Latitudinal pattern of the thermal sensitivity of running speed in the endemic lizard Liolaemus multimaculatus

Physiological performance in lizards may be affected by climate across latitudinal or altitudinal gradients.In the coastal dune barriers in central-eastern Argentina,the annual maximum environmental temperature decreases up to 2℃ from low to high latitudes,while the mean relative humidity of the air decreases from 50%to 25%.Liolaemus multimaculatus,a lizard in the family Liolaemidae,is restricted to these coastal dunes.We investigated the locomotor performance of the species at 6 different sites distributed throughout its range in these dune barriers.We inquired whether locomotor performance metrics were sensitive to the thermal regime attributable to latitude.The thermal performance breadth increased from 7%to 82%with latitude,due to a decrease in its critical thermal minimum of up to 5℃ at higher latitudes.Lizards from high latitude sites showed a thermal optimum,that is,the body temperature at which maximum speed is achieved,up to 4℃lower than that of lizards from the low latitude.At relatively low temperatures,the maximum running speed of high-latitude individuals was faster than that of low-latitude ones.Thermal parameters of locomotor performance were labile,decreasing as a function of latitude.These results show populations of L.multimaculatus adjust thermal physiology to cope with local climatic variations.This suggests that thermal sensitivity responds to the magnitude of latitudinal fluctuations in environmental temperature.

The Effect of Body Pitching on Leg-Spring Behavior in Quadruped Running

In this paper we investigated how the running speed would affect the dynamics of body pitching, and whether body inertiais important for animals. Passive trotting of spring-mass model and passive bounding of spring-beam model were studied atdifferent speeds for different sets of body parameters respectively. Furthermore, different body inertias were used in bounding.We found that running speed exerts effect on leg performance by means of centrifugal force. The centrifugal force can be understoodas an enhancement to the natural frequency of the spring-mass system. The disadvantage of body pitching may beoffset by the great increase in centrifugal force at high speed. The results also reveal that body mass distribution might not be themain reason for the difference in maximal running speeds of different animals.

Short-and long-term effects of an extreme case of autotomy:does“tail”loss and subsequent constipation decrease the locomotor performance of male and female scorpions?

In many taxa,individuals voluntarily detach a body part as a form to increase their chances of escaping predation.This defense mechanism,known as autotomy,has several consequences,such as changes in locomotor performance that may affectfitness.Scorpions of the genus Ananteris autotomize the“tail”,which in fact corresponds to the last abdominal segments.After autotomy,individuals lose nearly 25%of their body mass and the last portion of the digestive tract,including the anus,which prevents defecation and leads to constipation,because regeneration does not occur.Here,we experimentally investigated the short-and long-term effects of tail loss on the locomotor performance of Ananteris balzani.In a short-term experiment,the maximum running speed(MRS)of males and females did not change after autotomy.Moreover,the relative mass of the lost tail did not affect the change in MRS after autotomy.In a long-term experiment,autotomy had a negative effect on the MRS of males,but not of females.Autotomized over-fed individuals suffered from severe constipation but were not slower than autotomized normally fed individuals.In conclusion,tail loss has no immediate effect on the locomotor performance of scorpions.The long-term decrease in the locomotor performance of autotomized males may impair mate searching.However,because death by constipation takes several months,males have a long time tofind mates and reproduce.Thus,the prolonged period between autotomy and death by constipation is crucial for understanding the evolution of one of the most extreme cases of autotomy in nature.