A comparative ontogenetic study of the tetraodontiform caudal complex

Authors

  • Peter Konstantinidis,

    1. Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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  • G. David Johnson

    1. Department of Zoology, Division of Fishes, Smithsonian Institution, P.O. Box 37012, National Museum of Natural History, MRC 0159, Washington, District of Columbia 20013-7012, USA
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  • ‘ This type of research [i.e. morphological work] is laborious and requires specialized training, especially in the dissection and identification of minute nubbins of developing cartilage and bone that are usually overlooked by reasonable people.’

  • (Leis et al. 1997; in Proceedings of the symposium Fish Larvae and Systematics: Ontogeny and Relationships).

Peter Konstantinidis, Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. E-mail: Peter.Konstantinidis@uni-jena.de

Abstract

Konstantinidis P. and Johnson, G. D. 2012. A comparative ontogenetic study of the tetraodontiform caudal complex. —Acta Zoologica (Stockholm) 93: 98–114.

Interpretation of the caudal complex of adult Tetraodontiformes has proven problematic because of the consolidation of the component elements. Here, we show that an ontogenetic approach offers considerable elucidation of the homology of the caudal complex, resulting in a new understanding of the grundplan of these fishes. The reductions of structures of the caudal complex are interpreted in a phylogenetic context. The caudal skeleton of larval triacanthodids resembles that of many adult percomorphs; however, during subsequent development epural 3 disappears, while epural 2 is reduced so that it can hardly be distinguished from the uroneural remnants. Juvenile triacanthids have an epural 2 that is lost in ontogeny, and the cartilaginous parhypural becomes integrated into the large hypural plate. In ostraciids and diodontids, the parhypural is absent throughout development. The hypural plates of adult balistids, monacanthids and tetraodontids have a conspicuous diastema between the dorsal and ventral portions. However, in early stages of the former two, the dorsal and ventral portions are continuous in cartilage proximally and remain fused in the adults. In tetraodontids, the two hypurals are separate from their initial appearance in cartilage and never fuse, raising the question of homology of the individual hypurals among the different families.

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