Meeting Abstract

17.2  Thursday, Jan. 3  Visceral topography in elongate vertebrates WARD, A.B.*; KLEY, N.J.; Adelphi University; Stony Brook University award@adelphi.edu

Body elongation has evolved multiple times among vertebrates. In general, this involves modifications to the vertebral column such that there are either more vertebrae or longer vertebrae. Such modifications can occur across the entire vertebral column or in specific regions. For example, the polypteriform fish Erpetoichthys has twice as many abdominal vertebrae as its sister genus, Polypterus. In this study, we examined the effects of increasing the number of abdominal vertebrae on the topography of the abdominal viscera. We recorded the anterior and posterior positions of individual visceral organs in two species of polypteriform fishes and two species of anguid lizards. In the polypteriform comparison, we found that abdominal elongation leads to lengthening of the individual visceral organs. For cases in which the viscera spanned more vertebrae in Erpetoichthys than in Polypterus, the increase in segmental span was equivalent to the difference in the number of abdominal vertebrae. In addition, the anteroposterior segmental position of the individual organs differs between non-elongate and elongate species. This study provides an understanding of the anatomical changes that occur to the viscera in lineages that become elongate through the addition of abdominal vertebrae.