Physiological Analysis of Eleutherodactylus Specimens in West-Central Puerto Rico, 2021-2022

Amphibians are vulnerable to extinction owing, partly, to altered physiological processes induced by projected global warming and drying. Understanding the mechanisms behind their responses is essential to formulate adaptation strategies for their conservation. Puerto Rico harbors 15 endemic Eleutherodactylus frogs considered vulnerable to extinction due to poor vagility and sensitivity to environmental variability. Herein are reported the effects of four temperature treatments (15, 20, 25, and 30 degrees Centigrade) on metabolic rates associated with specific dynamic action (SDA) and standard metabolic rates (SMR) of four representative species of Eleutherodactylus employing a respirometer. All species in either experiment increased their excretion of CO2 with increasing temperature. CO2 excretion rates were higher immediately post-ingestion, subsiding to low levels by the third day (72 hours). SMR excretion rates of E. juanariveroi and E. antillensis increased up to 20 degrees Centigrade and then curbed. Rates of E. coqui increased linearly, whereas rates of E. wightmanae increased markedly from 20 to 25 degrees Centigrade, perishing at 30 degrees Centigrade. E. antillensis, E. wightmanae and E. juanariveroi exhibited a change in metabolic rates between 20 degrees Centigrade and 25 degrees Centigrade, the same range where occupancy shifts from lower to higher probability for all species. Climate projections suggest that species will be exposed to 2-3 additional hours during evenings at ≥25 degrees Centigrade below 300 m, and about 1 hour at 400-500 m. Species occurring in low elevations (≤400 m) may have to compensate for the additional energy expenditure induced by increased exposure and adjust their evening time budget. A continuing warming trend could begin to infringe on habitats of high elevation specialists like E. wightmanae.