reproductive pattern with maximum activity in spring and summer that appears to be influenced by temperature. Unlike small species of Sceloporus that inhabit pine–oak and tropical forests, S. jalapae exhibits an extended period of reproductive activity that allows females to produce at least two clutches of 3–7 eggs each, and contrary to other species of Sceloporus, in this species there is no correlation between female length and clutch size. The reproductive pattern of S. jalapae is like that shown by other oviparous species of the genus; nevertheless, some life history traits of this species are shared with oviparous and viviparous species of small size.     

Wildfire as a natural stressor and its effect on female phenotype and ornament development

Controlled low‐intensity fires are commonly used in ecosystem management for both habitat restoration and wildfire management. Animals in those ecosystems may respond to fire by shifting energy allocation away from reproduction and growth, and toward maintenance. Stress‐induced shifts in energy allocation may affect the expression of condition‐dependent sexual signals, which are sensitive to energetic and physiological trade‐offs mediated by glucocorticoids. Here, we examine the effect of fire on ornament expression, corticosterone, and other phenotypic traits in a population of striped plateau lizards, Sceloporus virgatus, affected by the Horseshoe 2 Fire in the Chiricahua Mountains, Arizona, USA. The condition‐dependent female ornament was significantly smaller the month following the fire than 2 years prior and was both smaller and less orange on the burned site relative to a nearby unburned site. These patterns are similar to those found in a previous experimental study examining the response of the ornament to corticosterone manipulations. Yet, in the current study, corticosterone levels were not different in lizards on the burned and unburned sites. Perhaps glucocorticoid levels already returned to baseline, or do not adequately track environmental change. Females tended to be smaller and lighter on the burned site than the unburned site; however, the year after the fire, body condition was higher for females on the burned site, indicating a rapid recovery and potential long‐term benefits in response to low‐intensity fires in this fire‐adapted ecosystem. We found that the lizards adjusted energy allocation away from sexual signaling and growth in response to low‐intensity fires. As fires and fire management are likely to increase in response to changing fire regimes across the globe, it will be important to consider behavioral and physiological responses of impacted species, as well as population‐, community‐, and ecosystem‐level responses.     

How to climb a tree: lizards accelerate faster,but pause more,when escaping on vertical surfaces

Many species of lizards effectively traverse both two and three‐dimensional habitats. However, few studies have examined maximum locomotor performance on different inclines. Do maximum acceleration and velocity differ on a level and inclined surface? Do lizards pause more on an inclined surface? To address these questions, Sceloporus woodi lizards (N = 12) were run in the laboratory on a level trackway and a vertical tree trunk. This species is known to frequently utilize both vertical and horizontal aspects of its habitat. Average maximum acceleration on the vertical surface exceeded that on the level surface, although average maximum velocity exhibited the opposite pattern. The average number of pauses during level locomotion was lower compared to vertical locomotion. In addition, the average location of the first pause on the level surface was 0.51 m, which is farther than the average for vertical locomotion where the first pause was at 0.35 m. The combination of performance and pause data suggests that the relative lack of pausing during level locomotion allows individuals to reach higher maximum velocities on level surfaces because they accelerate over greater distances. The increased pausing when moving vertically could be a result of high energetic demands of vertical locomotion, or greater microhabitat complexity as a result of branching and/or refuges. The faster acceleration exhibited during vertical locomotion by S. woodi likely offsets the frequent pauses. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 83–90.     

The ultrastructure of spermatid development during spermiogenesis within the rosebelly lizard,Sceloporus variabilis (Reptilia,Squamata, Phrynosomatidae)

Several recent studies have mapped out the characters of spermiogenesis within several species of squamates. Many of these data have shown both conserved and possibly apomorphic morphological traits that could be important in future phylogenetic analysis within Reptilia. There, however, has not been a recent study that compares spermiogenesis and its similarities or differences between two species of reptile that reside in the same genus. Thus, the present analysis details the changes to spermiogenesis in Sceloporus variabilis and then compares spermatid morphologies to that of Sceloporus bicanthalis. Many of the morphological changes that the spermatids undergo in these two species are similar or conserved, which is similar to what has been reported in other squamates. There are six main character differences that can be observed during the development of the spermatids between these two sceloporid lizards. They include the presence (S. variabilis) or absence (S. bicanthalis) of a mitochondrial/endoplasmic reticulum complex near the Golgi apparatus during acrosome development, a shallow (S. variabilis) or deep (S. bicanthalis) nuclear indentation that accommodates the acrosomal vesicle, filamentous (S. variabilis) or granular (S. bicanthalis) chromatin condensation, no spiraling (S. variabilis) or spiraling (S. bicanthalis) of chromatin during condensation, absence (S. variabilis) or presence (S. bicanthalis) of the longitudinal manchette microtubules, and the lack of (S. variabilis) or presence (S. bicanthalis) of nuclear lacunae. This is the first study that compares spermiogenic ultrastructural characters between species within the same genus. The significance of the six character differences between two distantly related species within Sceloporus is still unknown, but these data do suggest that spermiogenesis might be a good model to study the hypothesis that spermatid ontogeny is species specific. J. Morphol. 275:258–268, 2014. © 2013 Wiley Periodicals, Inc.