Alsodes pehuenche: Larval biology

Abstract

Alsodes pehuenche is a telmatobiine frog known only from the type locality, the Pehuenche Valley in the Central Andes of Argentina, on the frontier with Chile. This note provides basic information on the life history of the species regarding larval population structure and larval habitat. Out of about 9 streams visited in the area, A. pehuenche tadpoles were only found in the four located nearest the International Pass, between 2491 and 2523 m elevation. Streams with A. pehuenche tadpoles are in very steep areas, although they have long stretches with gentle gradients and numerous waterfalls, and are surrounded by hydrophilous meadows. They have a maximum width of 2 m, carry a low volume of water and are exposed to strong summer radiation, with water temperature reaching 19ºC at midday. Snowmelt water in the streams is very pure and contains a low concentration of ions, therefore having very low conductivity and low hardness. The concentration of sulphur is also very low. The pH was 5.9-7. No sulphur spring was found in the area. The tadpoles were concentrated in backwater sections of the streams, and their densities ranged from 30 to 80 individuals/m2. In all the streams, we found different cohorts of tadpoles of different sizes and stages living together. The great differences in size and development stage found among cohorts show that they belong to ovipositions of different summers, as reported for A. gargola, for which there are up to three simultaneous cohorts of tadpoles, each cohort having hatched during a different summer.