J. De Costa

Blood parameters in rainbow trout (Oncorhynchus mykiss): Simultaneous influence of various factors

Abstract The effect of the simultaneous influence of weight, temperature, density and O 2 concentration in the water on various blood parameters in rainbow trout ( Oncorhynchus mykiss ), namely haematocrit (Ht), haemoglobin (Hb), red blood cell (RBC), mean cell, mean cell haemoglobin content and mean cell haemoglobin concentration was studied. Nineteen lots with average weights ranging from 178 to 372 g were used. Initial density values were 7.2 to 38.8 kg/m 3 . Temperature ranged from 15 to 20°C and O 2 concentration in the water 5.8 ± 2 to 8.6 ± 2 ppm. Multiple correlation and regression analyses showed a strong dependence of Ht, Hb and RBC on the factors considered, the most influential of which was temperature. The relatively low r 2 values obtained, however, suggest the existence of additional factors which were not considered by us and which might explain the variability found in blood parameters.

Macronutrient selection through post-ingestive signals in sharpsnout seabream fed gelatine capsules and challenged with protein dilution

Sharpsnout seabream ability for macronutrient self-selection was studied using gelatine capsules containing pure macronutrients. In particular, the existence of non-oropharyngeal chemosensory pathways involved on protein (P), fat (F) and carbohydrate (CH) selection, as well as sharpsnout seabream response to dietary protein dilution were investigated. In a sequence of experimental phases, sharpsnout seabream were fed a pelleted complete diet, an encapsulated complete diet or a combination of separately encapsulated pure macronutrients. In order to induce associative learning, capsules containing a given macronutrient were paired with a particular colour. The animals composed a diet containing 62.7% P, 21.3% CH and 16.0% F, in terms of macronutrient percentage intake, and this selection pattern was maintained throughout all experimental phases. In a second experiment, individually kept sharpsnout seabream were challenged with protein dilution. After protein capsules were diluted (from 91.9% P to 56.3% P) with cellulose, the animals increased their protein intake to compensate for dilution in such a way that their energy intake was not significantly modified (17.4 kJ/100 g BW vs. 17.6 kJ/100 g BW after dilution). These results show that sharpsnout seabream feeding on encapsulated diets are able to select and maintain a particular diet composition, as well as sustain their energy intake, without using the diets oropharyngeal chemosensory properties. Moreover, they were also able to maintain their protein intake after dilution, which highlights the importance of this macronutrient in this omnivorous species.

Age-related changes in fatty acid profile and locomotor activity rhythms in Nothobranchius korthausae

The life cycle of Nothobranchius korthausae, a Cyprinodontiformes fish, was studied in our laboratory to characterise the ageing process. Some morphological changes, such as spine curvature, skin colour, and fin and eye appearance are described. Growth and survival curves reflected a fast life cycle with rapid initial growth until 4weeks of age, after which the fish grew more slowly before reaching their final size in week 40. Senescence onset was established at week 48 with a decrease in spawn size and viability and a general decline in the animals appearance (weight and colouration losses, caudal fin degradation, and cataractogenesis). The fatty acid composition changed with age, with high unsaturation in the adult stage as reflected by a high peroxidation index, a condition that is associated with high susceptibility to oxidative damage if elevated reactive oxygen species (ROS) production occurs. Senescent fish had an increase in monounsaturated fatty acid proportions and a lower peroxidation index (226.5±19.7 in adults versus 120.2±19.1 in senescent fish, P<0.05). The circadian system, as reflected by locomotor activity rhythms, showed noticeable changes with age. Twenty-four-week-old fish (adults) had a robust diurnal rhythm that showed a decrease in total activity, an increase in rhythm fragmentation, and a fall in amplitude and regularity with age. Changes were clearly reflected in the Circadian Function Index variations (0.56, 0.47 and 0.25 at 24, 48 and 72weeks of age, respectively). In conclusion, N. korthausae appears to be a species with appropriate characteristics for ageing studies because it manifests clear signs of progressive ageing. Comparing species of Nothobranchius genus with different lifespans may be useful for increasing our understanding of the ageing process.

Effects of intense exercise training on rainbow trout growth, body composition and metabolic responses.

Cultured fish are bound to experience a variety of potentially stressful situations. In principle, stress may be reduced by adapting fish to intense exercise. This article addresses the effects of chase-induced intense exercise training on rainbow trout. Training reduced fish growth and worsened their nutritional use of food, but had no effect on food intake, biometry or body composition, indicating that a significant fraction of the diet’s energy was being used for exercising rather than growth. Regarding metabolic responses, training significantly counterbalanced lactate, glucose and cortisol plasma concentration increases induced by intense exercise, while completely abolishing that of plasmatic proteins. These data suggest that this type of training adversely affects fish growth and food conversion, whereas it improves their metabolic response capacity and reduces the stress component of forced exercise.ResumenEn acuicultura, hay múltiples situaciones que pueden generar en los peces una situación de estrés. Un método posible para reducirlo sería habituar a los peces a la ejecución de ejercicio intenso. En este trabajo se estudia el efecto del entrenamiento al ejercicio intenso inducido mediante persecución en la trucha arco iris. Con el entrenamiento se produce una disminución del crecimiento, sin cambios en la ingesta, la biometría ni la composición corporal, pero empeorando la utilización nutritiva de la dieta, lo que indica que parte de la energía de dieta se utiliza en el ejercicio, y no en crecimiento. Con respecto a la respuesta metabólica, el entrenamiento disminuye el incremento en las concentraciones plasmáticas de lactato, glucosa y cortisol que se produce con el ejercicio intenso, y anula este incremento en el caso de las proteínas plasmáticas. Se concluye que este tipo de entrenamiento produce efectos adversos sobre el crecimiento y la conversión del alimento, mejorando, sin embargo, la capacidad metabólica de respuesta de los peces y reduciendo el componente estresante del ejercicio inducido.

Histochemical determination of muscle fiber types in locomotor muscles of anuran amphibians

1. A histochemical study using myosin ATPase, succinate dehydrogenase and alpha-glycerophosphate dehydrogenase reactions and a morphometric analysis with image analyser, was carried out in sartorius and gastrocnemius muscles of two anuran species, Rana perezi and Bufo calamita, that show different locomotor activities. 2. Four types of muscle fiber were found. There were interspecific variations in their proportions, with a predominance of oxidative muscle fibers in Bufo calamita. 3. These results agree with those obtained previously for the metabolic profile of several tissues from both species and point to a clear metabolic basis for the differences in locomotor activities between these two species.

Energy intake and macronutrient selection in sharpsnout seabream (Diplodus puntazzo) challenged with fat dilution and fat deprivation using encapsulated diets

Sharpsnout seabream fed pure macronutrient capsules were challenged to fat dilution and fat deprivation in order to investigate the effects of fat level on energy intake regulation and macronutrient selection by fish, as they lack oropharyngeal chemosensory information from the diet. During the control phase, the fish were fed three individually encapsulated macronutrients, from which they composed a diet containing 67.36% protein (P), 19.08% carbohydrates (CH) and 13.57% fat (F), in terms of macronutrient weight intake percentage. During the second phase of the experiment, a lipid content reduction in F capsules from 55.0% to 13.4% did not significantly modify this selection pattern, energy ingestion or the number of capsules ingested of each macronutrient. During the third phase, in which they were subjected to fat deprivation, starting on almost the first day, the fish increased their total energy intake and total ingested number of capsules. These results reveal that fish are capable of distinguishing and selecting each of the three macronutrients contained in gelatine capsules, and that fish selection of a balanced diet from pure macronutrients is remarkably stable. Fish are capable of sustaining their macronutrient selection pattern and energy intake with very low amounts of fat in their diets (Phase 2). A certain instability in the initial P, CH and energy intake was only observed when fat was totally deprived (Phase 3), which resulted in higher values than those observed in Phase 1. In order to examine any possible effects of diet encapsulation, digestibility assays were performed in a second experiment. The fish were divided into two experimental groups and fed the same complete commercial diet, the only difference being the way it was presented to each group (pelleted or encapsulated). No statistical differences between the experimental groups were found with regards to both apparent digestibility coefficients and fish growth.

The effects of temperature and pH on the kinetic properties of heart muscle lactate dehydrogenase from anuran amphibians

Abstract 1. 1. The response to variation in pH and temperature of heart LDH enzyme from two anuran amphibians, Rana perezi and Bufo calamita, of different behaviour and habitat is studied. 2. 2. Substrate (pyruvate and lactate) concentrations are measured in hearts from animals at rest and after exercise. In both species, substrate concentrations are higher than apparent Km values of heart enzyme. 3. 3. At physiological concentrations of substrate, pyruvate reductase activity is more affective by temperature increase when pH decreases simultaneously, whilst lactate oxidase reaction behaves conversely. 4. 4. The contribution of cardiac metabolism to supporting the exercise effort in both species of anuran amphibians is discussed.

The effects of pH and temperature on the kinetic properties of skeletal muscle lactate dehydrogenase from anuran amphibians

SummaryMuscle LDH activities were measured in two anuran amphibians with different behaviour and ecology, Rana perezi and Bufo calamita. Both pyruvate reduction and lactate oxidation were measured at temperatures of 15, 20 and 30°C, and at pH 7.0, 7.4, and 8.0. Pyruvate and lactate muscle concentrations were determined in individuals at rest and after exercise. R. perezi muscle used anaerobic glycolysis during 3 min of exhaustive exercise, with rising pyruvate and lactate concentrations. Enforced walking for 30 min caused high variability in lactate concentration in B. calamita muscle. Temperature and pH changes affected apparent Km values for pyruvate. When these factors varied simultaneously, enzyme affinity tended not to change. Thus, the thermodynamic effect on pyruvate reduction activity is high, especially at physiological substrate concentrations. In contrast, lactate oxidation activity tended to stabilize when temperature and pH varied jointly. Inhibition by substrate, pyruvate or lactate, seemed to have no importance in vivo.During exercise there was a rise in pyruvate concentration, and a probable decrease in pH, which increased pyruvate reduction reaction and decreased lactate oxidation, contributing to lactate accumulation in Rana perezi muscle. B. calamita muscle did not show pyruvate increase after exercise and its LDH was less dependent on pH at physiological concentrations. Pyruvate reduction rate did not therefore increase. R. perezi muscle enzyme had features of anaerobic LDH while B. calamita LDH muscle was more similar to mammalian heart enzyme, with differences in accordance with the different behaviour of these anurans.

COMPARATIVE STUDY IN GLYCOLYTIC CAPACITY IN ANURAN AMPHIBIANS

Abstract 1. 1. Hexokinase (HK). phosphofructokinse (PFK), pyruvate kinase (PK) and lactate dehydrogenase (LDH) activities in skeletal muscle, heart and liver from two amphibian species, Rana perezi and Bufo calamita , were measured. 2. 2. The results obtained showed interspecific differences in glycolytic capacity that affect the tissues in a different way. Rana perezi had higher glycolytic capacity in skeletal muscle than Bufo calamita while this species showed higher activity of glycolytic enzymes in heart muscle. These differences are related to interspecific differences in behaviour.

Factors simultaneously affecting the growth of the rainbow trout (Oncorhynchus mykiss)

Growth of rainbow trout (Oncorhynchus mykiss) is examined in relation to simultaneous variation of initial weight, initial density, temperature and time (days). Twenty-six lots of medium weight were set up, ranging from 92 to 372 g; initial density ranged from 7.2 to 38.8 kg/m3; and temperatures from 14 degrees C in winter to 20 degrees well into spring. Experimental periods carried out were of 7, 20, 38 and 26 days duration. By multiple correlation and regression analysis, predictive equations for increments in weight, final density were obtained in relation to the afore mentioned variables and ranges. The values of multiple correlation obtained were highly significant. We confirmed that the effect of each factor on growth is modified by the simultaneous action of the other variables.