Browsing by Author "Martins, C. I. M."
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- Cognitive appraisal of environmental stimuli induces emotion-like states in fishPublication . Cerqueira, M.; Millot, S.; Castanheira, Maria Filipa; Félix, Ana Sofia; Silva, T.; Oliveira, Gonçalo; Oliveira, C. C.; Martins, C. I. M.; Oliveira, Rui F.The occurrence of emotions in non-human animals has been the focus of debate over the years. Recently, an interest in expanding this debate to non-tetrapod vertebrates and to invertebrates has emerged. Within vertebrates, the study of emotion in teleosts is particularly interesting since they represent a divergent evolutionary radiation from that of tetrapods, and thus they provide an insight into the evolution of the biological mechanisms of emotion. We report that Sea Bream exposed to stimuli that vary according to valence (positive, negative) and salience (predictable, unpredictable) exhibit different behavioural, physiological and neuromolecular states. Since according to the dimensional theory of emotion valence and salience define a two-dimensional affective space, our data can be interpreted as evidence for the occurrence of distinctive affective states in fish corresponding to each the four quadrants of the core affective space. Moreover, the fact that the same stimuli presented in a predictable vs. unpredictable way elicited different behavioural, physiological and neuromolecular states, suggests that stimulus appraisal by the individual, rather than an intrinsic characteristic of the stimulus, has triggered the observed responses. Therefore, our data supports the occurrence of emotion-like states in fish that are regulated by the individual's perception of environmental stimuli.
- Daily oxygen consumption rhythms of Senegalese sole solea senegalensis (Kaup, 1858) juvenilesPublication . Castanheira, Maria Filipa; Martins, C. I. M.; Engrola, S.; Conceição, L. E. C.Senegalese sole is known to be a species with pronounced nocturnal feeding behaviour. However, as for most fish species, there is a lack of knowledge concerning the influence of such biological rhythmon metabolic rate. The aim of this study was to determine whether individual variation in routine and fed metabolic rate was affected by daily light–dark rhythms in juveniles of Senegalese sole. The individual oxygen consumption measurements in Senegalese sole juveniles were determined by flow-through respirometry, at fasted conditions and after the fish were fed a single meal, the meal time started at 0930 h and fish fed ad libitum for 30 min. The measurements were made during 22 h, of which 8 h was in the light and 14 h in the dark, and started immediately after transfer to the respiratory chambers at 1100 h. The results suggest an influence of light–dark cycles in routine metabolism. It was observed that oxygen consumption increased during the dark phase in fasted fish (FAST) but was higher during the light phase in fed fish (FEED). However, when feed is provided during the light phase, juveniles are capable of shifting oxygen consumption rhythms to respond to the energetic demands of digestion and growth. These results suggest that routine metabolism varies according to the species natural habits as Senegalese sole is known to be nocturnal. The findings of this study underline the importance of understanding the biological rhythms of the species under study before metabolic data are interpreted.
- Individual differences in cortisol levels and behaviour of Senegalese sole (Solea senegalensis) juveniles: evidence for coping stylesPublication . Silva, P. I. M.; Martins, C. I. M.; Engrola, S.; Marino, G.; Øverli, Ø.; Conceição, L. E. C.Individual variation in stress physiology and behaviour has been previously reported in several fish species. As seen in other vertebrates, existence of stress coping styles seemsto be reflected by the presence of individual variation. Aggressive behaviour, amongst others, is one of the most commonly used parameters to characterize coping styles. However, not all fish species exhibit aggressive behaviour, such as the flatfish Senegalese sole, Solea senegalensis (Kaup, 1858). Therefore, the goal of this study was to determine the magnitude of individual variation in behavioural parameters other than aggression (feeding motivation and activity during stress) as well as in growth and stress response in Senegalese sole. The relationship between these variables was investigated to determine whether they could be used as indicators of coping styles. Thirty-six juvenile fish (9.9 2.2 g) were individually housed for 73 days. Feedingmotivation,measured as the time(in s) taken by each fish to react to feed,was determined on days 10, 17, 24 and 31. Bloodsamples for plasmacortisol were collected on days 51 and 71 for determination of undisturbed and stress levels, respectively. Thestress test consisted of holding each fish individually in a net, outside the water, for 3min. Duration of escape attempts, i.e. the time takenby each fish to stop struggling (in an attempt to escape) in the net, was quantified. The results showed a pronounced individual variation in both control (CV = 54%) and acute stress (CV = 71%) cortisol levels. Senegalese sole also exhibited high coefficient of variationinthebehavioural parameters:75%in feeding latency and96%induration of escape attempts. Growth (RGR = 1.17 0.38) showed to be the parameter with lower variation of only 32% and was not correlated with any of the measured parameters. A significant correlation between undisturbed cortisol levels and duration of escape attempts was found. Undisturbed cortisol levels (8.08 4.36 ng/ml) were negatively correlated with duration of escape attempts (P = 0.009, rs = 0.503). Correlations between plasma cortisol levels after stress (398.45 282.67 ng/ml) and the behavioural parameters were not found. The observed individual variation in behaviour and stress physiology as well as their relationship suggests the existence of coping styles in Senegalese sole where proactive individuals exhibit shorter feeding latency, higher duration of escape attempts and lower undisturbed cortisol levels than passive individuals.
- Individual differences in metabolism predict coping styles in fishPublication . Martins, C. I. M.; Castanheira, Maria Filipa; Engrola, S.; Costas, B.; Conceição, L. E. C.Studies on metabolism usually rely on measurements of oxygen consumption obtained in respirometry chambers. Despite rigorous standardization there is still considerable interindividual variation in metabolic rates which is often ignored. Furthermore, housing in respirometry chambers implies handling and exposure to a new environment, conditions known to be a source of stress in animals. The extent of stress response is known to be dependent on an individual’s coping style. Therefore, the extent of individual variation in respirometry data may be related to the expression of coping styles. The goal of this study is to determine whether the variation in oxygen consumption after a stressor is the resultant of an individual’s coping style. Our approach was to determine oxygen consumption in fish immediately after transfer to respiratory chambers and during the subsequent 22 h. In addition, the same individuals were subjected to 3 respirometry runs (22 h each) to address the question whether habituation occurs when fish are used in multiple runs and whether habituation potential is linked to coping styles. The same individuals were then subjected to an acute stressor and the escape behaviour and plasma cortisol were determined to assess coping style. Taken as a whole, the findings of this study suggest that individual variation in oxygen consumption in respirometry chambers are related to the expression of coping styles: individuals with higher oxygen consumption at the start and throughout the measurement period were shown to react passively (longer latency to escape) in a confinement stress. In addition, successive respirometry runs should not be assumed to result in habituation, as depending on an individual’s coping style either habituation (in the case of passive copers) or sensitization (in the case of active copers) can occur.