First isolation of Tenacibaculum maritimum from wedge sole, Dicologoglossa cuneata (Moreau)

The first isolation of Tenacibaculum maritimum from wedge sole, Dicologoglossa cuneata, is reported. The pathogen was recovered from ulcers of cultured fish, from three different outbreaks. The six isolates obtained were biochemically and serologically characterized and diagnosis was confirmed by polymerase chain reaction using specific primers and partial 16S rRNA gene sequencing. The isolates constituted a homogeneous phenotypic group; however, they belong to two of the different serotypes described within this species. A virulence evaluation of the isolates using Wedge sole fry was also performed.     

An in vitro method to determine phosphorus digestibility of rainbow trout Oncorhynchus mykiss (Walbaum) feed ingredients

An in vitro method was developed to assess the digestibility of phosphorus in 12 plant and animal feed ingredients for rainbow trout Oncorhynchus mykiss (Walbaum). The method simulates the gastrointestinal tract of the rainbow trout with regard to pH and gastrointestinal enzymes. Phosphorus solubility was measured after acid digestion (pH 3) with and without gastric enzymes, after alkaline digestion (pH 9) with and without intestinal enzymes, and after a two-step process involving acid and alkaline digestion. Commercially available digestive enzymes from mammals were compared with digestive enzymes from rainbow trout. Correlating in vitro digestibility with in vivo digestibility showed that acid digestion with both commercial enzymes ( r ²=0.98, P  < 0.05) and trout enzymes ( r ²=0.94, P  < 0.05) predicted the in vivo digestibility of animal feed ingredients. Alkaline digestion with both enzyme systems (commercial r ²=0.79; trout r ²=0.74, P  < 0.05) or without ( r ²=0.82, P  < 0.05) enzymes predicted the in vivo digestibility of ingredients from animal byproducts but not those from plant products. The in vitro digestibility with two enzyme steps (acid and alkaline) predicted in vivo digestibility of plant and animal ingredients ( r ²=0.79 for commercial enzymes and r ²=0.74 for trout enzymes) better than did one-step acid or alkaline digestion.     

Morphometric and meristic characters in salmon, Salmo salar L., trout, Salmo trutta L., and their hybrids

Abstract. Atlantic salmon, Salmo salar L., brown trout, S. trutta L. and their hybrids are normally identified in the field by empirical differences in maxilla length, thickness of the caudal peduncle, degree of forking of the tail and overall body conformation. This study quantifies these characters and analyses their variations in electrophoretically identified hatchery-reared individuals. Means and variances of the various measures are presented for salmon, trout and hybrids separately. The morphometric characters do not satisfactorily distinguish hybrids from the pure species, and even within samples of the pure species, some individuals will be misclassified as hybrids, or as members of the opposite species, if single characters are used on their own. Hybrids often resemble one or other parent species in one or more characters and are less often intermediate in phenotype. Triploidized hybrids are more like salmon than diploid hybrids are, and triploidized salmon are not different from diploid salmon. The results confirm that frequencies of hybrids of these species cannot be reliably assessed by morphological characters alone, and even for individuals of the pure parental species, independent confirmation of species status is advisable. Early reports of hybrid frequencies in wild stocks should be treated with caution, and apparently higher levels of hybridization in more recent studies compared with older, traditional surveys may simply reflect the greater precision of electrophoretic identification.     

Protein metabolism during sexual maturation in female Atlantic salmon (Salmo salar L)

Body composition and fractional rates of protein synthesis (percentage of the protein mass synthesized per day) were determined in female Atlantic salmon returning to the River Tay, Scotland in July and in October after a 95 day period without food, during which time the animals became sexually mature. During the 95 day period of starvation/sexual maturation the ventricle and red muscle remained as a constant proportion of fresh weight whereas the liver, gill and ovary increased and the stomach and white muscle decreased. Fractional rates of protein synthesis increased markedly in the liver, stomach and ovary during the period of starvation/sexual maturation. In the gill, ventricle and white muscle fractional protein synthesis rates increased slightly or remained constant. From the estimated rates of protein loss or gain in the various tissues it is concluded that there is considerable protein turnover and repartitioning of amino acids during the period of starvation and sexual maturation. The absolute rate of protein synthesis rates in the ovary indicates that this tissue made the largest contribution to the energy and amino acid demands of the fish, whilst most of the amino acids required for maturation of the ovary were derived from white muscle, principally as the result of increased muscle protein degradation.     

Optimization of the protein fraction of microcapsules used in feeding of marine fish larvae using in vitro digestibility techniques

The development of artificial feeds for marine fish larvae is demanding and, taking into account the difficulties and costs associated with the rearing of the larvae of some fish, preliminary evaluation of feed ingredients using in vitro techniques may be an alternative to in vivo assays. Some proteins used in microfeeds for marine fish were tested in vitro for examination of their effect on the proteases of seabream larvae. Casein and cuttlefish meal did not affect protease activity of crude larval extracts, whereas ovalbumin produced a 60% inhibition. The use of a pH-stat for the assessment of the degree of hydrolysis (DH) of proteins confirmed the low nutritive value of ovalbumin, since a much lower value was obtained for microcapsules prepared using this protein source when compared with those prepared using casein or cuttlefish meal (3.2 vs. 7.3 and 7.6, respectively). Products resulting from such hydrolysis were analysed using sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE). Image analysis of such gels led to the formulation of an index named the coefficient of protein degradation (CPD) which expressed the extent to which the main protein fractions were hydrolysed by larval proteases in a given time. A significant correlation ( r ² = 0.98, P  < 0.05) was obtained between DH and CPD values measured for either protein sources or microcapsules. The combination of protease inhibition assays with measurements of DH and CPD is proposed as a preliminary evaluation of protein ingredients used in the formulation of artificial feeds for larval fish.     

Carbonic anhydrase and Na/K-ATPase activities at different molting stages of the giant freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

ABSTRACT:   In the present study, the role of carbonic anhydrase (CA) and Na/K-ATPase in the gill and epidermal tissues in the giant freshwater prawn Macrobrachium rosenbergii was examined as a function of molting stage. CA activity levels in the front and back gills were low at the intermolt stage C₀, but increased significantly at premolt stage D₃, and then decreased after molting. In the epidermal tissue, activity levels decreased gradually towards premolt to a minimum level at stage D₃, but became elevated at postmolt stages A and B. Na/K-ATPase levels in the front and back gills did not change significantly during the molt cycle. CA in the gill is possibly involved in supplying counter-ions for ion uptake, while CA in the epidermal tissue may play a role in mineralizing the exoskeleton after ecdysis. Na/K-ATPase in the gills may function in ion uptake from the ambient medium; however, since its activity was not influenced by the molt cycle, it probably does not have a major role in osmoregulation in the freshwater environment.     

The nature of hematological response in fish

Hematological status was examined in rainbow trout,Oncorhynchus mykiss, held for 3–4 weeks under temperature, photoperiod and P_{O 2} conditions approximating those of their winter, spring and summer habitats. The most striking change observed was in red cell population composition. In winter fish mature cells were predominant; juvenile and developing erythrocytes characterized spring and summer animals. Hemoglobin, hematocrit and both mean erythrocytic volume and hemoglobin were modestly lower in spring and summer than in winter fish. Red cell numbers were not significantly affected. These observations suggest that avoidance of viscosity-based increases in circulatory work cost is more advantageous than elevation of blood O₂-carrying capacity. Although hemoglobin isomorph profiles were significantly altered, there is little evidence that such changes are of critical adaptive importance. Given presumed age-based reduction in gas transport effectiveness, the replacement of mature and senescent cells by more metabolically-competent juvenile cells appears to be the pivotal event in hematological response. Leucocyte counts were significantly elevated in spring and summer as compared to winter fish. Lymphocyte/heterophil ratios declined from 8.27 in winter fish to 3.13 in summer trout. Thrombocyte, monocyte, eosinophil and basophil abundances were little changed.     

Long-term nutritional effects on the primary liver and kidney metabolism in rainbow trout (Oncorhynchus mykiss). II. Adaptive response of glucose 6-phosphate dehydrogenase activity to high-carbohydrate/low-protein and high-fat/non-carbohydrate diets

The influence of long-term administration of high-carbohydrate/low-protein and high-fat/non-carbohydrate diets were studied in relation to kinetic behaviour of glucose 6-phosphate dehydrogenase in liver and kidney of rainbow trout. In all cases studied, the saturation curves of these enzyme showed typical hyperbolic kinetics without evidence of sigmoidicity. After 30 days of feeding with a high-fat diet (170 g kg^?1), there was a significant decrease in V_max and specific activity (45%) as well as catalytic efficiency (39%) without changes in K_m or activity ratio of hepatic glucose 6-phosphate dehydrogenase. These changes agree more with a clearly decreased cell concentration than with an inhibition of the pre-existing enzyme. The administration of a high-carbohydrate diet (60 g kg^?1), contrary to what was previously thought, decreased V_max by 21% and specific activity and catalytic efficiency by 30%, without significant changes in the other kinetic parameters of the hepatic enzyme. The kinetic behaviour under these nutritional conditons was due to the rejection of this diet by the fish and thus could be considered a low-feeding situation. On the other hand, no variations in the kinetics of renal glucose 6-phosphate dehydrogenase were found, clearly demonstrating that in this organ, the pentosephosphate pathway showed no adaptive response related to fattyacid and other lipid synthesis. The activity of the renal enzyme was consistently half that of the hepatic enzyme.