Diet and temperature modify the relationship between energy use and ATP production to influence behaviour in zebrafish (Danio rerio)

Food availability and temperature influence energetics of animals, and can
alter behavioural responses such as foraging and spontaneous activity.
Food availability, however, is not necessarily a good indictator of energy
(ATP) available for cellular processes. The efficiency of energy
transduction from food-derived substrate to ATP in mitochondria can change
with environmental context. Our aim was to determine whether the
interaction between food availability and temperature affects
mitochondrial efficiency and behaviour in zebrafish (Danio rerio). We
conducted a fully factorial experiment to test the effects of feeding
frequency, acclimation temperature (three weeks to 18 or 28°C), and acute
test temperature (18 and 28°C) on whole-animal oxygen consumption,
mitochondrial bioenergetics and efficiency (ADP consumed per oxygen atom;
P:O ratio), and behaviour (boldness and exploration). We show that
infrequently fed (once per day on four days per week) zebrafish have
greater mitochondrial efficiency than frequently fed (three times per day
on five days er week) animals, particularly when warm-acclimated. The
interaction between temperature and feeding frequency influenced
exploration of a novel environment, but not boldness. Both resting rate of
producing ATP and scope for increasing it were positively correlated with
time spent exploring and distance moved in standardised trials. In
contrast, behaviour was not associated with whole-animal aerobic (oxygen
consumption) scope, but exploration was positively correlated with resting
oxygen consumption rates. We highlight the importance of variation in both
metabolic (oxygen consumption) rate and efficiency of producing ATP in
determining animal performance and behaviour. Oxygen consumption
represents energy use, and P:O ratio is a variable that determines how
much of that energy is allocated to ATP production. Our results emphasise
the need to integrate whole-animal responses with subcellular traits to
evaluate the impact of environmental conditions on behaviour and movement.
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