a1 Queen's University Belfast, School of Biological Sciences, Lisburn Road, Belfast, BT9 7BL, Northern Ireland
a2 Queen's University Belfast Marine Laboratory, 12–13 The Strand, Portaferry, County Down, BT22 1PF, Northern Ireland
a3 The University of British Columbia, Department of Zoology, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
a4 CML, Institute of Environmental Sciences, Leiden University, PO Box 9518, 2300 RA, Leiden, The Netherlands
Polyplacophoran molluscs (chitons) are phylogenetically ancient and morphologically constrained, yet multiple living species are often found co-occurring within widely overlapping ecological niches. This study used two sets of experiments to compare interspecific variation among co-occurring species in the North Atlantic (Ireland) and separately in the North Pacific (British Columbia, Canada) chiton faunas. A complementary review of historical literature on polyplacophoran physiology provides an overview of the high level of metabolic variability in this group of ‘living fossils’. Species examined in de novo experiments showed significant variation in oxygen consumption both under air-saturated water conditions (normoxia), and in response to decreasing oxygen availability (hypoxia). Some species demonstrate an ability to maintain constant oxygen uptake rates despite hypoxia (oxyregulators), while others oxyconform, with uptake rate dependent on ambient oxygen tension. These organisms are often amalgamated in studies of benthic communities, yet show obvious physiological difference that may impact their response or tolerance to environmental change.
(Received March 29 2012)
(Accepted April 22 2012)
(Online publication October 22 2012)