Swimming in air‐breathing fishes

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 (Ṁ O2,air ) and the percentage of RMR obtained from air (%Ṁ O2,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 Ṁ O2,air across all contexts but a positive influence on %Ṁ O2,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 Ṁ O2,air or %Ṁ O2,air , there was a negative relationship between T res and %Ṁ O2,air in daylight, in normoxia and hypoxia. There were two T res response groups, 'bold' phenotypes with T res below 75 min (N=13) which, in daylight, breathed proportionally more air than 'shy' phenotypes with T res 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.

Section: General Patterns Of Respiratory Metabolism and Boldnesssupporting

confidence: 60%

Section: General Patterns Of Respiratory Metabolism and Boldnessmentioning

confidence: 99%

Section: General Patterns Of Respiratory Metabolism and Boldnessmentioning

confidence: 99%

See 1 more Smart Citation

To boldly gulp: standard metabolic rate and boldness have context-dependent influences on risk-taking to breathe air in a catfish

McKenzie

Belão

Killen

et al. 2015

“…Indeed, the FAS of the humpbacked conch is comparable to that of many fishes (e.g. Killen et al, 2007;Nilsson et al, 2009;Lefevre et al, 2014a), which have a much more active lifestyle. The smaller tropical coral reef fish, however, tend to have lower scopes ranging from 1.5 to 3.5 in some damselfishes and 3 to 4.5 in some cardinalfishes Gardiner et al, 2010;Donelson et al, 2012).…”

Section: Discussion General Aspects Of Aerobic Performance Of the Hummentioning

confidence: 84%

Will jumping snails prevail? Influence of near-future CO2, temperature and hypoxia on respiratory performance in the tropical conchGibberulus gibberulus gibbosus

Lefevre

Watson

Munday

et al. 2015

Tropical coral reef organisms are predicted to be especially sensitive to ocean warming because many already live close to their upper thermal limit, and the expected rise in ocean CO 2 is proposed to further reduce thermal tolerance. Little, however, is known about the thermal sensitivity of a diverse and abundant group of reef animals, the gastropods. The humpbacked conch (Gibberulus gibberulus gibbosus), inhabiting subtidal zones of the Great Barrier Reef, was chosen as a model because vigorous jumping, causing increased oxygen uptake (Ṁ O2 ), can be induced by exposure to odour from a predatory cone snail (Conus marmoreus). We investigated the effect of present-day ambient (417-454 µatm) and projected-future (955-987 µatm) P CO2 on resting (Ṁ O2,rest ) and maximum (Ṁ O2,max ) Ṁ O2 , as well as Ṁ O2 during hypoxia and critical oxygen tension (P O2,crit ), in snails kept at present-day ambient (28°C) or projectedfuture temperature (33°C). Ṁ O2,rest and Ṁ O2,max were measured both at the acclimation temperature and during an acute 5°C increase. Jumping caused a 4-to 6-fold increase in Ṁ O2 , and Ṁ O2,max increased with temperature so that absolute aerobic scope was maintained even at 38°C, although factorial scope was reduced. The humpbacked conch has a high hypoxia tolerance with a P O2,crit of 2.5 kPa at 28°C and 3.5 kPa at 33°C. There was no effect of elevated CO 2 on respiratory performance at any temperature. Long-term temperature records and our field measurements suggest that habitat temperature rarely exceeds 32.6°C during the summer, indicating that these snails have aerobic capacity in excess of current and future needs.

“…a major drive during the evolution of air breathing in many species, it is also known that several extant fishes utilise it under conditions of increased oxygen demand, such as during swimming (reviewed by Lefevre et al, 2014b), digestion (e.g. Iftikar et al, 2008;Lefevre et al, 2012) and elevated temperature (e.g.…”

mentioning

confidence: 99%

Air breathing in the Arctic: influence of temperature, hypoxia, activity and restricted air access on respiratory physiology of Alaska blackfish (Dallia pectoralis)

Lefevre

Damsgaard

Pascale

et al. 2014

The Alaska blackfish (Dallia pectoralis) is an air-breathing fish native to Alaska and the Bering Sea islands, where it inhabits lakes that are ice-covered in the winter, but enters warm and hypoxic waters in the summer to forage and reproduce. To understand the respiratory physiology of this species under these conditions and the selective pressures that maintain the ability to breathe air, we acclimated fish to 5°C and 15°C and used respirometry to measure: standard oxygen uptake (Ṁ O2 ) in normoxia (19.8 kPa P O2 ) and hypoxia (2.5 kPa), with and without access to air; partitioning of standard Ṁ O2 in normoxia and hypoxia; maximum Ṁ O2 and partitioning after exercise; and critical oxygen tension (P crit ). Additionally, the effects of temperature acclimation on haematocrit, haemoglobin oxygen affinity and gill morphology were assessed. Standard Ṁ O2 was higher, but air breathing was not increased, at 15°C or after exercise at both temperatures. Fish acclimated to 5°C or 15°C increased air breathing to compensate and fully maintain standard Ṁ O2 in hypoxia. Fish were able to maintain Ṁ O2 through aquatic respiration when air was denied in normoxia, but when air was denied in hypoxia, standard Ṁ O2 was reduced by ~30-50%. P crit was relatively high (5 kPa) and there were no differences in P crit , gill morphology, haematocrit or haemoglobin oxygen affinity at the two temperatures. Therefore, Alaska blackfish depends on air breathing in hypoxia and additional mechanisms must thus be utilised to survive hypoxic submergence during the winter, such as hypoxia-induced enhancement in the capacities for carrying and binding blood oxygen, behavioural avoidance of hypoxia and suppression of metabolic rate.