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      Sequência de ossificação do sincrânio e hioide em embriões de Caiman yacare (Crocodylia, Alligatoridae) Translated title: Ossification sequence of skull and hyoid in embryos of Caiman yacare (Crocodylia, Alligatoridae)

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          Abstract

          O crânio representa uma estrutura única e complexa dos vertebrados, sendo foco relevante objeto de estudos morfológicos e sistemáticos. Embora os crocodilianos constituam um importante grupo representante dos Archosauria, nossos conhecimentos acerca de seu desenvolvimento e homologias ainda são escassos. Aqui descrevemos uma sequência detalhada de ossificação dos ossos do crânio de Caiman yacare (Daudin, 1802), objetivando contribuir com informações de foco anatômico. Coletaram-se ao acaso embriões em intervalos regulares durante todo o período de incubação, sendo estes posteriormente submetidos a protocolo de diafanização e coloração de ossos. O padrão de ossificação em C. yacare segue parâmetros gerais em répteis e outros tetrápodes. Os primeiros centros de ossificação correspondem aos ossos dérmicos, envolvidos com funções primárias como a alimentação e respiração (e.g. maxila, dentário, esplenial, angular, pterigoide, ectopterigoide e jugal, incluindo ainda os dentes). Os ossos da porção dorsal do neurocrânio se ossificam posteriormente, evidenciando uma fontanela cranial que permanece até o momento da eclosão. Os ossos parietal, frontal e opstótico possuem mais de um centro de ossificação que se fundem durante a ontogenia. O centro de ossificação do parisfenoide está ausente, e apenas um centro de ossificação está presente para o basisfenoide. A porção posterior do crânio é formada por centros de substituição do condrocrânio que se ossificam em estágios posteriores.

          Translated abstract

          The skull is a unique and complex structure of vertebrates and a main focus of morphological and systematic studies. Although Crocodilians represent an important component of Archosauria group, our knowledge of the development and homology are few. Herein, we describe the detailed development sequence of skull of the Caiman yacare (Daudin, 1802) in an effort to contribute to filling this anatomical gap. Embryos were sampled randomly at a regular intervals during full incubation period and morphological descriptions are based on cleared and stained and embryos. The ossification pattern of C. yacare follow general aspects for reptiles and others tetrapods. The first ossification centers occur in dermal bones involved in primary functions such as feeding and breathing, like maxillae, dentary, splenial, angular, pterygoid, ectopterygoid and jugal, including the teeth. Bones of dorsal portion of the neurocraniun ossify later, showing a cranial fontanelle that remains at the hatching. The parietal, frontal and opisthotic have more than one ossification center that fuse during ontogeny. The ossification center for parasphenoid was absent and only one ossification center is present for basisphenoid bone. The posterior portion of the skull is formed for ossification centers of chondrocranium substitution that ossify in later stages.

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          Size and shape in ontogeny and phylogeny

          We present a quantitative method for describing how heterochronic changes in ontogeny relate to phyletic trends. This is a step towards creating a unified view of developmental biology and evolutionary ecology in the study of morphological evolution. Using this representation, we obtain a greatly simplified and logical scheme of classification. We believe that this scheme will be particularly useful in studying the data of paleontology and comparative morphology and in the analysis of processes leading to adaptive radiation. We illustrate this scheme by examples drawn from the literature and our own work.
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            Neural crest and the origin of vertebrates: a new head.

            Most of the morphological and functional differences between vertebrates and other chordates occur in the head and are derived embryologically from muscularized hypomere, neural crest, and epidermal (neurogenic) placodes. In the head, the neural crest functions as mesoderm and forms connective, skeletal, and muscular tissue. Both the neural crest and the epidermal placodes form special sense organs and other neural structures. These structures may be homologous to portions of the epidermal nerve plexus of protochordates. The transition to vertebrates apparently was associated with a shift from a passive to an active mode of predation, so that many of the features occurring only in vertebrates became concentrated in the head.
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              The Origin and Early Evolution of Turtles

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                Author and article information

                Journal
                isz
                Iheringia. Série Zoologia
                Iheringia, Sér. Zool.
                Museu de Ciências Naturais (Porto Alegre, RS, Brazil )
                0073-4721
                1678-4766
                September 2011
                : 101
                : 3
                : 161-172
                Affiliations
                [04] Lagoa Santa MG orgnameInstituto Chico Mendes para Conservação da Biodiversidade orgdiv1Centro de Conservação e Proteção de Répteis e Anfíbios Brasil
                [02] Uberlândia MG orgnameUniversidade Federal de Uberlândia orgdiv1Faculdade de Medicina Veterinária orgdiv2Laboratório de Ensino e Pesquisa em Animais Silvestres Brasil quagliatto@ 123456famev.ufu.br
                [01] Jataí GO orgnameUniversidade Federal de Goiás orgdiv1Laboratório de Anatomia Humana e Comparativa Brasil
                [03] Brasília DF orgnameUniversidade de Brasília orgdiv1Laboratório de Anatomia Comparativa dos Vertebrados Brasil
                Article
                S0073-47212011000200003 S0073-4721(11)10100303
                10.1590/S0073-47212011000200003
                7c57fe13-f45a-459d-9471-e8f4b793a933

                This work is licensed under a Creative Commons Attribution 4.0 International License.

                History
                : 30 March 2010
                : 05 April 2011
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 63, Pages: 12
                Product

                SciELO Brazil


                jacaré-do-pantanal,reptiles,Pantanal caiman,ossification,ontogeny,Morphology,répteis,ossificação,ontogenia,Morfologia

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