Current address: Department of Ecology and Evolutionary Biology, Box G-B210, Brown University, Providence, RI 02912, USA.
Evolution of axial patterning in elongate fishes
Article first published online: 9 JAN 2007
Biological Journal of the Linnean Society
Volume 90, Issue 1, pages 97–116, January 2007
How to Cite
WARD, A. B. and BRAINERD, E. L. (2007), Evolution of axial patterning in elongate fishes. Biological Journal of the Linnean Society, 90: 97–116. doi: 10.1111/j.1095-8312.2007.00714.x
- Issue published online: 9 JAN 2007
- Article first published online: 9 JAN 2007
- Received 7 July 2005; accepted for publication 1 March 2006
- comparative methods;
- vertebral column
Within the ray-finned fishes, eel-like (extremely elongate) body forms have evolved multiple times from deeper-bodied forms. Previous studies have shown that elongation of the vertebral column may be associated with an increase in the number of vertebrae, an increase in the length of the vertebral centra, or a combination of both. Because the vertebral column of fishes has at least two anatomically distinct regions (i.e. abdominal and caudal), an increase in the number and relative length of the vertebrae could be region-specific or occur globally across the length of the vertebral column. In the present study, we recorded vertebral counts and measurements of vertebral aspect ratio (vertebral length/width) from museum specimens for 54 species representing seven groups of actinopterygian fishes. We also collected, from published literature, vertebral counts for 813 species from 14 orders of actinopterygian and elasmobranch fishes. We found that the number of vertebrae can increase independently in the abdominal and caudal regions of the vertebral column, but changes in aspect ratio occur similarly in both regions. These findings suggest that abdominal vertebral number, caudal vertebral number, and vertebral aspect ratio are controlled by separate developmental modules. Based on these findings, we suggest some candidate developmental mechanisms that may contribute to vertebral column patterning in fishes. Our study is an example of how comparative anatomical studies of adults can generate testable hypotheses of evolutionary changes in developmental mechanisms. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90, 97–116.