Comparative development in Moenkhausia pittieri and Paracheirodon innesi (Ostariophysi: Characiformes) with comments on heterochrony and miniaturization in the Characidae.

Developmental heterochronies between the small-sized Moenkhausia pittieri and the miniature Paracheirodon innesi were determined by describing and comparing external morphological development in both species. Despite being classified as miniature, P. innesi was larger and more developed in the flexion and post-flexion larval stages than M. pittieri. Broader patterns within the Characidae suggest that body size reduction in P. innesi is tied to accelerated development and higher growth rate along with early maturation and precocious cessation of growth, which are characteristic of miniature species. Comments on adipose-fin loss in Characidae as a consequence of developmental truncation are included.