Meeting Abstract
Arguably the most athletic of marine invertebrates, squids can achieve a wide range of swimming speeds and maneuvers, including the powerful jet-propelled escape response. Underlying locomotion in many species of squid are two parallel motor-nerve pathways, the giant and non-giant axon systems, which can act individually or in concert to coordinate jetting. Because squids cannot thermoregulate and they have a high oxygen demand to sustain muscular activity, the maintenance of essential behaviors in the face of environmental variation poses a major challenge. Doryteuthis opalescens (California market squid) found in Monterey Bay often encounters intrusions of cold, hypoxic water from offshore, but effects of hypoxia on locomotion and its underlying mechanisms in this species remain unexplored. In this study, we elicited escape jets using a strobe-flash stimulus and recorded stellar nerve activity in conjunction with pressure inside the mantle cavity in restrained squid exposed to normoxic (>250 μmol/kg ≈ 8 mg/L) and acutely hypoxic (60 μmol/kg ≈ 2 mg/L) conditions at 8°C. Escape jet amplitude was lower and latency was longer under hypoxic conditions, but only for individuals that were exposed to hypoxia before normoxia. Squid exposed to normoxia followed by hypoxia did not show these differences, but they did show slightly increased latency and decreased jet amplitude upon return to normoxic conditions. The increase in latency and decrease in jet amplitude appear to coincide with a reduction in giant axon activity. These results suggest that exposure to hypoxia may primarily affect locomotor performance in D. opalescens by impairing giant axon activity.
