Meeting Abstract

P2.70  Wednesday, Jan. 5  Longitudinal variation in the axial muscles of colubrid and booid snakes NICODEMO, P.*; JAYNE, B. C.; University of Cincinnati; University of Cincinnati nicodepp@mail.uc.edu

In snakes, each axial muscle segment corresponds directly with a single vertebra, but individual axial muscles may span dozens of vertebrae. Consequently, a muscle that normally extends anteriorly has a constraint on segmental length at the anterior end of the snake. However, this and other aspects of longitudinal variation in axial muscle morphology are not well documented either within most species of snakes, or between different species of snakes. Thus, we compared the patterns of segmentation and morphology of the anterior (10% snout-vent length) axial muscles of a colubrid, Pantherophis guttata, and booid, Boa constrictor, species of snake. In Pantherophis, the length of the anterior tendon of the spinalis-semispinalis (SSP) reduced by 50% (10 to 5 vertebrae) anteriorly, whereas both the contractile tissue of the SSP exhibited patterns of segmental elongation, especially in the anteriormost muscles (+2-3 vertebrae). The anteriormost SSP bellies receive medial tendons from 3-4 longissimus dorsi (LD), whereas posterior SSP receive medial tendons from a single LD. In Boa, minor reduction occurred in the anterior tendon of the SSP (1/2 vertebrae.) anteriorly, as well as minor elongation of contractile tissue (1/2 vertebrae.). In Boa the anterior trunk differs from the posterior trunk as a result of the medial tendons of the LD attaching to contractile tissue which interlaces with the spinalis capitus muscle and inserts on the cranium, thus representing the semispinalis cervicus.