Meeting Abstract

38.4  Sunday, Jan. 5 08:45  Energetics of active sensory and communication signals in the weakly electric fish Eigenmannia virescens: Organismal, cellular, and molecular perspectives. MARKHAM, M.R.*; SINNETT, P.M.; BAN, Y; AHADIZADEH, E.N.; Univ. of Oklahoma; Univ. of Oklahoma; Univ. of Oklahoma; Univ. of Oklahoma markham@ou.edu

Electric fish generate brief electric organ discharges (EODs) for electrolocation and communication. The EOD is generated by the synchronized action potentials (APs) of the electric organ cells (electrocytes) which generate large membrane currents and incur correspondingly high energetic demands. These energetic demands are driven primarily by the activity of the Na⁺/K⁺ ATPase which requires ATP to actively transport Na⁺ and K⁺ across the cell membrane following each AP. The gymnotiform electric fish Eigenmannia virescens generates a quasi-sinusoidal electric organ discharge (EOD) at frequencies of 300-600Hz. These high firing rates further amplify the energetic demand of EOD production, potentially consuming up to 30% of the animal’s energy budget. We have identified physiological adaptations at the organismal, cellular, and molecular levels through which Eigenmannia manages energetic requirements of the EOD during normal conditions and under metabolic stress. Eigenmannia reduces EOD amplitude during food deprivation and restores signal amplitude following feeding, a change mediated by circulating endocrine factors that regulate electrocyte function. Electrocytes possess several design features that reduce energetic requirements of signal production including the compartmentalization of the ion channels and Na⁺/K⁺ ATPases that generate the electrocyte AP and restore ion gradients following the AP, as well as the expression of Na⁺-activated K⁺ channels that terminate the AP. We found also that the Na⁺/K⁺ ATPase shows several amino acid substitutions associated with increases in pump turnover rate in other organisms, a feature that further shapes energy demand at high EOD rates.