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Background. The usage of common carp pituitaries has been associated with very high costs, resulting from sacrificing the valuable broodstock. A close taxonomic proximity between the Common carp, Cyprinus carpio L., and Prussian carp, Carassius gibelio (Bloch, 1782), reflected in the presence of high levels of the homologous carp LH hormone in Prussian carp pituitaries, was recently demonstrated. This prompted the present authors to evaluate the Prussian carp pituitaries as a less expensive alternative to carp pituitaries, for inducing spawning in common carp. Materials and Methods. Prussian carp were fished in Lake Pamvotis (NW Greece) on April 4, 2007 and 204 pituitaries were extracted and processed. Accordingly, the prepared pituitary liquid extract was injected in 30 female common carp (experimental group) in the State Carp Hatchery in Psathotopi, (western Greece). Common carp pituitary extract was used for the hypophysation of female common carp in the control group (n = 30). In both groups, standard hatchery procedures were followed concerning broodstock handling during the artificial propagation of common carp. Fertilized eggs were incubated in 7-L Zugar jars after removing the sticky substrate and hatching percentage was calculated. Results. Spawning success was 73.3%, total egg yield was 5.94 kg, total relative fecundity was 112.5 g · kg-1 of body weight (150.0 g · kg-1 of body weight based on fertile broodstock), and hatching percentage reached 85.2%. Statistically, all the above performance values were not significantly different compared to the controls. Conclusion. Taking advantage of a natural resource practically unexploited, the use of Prussian carp pituitaries in the artificial propagation of common carp was equally effective to common carp pituitaries, contributing to lower running costs in the hatchery.
Background. The majority of the European populations of the Prussian carp, Carassius gibelio, consist predominantly of females reproducing by gynogenesis but include a small portion of males. Mechanisms for the occurrence of males in natural populations and their functions are still unclear. The aims of this study were to show the ploidy level by karyotype, some taxonomic characteristics by analysis of morphology, and the reproductive potential by histology of gonads of Prussian carp individuals of a certain age from two types of naturally existing unisexual triploid and a diploid-polyploid populations. Materials and methods. In total 31 specimens from three different populations inhabiting the Vistula River basin, the Baltic Sea watershed, have been analyzed. Kidneys were used to prepare chromosome slides using standard procedures. Air-dried slides were stained with Giemsa solution. For each fish, 23 metric characteristics of the body were measured. Selected meristic characteristics (external and internal) were determined. The gonads were fixed in buffered formalin or in Bouin’s solution; histological sections were stained with haematoxylin and eosin (HE). The developmental stages of germ cells and gonads were determined according to Rinchard and Kestemont and Billard. Results. All individuals of two populations were triploid females with high chromosomal variability from 150 to 160 chromosomes (and microchromosomes). Among individuals of the third population, males and females of 2n = 100 and one triploid male 3n = 160 (151–162) chromosomes were detected. The individuals from analyzed populations differed in the number of: branched rays in the dorsal fin, lateral line scales, serration in dorsal D and anal A fin rays, and vertebrae. Gonad histology of the ovaries indicated the females were mature at the age of 3. Testes morphology of diploids and one triploid male indicated their reproductive abilities. Conclusion. The results of the study confirmed the tendency to increase the number of males in C. gibelio populations. In several or some populations apart from diploid males a small number of fertile triploid males occur. High chromosomal variability within the females from unisexual populations may be influenced by their different mode of origin. The future research should be focused on karyological identification of other C. gibelio populations to explain the origin of triploid males and their role in reproduction.
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