Ontogeny of the skeleton of Moenkhausia pittieri (Ostariophysi: Characiformes) with discussion on functional demands and ossification patterns in the Characidae

Abstract

Abstract Most fishes must face their environment alone in the early stages of life. The overall sequence of bone appearance is related to functional demands of the early developmental stages. This study offers detailed data on the skeletogenesis of Moenkhausia pittieri, as an example of a "generalized characid". The sequence of ossification is determined and discussed in response to functional demands. Early developmental stages involve the rapid development of bones related to respiration and feeding. The last sets of bones to appear include those of the paired fins and infraorbitals. Patterns in the order of ossification are highlighted, and heterochronies are detected and discussed. Loss of late developmental stages related to miniaturization, a trend in the evolution of Characidae, is discussed in the light of comparative anatomy and ontogenetic data. Furthermore, morphological particularities found in M. pittieri and other characids are discussed in an ontogenetic perspective, offering a background for future phylogenetic studies to understand the homology of certain structures and serving as a further step to elucidate the relationships in ostariophysans.