Sprint speed is unaffected by dietary manipulation in trained male Anolis carolinensis lizards

Impact of food availability on the thermal performance curves of male European green lizards (Lacerta viridis)

In a changing environment, characterized by human-induced rapid environmental change (HIREC), understanding the impacts of environmental stressors on reptile species is crucial. Preferred body temperatures (PBT) and thermal performance curves (TPCs) are comprehensive thermal physiology traits reflecting overall physiological performance and crucial for predicting species-specific responses to environmental changes. There is limited or conflicting information on how food availability affect the PBT and TPCs of lizard species, despite their significance in the context of the global decline in reptile species. The aim of this study was to experimentally investigate how food deprivation affects the PBT and TPCs of the European green lizards (Lacerta viridis). We exposed 30 adult male European green lizards to optimal and suboptimal food treatments. We assessed PBTs, and characterized the TPCs based on the thermal optimum (To), the maximum performance (Pmax) and performance breadth (B80) of the lizards. We found that food availability had a significant impact on preferred body temperature and locomotor performance. Lizards experiencing suboptimal conditions showed a preference for lower body temperatures, indicating an intention to minimize energy expenditure during fasting. Additionally, food-deprived lizards had wider B80 range, suggesting their thermal acclimatization to maintain effective performance across a broader temperature range. Our findings highlight the importance of food availability as a key environmental stressor influencing thermoregulation strategies. As habitat modifications and global warming continue, it is crucial to evaluate the impacts of these changes on species for the development of effective conservation strategies.

Stable isotopes reveal sex- and context-dependent amino acid routing in green anole lizards (Anolis carolinensis)

Allocation of acquired resources to phenotypic traits is affected by resource availability and current selective context. While differential investment in traits is well documented, the mechanisms driving investment at lower levels of biological organization, which are not directly related to fitness, remain poorly understood. We supplemented adult male and female Anolis carolinensis lizards with an isotopically labelled essential amino acid (13C-leucine) to track routing in four tissues (muscle, liver, gonads and spleen) under different combinations of resource availability (high- and low-calorie diets) and exercise training (sprint training and endurance capacity). We predicted sprint training should drive routing to muscle, and endurance training to liver and spleen, and that investment in gonads should be of lower priority in each of the cases of energetic stress. We found complex interactions between training regime, diet and tissue type in females, and between tissue type and training, and tissue type and diet in males, suggesting that males and females adjust their 13C-leucine routing strategies differently in response to similar environmental challenges. Importantly, our data show evidence of increased 13C-leucine routing in training contexts not to muscle as we expected, but to the spleen, which turns over blood cells, and to the liver, which supports metabolism under differing energetic scenarios. Our results reveal the context-specific nature of long-term trade-offs associated with increased chronic activity. They also illustrate the importance of considering the costs of locomotion in studies of life-history strategies.

Toward a Robust Definition of Sport Sex

Elite individual sports in which success depends on power, speed, or endurance are conventionally divided into male and female events using traditional binary definitions of sex. Male puberty creates durable physical advantages due to the 20- to 30-fold increase in circulating testosterone producing a sustained uplift in men's muscle, bone, hemoglobin, and cardiorespiratory function resulting from male puberty and sustained during men's lives. These male physical advantages provide strong justification for a separate protected category of female events allowing women to achieve the fame and fortune from success they would be denied if competing against men. Recent wider social acceptance of transgender individuals, together with the less recognized involvement of intersex individuals, challenge and threaten to defeat the sex classifications for elite individual female events. This can create unfair advantages if seeking inclusion into elite female events of unmodified male-bodied athletes with female gender identity who have gained the physical advantages of male puberty. Based on reproductive physiology, this paper proposes a working definition of sport sex based primarily on an individual's experience of male puberty and can be applied to transgender and various XY intersex conditions. Consistent with the multidimensionality of biological sex (chromosomal, genetic, hormonal, anatomical sex), this definition may be viewed as a multistrand cable whose overall strength survives when any single strand weakens or fails, rather than as a unidimensional chain whose strength is only as good as its weakest link.

The maternal energetic environment affects both egg and offspring phenotypes in green anole lizards (Anolis carolinensis)

Animals exist in dynamic environments that may affect both their own fitness and that of their offspring. Maternal effects might allow mothers to prepare their offspring for the environment in which they will be born via several mechanisms, not all of which are well understood. Resource scarcity and forced resource allocation are two scenarios that could affect maternal investment by altering the amount and type of resources available for investment in offspring, albeit in potentially different ways. We tested the hypothesis that maternal dietary restriction and sprint training have different consequences for the offspring phenotype in an oviparous lizard (Anolis carolinensis). To do this, we collected and reared eggs from adult diet-manipulated females (low-diet [LD] or high-diet [HD]) and sprint-trained females (sprint trained [ST] or untrained [UT]) and measured both egg characteristics and hatchling morphology. ST and LD mothers laid both the fewest and heaviest eggs, and ST, UT, and LD eggs also had significantly longer incubation periods than the HD group. Hatchlings from the diet experiment (LD and HD offspring) were the heaviest overall. Furthermore, both body mass of the mother at oviposition and change in maternal body mass over the course of the experiment had significant and sometimes different effects on egg and offspring phenotypes, highlighting the importance of maternal energetic state to the allocation of maternal resources.

Sprint training interacts with body mass to affect hepatic insulin-like growth factor expression in female green anoles (Anolis carolinensis)

Locomotor performance is a key predictor of fitness in many animal species. As such, locomotion integrates the output of a number of morphological, physiological, and molecular levels of organization, yet relatively little is known regarding the major molecular pathways that bolster locomotor performance. One potentially relevant pathway is the insulin and insulin-like signaling (IIS) network, a significant regulator of physiological processes such as reproduction, growth, and metabolism. Two primary hormones of this network, insulin-like growth factor 1 (IGF1) and insulin-like growth factor 2 (IGF2) are important mediators of these processes and, consequently, of life-history strategies. We sprint-trained green anole (Anolis carolinensis) females to test the responsiveness of IGF1 and IGF2 hepatic gene expression to exercise training. We also tested how sprint training would affect glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and eukaryotic elongation factor 2 (EEF2). The former is a crucial enzyme for glycolytic function in a cell, and the latter is necessary for protein synthesis. Resistance exercise forces animals to increase investment of resources towards skeletal muscle growth. Because IGF1 and IGF2 are important hormones for growth, and GAPDH and EEF2 are crucial for proper cellular function, we hypothesized that these four genes would be affected by sprint training. We found that sprint training affects IGF and EEF2 expression, such that larger sprint-trained lizards express hepatic IGF1, IGF2, and EEF2 to a lesser extent than similarly sized untrained lizards. These results demonstrate that the IIS, and pathways connected to it, can react in a size-dependent manner and are implicated in the exercise response in reptiles.

Sex-specific multivariate morphology/performance relationships in Anolis carolinensis

Animals rely on their ability to perform certain tasks sufficiently well to survive, secure mates, and reproduce. Performance traits depend on morphology, and so morphological traits should predict performance, yet this relationship is often confounded by multiple competing performance demands. Males and females experience different selection pressures on performance, and the consequent sexual conflict over performance expression can either constrain performance evolution or drive sexual dimorphism in both size and shape. Furthermore, change in a single morphological trait may benefit some performance traits at the expense of others, resulting in functional trade-offs. Identifying general or sex-specific relationships between morphology and performance at the organismal level thus requires a multivariate approach, as individuals are products both of an integrated phenotype and the ecological environment in which they have developed and evolved. We estimated the multivariate morphology→performance gradient in wild-caught, green anoles (Anolis carolinensis) by measuring external morphology and fore- and hindlimb musculature, and mapping these morphological traits to seven measured performance traits that cover the broad range of ecological challenges faced by these animals (sprint speed, endurance, exertion distance, climbing power, jump power, cling force, and bite force). We demonstrate that males and females differ in their multivariate mapping of traits on performance, indicating that sex-specific ecological demands likely shape these relationships, but do not differ in performance integration.

Daily running trials increase sprint speed in endangered lizards (Gallotia simonyi)

Due to increasing number of animal species in danger of extinction, captive breeding of individuals has become a necessary procedure for many recovery programs. As specimens born and raised in captivity during several generations may not develop some behavioral and performance aptitudes properly, several types of training are useful to apply before releasing them into the wild. We present here the results of experiments aiming to detect the effect of daily running trials in young males of the endangered lizard (Gallotia simonyi) from El Hierro (Canary Islands). We made individuals run in a racetrack twice every day, for five days a week between the end of July and the end of September. We filmed all running trials and calculated running speed for each individual dividing the distance run by the time used. Running speed did not correlate with body condition of the lizards but there was variation in running speeds of some individuals with similar body conditions. Running speed of lizards used in the experiments significantly increased along the whole trial period. By contrast, mean running speed did not change significantly in a control group, participating twice in running trials, one at the beginning and the other at the end of the experimental period. From these results we suggest that locomotor training contributed to increasing final running speeds of experimental lizards.

Recovery from discrete wound severities in side-blotched lizards (Uta stansburiana): implications for energy budget, locomotor performance, and oxidative stress

Wounding events (predation attempts, competitive combat) result in injuries and/or infections that induce integrated immune responses for the recovery process. Despite the survival benefits of immunity in this context, the costs incurred may require investment to be diverted from traits contributing to immediate and/or future survival, such as locomotor performance and oxidative status. Yet, whether trait constraints manifest likely depends on wound severity and the implications for energy budget. For this study, food intake, body mass, sprint speed, and oxidative indices (reactive oxygen metabolites, antioxidant capacity) were monitored in male side-blotched lizards (Uta stansburiana) healing from cutaneous wounds of discrete sizes (control, small, large). Results indicate that larger wounds induced faster healing, reduced food consumption, and led to greater oxidative stress over time. Granted wounding did not differentially affect body mass or sprint speed overall, small-wounded lizards with greater wound area healed had faster sprint speeds while large-wounded lizards with greater wound area healed had slower sprint speeds. During recovery from either wound severity, however, healing and sprint performance did not correspond with food consumption, body mass loss, nor oxidative status. These findings provide support that energy budget, locomotor performance, and oxidative status of a reptile are linked to wound recovery to an extent, albeit dependent on wound severity.

Immune activation affects whole-organism performance in male but not female green anole lizards (Anolis carolinensis)

Immune responses are intuitively beneficial, but they can incur a variety of costs, many of which are poorly understood. The nature and extent of trade-offs between immune activity and other components of the integrated phenotype can vary, and depend on the type of immune challenge, as well as the energetic costs of simultaneously expressing other traits. There may also be sex differences in both immune activity and immunity-induced trade-offs, particularly in the case of trade-offs involving functional traits such as whole-organism performance capacities that might be of different fitness value to males and females. We tested the response of three performance traits (sprinting, endurance, and biting) to two different immune challenges (LPS injection and wound healing) in both male and female Anolis carolinensis lizards. We found clear differences in how male and female performance capacities were affected by immune activation. LPS injection and wound healing had interactive effects on all three performance traits in males, but immune activation did not affect female performance. We also found that the degree of wound healing exhibited complex interactive effects involving sex and type of immune activation that varied depending on the performance trait in question. These results demonstrate that male and female green anoles experience different consequences of immune responses, and also that the type and extent of that activation can drive trait-specific performance trade-offs.