TY - JOUR
T1 - Leap of faith
T2 - Voluntary emersion behaviour and physiological adaptations to aerial exposure in a non-aestivating freshwater fish in response to aquatic hypoxia
AU - Urbina, Mauricio A.
AU - Forster, Malcolm E.
AU - Glover, Chris N.
N1 - Funding Information:
The authors acknowledge the excellent technical assistance of Gavin Robinson and Renny Bishop, and thank Dr. Ximena Nelson for useful discussions. We are grateful for the feedback from three anonymous referees that greatly improved this manuscript. This work was supported by a Marsden Grant from the Royal Society of New Zealand ( UOC0711 ). M.A.U was supported by a PhD scholarship from the Chilean Government, CONICYT . Funding bodies had no direct role in the study.
PY - 2011/5/3
Y1 - 2011/5/3
N2 - Lowland stream fauna in areas of intensive agriculture are increasingly under threat from anthropogenic activities leading to eutrophication and subsequent hypoxia. Survival of hypoxic episodes depends upon a combination of behavioural and physiological adaptations. Responses of inanga (Galaxias maculatus: Galaxiidae) to aquatic hypoxia were investigated in the laboratory. Contrary to expectation inanga did not display behaviour that might reduce energy expenditure during oxygen limitation, with swimming activity slightly, but significantly elevated relative to normoxia. Instead, as dissolved oxygen concentrations decreased, the fish moved higher in the water column, increased their swimming speed and exhibited aquatic surface respiration. Physiological changes such as enhanced opercular frequency were also noted. As hypoxia deepened inanga started to leap out of the water, emersing themselves on a floating platform. Once emersed, fish exhibited an enhanced oxygen consumption rate compared to hypoxic fish. Thus inanga appear better adapted to escape hypoxia (a behavioural adaptation) rather than tolerate it (physiological adaptation). The emersion strategy used for inanga in response to severe hypoxia is in agreement with their ability to take up more oxygen from the air than from hypoxic water and therefore may justify the potentially increased risks of desiccation and predation associated with leaving the water.
AB - Lowland stream fauna in areas of intensive agriculture are increasingly under threat from anthropogenic activities leading to eutrophication and subsequent hypoxia. Survival of hypoxic episodes depends upon a combination of behavioural and physiological adaptations. Responses of inanga (Galaxias maculatus: Galaxiidae) to aquatic hypoxia were investigated in the laboratory. Contrary to expectation inanga did not display behaviour that might reduce energy expenditure during oxygen limitation, with swimming activity slightly, but significantly elevated relative to normoxia. Instead, as dissolved oxygen concentrations decreased, the fish moved higher in the water column, increased their swimming speed and exhibited aquatic surface respiration. Physiological changes such as enhanced opercular frequency were also noted. As hypoxia deepened inanga started to leap out of the water, emersing themselves on a floating platform. Once emersed, fish exhibited an enhanced oxygen consumption rate compared to hypoxic fish. Thus inanga appear better adapted to escape hypoxia (a behavioural adaptation) rather than tolerate it (physiological adaptation). The emersion strategy used for inanga in response to severe hypoxia is in agreement with their ability to take up more oxygen from the air than from hypoxic water and therefore may justify the potentially increased risks of desiccation and predation associated with leaving the water.
KW - Aquatic surface respiration
KW - Behaviour
KW - Emersion
KW - Hypoxia
KW - Opercular frequency
KW - Oxygen consumption
UR - http://www.scopus.com/inward/record.url?scp=79952754422&partnerID=8YFLogxK
U2 - 10.1016/j.physbeh.2011.02.009
DO - 10.1016/j.physbeh.2011.02.009
M3 - Journal Article
C2 - 21316378
AN - SCOPUS:79952754422
SN - 0031-9384
VL - 103
SP - 240
EP - 247
JO - Physiology and Behavior
JF - Physiology and Behavior
IS - 2
ER -