P2.87 Thursday, Jan. 5 Determinants of the postprandial metabolic response and specific dynamic action of the tarantula Grammostola rosea BELANICH, Jonathan R.*; SHILLINGTON, Cara; SECOR, Stephen M.; University of Alabama; Eastern Michigan University; University of Alabama firstname.lastname@example.org
A mandatory physiological response to meal digestion and assimilation is an increase in metabolic rate; the accumulative cost of which is referred to as specific dynamic action (SDA). While SDA has been examined for a wide spectrum of invertebrate and vertebrate groups, there has been relatively little attention on the postprandial metabolic responses of arachnids. In this study, we characterize the postprandial metabolic profile of the Chilean rosehair tarantula, Grammostola rosea, following the consumption of crickets (Acheta domesticus), hornworms (Manduca sexta), and neonatal rats. Meal size of each prey type averaged 6.4%, 19.5%, and 28.9% of tarantula body mass, respectively. Because tarantulas do not completely consume their prey, individuals were weighed immediately prior to and after feeding to obtain an accurate measure of meal size. Tarantulas responded to all three meals with a characteristic rapid increase in metabolic rate that peaked at six hours after feeding. For each meal type, metabolic rates peaked at 4, 6, and 12-fold of standard metabolic rates and returned to resting levels within 24, 36, and 72 h after feeding, respectively. SDA for each meal averaged 0.16, 0.42, and 1.56 kJ, respectively, equivalent to 2.2%, 5.5%, and 5.3% of the meal’s energy. Effects of meal size for a common meal type were examined with cricket meals ranging from 1.2-7.0% of body mass. A four-fold increase in meal size generated an 80% in peak VO2, a 50% increase in duration, and a 110% increase in SDA. Over a 270-fold range in body mass, SDA generated from cricket meals of ~5% of body mass scaled (log-log) with a mass exponent of 0.94. Tarantulas exhibit the characteristic SDA response, the magnitude of which is influenced by meal type and size.