Ontogeny of the Skeleton of Leporinus oliveirai (Characiformes, Anotomidae)

Abstract

The skeleton is a rich source of characters used in phylogenetic studies of teleost fishes. However, the development of bones was studied in a limited number of species and few studies have been published describing the ontogeny of the Characiformes skeleton. We provide the first complete description of the skeleton ontogeny of an anostomid, Leporinus oliveirai, based on specimens bred in captivity and sampling the first 60 days post-hatching, with sizes ranging from 3.8 mm (notochord length, NL) to 33.2 mm (standard length, SL). Sixty-three specimens were cleared and double stained and subsequently dissected and photographed. The developmental sequence of 141 bony elements is documented. Photography of all anatomical complexes is presented during the development. The first bone to develop is the cleithrum (5.1 mm NL) and the last ones are infraorbitals 4, 5 and 6, extrascapular and sclerotic bones (27.2-29.7 mm SL), similar to what is observed in the development of other characiforms. The main discoveries are numerous conical teeth on the premaxilla and dentary from 5.1 mm NL to 10.4 mm SL that are replaced with three or four large incisiform multicuspid teeth, that become unicuspid in juveniles and adults. The infraorbitals 4 and 5, seen only in juveniles, develop fused, a condition that is in contrast to most anostomids. The autopalatine cartilage begins its development straight, becoming curved during development. The developmental sequence is compared with other Characiformes and the unique characteristics of Anostomidae are discussed concerning the phylogenetic relationships among the family members.