To boldly gulp: standard metabolic rate and boldness have context-dependent influences on risk-taking to breathe air in a catfish
|Author(s)||McKenzie David1, 2, Belao Thiago C.3, Killen Shaun S.4, Rantin F. Tadeu1|
|Affiliation(s)||1 : Univ Fed Sao Carlos, Dept Physiol Sci, BR-13565905 Sao Carlos, SP, Brazil.
2 : Univ Montpellier, Ctr Marine Biodivers Exploitat & Conservat Marbec, UMR9190, F-34095 Montpellier 5, France.
3 : Sao Paulo State Univ, Fed Univ Sao Carlos UFSCar, Joint Grad Program Physiol Sci, BR-14801903 Araraquara, SP, Brazil.
4 : Univ Glasgow, Coll Med Vet & Life Sci, Inst Biodivers Anim Hlth & Comparat Med, Glasgow G12 8QQ, Lanark, Scotland.
|Source||Journal Of Experimental Biology (0022-0949) (Company Of Biologists Ltd), 2015-12 , Vol. 218 , N. 23 , P. 3762-3770|
|WOS© Times Cited||20|
|Keyword(s)||Bimodal respiration, Energy metabolism, Hypoxia, Personality, Respiratory partitioning, Risk-taking|
The African sharptooth catfish Clarias gariepinus has bimodal respiration, it has a suprabranchial air-breathing organ alongside substantial gills. We used automated bimodal respirometry to reveal that undisturbed juvenile catfish (N=29) breathed air continuously in normoxia, with a marked diurnal cycle. Air breathing and routine metabolic rate (RMR) increased in darkness when, in the wild, this nocturnal predator forages. Aquatic hypoxia (20% air saturation) greatly increased overall reliance on air breathing. We investigated whether two measures of risk taking to breathe air, namely absolute rates of aerial O-2 uptake ((M) over dotO(2), air) and the percentage of RMR obtained from air (% (M) over dotO(2), air), were influenced by individual standard metabolic rate (SMR) and boldness. In particular, whether any influence varied with resource availability (normoxia versus hypoxia) or relative fear of predation (day versus night). Individual SMR, derived from respirometry, had an overall positive influence on (M) over dotO(2), air across all contexts but a positive influence on % (M) over dotO(2), air only in hypoxia. Thus, a pervasive effect of SMR on air breathing became most acute in hypoxia, when individuals with higher O-2 demand took proportionally more risks. Boldness was estimated as time required to resume air breathing after a fearful stimulus in daylight normoxia (T-res). Although T-res had no overall influence on (M) over dotO(2), air or % (M) over dotO(2), air, there was a negative relationship between Tres and % (M) over dotO(2), air in daylight, in normoxia and hypoxia. There were two Tres response groups, 'bold' phenotypes with Tres below 75 min (N= 13) which, in daylight, breathed proportionally more air than 'shy' phenotypes with Tres above 115 min (N= 16). Therefore, individual boldness influenced air breathing when fear of predation was high. Thus, individual energy demand and personality did not have parallel influences on the emergent tendency to take risks to obtain a resource; their influences varied in strength with context.