African clawed frogs, genus Xenopus, are extraordinary among vertebrates in the diversity of their polyploid species and the high number of independent polyploidization events that occurred during their diversification. Here we update current understanding of the evolutionary history of this group and describe six new species from west and central sub-Saharan Africa, including four tetraploids and two dodecaploids. We provide information on molecular variation, morphology, karyotypes, vocalizations, and estimated geographic ranges, which support the distinctiveness of these new species. We resurrect Xenopus calcaratus from synonymy of Xenopus tropicalis and refer populations from Bioko Island and coastal Cameroon (near Mt. Cameroon) to this species. To facilitate comparisons to the new species, we also provide comments on the type specimens, morphology, and distributions of X. epitropicalis, X. tropicalis, and X. fraseri. This includes significantly restricted application of the names X. fraseri and X. epitropicalis, the first of which we argue is known definitively only from type specimens and possibly one other specimen. Inferring the evolutionary histories of these new species allows refinement of species groups within Xenopus and leads to our recognition of two subgenera (Xenopus and Silurana) and three species groups within the subgenus Xenopus (amieti, laevis, and muelleri species groups).

Here we describe a new octoploid species of clawed frog from the Itombwe Massif of South Kivu Province, Democratic Republic of the Congo. This new species is the sister taxon of Xenopus wittei, but is substantially diverged in morphology, male vocalization, and mitochondrial and autosomal DNA. Analysis of mitochondrial "DNA barcodes" in polyploid clawed frogs demonstrates that they are variable between most species, but also reveals limitations of this type of information for distinguishing closely related species of differing ploidy level. The discovery of this new species highlights the importance of the Itombwe Massif for conservation of African biodiversity south of the Sahara.

No abstract

The biological effects of exposure to radioactive fluorodeoxyglucose (18F-FDG) were investigated in the lymphocytes of patients undergoing positron emission tomography (PET) procedures. Low-dose, radiation-induced cellular responses were measured using 3 different end points: (1) apoptosis; (2) chromosome aberrations; and (3) γH2AX foci formation. The results showed no significant change in lymphocyte apoptosis, or chromosome aberrations, as a result of in vivo 18F-FDG exposure, and there was no evidence the PET scan modified the apoptotic response of lymphocytes to a subsequent 2 Gy in vitro challenge irradiation. However, lymphocytes sampled from patients following a PET scan showed an average of 22.86% fewer chromosome breaks and 39.16% fewer dicentrics after a subsequent 2 Gy in vitro challenge irradiation. The effect of 18F-FDG exposure on phosphorylation of histone H2AX (γH2AX) in lymphocytes of patients showed a varied response between individuals. The relationship between γH2AX foci formation and increasing activity of 18F-FDG was not directly proportional to dose. This variation is most likely attributed to differences in the factors that combine to constitute an individual’s radiation response. In summary, the results of this study indicate18F-FDG PET scans may not be detrimental but can elicit variable responses between individuals and can modify cellular response to subsequent radiation exposures.

No abstract