Meeting Abstract

P1.39  Saturday, Jan. 4 15:30  Competition-induced gut length plasticity, food intake and growth in red-eyed treefrogs RODRIGUEZ, WB*; JENNINGS, KX; BOUCHARD, SB; WARKENTIN, KM; Otterbein Univ., Westerville OH; Otterbein Univ., Westerville OH; Otterbein Univ., Westerville OH; Boston Univ. sbouchard@otterbein.edu

Red-eyed treefrogs, Agalychnis callidryas, vary greatly in larval growth rate, larval period, and size at metamorphosis due to intraspecific competition. High larval density also induces longer guts, which increase diet transit time and presumably digestive efficiency. We tested if gut plasticity allows larvae to compensate for initially slow growth rates, should resources become available. Larvae were reared in mesocosms at three densities. Upon reaching a common size (40 mm total length), at different ages, a subset from each density was transferred to identical low density, high resource conditions. We predicted that, because they have longer guts, larvae from higher densities would grow or develop faster than those from the low density. To understand growth patterns, we used a second subset of size-matched larvae to estimate food intake. We fed them carbon to establish a gut content mark, gave them algae ad libitum for a standard period, then euthanized them and examined their guts. Intake was measured as the length of algae-filled gut anterior to the carbon. Larvae from the low density ate more than did those from higher densities, possibly reflecting intake levels in their original conditions. Despite this difference in intake, one-week growth rates, time from transfer to metamorph emergence, and metamorph snout-vent lengths (22 mm) did not differ, although metamorphs from the high density had slightly lower mass. This suggests that, with ample resources, the combination of low intake and long guts can achieve the same result as high intake and short guts, and that initially slow-growing larvae can dramatically change their growth trajectory late in larval life.