Myxozoa parasites from annelids and aquaculture fishes
Başlık:
Myxozoa parasites from annelids and aquaculture fishes
Yazar:
Rangel, Luís Filipe da Cunha Melo Silva, author.
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (222 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-07C.
Özet:
Overfishing exerts an enormous pressure on marine resources and, consequently, it is urgent to develop alternative ways to meet the world's food requirements. One such alternative is fish farming which, in recent years, has experienced a great increase in production. However, fish farming can only succeed if it is economically viable. Amongst the problems that threaten the economic viability of the fish farming industry, disease and parasites are the most relevant. Thus, the study and development of the body of knowledge on fish diseases and parasites are crucial. Amongst the most frequent parasites in fish farms, with tendency to increase in the near future, are the myxozoans. These parasites can have very adverse effects and cause major losses in fish production. However, there is still a huge gap in the body of knowledge on this particular group of parasites, especially in what concerns the life cycle. This unsolved problem leads the main aims of the present thesis work, which includes the survey and elucidation of the life cycles of myxozoan parasites infecting farmed fishes with great economic value, moreover, the European seabass (Dicentrarchus labrax) and the gilthead seabream (Sparus aurata), in Algarve, and the actinospores survey in the fish farm tanks and in wild environment, in Algarve and Aveiro Estuary.
While conducting this work, two new species of myxosporeans were described: Ortholinea auratae n. sp., isolated from the European seabass, and Ortholinea labracis n. sp., isolated from the gilthead seabream, both from the Algarve fish farm. Both species were found infecting the urinary bladder and, less frequently, the kidneys of their hosts. The life cycles of these two species were elucidated. Actinosporean stages of Ortholinea auratae n. sp. developed in the intestinal epithelium of Limnodriloides agnes oligochaetes, producing triactinomyxon actinospores. Ortholinea labracis n. sp. developed in the intestinal epithelium of Tectidrilus sp. oligochaetes, also producing triactinomyxons actinospores. Both invertebrate hosts were collected from the mud of the fish farm tanks.
The life cycle of Sphaerospora dicentrarchi, a systemic parasite of the European seabass, was also elucidated. This result was achieved after finding a new type of tetractinomyxon actinospore in the coelomic cavity of Capitella sp., a capitelid polychaete collected in European seabass farming tanks in the Algarve fish farm. While analysing the 18S ribosomal RNA gene sequences of both polychaete actinospore and fish myxospore, it was possible to determine a 99.9% similarity. Therefore, it is possible to infer that they represent the two S. dicentrarchi life cycle stages.
Myxosporean surveyed in annelids from estuaries revealed new types of actinospores with implications for the taxonomy and differentiation of actinospore collective groups. From Alvor Estuary (Algarve), a new type of echinactinomyxon was described from the coelomic cavity of the capitelid polychaete Heteromastus filiformis. Previously, these types of actinospore were always described from freshwater oligochaetes, and its presence in marine polychaetes is here recorded for the first time. Also, the 18S ribosomal RNA gene sequence was found to exhibit 94% of similarity with marine Sphaeromyxa species. In phylogenetic terms, Sphaeromyxa species cluster within myxosporeans of the freshwater lineage. From Aveiro Estuary, 10 new types of sphaeractinomyxon were described from the coelomic cavity of two oligochaete hosts (L. agnes and Tubificoides pseudogaster). Morphological and development analysis raised questions about the validity of the endocapsa and tetraspora actinospore collective groups.
Developmental stages from the invertebrate hosts were studied by ligth microscopy and transmission electron microscopy. The most significant result was the record of the internalization or engulfment of one cell by another in myxosporeans, leading to secondary cells origin, as it was previously demonstrated for the malacosporeans.
Notlar:
School code: 5896
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(678844.1) | 678844-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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