Meeting Abstract

102.1  Sunday, Jan. 6  When Metabolic Scaling Relationships Collapse: The Thermodynamic Nightmare of Development HUNT VON HERBING, I.*; PAN, F.; MAYORGA, M.; University of North Texas, Denton; University of Southern California, Los Angeles; Autonomous University of the State of Mexico, Toluca vonherbing@unt.edu

In a series of unique experiments in which developing Danio rerio were exposed to a combination of chronic and acute high temperature and hypoxia treatments, metabolic scaling relationships collapsed in most conditions. Given the unexpected results, non-equilibrium thermodynamics was applied to understand the underlying mechanics. In this study, larvae were reared in a 2 (28 & 31°C) x 2 (PO₂ of 10 & 21 kPa), factorial design from fertilization to 7 days post-fertilization. Larval oxygen consumption was measured at: 1) normoxia (PO₂ of 21 kPa at 28°C); 2) acute hypoxia (PO₂ of 10 kPa at 28°C); 3) acute high temperature (PO₂ of 21 kPa at 31°C); and 4) acute hypoxia & high temperature (PO₂ of 10 kPa at 31°C). Larvae reared in normoxia when exposed to acute hypoxia showed steep allometric scaling relationships; b of 1.79 ± 0.28 (28°C) & 1.33 ± 0.37 (31°C) compared to b of 0.80 ± 0.29 (28°C) and 0.69 ± 0.23 (31°C). In contrast, larvae reared in chronic high temperature and hypoxia had no significant metabolic scaling relationships. As living systems rely on vascular networks for heat and energy input and dissipation, power law relationships between metabolism and mass may be expected. In development, vascular systems are immature, and rapid changes occur across many gradients (chemical, thermodynamic and pressure), which affect the equilibrium of a dynamic, open (non-linear) system. In our experiments rapidly developing larvae exposed to acute and/or chronic abiotic change may experience energy inputs that exceed rates of dissipation. Thermodynamic gradients and their coupled transport processes may begin to break down resulting in disorder and collapse of metabolic scaling relationships creating conditions inimical to life.