title: It's all in the gills: evaluation of O2 uptake in Pacific hagfish refutes a major respiratory role for the skin.
abstract: Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, whether cutaneous O2uptake is the dominant route of uptake remains under debate; all evidence supporting this hypothesis has been derived using indirect measurements. Here, we used partitioned chambers and direct measurements of oxygen consumption and ammonia excretion to quantify cutaneous and branchial exchanges in Pacific hagfish (Eptatretus stoutii) at rest and following exhaustive exercise. Hagfish primarily relied on the gills for both O2uptake (81.0%) and ammonia excretion (70.7%). Following exercise, both O2uptake and ammonia excretion increased, but only across the gill; cutaneous exchange was not increased. When branchial O2availability was reduced by exposure to anteriorly localized hypoxia (∼4.6 kPa O2), cutaneous O2consumption was only slightly elevated on an absolute basis. These results refute a major role for cutaneous O2acquisition in the Pacific hagfish.
authors.affiliation: Department of Biological Sciences, University of Alberta, 116 St. and 85 Ave., Edmonton, AB, Canada T6G 2R3 Bamfield Marine Sciences Centre, 100 Pachena Rd, Bamfield, BC, Canada V0R 1B0 alex.clifford@ualberta.ca.
authors.forename: Alexander M
authors.identifier: http://orcid.org/0000-0002-2836-5832
authors.initials: AM
authors.lastname: Clifford
authors.affiliation: Bamfield Marine Sciences Centre, 100 Pachena Rd, Bamfield, BC, Canada V0R 1B0 Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Zimmer
authors.affiliation: Bamfield Marine Sciences Centre, 100 Pachena Rd, Bamfield, BC, Canada V0R 1B0 Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
authors.affiliation: Department of Biological Sciences, University of Alberta, 116 St. and 85 Ave., Edmonton, AB, Canada T6G 2R3 Bamfield Marine Sciences Centre, 100 Pachena Rd, Bamfield, BC, Canada V0R 1B0.
authors.forename: Greg G
authors.initials: GG
authors.lastname: Goss
keywords: Agnathan; Ammonia; EPOC; Exercise; Metabolic rate; Respiration