When things get hot: Thermoregulation behavior in the lizard Sceloporus aeneus at different thermal conditions.

Rising environmental temperatures have become a global threat for ectotherms, with the increasing risk of overheating promoting population declines. Flexible thermoregulatory behavior might be a plausible mechanism to mitigate the effects of extreme temperatures. We experimentally evaluated thermoregulatory behavior in the bunchgrass lizard, Sceloporus aeneus, at three different environmental temperatures (25, 35 and 45 °C) both with and without a thermal refuge. We recorded themoregulatory behaviors (body posture and movement between hot and cold patches) and compared individual lizards across all experimental temperature and shelter combinations. Behavioral thermoregulation in S. aeneus was characterized by the expression of five body postures, whose frequencies varied based on environmental temperature and microthermal conditions. Behavioral responses allowed lizards to maintain a mean body temperature <40 °C, the critical thermal maximum for temperate species, even at extreme environmental temperatures (45 °C). Although S. aeneus express an array of behavioral postures that provide an effective mechanism to cope with elevating temperatures, the presence of a thermal refuge was important to better achieve this. Together, our study offers a novel method to evaluate microhabitat preference that encompasses both behavioral observations and time-space analysis based on the ambient thermal distribution, a consideration that can aid in the formulation of more accurate predictions on ectotherm vulnerability related to increasing global environmental temperatures.

A new species of Acroeimeria Paperna & Landsberg, 1989 (Apicomplexa: Eimeriidae) in Wiegmann's torquate lizard Sceloporus torquatus torquatus Weigmann (Sauria: Phrynosomatidae) from Toluca Valley, México.

A new species of Acroeimeria Paperna & Landsberg, 1989 is described from Wiegmann's torquate lizard Sceloporus torquatus torquatus Wiegmann from Toluca, México. Oöcysts of Acroeimeria wiegmanni n. sp. are sub-spheroidal with a smooth bi-layered wall, measure on average 28.6 × 23.6 µm, and have a length/width (L/W) ratio of 1.2; a micropyle and an oocyst residuum are absent but polar granule(s) are present. Sporocysts are ellipsoidal and measure on average 11.7 × 8.6 µm, L/W 1.3; Stieda, sub-Stieda and para-Stieda bodies are absent. The sporocyst residuum is composed of numerous spheroidal granules in the center of the sporocyst. Endogenous stages of the new species develop in the duodenum of hosts. This is the first species of coccidian reported from S. t. torquatus and one of the few reported from a reptile in México.

Response to environmental change in rainbow trout selected for divergent stress coping styles.

An extensive literature has documented differences in the way individual animals cope with environmental challenges and stressors. Two broad patterns of individual variability in behavioural and physiological stress responses are described as the proactive and reactive stress coping styles. In addition to variability in the stress response, contrasting coping styles may encompass a general difference in behavioural flexibility as opposed to routine formation in response to more subtle environmental changes and non-threatening novelties. In the present study two different manipulations, relocating food from a previously learned location, and introducing a novel object yielded contrasting responses in rainbow trout selected for high (HR) and low (LR) post stress plasma cortisol levels. No difference was seen in the rate of learning the original food location; however, proactive LR fish were markedly slower than reactive HR fish in altering their food seeking behaviour in response to relocated food. In contrast, LR fish largely ignored a novel object which disrupted feeding in HR fish. Hence, it appears that the two lines appraise environmental cues differently. This observation suggests that differences in responsiveness to environmental change are an integral component of heritable stress coping styles, which in this particular case, had opposite effects on foraging efficiency in different situations. Context dependent fitness effects may thus explain the persistence of stable divergence of this evolutionary widespread trait complex.

Behavioral plasticity in rainbow trout (Oncorhynchus mykiss) with divergent coping styles: when doves become hawks.

Consistent and heritable individual differences in reaction to challenges, often referred to as stress coping styles, have been extensively documented in vertebrates. In fish, selection for divergent post-stress plasma cortisol levels in rainbow trout (Oncorhynchus mykiss) has yielded a low (LR) and a high responsive (HR) strain. A suite of behavioural traits is associated with this physiological difference, with LR (proactive) fish feeding more rapidly after transfer to a new environment and being socially dominant over HR (reactive) fish. Following transport from the UK to Norway, a switch in behavioural profile occurred in trout from the 3rd generation; HR fish regained feeding sooner than LR fish in a novel environment and became dominant in size-matched HR-LR pairs. One year after transport, HR fish still fed sooner, but no difference in social dominance was found. Among offspring of transported fish, no differences in feeding were observed, but as in pre-transported 3rd generation fish, HR fish lost fights for social dominance against size-matched LR opponents. Transported fish and their offspring retained their distinctive physiological profile throughout the study; HR fish showed consistently higher post-stress cortisol levels at all sampling points. Altered risk-taking and social dominance immediately after transport may be explained by the fact that HR fish lost more body mass during transport than did LR fish. These data demonstrate that some behavioural components of stress coping styles can be modified by experience, whereas behavioural plasticity is limited by genetic effects determining social position early in life story.