Social dynamics obscure the effect of temperature on air breathing in Corydoras catfish

Abstract

In some fishes, the ability to breathe air has evolved to overcome constraints in hypoxic environments but comes at a cost of increased predation. To reduce this risk, some species perform group air breathing. Temperature may also affect the frequency of air breathing in fishes, but this topic has received relatively little research attention. This study examined how acclimation temperature and acute exposure to hypoxia affected the air-breathing behaviour of a social catfish, the bronze corydoras Corydoras aeneus, to determine whether individual oxygen demand influenced the behaviour of entire groups. Groups of seven fish were observed in an arena to measure air-breathing frequency of individuals and consequent group air-breathing behaviour, under three oxygen concentrations (100%, 60%, 20% air saturation) and two acclimation temperatures (25°C & 30°C). Intermittent flow respirometry was used to estimate oxygen demand of individuals. Increasingly severe hypoxia increased air-breathing at the individual and group levels. While there were minimal differences in air-breathing frequency among individuals in response to an increase in temperature, the effect of temperature that did exist manifested as an increase in group air-breathing frequency at 30°C. Groups that were more socially cohesive during routine activity took more breaths but, in most cases, air-breathing among individuals this was not temporally clustered. There was no association between an individual's oxygen demand and its air-breathing frequency in a group. For Corydoras aeneus, while air-breathing frequency is influenced by hypoxia, behavioural variation among groups could explain the small overall effect of temperature on group air-breathing frequency.

Evidence that standard metabolic rate and risk-taking to breathe air are linked to boldness, activity level and exploratory behaviour in a catfish

“…Further research is required to understand whether an apparent dichotomy of boldness might be context dependent, visible by some measures but not others. Air-breathing fishes are useful models to explore relationships between physiology and behaviour (McKenzie et al ., 2015; Killen et al ., 2018; Pineda et al ., 2020), future research should confirm that behavioural tendencies are temporally stable and therefore constitute elements of personality (Conrad et al, 2011; Niemelä & Dingemanse, 2018). These species could then be used to test hypotheses about how energy metabolism links to personality.…”

“…Fishes that breathe air provide an excellent model to investigate how individual variation in MR and associated risk-taking to obtain a resource, aerial oxygen, are linked to behavioural tendencies (McKenzie et al ., 2015; Killen et al ., 2018; Pineda et al ., 2020). Air is much richer in oxygen than water and various species of fish have evolved adaptations to rise to the surface and breathe it.…”

The Potential for Physiological Performance Curves to Shape Environmental Effects on Social Behavior

“…Group-level behaviors and dynamics are likely to vary across environments (e.g., increased water temperature and hypoxia may decrease group cohesion in aquatic ectotherms), which can strongly affect how social information is transmitted (e.g., visual information, MacGregor et al, 2020 ). Any changes in group cohesion could in turn alter the potential for information transfer among groupmates due to changes in spatial distances among individuals and their ability to give and receive social cues ( Pineda et al, 2020 ). In addition, the extent that individuals use social learning can be dependent on group behavioral composition.…”

The potential for physiological performance curves to shape environmental effects on social behaviour

“…visual information, MacGregor et al, 2020). Any changes in group cohesion could in turn alter the potential for information transfer among groupmates due to changes in spatial distances among individuals and their ability to give and receive social cues (Pineda et al, 2020). In addition, the extent that individuals use social learning can be dependent on group behavioural composition.…”