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Zimmerman PA; Katholi CR; Wooten MC; Lang-Unnasch N; Unnasch TR 《Molecular biology and evolution》1994,11(3):384-392
Polymerase chain reaction (PCR) products were characterized for a repeated
sequence family (designated "O-150") of the human filarial parasite
Onchocerca volvulus. In phylogenetic inferences, the O-150 sequences
clustered into closely related groups, suggesting that concerted evolution
maintains sequence homology in this family. Using a novel mathematical
model based on a nested application of an analysis of variance, we
demonstrated that African rainforest and savannah strain parasite
populations are significantly different. In contrast, parasites collected
in the New World are indistinguishable from African savannah strains of O.
volvulus. This finding supports the hypothesis that onchocerciasis was
recently introduced into the New World, possibly as a result of the slave
trade.
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Krueger A Mustapha M Kalinga AK Tambala PA Post RJ Maegga BT 《Medical and veterinary entomology》2006,20(1):76-92
A revision of the taxonomy of the Ketaketa subcomplex of the Simulium damnosum Theobald complex (Diptera: Simuliidae) is presented including new material from Tanzania, Malawi and South Africa. The cytotaxonomy, morphology and molecular identity of known and new taxa are described. The Ketaketa subcomplex is cytotaxonomically defined by the paracentric inversion 1L-7. We recognize three sibling species, namely Simulium latipollex (Enderlein), Simulium plumbeum Krueger, sp.n. and Simulium kipengere Krueger, sp.n., the latter comprising three cytoforms: 'Typical', 'Linthipe' and 'Mombo'. The cytoforms 'Mwamphanzi', 'Ketaketa' and 'Hammerkopi' are synonymized with S. plumbeum. Identification keys are provided on the basis of chromosomal and morphological characters. In view of their potential role as vectors of human onchocerciasis (river blindness) we also discuss the possible medical importance of the different cytoforms and their geographical distribution. 相似文献
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The African freshwater oyster Etheria elliptica, which is of great economic importance throughout the continent, is facing overharvesting in many fisheries in West Africa. Its reproductive traits (sex ratio, size at sexual maturity, oocyte diameter and fecundity) were studied at four stations located along the Pendjari River, northern Benin, in April 2013. Histological techniques were implemented to identify sex and gonad development stages. Oocyte sizes were measured based on the histological images and mean oocyte diameter was 38 µm. Fecundity, estimated by counting the developing eggs, averaged 106 724 eggs and increased significantly with shell size. The average sex ratio was approximately 1:1. Hermaphrodites were rare. Males reached sexual maturity at 57.6 mm dorsoventral height, earlier than females at 64.7 mm. The majority of the oyster specimens were in ripe-spawning stages, indicating that reproductive activities partly took place towards the end of the dry season. Both mature and immature individuals were subjected to harvesting at all the investigated fishing sites. The mean size of exploited oysters was 60.6 mm, lower than the size of females at maturity. Management strategies must enforce the minimum size of 65 mm required for harvesting, particularly in open access sites where juveniles are mostly harvested. 相似文献
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