Meeting Abstract
P3.88 Sunday, Jan. 6 Documenting the Mechanisms of Elongation Across the Ophidiiformes GALLOWAY, K.A*; MEHTA, R.S; WARD, A.B; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; Adelphi University kategalloway12@gmail.com
Body elongation is pervasive throughout actinopterygian fishes; it has evolved multiple times independently, and over fifteen percent of the diversity has this body plan. Axial elongation can occur through a variety of morphological changes including increasing the number of vertebrae or lengthening the individual vertebral centra. Each morphological change has significant effects on body flexibility. Having a highly flexible body seems to offer many behavioral advantages such as the ability to fit into tight crevices and locomote both aquatically and terrestrially. Our study quantifies elongation in the diverse and little known teleost group, the Ophidiiformes and seeks to understand how elongation may lead to behavioral adaptations and specializations. The Ophidiiformes, collectively known as cusk eels, exhibit elongated bodies, but with varying degrees of flexibility. Pearlfishes (Carapidae) have the greatest degree of axial flexibility, enabling members of this group to enter and exit their invertebrate hosts, such as sea cucumbers. Through morphological metrics such as elongation ratio (ER) and axial elongation index (AEI), we compare the highly flexible axial skeleton of pearlfishes to members of four other ophidiiform clades. We find that pearlfishes and spotted cusk eels (Ophidiidae) have the highest ERs indicating more elongate body plans while the basketweave cusk eel and brotulas exhibit the lowest ERs indicating deeper bodies, albeit still elongate body plans. Our study shows that vertebral numbers in the caudal region of the axial skeleton are driving elongation in the Ophidiiformes. Pearlfishes, however, exhibit a two-fold increase in caudal vertebral numbers enabling them to be extremely flexible and probe small crevices to enter their invertebrate hosts.
