M.Sc. (Nematology) / Please refer to full text to view abstract

Ph.D. (Nematology) / This thesis consists of three parts: the first and major part dealing with Xiphinema species from southern Africa. the second shorter part with Xiphinema species from the Aldabra Atoll. and the last part with aspects of the ultrastructure of Xiphidorus balcarceanus Chaves & Coornans, 1984 from Argentina. Nine new Xiphinema species are described from southern Africa. The three new species X. erriae, X. ripogranum and X. lacrimaspinae are all related to X. meridianum Heyns. 1971. but can be differentiated by the nature of the uterine spines and inclusions in the pseudo-Z-organ. tail shape. ovejector shape and the presence or absence of males. Two new longtailed species related to X. fJagellicaudatum Luc, 1961. viz. X. judex and X. dracomontanum, can be distinguished by body length. tail length and shape. the nature of the pseudo-Z-organ and presence or absence of males. Three new species with digitate or subdigitate tails are described, viz. X. capriviense from South West Africa-Namibia, which is characterised i.a. by peculiar inclusions in the uterus. X. pongolense from northern Natal which is quite similar to X. umobae Heyns & Spaull, 1979. and X. simplex from the Transkei, in which the uterus is devoid of any inclusions. The last new species to be described is X. ometizulu, which belongs to the X. zulu Heyns, 1965 and X. mampara Heyns, 1979 species complex. The abovementioned species complex was studied in detail, and X. mampara was found to consist of three different forms, one amphimictic, which is herein called X. mampara f. bisexuale. and two parthenogenetic forms. called X. mampara f. major and X. mampara f. minor. Redescriptions based on new populations are given for X. clavatum Heyns, 1965 and X. imitator Heyns, 1965. and additional information is also offered for X. umobae. A dichotomous key is presented for the identification of the 54 species of Xiphinema recorded from southern Africa. and the known distribution of these species is shown in a series of maps. X. brevicolle Lordello & Da Costa. 1961. X. italiae Meyl. 1953 and X. malagasi tuc, 1973 are reported from the Aldabra Atoll. All three species are described and figured, and compared with previous descriptions. The ultrastructure of the cuticle and feeding apparatus of Xiphidorus ba/carceanus was studied and compared with some other Longidoridae species.

Made available in DSpace on 2015-03-26T13:37:44Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2275895 bytes, checksum: d1f4e8c4d24b299b4ddf661a62268693 (MD5) Previous issue date: 2011-02-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Biodiversity is one of the most valuable resources in the earth and in order to its maintenance and best use, there is a need of its profound knowledge on the basis of taxonomic and ecological works. The studies of the nematodes communities in soils under cultivation or native vegetation is becoming an area of growing interest in recent years. In relation to communities of nematodes in natural ecosystems, the studies are justified by the great representative of the Nematoda phylum and by the need to understand the nematodes' ecology in their original setting, since the agricultural important species, that have adapted in the cultivated areas, originated from natural ecosystems. The aim was to identify longidorid species associated with natural vegetation in Atlantic Forest, Savannah and in growing areas in Minas Gerais. Complementarily intended determine and compare the richness and diversity of phytonematodes communities in these areas. Seven species of Xiphinema (X. brasiliense, X. diffusum, X. elongatum, X. ensiculiferum, X. krugi, X. variegatum,and X. surinamense) and two species of Xiphidorus (X. cf. parthenus and X. amazonensis) were found, and beyond two new species to science, Xiphinema sp. and Xiphidorus sp., not yet identified. Populations of X. krugi, X. elongatum, X. ensiculiferum and Xiphidorus cf. parthenus showed great morphometric variability. Because of the great morphometric and morphological variabilities reported in the literature, the morphometric data of X. krugi populations were subjected to principal component analysis with standards population available in the literature. This analysis indicated that variations in morphometric characters may reflect differences in these genotypes, whereas they were grouped with three of these standards. Three populations appear to represent a new genotype not yet characterized. The phytonematodes communities associated with cover crops from Savannah and Atlantic Forest showed greater diversity and richness. The highest abundance and richness were present in Atlantic Forest communities and the greater diversity in the communities associated with Savannah. The genera with significant populations were Discocriconemella spp. Macroposthonia spp. Meloidogyne spp. and Rotylenchus spp. in Atlantic Forest, Rotylenchulus spp. and Rotylenchus spp. in Savannah, and Helicotylenchus spp. Meloidogyne spp. and Rotylenchulus spp. in growing areas. / A biodiversidade é um dos recursos mais valiosos da Terra e, para a sua manutenção e melhor aproveitamento, há a necessidade de que seja conhecida em maior profundidade com base em trabalhos taxonômicos e ecológicos. Conhecer as comunidades de nematoides em solos sob cultivo ou vegetação natural, vem se tornando uma área de interesse crescente, nos últimos anos. Em relação às comunidades de fitonematoides em ecossistemas naturais, os estudos se justificam pela grande representatividade do filo Nematoda e pela necessidade de compreender a ecologia desses em seu ambiente original, uma vez que as espécies de importância agrícola originaram-se de ecossistemas naturais que se adaptaram às áreas cultivadas. Assim, objetivou-se identificar espécies de longidorídeos associados à vegetação natural de Mata Atlântica, Cerrado e em área de cultivo em municípios de Minas Gerais, além de determinar e comparar a riqueza e diversidade das comunidades de fitonematoides presentes nessas áreas. Encontraram-se sete espécies de Xiphinema (X. brasiliense, X. diffusum, X. elongatum, X. ensiculiferum, X. krugi, X. variegatum e X. surinamense) e duas espécies de Xiphidorus (X. cf. parthenus eX. amazonensis), além de duas novas espécies para a ciência, Xiphinema sp. e Xiphidorus sp., ainda não identificadas. Populações de X. krugi, X. elongatum, X. ensiculiferume Xiphidorus cf. parthenus apresentaram grande variabilidade morfométrica. Em vista da grande variabilidade morfométrica e morfológica relatada na literatura, os dados morfométricos obtidos das populações de X. krugi, foram submetidos a análise de componente principal juntamente com populações padrões, disponíveis na literatura. Essa análise indicou que as variações nos caracteres morfométricos podem refletir diferenças nos genótipos dessas, visto que se agruparam com três desses padrões. Três populações pareceram representar um novo genótipo ainda não caracterizado. As comunidades de fitonematoides associadas às coberturas vegetais de Cerrado e Mata Atlântica apresentaram maiores diversidade e riqueza. A maior abundância e riqueza estavam presentes nas comunidades de Mata Atlântica e a maior diversidade nas comunidades associadas ao Cerrado. Os gêneros com populações mais expressivas foram Discocriconemella spp., Macroposthonia spp. Meloidogyne spp. e Rotylenchus spp. em Mata Atlântica, Rotylenchulus spp. e Rotylenchus spp. no Cerrado, e em área de cultivo, Helicotylenchus spp., Meloidogyne spp. e Rotylenchulus spp.