Ontogenia conundrum

JOURNAL OF MORPHOLOGY 000:000 – 000 (2004)

Leis’ Conundrum: Homology of the Clavus of the Ocean Sunfishes. 1. Ontogeny of the Median Fins and Axial Skeleton of Monotrete leiurus (Teleostei, Tetraodontiformes, Tetraodontidae)
Ralf Britz1,2* and G. David Johnson1
1 2

Divison of Fishes, National Museum of Natural History, Smithsonian Institution, Washington DC, USA Department of Zoology, The Natural History Museum, London, UK

ABSTRACT We describe the ontogeny of the axial skeleton and median fins of the Southeast Asian freshwater puffer Monotrete leiurus, based on a reared developmental series. Most elements of the axial skeleton in M. leiurus arise in membrane bone. Only the base of the anterior three neural arches, the base of the hemal arches of the third preural centrum, the neural and hemal arches and spines of the second preural centrum, the parhypural, the two hypural plates, and the single epural are preformed in cartilage. In contrast to most teleosts, the proximalmiddle radials of the dorsal and anal fins are upright and symmetrical and their distal tips coalesce during development to form a deep band of cartilage, from which the spherical distal radials are spatially separated. J. Morphol. 000:000 – 000, 2004. © 2004 Wiley-Liss, Inc. KEY WORDS: vertebral column; median fins; pterygiophores; ontogeny; homology; Tetraodontidae

The Tetraodontiformes are a monophyletic group of teleosts, comprising 10 families with approximately 100 genera and 340 species (Nelson, 1994), the relationships of which to other bony fishes remain unclear. They are well known at the alphalevel, and their anatomy has been described in great detail in numerous articles, obviously because of their unusual and diverse structure. The most recent and comprehensive anatomical monographs on tetraodontiforms are those of Winterbottom (1974) on the musculature and Tyler (1980) on the skeleton. Although adult Tetraodontiformes have received considerable interest and study from