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The first record of imperial blackfish, Schedophilus ovalis (Cuvier, 1833), in the Greek waters of the Aegean Sea is herewith documented. This record increases the knowledge on the richness of the Hellenic marine ichthyofauna and may suggest an expansion of the geographical distribution of the species from the southern Levantine waters to northern areas.
Seriolella porosa (Silver warehou) is an important fish resource in the Argentine Sea. No previous studies have been carried out to date on its parasite fauna. The present study aims to (i) identify the digenean trematodes that parasitize Silver warehou, (ii) estimate parasite frequency and abundance, and (iii) establish their relationship with fish size and sex. A total of 100 specimens of S. porosa from San Matías Gulf, Argentina were examined between September and October 2006. Host size and sex were determined. Parasites extracted from the stomach lumen were fixed, conserved in 5% formalin, and stained with Langeron’s hydrochloric carmine. The following parameters were also determined: dispersion coefficient, prevalence, intensity, and parasite abundance. Differences in parasitism were assessed using non-parametric tests. Four adult digenean species were found in the stomach, namely Lecithocladium cristatum, Aponurus laguncula, Elytrophalloides oatesi and Gonocerca cf. phycidis. L. cristatum was not only dominant but also the most prevalent and abundant species. None of the digeneans showed interspecific association with each other and therefore they might follow different patterns of colonization (i.e., different intermediate hosts, seasonal and/or spatial distribution of the infective stages). Significant differences were observed among the digeneans analyzed in respect to the sex of the host. Results from this study show that Silver warehou plays a key role as a final host of a significant number of digeneans in the ecosystem. This study is the first step in an attempt to further determine the larval stages in intermediate hosts in San Matías Gulf.
The glands in the pseudoscolex of the echinophallid cestode Paraechinophallus japonicus (Bothriocephalidea), a parasite of the bathypelagic fish Psenopsis anomala (Perciformes, Centrolophidae), were studied using scanning and transmission electron microscopy. Two types of glands, with different morphological types of secretory granules and mechanisms for discharging their glandular secretion, were observed. Both types of gland cell bodies are localized in the parenchyma of the pseudoscolex. The syncytial glands of type I are characterized by the production of small (all ∼0.25 μm in diameter), rounded, dense secretory granules which pass though thin projections into the distal tegumental layer of the pseudoscolex. This type of gland has a unique method of discharging its secretory granules, which we call tumulogenesis. The elimination of the secretory products is realized by an encroachment of the basement membrane and underlying tegumental muscles into the surface region of the distal cytoplasm of the tegument, resulting in the formation of a ‘glandular stalk’ above which develops a superficial glandular tumulus. In the region of the glandular material of the tumulus, the basement membrane of the stalk forms a dilation, and the appearance of a membrane-bound area serves to separate the tumulus from the distal cytoplasm of the tegument. Unicellular glands of type II are characterized by large granules (0.4–0.9 μm in diameter), the presence of peripheral microtubules in the terminal region of their ducts and an eccrine mechanism for the discharge of their secretory granules. A comparative analysis of the distribution and morphology of the types of scolex glands among members of the different families of the ‘Pseudophyllidea’ (currently believed to represent two distinct orders, Bothriocephalidea and Diphyllobothriidea) is presented.
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