The effects of heterochrony on frog life histories.

FABREZI, MARISSA

Punta del Este

Simposio; "Life history effects on development and morphology in Amphibians. 9th International Congress of Vertebrate Morphology.; 2010

Division of Vertebrate Morphology-Society for Integrative & Comparative Biology

Heterochrony refers to those permutations in timing of differentiation events, and those changes in rates of development through which morphological changes and novelties originate during phyletic evolution. This research analyzes morphological variation during the ontogeny of 20 different anuran species that inhabit semi-arid environments of Northwestern Argentina. I use collection data and anatomical methods to compare larval growth, developmental timing, and sequences of ontogenetic events. Most species present a similar pattern of metamorphic transformations, with a size at metamorphosis related to the duration of larval period, independently of rates of postmetamorphic growth. The sequence of metamorphic events (vent tube loss, keratinized larval mouth part loss, posterior displacement of the angle of mouth, tail reduction, differentiation of eyelids and stomach, and skull ossification) occurs in a short period between forelimb emergence and total absence of tail. Exceptions are: (1) Lepidobatrachus spp. that reach large sizes at metamorphosis by accelerate developmental rates and exhibit heterochronic features in oral and digestive structures. These developmental changes have effects on the adult’s ability to feed underwater on large prey. (2) Pseudis platensis has both long larval development and missing juvenile postmetamorphic stages. Curiously, among the 20 species studied, the species that showed the most important ontogenetic differences (Lepidobatrachus spp. and Pseudis platensis) are the only ones with aquatic adults. These findings reveal reciprocal influences of larval and adult body plans; suggesting different patterns of larval development evolved concomitantly with adult life styles over similar geographical and ecological ranges.