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Biomedical subjects

Victoria A Braithwaite

Publications and source records attributed to Victoria A Braithwaite.

7 recordsLinked to original sources
PubMed2005

Environmental variability in the early rearing environment generates behaviourally flexible cod: implications for rehabilitating wild populations.

The release of hatchery-reared fishes for restoring threatened and endangered populations is one of the most controversial issues in applied ecology. A central issue has been to determine whether releases cause extinction of local wild populations. This may arise either through domesticated or non-local fishes hybridizing with wild fishes, or through inappropriate behavioural interactions; for example, many hatchery fishes show exaggerated aggressive and competitive behaviour and out-compete wild counterparts. The impact of the impoverished hatchery environment in shaping behaviour is only now receiving attention. Attempts to counteract hatchery-related behavioural deficiencies have utilized intensive training programmes shortly before the fishes are released. However, we show here that simple exposure to variable spatial and foraging cues in the standard hatchery environment generates fishes with enhanced behavioural traits that are probably associated with improved survival in the wild. It appears that fishes need to experience a varying and changeable environment to learn and develop flexible behaviour. Using variable hatchery rearing environments to generate suitable phenotypes in combination with a knowledge of appropriate local genotypes, rehabilitation of wild fishes is likely to succeed, where to date it has largely failed.

Analysis of Variance↗
PubMed2005

Differential stress responses in fish from areas of high- and low-predation pressure.

We subjected fish from regions of high and low levels of predation pressure in four independent streams to a mild stressor and recorded their opercular beat rates. Fish from low-predation areas showed higher maximum, minimum and mean opercular beat frequencies than fish from high-predation regions. The change in opercular beat frequency (scope) was also significantly greater in fish from low- than in fish from high-predation regions. Under normal activity levels, however, low predation fish showed a reduced opercular beat frequency, which may be indicative of reduced activity levels or metabolic rate. Opercular beat frequency was negatively correlated with standard length as one would expect based on higher metabolic rates in smaller fish. We suggest that these contrasting stress responses are most likely the result of differential exposure to predators in fish from high- and low-predation areas. We argue that reduced stress responses in high-predation areas evolved to prevent excessive energy expenditure by modulating the fright response.

Adaptation, Physiological↗
PubMed2003

Do fishes have nociceptors? Evidence for the evolution of a vertebrate sensory system.

Nociception is the detection of a noxious tissue-damaging stimulus and is sometimes accompanied by a reflex response such as withdrawal. Pain perception, as distinct from nociception, has been demonstrated in birds and mammals but has not been systematically studied in lower vertebrates. We assessed whether a fish possessed cutaneous nociceptors capable of detecting noxious stimuli and whether its behaviour was sufficiently adversely affected by the administration of a noxious stimulus. Electrophysiological recordings from trigeminal nerves identified polymodal nociceptors on the head of the trout with physiological properties similar to those described in higher vertebrates. These receptors responded to mechanical pressure, temperatures in the noxious range (more than 40 degrees C) and 1% acetic acid, a noxious substance. In higher vertebrates nociceptive nerves are either A-delta or C fibres with C fibres being the predominating fibre type. However, in the rainbow trout A-delta fibres were most common, and this offers insights into the evolution of nociceptive systems. Administration of noxious substances to the lips of the trout affected both the physiology and the behaviour of the animal and resulted in a significant increase in opercular beat rate and the time taken to resume feeding, as well as anomalous behaviours. This study provides significant evidence of nociception in teleost fishes and furthermore demonstrates that behaviour and physiology are affected over a prolonged period of time, suggesting discomfort.

Acetic Acid↗
PubMed2003

The evolution of sex differences in spatial ability.

It is widely believed that male mammals have better spatial ability than females. A large number of evolutionary hypotheses have been proposed to explain these differences, but few species have been tested. The authors critically review the proposed evolutionary explanations for sex differences in spatial cognition and conclude that most of the hypotheses are either logically flawed or, as yet, have no substantial support. Few of the data exclusively support or exclude any current hypotheses. The hypothesis with the strongest support proposes that range size was the selection pressure that acted to increase spatial ability. The authors suggest ways in which these hypotheses could be tested by presenting explicit predictions and suggesting suitable test species or conditions.

Animals↗
PubMed2003

Novel object test: examining nociception and fear in the rainbow trout.

This study aimed to assess fear responses to a novel object while experiencing a noxious event to determine whether nociception or fear will dominate attention in a fish in novel object testing paradigm. This experimentally tractable animal model was used to investigate (1) the degree of neophobia to a novel object while experiencing noxious stimulation, (2) the response of the fish after removing the fear-causing event by using a familiar object, and (3) the effects of removing the nociceptive response by morphine administration and examining the response to a novel object. Control animals displayed a classic fear response to the novel objects and spent most of their time moving away from this stimulus, as well as showing an increase in respiration rate when the novel object was presented. In contrast, noxiously stimulated animals spent most of their time in close proximity to the novel object and showed no additional increase in respiration rate to novel object presentation. There was evidence of a slight hypoalgesia in noxiously stimulated animals. The responses to familiar objects demonstrated that by familiarizing the animal with the object, fear was removed from the experiment. Both control and noxiously treated animals responded in similar ways to a novel object by spending the majority of their time in close proximity. Treatment with morphine reduced effects of noxious stimulation and appears to be an effective analgesic. After morphine administration, the acid-injected animals showed a neophobic response to a novel object and this was similar to the response of the control fish, with a similar amount of time spent moving away from the object and an increase in ventilation in response to the novel object. Morphine affected the fear response because both groups approached the novel object more quickly than the non-morphine controls. These results suggest that nociception captures the animal's attention with only a relatively small amount of attention directed at responding to the fear of the novel object.

Analgesics, Opioid↗
PubMed2002

The long-term benefits of human generosity in indirect reciprocity.

Among the theories that have been proposed to explain the evolution of altruism are direct reciprocity and indirect reciprocity. The idea of the latter is that helping someone or refusing to do so has an impact on one's reputation within a group. This reputation is constantly assessed and reassessed by others and is taken into account by them in future social interactions. Generosity in indirect reciprocity can evolve if and only if it eventually leads to a net benefit in the long term. Here, we show that this key assumption is met. We let 114 students play for money in an indirect and a subsequent direct reciprocity game. We found that although being generous, i.e., giving something of value to others, had the obvious short-term costs, it paid in the long run because it builds up a reputation that is rewarded by third parties (who thereby themselves increase their reputation). A reputation of being generous also provided an advantage in the subsequent direct reciprocity game, probably because it builds up trust that can lead to more stable cooperation.

Altruism↗