Hypoxia-Limited Survival, Respiration, and Mate-Guarding Behavior in the Amphipod Gammarus Pseudolimnaeus Bousfield
Survival in hypoxia, oxygen-limitation of respiration and effects of hypoxia on precopulatory mate-guarding behavior of the amphipod, Gammarus pseudolimnaeus, were tested to determine if seasonal hypoxia in Lake Taneycomo could be a limiting factor for amphipods in the lake. Currently, the Army Corps of Engineers uses oxygenation procedures at Table Rock Dam to defend 4.0 ppm dissolved oxygen (D.O.) in water entering Lake Taneycomo. However, little information exists to indicate whether this level of oxygenation is sufficient for survival, growth, and reproduction of G. pseudolimnaeus. Male, female, and juvenile amphipods survived 48 hours exposure to dissolved oxygen below the minimum daily average that is currently defended in the lake. Survival of hypoxia below 3.5 ppm was differed among genders and age with females being most sensitive, and juveniles being least sensitive. Sensitivity to hypoxia increased with an increase in temperature. Respiration of adult G. pseudolimnaeus was found to be oxygen-limited at all levels of D.O. below air saturation. Females had higher mass-specific rates of respiration and were more oxygen dependent than males at 10°C, but neither rate nor oxygen dependence of respiration differed among genders at 15 or 20°C. Hypoxia was found to inhibit mate-guarding behavior by male G. pseudolimnaeus at levels substantially above the minimum defended in Lake Taneycomo. Hypoxia limited both the male's ability to regain a female when separated and the male's ability to maintain mate-carrying behavior until mating could take place. It appears from the data that an increase in oxygenation procedures to defend 5 ppm instead of 4 ppm would substantially increase both respiration and mating behavior.
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