Thermal biology and locomotor performance in Phymaturus calcogaster:are Patagonian lizards vulnerable to climate change?

Behavioral and physiological traits of ectotherms are especially sensitive to fluctuations of environmental temperature.In particular,niche-specialist lizards are dependent on their physiological plasticity to adjust to changing environmental conditions.Lizards of the genus Phymaturus are viviparous,mainly herbivorous,and inhabit only rock promontories in the steppe environments of Patagonia and the Andes.Herein,we examine the vulnerability of the southernmost Phymaturus species to global warming:the endemic Phymaturus calcogaster,which lives in a mesic environment in eastern Patagonia.We studied body temperatures in the field(T_(b)),preferred body temperatures in a thermogradient(T_(pref)),the operative(T_(e))and environmental temperatures,and the dependence of running performance on body temperature.P.calcogaster had a mean T_(b)(27.04℃)and a mean Te(31.15℃)both lower than their preferred temperature(T_(pref)=36.61℃)and the optimal temperature for running performance(T_(o)=37.13℃).Lizard activity seems to be restraint during the early afternoon due high environmental temperatures.However,both,the high safety margin and warming tolerance suggest that the expected increase in environmental temperatures due to global warming(IPCC report in 2018)would not threaten,but indeed enhance locomotor performance in this population.

Effect of thermal acclimation on thermal preference, resistance and locomotor performance of hatchling soft-shelled turtle

The significant influence of thermal acclimation on physiological and behavioral performance has been documented in many ectothermic animals, but such studies are still limited in turtle species. We acclimated hatchling soft-shelled turtles Pelodiscus sinensis under three thermal conditions （10, 20 and 30~C） for 4 weeks, and then measured selected body temperature （Tsel）, critical thermal minimum （CTMin） and maximum （CTM^x）, and locomotor performance at different body temperatures. Thermal acclimation significantly affected thermal preference and resistance of P sinensis hatchlings. Hatchling turtles accli- mated to 10~C selected relatively lower body temperatures and were less resistant to high temperatures than those acclimated to 20~C and 30~C. The turtles＇ resistance to low temperatures increased with a decreasing acclimation temperature. The thermal re- sistance range （i.e. the difference between CTM^x and CTMin, TRR） was widest in turtles acclimated to 20~C, and narrowest in those acclimated to 10~C. The locomotor performance of turtles was affected by both body temperature and acclimation tem- perature. Hatchling turtles acclimated to relatively higher temperatures swam faster than did those acclimated to lower temperatures. Accordingly, hatchling turtles acclimated to a particular temperature may not enhance the performance at that temperature. Instead, hatchlings acclimated to relatively warm temperatures have a better performance, supporting the ＂hotter is better＂ hypothesis.

Tail Autotomy Does Not Increase Locomotor Costs in the Oriental Leaf-toed Gecko Hemidactylus bowringii

Tail autotomy is a defense mechanism used by many lizards to evade predators, but it entails costs. We used the oriental leaf-toed gecko Hemidactylus bowringii as a model animal to evaluate locomotor costs of tail autotomy. We removed the tail about 5 mm from the tail base from each of the experimental geckos(adult males) initially having intact tails. Tailless experimental geckos and tailed control geckos were measured for overall speed and sprint speed in both vertical and horizontal directions. Overall speed and sprint speed did not differ between tailless and tailed geckos. The influence of locomotor direction on both overall speed and sprint speed was significant, with horizontal speed being greater than vertical speed. The interaction between tail condition and locomotor direction was not significant in overall speed, but was significant in sprint speed. Tailless geckos had faster vertical sprint speed than the tailed individuals. Of the 130 field-caught adults, 59 had previously lost their tails, with most(about 61%) of them shedding their tails near the tail base. Neither the proportion of geckos with tail autotomy nor the frequency distribution of locations of the tail break differed between the sexes. Our data show that tail loss of H. bowringii occurs frequently in nature. However, tail loss does not incur locomotor costs in this gecko.

Morphological determinants of jumping performance in the Iberian green frog

Predation is one of the main selective forces in nature, frequently selecting potential prey for developing escape strategies. Escape ability is typically influenced by several morphological parameters, such as morphology of the locomotor appendices, muscular capacity, body mass, or fluctuating asymmetry, and may differ between sexes and age classes. In this study, we tested the relationship among these variables and jumping performance in 712 Iberian green frogs Pelophylax perezi from an urban population. The results suggest that the main determinant of jumping capacity was body size (explaining 48% of variance). Larger frogs jumped farther, but jumping performance reached an asymptote for the largest frogs. Once controlled by structural body size, the heaviest frogs jumped shorter distances, suggesting a trade-off between fat storage and jumping performance. Relative hind limb length also determined a small but significant percentage of variance (2.4%) in jumping performance-that is, the longer the hind limbs, the greater the jumping capacity. Juveniles had relatively shorter and less muscular hind limbs than adults (for a given body size), and their jumping performance was poorer. In our study population, the hind limbs of the frogs were very symmetrical, and we found no effect of fluctuating asymmetry on jumping performance. Therefore, our study provides evidence that jumping performance in frogs is not only affected by body size, but also by body mass and hind limb length, and differ between age classes.

High-elevation hypoxia impacts perinatal physiology and performance in a potential montane colonizer

Climate change is generating range shifts in many organisms,notably along the elevational gradient in mountainous environments.However,moving up in elevation exposes organisms to lower oxygen availability,which may reduce the successful reproduction and development of oviparous organisms.To test this possibility in an upwardcolonizing species,we artificially incubated developing embryos of the viperine snake(Natrix maura)using a split-clutch design,in conditions of extreme high elevation(hypoxia at 2877 m above sea level;72%sea-level equivalent O2 availability)or low elevation(control group;i.e.normoxia at 436 m above sea level).Hatching success did not differ between the two treatments.Embryos developing at extreme high elevation had higher heart rates and hatched earlier,resulting in hatchlings that were smaller in body size and slower swimmers compared to their siblings incubated at lower elevation.Furthermore,post-hatching reciprocal transplant of juveniles showed that snakes which developed at extreme high elevation,when transferred back to low elevation,did not recover full performance compared to their siblings from the low elevation incubation treatment.These results suggest that incubation at extreme high elevation,including the effects of hypoxia,will not prevent oviparous ectotherms from producing viable young,but may pose significant physiological challenges on developing offspring in ovo.These early-life performance limitations imposed by extreme high elevation could have negative consequences on adult phenotypes,including on fitness-related traits.

Tail loss affects fecundity but not offspring traits in the Chinese skink Eumeces chinensis

We used the Chinese skink Eumeces chinensis as a model animal to study the effects of tail loss on reproductive in- vestment and offspring traits. A total of 147 wild-captured adult females were divided into four groups according to their tail con- ditions. Tail breaks occurred most frequently in the proximal portion of the tail and least frequently in the distal portion, with the middle portion in between. This finding suggests that tail breaks occurring in nature often entails substantial energetic costs in E. chinensis where the tail is a major site of energy storage. The proportion of females that laid eggs was higher in females with in- tact or completely regenerated tails than in those with broken tails. Following whole-tail autotomy, the clutch size was reduced by 17%, and the clutch mass was reduced by 14%. Females undergoing substantial tail autotomy reduced reproductive investment, and they did so by reducing the number but not the size of eggs produced. None of the egg and hatchling traits was affected by tail loss. Comparing our data with those reported for other oviparous and viviparous skinks allows us to draw two general conclu- sions： one is that fecundity （clutch or litter size） is affected by tail loss in all species so far studied, whereas offspring size is af- fected by tail loss in some species, but not in others; the other is that the reduction in fecundity following tail loss is more evident in species lacking abdominal fat bodies

Influence of incubation temperature on sea turtle hatchling quality

Since the 1980s it has been known that incubation temperature influences the sex ratio of sea turtle hatchlings emerging from their nests,and there has been much speculation on how global climate change might threaten sea turtle populations by raising nest temperatures and causing highly female-biased hatchling sex ratios.More recently,studies have indicated that incubation temperature can also influence the size and locomotor performance of sea turtle hatchlings.Here I review recent studies that have explored the influence of incubation temperature on sea turtle hatchling quality in terms of hatchling morphology and locomotor performance.I also discuss the likely underlying mechanisms responsible for incubation temperature-induced differences in hatchling locomotor performance,and how an increase in nest temperature associated with global warming might affect recruitment of sea turtle hatchlings.

The movement dynamics of autotomized lizards and their tails reveal functional costs of caudal autotomy

Autotomy has evolved independently several times in different animal lineages.It frequently involves immediate functional costs,so regeneration evolved in many instances to restore the functionality of that body part.Caudal autotomy is a widespread antipredator strategy in lizards,although it may affect energy storage,locomotion dynamics,or survival in future encounters with predators.Here,we assessed the effect of tail loss on the locomotor performance of wall lizards(Podarcis muralis),as well as the recovery of locomotor functionality of lizards with regenerated tails,and the movement dynamics of shed tails that were either intact or having regenerated portions.Tail loss had no effect on locomotion over unhindered spaces,possibly due to compensation between a negative effect on the stride of front limbs,and a positive effect of losing mass and friction force.We found a clear negative impact of tail loss on locomotion in spaces with interspersed obstacles,in which tailed lizards jumped larger distances when leaving the obstacles.Besides,lizards that used the tail to push off the ground were able to approach the obstacles from further,so that the tail seemed to be useful when used during jumping.Regeneration fully restores lizard’s locomotor capacities,but tail antipredator value,as indicated by the intensity of post-autotomic movements,is only partially retrieved.From these results,we propose that,together with the recovery of post-autotomy antipredator capacities,the restoration of the organismal locomotor performance may have been an important,yet frequently neglected factor in the evolution of lizard’s regeneration ability.