No description available.

Bibliography: leaves 109-126.

Rhabdocoels of the genus Paravortex are parasites of marine molluscs. The bent-nosed clams, Macoma nasuta(Conrad, 1837) of Yaquina Bay, Lincoln County, Oregon are commonly infected with a new species of Paravortex. The morphology of the adult worm has been described and it has been compared to the other three species of this genus. The percent infection increased as the size of the clams increased. Analysis of the size frequency distribution of the clam population suggests at least two age classes. Incidence of infection was substantially lower in the younger of these two classes. Clams less than 14 mm in length were not infected. Possible reasons for this distribution of the parasite population were discussed. A peak in the percent of infection, in the incidence of multiple infection, and in the abundance of immature worms was found during April, May, and June, 1968. These data suggest a seasonal periodicity in the reproduction of Paravortex sp. nov. A correlation between the sex of the bent-nosed clams and the incidence and degree of infection could not be established. Paravortex sp. nov. was found only in the pericardial cavity of Macoma nasuta. It is postulated that the rhabdocoel enters this cavity from the suprabranchial space by passing through the kidney. Possible methods by which this endoparasitic rhabdocoel obtains food were discussed. Physical damage to the host clam could not be shown to be the result of parasitic infections. Multiple infections of as many as 28 worms did not appear to physically impair the clam. Observations of the morphology and behavior of living worms were made and conclusions were reached concerning the nature of the symbiotic relationship between Paravortex sp. nov. and its host. Examination of collections of Macoma nasuta made in Coos Bay, Oregon, and Puget Sound, Washington,produced no rhabdocoels. / Graduation date: 1970

Microorganisms are a goidmine for evolutionary genetics as their genomes can evolve at an extraordinary rate which results in some of the most extravagant adaptations in terms of genome structure and function as well as survival in the most unusual environments. One trend observed in several evolutionary scenarios is genome degeneration. It is most prominent in endosymbionts and obligate intracellular parasites and is a consequence of many constraints encountered in the intracellular environment. The process involves loss of many protein-coding genes, resulting in greater dependence on the host, and loss of non-coding DNA such as intergenic regions, which has a direct impact on regulation of genome function. I have chosen two evolutionarily distinct systems to analyze the stages and functional consequences of genome degeneration, namely the impact of genome compression on transcription in an obligate parasite Antonospora locustae (genus Microsporidia), and gene content in the mitochondrion of a diatom endosymbiont found in the dinoflagellate Durinskia baltica. I have successfully mapped transcriptional start and termination sites from 14 loci in Antonospora locustae, and cloned fragments of two genes that are part of the electron transport chain from the mitochondrion of the diatom endosymbiont in Durinskia baltica. My analysis reveals that transcription in A. locustae is always initiated immediately upstream of the open reading frame at a single point for every locus, whereas transcriptional termination can occur at several points for a single gene and, in some instances overlaps with a downstream reading frame. The identification ofNADH5 and ATPase9 from the mitochondrion of the endosymbiont in D. baltica is further evidence for the preservation of function in this enigmatic organelle.

Reproduction de : Thèse d'exercice : Médecine vétérinaire : Toulouse 3 : 2007. / Titre provenant de l'écran titre. Bibliogr. p. 88-95.

Random amplified polymorphic DNA (RAPD) was tested for the identification and classification of Leishmania. RAPD was found to be useful for the identification of species of L. (Leishmania) and L. (Yiannia) and for the classification of L. (Yiannia) species. The polymerase chain reaction (PCR) was tested for the identification of Leishmania from mammals and lizards, using both published primers and new primers which amplify kinetoplast minicircle DNA. The size of the PCR product was found to be useful for discriminating between some sympatric pairs of species such as L. braziliensis and L. mexicana. Isotopically labelled probes prepared from the variable region of the kinetoplast minicircle were tested for specificity for the identification of New and Old World species of Leishmania. The specificity was dependent on the concentration of target DNA and was manipulated to investigate relationships between Leishmania species. Restriction digests of kinetoplast DNA (schizodemes) prepared by PCR and by centrifugation through 20% sucrose were compared for the identification of strains of L. infantum and L. chagasi. Twenty three strains of L. chagasi from cases of visceral and cutaneous leishmaniasis in Honduras were examined by RAPD, schizodemes, differential display, isoenzyrnes, RFLPs and PFGE to discover whether genetic differences existed between parasites causing the two different pathologies. The parasites were found to be unusually homogeneous and no differences were found which correlated with pathology by any of these methods. Restriction digests of PCR amplified small subunit ribosomal DNA (SSU rDNA) (ribodemes) were tested to find markers specific for the genus Leishmania. A classification of the Leishmania based on the restriction fragments indicated that L. hertigi and L. herreri were more closely related to Endotrypanum than to Leishmania, and that the lizard Leishmania could not be placed in separate genus from the Leishmania. Ribodemes were used to identify two strains of parasites supplied by colleagues in Central America that could not be identified by existing methods for the identification of Leishmania. One of these strains appeared to be identical to a C. luciliae reference strain. The other strain produced a fingerprint unlike any of the available reference strains. A variable region of the SSU rRNA gene was identified that was suitable for classifying trypanosomatids and the sequence of this region was used to classify the strain that could not be identified by fingerprinting.

Brief history and background of aquaculture and fish health in Sri Lanka In the past, the Sri Lankan fish industry was mainly comprised of capture fisheries, with a heavy dependence on the marine section. Landings from inland fisheries increased enormously following the introduction of the tilapia Oreochromis mossambicus (Peters) in 1952. Sri Lanka has a high potential for the development of freshwater fisheries in its several thousand irrigation reservoirs. Therefore, in the last few decades, attention has been focused on reservoirs mainly for the following reasons; their high potential. there is less cost incurred in their development than in marine fisheries, and because of their great socio-economic importance with regard to food supply and employment opportunities.

No description available.

No description available.

No description available.