Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, whether cutaneous O2 uptake 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 O2 uptake (81.0%) and ammonia excretion (70.7%). Following exercise, both O2 uptake and ammonia excretion increased, but only across the gill; cutaneous exchange was not increased. When branchial O2 availability was reduced by exposure to anteriorly localized hypoxia (∼4.6 kPa O2), cutaneous O2 consumption was only slightly elevated on an absolute basis. These results refute a major role for cutaneous O2 acquisition in the Pacific hagfish.
The authors declare no competing or financial interests.
The study was conceived and conducted by A.M.C. and A.M.Z.; A.M.C. and A.M.Z. analysed the data; A.M.C. wrote the manuscript; all authors revised and approved the final manuscript.
G.G.G. and C.M.W. are supported by Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants. A.M.C. is supported by an NSERC-PGSD, The Donald M. Ross Scholarship, the R. E. Peter Memorial Scholarship, the Andrew Stewart Memorial Prize, the Western Canadian Universities Marine Sciences Society Graduate Student Award and the Dick & Leona Peter BMSC residential Bursary.
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.141598.supplemental
- Received April 14, 2016.
- Accepted July 1, 2016.
- © 2016. Published by The Company of Biologists Ltd