ECOLOGY OF THE HAGFISH, MYXINE-GLUTINOSA L IN THE GULF-OF-MAINE .1. METABOLIC RATES AND ENERGETICS

The hagfishes, as an extant group, represent the most primitive living craniates. Although of interest to evolutionary biologists, little is known about the physiological ecology of hagfish, despite the occurre nce of large, commercially exploited populations around the world. In the Gulf of Maine, the Atlantic hagfish, Myxine glutinosa L., is a nui sance to the groundfishing industry, but may play an important role in the ecology of soft-bottom habitats. The recent exploitation of these hagfish populations for the ''eelskin'' fishery has resulted in renew ed interest regarding their ecology and physiology. Direct measurement of oxygen consumption rates for M. glutinosa with versus without gill pouch perfusion indicate that the majority of oxygen uptake at rest o ccurs cutaneously. The measured rates of oxygen consumption imply extr emely low energetic demands. Hagfish adaptations to hypoxic environmen ts, which include cutaneous respiration, allow them to occupy burrows where oxygen concentrations are low. These adaptations would also perm it long intervals between periods of opportunistic feeding. Although t he energetic demands of individual hagfish is low, the impact of large populations of hagfish on commercially important species could be sig nificant.