Meeting Abstract

P3.48  Sunday, Jan. 6  Developmental shifts in heart position for the diamondback water snake ANDERSON, G.E.*; SECOR, S.M.; University of Alabama, Tuscaloosa; University of Alabama, Tuscaloosa ganderson@crimson.ua.edu

Heart position in snakes relative to body length has been hypothesized to be adaptively correlated with habitat (aquatic, terrestrial, and arboreal) and shown to be conserved phylogenetically. Among snake species that are phylogenetically diverse, relative heart position shifts with increased length, becoming relatively closer to the head with size. Unknown is whether heart position is fixed to body segment and segments develop differentially with age and size, or if position shifts independently. We examined relative heart position for the diamondback water snakes (Nerodia rhombifer) across a 6-fold range in snout vent length (250-fold range in body mass) to demonstrate that the heart moves relatively forward with length (23% to 17% of snout-vent length). We determined that ventral scale number corresponded closely with the number of vertebra. Therefore, ventral scale number was recorded at the anterior edge of the heart to identify the corresponding vertebral segment. Across body lengths, heart position was closely aligned with the 26th – 29th vertebrae with no trend of a more anterior placement of the heart with respect to the vertebrae number. Therefore, heart position appears fixed with respect to body segment. Apparently as water snakes increase in length the seemingly anterior movement of their heart is a function of the differential growth of different body areas. The middle and/or distal portions of the snake’s body experience a greater rate of lengthening compared to the anterior portion.