LAUSR

Abstract. We describe for the first time the tadpole of two endemic harlequin frogs of the Sierra Nevada de Santa Marta, north of Colombia: Atelopus nahumae and A. laetissimus. In addition, we provide further morphological data for a third species, A. carrikeri. We also discuss some external morphological features for the tadpoles of these species and compare them with data currently available in the literature for the genus and with other larvae deposited in the amphibian collection of the Instituto de Ciencias Naturales of the National University of Colombia. The examined characters comprise eight morphometric variables and many traits of external morphology related with the oral apparatus, abdominal disc, fins, and dorsal color pattern. The tadpoles of A. nahumae and A. laetissimus are gastromyzophorous and morphologically similar, sharing a great number of features with their congeners. The tadpoles of A. nahumae, A. laetissimus, and A. carrikeri contrast morphometrically; total length and tail width are the morphometric traits that are useful to differentiate among them. They are also differentiated by the size of the abdominal sucker and spiracle. In A. carrikeri, the abdominal sucker is large relative to that of A. nahumae and A. laetissimus; the spiracle of A. laetissimus and A. carrikeri is not visible in ventral and dorsal view, whereas it is large and conspicuous in A. nahumae. The tadpoles of the species from Sierra Nevada de Santa Marta differ from most of their congeners found in the Cordillera Oriental and Central of Colombia by lacking a dark band on the fins and caudal musculature. We recorded abiotic factors of the microhabitat where tadpoles of A. nahumae were observed (temperature, dissolved oxygen, and water depth). Our results indicate that the probability of finding A. nahumae tadpoles depends on the depth of the stream.