Osteology of Priocharax and Remarkable Developmental Truncation in a Miniature Amazonian Fish (Teleostei: Characiformes: Characidae)

Autor(es)

Mattox, George M. T. ^{[1, 2]} ; Britz, Ralf ^[3] ; Toledo-Piza, Monica ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Zool, Inst Biociencias, BR-05508090 Sao Paulo - Brazil

^[2] Univ Fed Sao Carlos, Dept Biol, Campus Sorocaba Rodovia Joao Leme dos Santos SP 2, BR-18052780 Sorocaba, SP - Brazil

^[3] Nat Hist Museum, Dept Life Sci, Cromwell Rd, London SW7 5BD - England

• Tipo de documento: Artigo Científico
• Fonte: Journal of Morphology; v. 277, n. 1, p. 65-85, JAN 2016.
• Citações Web of Science: 6

Resumo

Establishing phylogenetic relationships of miniature fishes is challenging in taxa with developmental truncation. Within the Characiformes, developmental truncation appears to be relatively rare, with the Neotropical genus Priocharax being an example. Priocharax includes three miniature species among the smallest of the order and has been hypothesized to belong to the Heterocharacinae. The pronounced reduction in its skeleton, however, prevented a clearer evaluation of its relationships. The present detailed osteological study was designed to address this question and revealed that 21 bones are absent and nine other skeletal structures are simplified in Priocharax when compared to other characids. Comparison of the skeleton of adult Priocharax with early developmental stages of other characids demonstrated that most of the absences and simplifications can be interpreted as developmental truncations. The most striking developmental truncations are in the pectoral girdle, in which the endoskeleton remains entirely cartilaginous. Other interesting truncations are in the ethmoid region of the skull, infraorbital series, and Weberian apparatus, in which the claustrum is absent. Our study also revealed some unusual sexual dimorphisms in the pelvic girdle. Two cladistic analyses were performed to assess the relationships of Priocharax within the Heterocharacinae. The first consisted of a traditional analysis in which all absences and reductions of Priocharax were coded in the same way as in the remaining taxa. This resulted in three equally most parsimonious topologies, all of which have Priocharax as the most basal taxon of the Heterocharacinae. The second analysis incorporated ontogenetic information, and most absences and reductions of Priocharax were reinterpreted as apomorphic conditions and thus, coded differently from similar conditions in outgroups. This resulted in a single phylogenetic hypothesis with Priocharax and Gnathocharax as sister groups based on seven synapomorphies. Our approach demonstrates the importance of developmental studies to better understand morphological evolution of miniaturized, truncated taxa, and to generate hypotheses of their relationships. (C) 2015 Wiley Periodicals, Inc. (AU)

• Processo FAPESP: 11/50282-7 - Inventário da fauna de Characiformes (Teleostei, Ostariophysi) da América do Sul
• Beneficiário: Naercio Aquino Menezes
• Modalidade de apoio: Auxílio à Pesquisa - Programa BIOTA - Temático
• Processo FAPESP: 11/13735-3 - Coleta, manutenção e preservação de exemplares de peixes miniatura e obtenção de séries ontogenéticas de peixes: importância destas etapas para o êxito de estudos do processo de miniaturização
• Beneficiário: Mônica de Toledo-Piza Ragazzo
• Modalidade de apoio: Auxílio à Pesquisa - Pesquisador Visitante - Internacional
• Processo FAPESP: 12/01075-1 - Proposta de estágio de pesquisa no exterior associado ao projeto de pós-doutorado Estudo Filogenético de Priocharax Weitzman & Vari (Teleostei, Characiformes, Characidae) em um Contexto Ontogenético: uma Abordagem do Processo de Miniaturização
• Beneficiário: George Mendes Taliaferro Mattox
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado
• Processo FAPESP: 10/50941-8 - Estudo filogenético de Priocharax Weitzman & Vari (Teleostei, Characiformes, Characidae) em um contexto ontogenético: uma abordagem do processo de miniaturização
• Beneficiário: George Mendes Taliaferro Mattox
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado