Meeting Abstract

26.1  Jan. 5  Predictors of heart position in snakes GARTNER, G.E.A.*; HICKS, J.W.; MANZANI, P.R.; ANDRADE, D.; GARLAND, T.; Univ. of California, Riverside; Univ. of California, Irvine; Instituto de Biociencias, Rio Claro Brazil; Instituto de Biociencias, Rio Claro Brazil; Univ. of California, Riverside ggart001@ucr.edu

Snake cardiovascular systems must resist strong gravitational pressure gradients when assuming vertical postures during climbing or rearing. Thus, arboreal species might be expected to have hearts placed more anteriorly. Aquatic species, on the other hand, might be able to have hearts placed in a more posterior position because external hydrostatic pressure would counteract internal pressure gradients. A previous non-phylogenetic analysis of snake head-heart distance was partially consistent with these ideas, finding the heart located 15-25% of total body length from the head in terrestrial and arboreal species, but 25-45% in aquatic species (Seymour 1987). It also found that viperids had relatively posteriorly placed hearts, regardless of habitat. We analyzed an independent data set of 108 species (mostly from South America) from 4 major Alethinophidian families using both conventional phylogenetically based statistical methods. Considering all 108 species and controlling for snout-vent-length (log-log transformation), heart position showed strong phylogenetic signal (P << 0.001, K = 1.224 [see Blomberg et al. 2003]). We then categorized species as terrestrial, aquatic, semi-aquatic, arboreal or fossorial and performed analysis of covariance with SVL. Arboreal species were significantly different from terrestrial species, the former having hearts placed more posteriorly, i.e., opposite to what might be expected. Viperids also had relatively posteriorly placed hearts, irrespective of habitat, consistent with Seymour's finding. Data for additional taxa will be required to further elucidate the relationships between habitat, phylogeny, and heart position in snakes.