|Title||The caudal skeleton of ostariophysan fishes (Telostei): intraspecific variation in Trichomycteridae (Siluriformes)|
|Publication Type||Journal Article|
|Year of Publication||1983|
|Journal||Journal of Morphology|
|Keywords||Chordates Fish Vertebrates Skeletal and supporting structures Skeleton Axial skeleton Life cycle and development Development Evolution Variation|
The different elements of the caudal skeleton of the South American catfish genera Nematogenys (Nematogenyinae) and Trichomycterus, Hatcheria and Bullockia (Pygidiinae) (Siluriformes, Trichomycteridae) were examined. Ontogenetic transformation of the 2nd ural centrum in Trichomycteridae separates the subfamilies Nematogenyinae and Pygidiinae. In the former, the 2nd ural centrum is aligned and the 1st ural centrum in early stages of ontogeny; it is not fused with the bases of hypurals 3 and 4 in any stage of development. In the Pygidiinae, the 2nd ural centrum is connected with the base of hypural 3 from an early stage of development on. One of the most noteworthy features of the Pygidiinae is the epural, a polymorphic element with 3 or 4 morphotypes that are species specific. The primitive catfish Nematogenys shows intraspecific variation in the ural centra, segmentation of procurrent caudal rays and principal caudal ray formulae. Species of Trichomycterus, Hatcheria and Bullockia are characterized by great intraspecific variability that involves ural centra, the epural, hypurapophyses and the neural arches of the compound centrum. There is intraspecific variation in the fusion of the hypurals in some species of Trichomycterus. Intraspecific variation of the caudal skeleton of fishes of the family Trichomycteridae involves the presence and frequency of different morphotypes of the epural, neural arch of the compound centrum, fusion of hypurals and principal caudal ray formulae. Ontogenetic changes of the 1st and 2nd ural centra, hypurapophyses (with the exception of Nematogenys) and segmentation of procurrent caudal rays (in Nematogenys) are involved also.