The respiratory response to asphyxia of Typhlogobius californiensis (Teleostei: Gobiidae) and some related gobies.

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1. The respiratory, metabolic, and behavioral responses to asphyxia of three gobiid fishes are compared. Adult specimens of Typhlogobius californiensis and Gillichthys mirabilis are subject to hypoxic stress in their natural habitats, while Coryphopterus nicholsii generally is not.2. Oxygen tensions in burrows of the ghost shrimp Callianassa affinis, commensal host of Typhlogobius, fall rapidly to nearly anoxic levels following exposure of the burrow openings by the outgoing tide.3. The resting oxygen consumption of Typhlogobius is extremely low; the one gram intercept for the wet weight-oxygen uptake regression is 17 µl O2/g/hr. The other two species consume oxygen 3 to 5 times as rapidly at rest.4. Resting specimens of Typhlogobius are capable of maintaining a constant rate of oxygen uptake down to a critical ambient oxygen tension of 9-16 mm Hg. Gillichthys and Coryphopterus are capable of regulating oxygen uptake down to critical levels of 16-25 mm Hg and 19-28 mm Hg respectively.5. Both Typhlogobius and Gillichthys metabolize gasbladder oxygen during the initial few hours of asphyxia.6. Typhlogobius accumulates lactate ion during periods of prolonged asphyxia, indicating that maintenance energy is derived from anaerobic metabolism. The 95% confidence limits for the rate of lactate accumulation are energetically equivalent to 33% to 52% of the respirometrically measured aerobic metabolic rate.7. The survival time of Typhlogobius in deoxygenated seawater varies with the volume of seawater. In very small volumes of seawater (< 10-20 ml), survival time is less than 24 hours. In larger volumes of seawater, survival time asymptotically approaches 80 to 100 hours. The decreased asphyxial survival time in small volumes of seawater may result from rapid accumulation of an excreted acid byproduct of anaerobic metabolism.Gillichthys survives exposure to deoxygenated seawater for a relatively short period of time; survival times varied from 6.5 to 12.5 hours and were independent of seawater volume. Coryphopterus survives anoxia only 28 to 42 minutes.8. It is hypothesized that the ability of Typhlogobius to function as a facultative anaerobe may be related to the low energy demand of the brain, to vascular adaptations which facilitate the exchange of metabolites between brain and circulating blood, and to an ability to excrete the acid by-product(s) of anaerobic metabolism.