Parasites of the round goby in the North-Western Black Sea region and the Gulf of Gdask have been investigated. Only Acanthocephalus lucii that infect the round goby from the Black Sea were found in one specimen from the Baltic Sea. A lot of the round gobys parasites are fresh water species (Diplostomum spp., A. lucii, Ergasilus sieboldi). The round gobys parasites which are most widespread in the Black Sea (Cryptocotyle spp., Dichelyne minutus) do not infect the goby in the Baltic Sea but are present for other fishes (Gobius niger, Platichthyes flesus). It is possible that the Baltic population of the round goby have a fresh water origin, because independently of the fact that marine parasites, Cryptocotyle concavum and D. minutus, inhabit the Gulf they do not infect the round goby.
In this study the concentrations of trace metals in typical parasites of the three-spined stickleback, i.e. Schistocephalus solidus (Cestoda) and Thersitina gasterostei (Copepoda), and in the sticklebacks (infected or uninfected) were compared. Concentrations of Mn, Co, Ni, Cu, Zn, Cd and Pb were determined. The accumulations of metals suggested that S. solidus, T. gasterostei and their hosts could serve as biological indicators of heavy metal contamination.
A total of 1509 specimens of flounder Platichthys flesus (L.) were sampled in the period from April 1998 to March 2000 from the Gulf of Gdansk. The seasonal occurrence of all parasite species was calculated. The results indicated that some parasite species occur seasonally (Diplostomum sp., Raphidascaris acus, Dichelyne minutus, Echinorhynchus gadi and Pomphorhynchus laevis), while others do not (Trichodina borealis, Hysterothylacium aduncum, Cucullanus heterochrous). Since some parasites occurred year-round at low levels of infection, it was difficult to determine if they exhibited seasonality or not (Glugea anomala, Gyrodactylus unicopula, Diplostomum mergi, Bothriocephalus scorpii and Lampetra sp.). Gyrodactylus flesi was noted occasionally
In the ovarioles of Liophloeus lentus (Insecta, Coleoptera, Curculionidae) two types of bacteria and parasitic microorganisms belonging to Microsporidia have been found. This study shows that the different microsporidian life stages (meronts, sporonts, sporoblasts and spores) infect the outer ovariole sheath, trophic chambers, follicular cells, late previtellogenic and vitellogenic oocytes and eggs. In trophic chambers the parasites are very abundant and are distributed unevenly, i.e. their large mass occupies the syncytial cytoplasm between the nurse cell nuclei, whereas the neck region of the trophic chamber (which houses young oocytes, prefollicular cells and trophic cords) is almost free of parasites. The developing oocytes and eggs contain a lower number of parasites which are usually distributed in the cortical ooplasm. The gross morphology of the ovaries is similar in infected and non-infected specimens. Similarly, the presence of a parasite seems to not disturb the course of oogensis. The only difference was found in the ultrastructure of mitochondria in young previtellogenic oocytes. In the infected females they are unusual i.e. bigger and spherical with tubullar cristae, whereas in the non-infected insects they are elongated and have lamellar cristae. As oogenesis progresses the unusual mitochondria rapidly change their morphology and become similar to the mitochondria in non-infected females. Taking into account the distribution of parasites within the ovarioles, it is suggested that they infect growing oocytes via outer ovariole sheath and follicular epithelium rather than via trophic cords.
A total of 233 perch, Perca fluviatilis L. specimens caught within April 1995?June 1997 at two sites in the Gulf of Gdansk were examined. The fish were found to host flukes (metacercariae of Tylodelphys clavata, Diplostomum spp. and adult Bunodera luciopercae), cestodes (plerocerkoids of Eubothrium crassum and Triaenophorus nodulosus, and adult Proteocephalus percae), nematodes (Camallanus lacustris, C. truncatus, Hysterothylacium aduncum L3 and adult), and acanthocephalans (Acanthocephalus lucii, A. clavula). Most prevalent were A. lucii (33.9%) and T. clavata (28.8%). Most of the parasites were found in the perch caught off the Vistula mouth and the level of infection was higher there than elsewhere in the Gulf, which indicates that ecological and hydrological conditions in the area enhance parasitism.
Initially, most eukaryotic sequence projects were devoted to typical animals, fungi and plants. Now more and more effort is put into sequencing protist genomes. Protists are an artificial assemblage containing mostly unicellular eukaryotes from different phylogenetic lineages, and are much more diversified and widespread than higher Eukaryota. Sequenced protist genomes are essential for reconstructing the Tree of Life and understanding significant events in eukaryotic evolution and diversification. Many protists are parasites and pathogens with medical and economic significance, while others play important ecological roles as primary producers and crucial links in food webs. A number of protists also serve as model organisms in various biological fields and are becoming important in biotechnology. Thirty-seven protist genomes were published by the beginning of 2010 and 217 projects are ongoing. Knowledge coming from these projects will be helpful in developing more efficient protection from pathogenic protists and their effective elimination. Sequenced genomes of ecologically important protists could help to understand key environmental phenomena and even to control them. Newly sequenced protist genomes encode previously unknown enzymes and metabolic pathways, which will be useful in further development of biotechnology.
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