Effects of Temperature and Oxygen on the Escape Response in California Market Squid (Doryteuthis opalescens)

Abstract

Califonia market squid (Doryteuthis opalescens) is a nearshore cephalopod that is both ecologically and economically relevant. This species supports many types of fish, mammals, and birds in the marine trophic web as well as one of the largest commercial fisheries in Monterey Bay, California. Recently, the Bay has been experiencing larger and more frequent intrusions of cold, oxygen-poor water coming inshore from offshore currents. Despite being a poikilotherm, D. opalescens is able to maintain critical physiological and behavioral functionality amidst thermal variability. However, it is unclear how the impact of hypoxia fits into the maintenance of defensive behaviors crucial for survival, such as the escape response. In order to understand the effects of a changing habitat on such a vital behavior, I compared the escape responses of D. opalescens exposed to normal ambient oxygen and to hypoxia along a temperature range of 6ºC – 14ºC. The findings presented here provide support for previous work, which revealed a thermal dependence of the escape response; however, the results from this study do not match previous evidence for a compensation mechanism at low temperature. Rather, D. opalescens exhibits a thermal dependence that suggests there is a lack of inhibition of the response at high temperature, which may be advantageous. Additionally, D. opalescens appears to be resilient to the adverse effects of hypoxia, but only at low temperature. Results suggest that animals may experience irreversible stress that hinders the escape response in hypoxia at high temperature. While the combination of hypoxia and high temperature does not naturally occur in the habitat of this species, this scenario is equally important as more ecologically relevant ones. Understanding the consequences of both types of scenarios can provide information on functional limits of maintaining behavioral and physiological processes at environmental extremes.