CONICET | Buscador de Institutos y Recursos Humanos

Rhinella spinulosa is ananuran toad species distributed latitudinal and altitudinal(1200?5000m)from Peru to Argentina,in habiting mountain valleys in the Andes.Considering the broad range of habitats where they live,it is important to understand the thermal physiological mechanisms,thermal tolerancesand physiological adaptations for surviving in rigorous environments.We investigated the thermal parameters(field body temperature,selected body temperature,locomotor performance in field and laboratory conditions,and thermal extremes)during diurnal activity for a population of juvenile,post?metamorphosed toads(Rhinella spinulosa) from the Monte Desert of San Juan,Argentina.Post-metamorphic toads are active from approximately 1100 1900(in contrast to nocturnal adult toads).Our findings show that these toads have a wide thermal tolerance range,ranging from a critical thermal maximum of 36.9 °C to crystallization temperatures below 0 °C. During their active period,toads always showed suboptimal thermal conditions for locomotion. Despite the suboptimal condition for the locomotion, diurnal activity is likely to confer thermal advantages,allowing them to search for food and increase digestion and growth rates. Weal so found that the toads are capable of super-cooling, whichprevents mortality from freezing when the environmental temperatures drop below 0 °C. The environmental temperatures are below zero at night,when toads are inactive and take refuge under rocks.In summary,this toad population demonstrates high thermal plasticity,as shown by are latively high levelof activity sustained over a wide range of ambient temperature(35 °C). These thermal adaptations allow this species of juvenile toads to in habit a wide range of altitudes and latitudes.