No description available.

A família Trypanosomatidae compreende parasitas obrigatórios de vertebrados, plantas e invertebrados, as espécies exclusivas de insetos infectam principalmente dípteras e hemípteras. Nós revisamos a taxonomia de Herpetomonas e tripanossomatídeos de insetos que abrigam simbionte (SHT), comparando tripanossomatídeos da América do Sul e África. As filogenias revelaram duas novas espécies e possibilitou revalidar os gêneros Strigomonas e Angomonas. As análises filogenéticas revelaram três novas espécies de endossimbiontes proteobacteriano e apoiam a história evolutiva convergente entre hospedeiros e simbiontes. O DNA barcoding de 364 culturas de moscas identificaram 70 culturas (20%) como Angomonas, 71% deles de Calliphoridae. O gênero Herpetomonas compreende agora 13 espécies válidas, incluindo cinco novas espécies. Algumas espécies de Herpetomonas são parasitas generalistas de moscas e parecem ser tão cosmopolita como seus hospedeiros. Os taxon propostos podem ajudar a elaborar critérios mais eficientes para uma classificação melhor dos tripanossomatídeos. / Trypanosomatidae comprises obligate parasites of vertebrates, plants and invertebrates, the species exclusive of insects infect mostly dipterans and hemipterans. We revise the taxonomy of Herpetomonas and Symbiont Harboring Trypanosomatids (SHTs), by comparing trypanosomatids from South America and Africa. The phylogenies disclosed two new species and revalidated the genera Strigomonas and Angomonas. Phylogenetic analyses revealed 3 new species of proteobacterial endosymbionts and support a co-divergent host-symbiont evolutionary history. DNA barcoding of 364 cultures from flies identified 70 cultures (20%) as Angomonas, 71% of them from Calliphoridae. The recent dispersion of calliphorids was important in the dispersal of Angomonas worldwide. The genus Herpetomonas now comprises 13 valid species including 5 new species. Some species of Herpetomonas are generalist parasites of flies and appear to be as cosmopolitan as their hosts. The proposed taxa may help to elaborate more efficient criteria for a better classification of the Trypanosomatidae.

No description available.

The incidence of parasitism by Bunodera mediovitellata in Trichoptera in Tin Can Creek was investigated. Larvae of Lepidostoma roafi had a low incidence of infection , while Psychoglypha alascensis larvae had a high incidence of infection. The encapsulation reactions of these Trichoptera larvae to internal Epon implants, and metacercariae of the parasite encysted within the silk glands, were examined in vivo to determine the details of the cellular encapsulation reactions of Trichoptera to foreign objects in both of these sites, and to determine which hemocytes are involved in the reaction. The hemocytes of larvae of P. alascensis were capable of encapsulating Epon implants within the hemocoele; the reaction took approximately twenty days longer than those of other insects that have been maintained at 20°C. The hemocytes of larvae of P. alascensis are also capable of encapsulating the metacercariae of their natural parasite B. mediovitellata in the silk glands despite the normal absence of hemocytes from the silk gland lumen. The hemocyte capsules around both the non-living and living objects was typical of the 'ordinary encapsulation reaction' described by Salt (1970). The capsule consisted of an inner layer of flattened cells which were densely packed and an outer layer of cells which were not flattened to the same extent as those of the inner layer. The hemocytes which took part in both capsules around implants and capsules around parasites were flattened elongated hemocytes which probably correspond to plasmatocytes or granulocytes. However, the production of a Summary Fate Map of free circulating hemocytes demonstrated that hemocyte types are stages in the development of a number of lines of hemocyte types. It appears that the hemocytes taking part in the encapsulation reactions belong to two of these lines of hemocyte types. / Science, Faculty of / Zoology, Department of / Graduate

Providence virus (PrV) is a member of the Tetraviridae, a family of small, positive sense, single-stranded RNA viruses, which characteristically infect the midgut tissue of heliothine larvae. PrV is the only known tetravirus that replicates in cultured insect cells. The virus comprises a monopartite genome resembling members of the genus Betatetravirus with the capsid precursor protein undergoing autoproteolytic cleavage at its C-terminus consistent with other tetravirus capsid precursor proteins. Analysis of viral cDNA predicted the presence of three potential overlapping gene products (from 5` to 3`): (1) p130, a protein of unrecognized nucleotide or amino acid homology with a 2A-like processing site at its N-terminus; (2) p104, the replicase ORF, which was found to be phylogenetically related to tombus-and umbraviruses replicases. The presence of a read-through stop signal in the p104 ORF was proposed to produce and amino terminal product with a predicted MW of 40 kDa (p40) and (3) the capsid protein precursor (81 kDa) which has two 2A-like processing sites at its N-terminus. Metabolic radiolabelling of viral translation products in persistently infected MG8 cells and in vitro translation of the individual ORFs were performed in order to analyse the expression of PrV gene products. p130 was translated with no evidence of 2A-like processing. Two products of 40 kDa and 104 kDa were translated from the p104 ORF, indicating that the read-through stop signal was likely to be functional. Finally, the capsid protein precursor ORF produced a major translation product of 68 kDa corresponding to the capsid protein precursor as well a peptide of 15 kDa that was attributed to the activity of the second 2A-like site at the N-terminus of the p81 ORF. The subcellular distribution of viral RNA (vRNA) and p40 in MG8 cells was investigated using immunofluorescence and biochemical fractionation. The results showed that p40/p104 and vRNA accumulated in polarized, punctate structures in some but not all MG8 cells and in some cases, co-localization was observed. This thesis concludes that PrV is a novel tetravirus with significant similarities plant carmolike viruses that should be re-classified at the family level.

Since becoming a pest in graminaceous crops in Africa, the African sugarcane stalkborer Eldana saccharina Walker has been the subject of much study. Its very cryptic habits have precluded more commonly available control measures being used against it. Biological control is regarded as a viable control option, but the apparent paucity of parasitoids in graminaceous crops leads to E. saccharina being regarded as lacking parasitoids, and thus not a good candidate for biological control in the classical sense. In contrast, this project argues that interactions in indigenous hosts of E. saccharina had been ignored, and that classical biocontrol principles and basic ecological theory could be applied by the discovery, collection and introduction of parasitoids from its indigenous habitat to its newly adapted habitat, sugarcane. The habitat offered by Cyperus papyrus L. was shown to be heterogenous both temporarily and spatially. Umbels, from young through mature to senescent, were available in the same proportion for colonisation throughout the year. Umbels with sexual reproductive stages (seeds) were present from early spring into late summer, and provided an additional component to the already heterogenous environment. Young umbels, in addition, developed from rhizomes in an environment regarded as sub-optimal for photosynthesis, until they reached the canopy. All stages of umbels were attacked by E. saccharina, but larvae were only found in rays of umbels and in the apex of the culm, which was the meristematic area for rays, both high nutrient areas. Young umbels were never found with borer pupae, only smaller larvae, indicating that E. saccharina development matched growth of young umbels until they reached canopy height. Also, the majority of borings found were occupied, indicating that infestation of young umbels was recent. All stages of E. saccharina development were found in mature umbels, which were also most abundant at anyone time. Numerous empty borings were found in addition to those occupied, indicative of past occupation by E. saccharina. Very few young larvae were found in old umbels, the majority of life stages found being pupae or empty pupal cases, and also many empty borings, showing that old umbels were not suitable for E. saccharina development. A guild of parasitoids which comprised Orgilus bifasciatus Turner, the most common parasitoid of small and smaller medium E. saccharina larvae, Goniozus indicus Ashmead the most common parasitoid of larger medium and large larvae, and an entomogenous fungus Seauveria bassiana (Sals.) Vuill. attacking all life stages of E. saccharina was found. Three uncommon parasitoids of smaller saccharina were also found, viz. Sassus sublevis (Granger), Iphiaulax sp. and Venturia sp. The former three natural enemies were instrumental in depressing a major outbreak within two months of it being observed and then maintaining the host population at a lower level in C. papyrus. G. indicus and B. bassiana were most effective during the summer and autumn months, and O. bifasciatus most effective during the winter months. This study supports the hypotheses that the apparent paucity of parasitoids and lack of biological control success thus far against E. saccharina in sugarcane has been because very little was known about its ecology and biology in its numerous indigenous host plants, and that studies of the latter factors coupled with ecological theory could enhance biological control programmes against this borer. As more indigenous host plants are investigated in the same way as has been done with C. papyrus, more will become known of natural enemies of E. saccharina. Parasitoid guilds could be selected, even from rare parasitoids in the more stable indigenous habitats, which would provide control in the unstable habitat of sugarcane. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.