Meeting Abstract

13-8  Thursday, Jan. 4 11:45 - 12:00  Recovery of giant-axon-mediated escape jetting after exposure to severe hypoxia in Doryteuthis opalescens (California market squid) LI, DH*; GILLY, WF; Hopkins Marine Station of Stanford University; Hopkins Marine Station of Stanford University lidh@stanford.edu

Squids display a wide range of swimming behaviors including the powerful escape jet mediated by the giant and non-giant axon systems, which can act individually or in concert. Due to the squid’s high oxygen demand to sustain muscular activity, maintaining essential behaviors against environmental variation poses a major challenge. Doryteuthis opalescens found in Monterey Bay, CA often encounters cold, hypoxic water from offshore, but the effects of hypoxia on locomotion and its underlying mechanisms have remained unexplored. We recorded stellar nerve activity and simultaneous pressure inside the mantle cavity of escape jets elicited in D. opalescens (N=16). Squid were exposed to a dissolved oxygen ramp at 8°C from normoxia (8 mg/L) to hypoxia (0.5 mg/L) and back to normoxia, spending up to 1 hour (LT50) at 0.5 mg/L. Nine squid produced giant-axon-mediated escape jets during the whole experiment including the hour at 0.5 mg/L. In the other seven squid, the giant axon system and subsequent jetting failed after an average of 23.1 minutes (range 5-39 min) at 0.5 mg/L. Four squid recovered upon return to normoxia whereas three died. Across all squid, jets elicited under hypoxia had smaller peak pressure, longer latency, and reduced giant axon activity than those in initial normoxic conditions. Jets from squid that recovered in final normoxic conditions had larger peak pressure and shorter latency than those in hypoxia but were still hindered when compared to initial conditions. Our results suggest that exposure to hypoxia affects locomotor performance in D. opalescens by impairing giant axon activity, though the ability to recover shows inter-individual variation.