Paradoxical anaerobism in desert pupfish

Abstract

In order to estimate metabolic demands of desert pupfish for conservation purposes, we measured oxygen consumption in fish acclimated to the ecologically relevant temperatures of 28 or 33°C. For these experiments, we used fish derived from a refuge population of Devils Hole pupfish (Cyprinodon diabolis). Measurement of routine oxygen consumption (V O2,routine ) revealed some 33°C-acclimated fish (10% of 295 assayed fish) periodically exhibited periods of no measurable oxygen consumption despite available ambient oxygen tensions that were above the critical P O2 . We call this phenomenon paradoxical anaerobism. The longest observed continuous bout with no oxygen consumption was 149 min, although typical bouts were much shorter. Fish maintained normal posture and ventilation rate (>230 ventilations per minute) during paradoxical anaerobism. Fish rarely demonstrated a compensatory increase in oxygen use following a period of paradoxical anaerobism. In contrast, only one out of 262 sampled fish acclimated at 28°C spontaneously demonstrated paradoxical anaerobism. Muscle lactate concentration was not elevated during periods of paradoxical anaerobism. However, the amount of ethanol released by the 33°C-acclimated fish was 7.3 times greater than that released by the 28°C acclimation group, suggesting ethanol may be used as an alternative end product of anaerobic metabolism. Exposure to exogenous ethanol, in concentrations as low as 0.1%, produced periods of paradoxical anaerobism even in 28°C-acclimated fish.

The Gut Microbiome, Energy Homeostasis, and Implications for Hypertension

“…The team then demonstrated that anaerobic metabolism did not contribute any substantial fraction of total energy expenditure in an ectotherm (ball python) [41]. The van Breukelen team has also recently demonstrated anaerobic metabolism in desert pupfish even in the absence of anoxia (paradoxical anaerobism) [42]. In 2013, our team demonstrated that anaerobic metabolism accounted for roughly 10% of total energy expenditure in laboratory mice (both C57BL/6J and FVB/NCrl strains) [43].…”

New evidence for the recent divergence of Devil's Hole pupfish and the plausibility of elevated mutation rates in endangered taxa

“…Higher metabolism is strongly correlated with environmental temperature in fishes (Clarke & Johnston, ) and DHP persist in one of the hottest environments of any vertebrate species at 32°C year‐round in Devil's Hole (Stoike & Pister, ). Furthermore, DHP periodically goes into states of anaerobic metabolism for up to 2 hr, paradoxically reducing its metabolic efficiency even in the presence of oxygen and driving up its metabolic rate (Heuton, Ayala, Burg, & Dayton, ; Hillyard, Burg, McKenna, & Urbina, ). Second, higher metabolism is also correlated with smaller size (Gillooly, Brown, West, & Savage, ) and Devil's Hole pupfish are the smallest species of Cyprinodon (Stoike & Pister, ).…”

Oxygen Consumption is Limited at an Ecologically Relevant Rearing Temperature in Pupfish Eggs

“…This point precedes blood circulation. Recently, our group reported unexpected oxygen consumption patterns in adult pupfish acclimated to 33°C (Heuton et al, 2015). Adult pupfish exhibit extended periods of little or no oxygen consumption that may be as long as 149 min continuous.…”