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A taxonomic revision was performed on the New World scarabaeoid genus Aegidinus Arrow (Coleoptera: Scarabaeidae: Orphninae). Twelve new species and three previously described species are included in the revision. Keys to New World genera, species of the genus Aegidinus, and distribution maps are provided. Phylogenetic analyses of the world genera of the Orphninae were conducted using 30 adult, morphological characters from representatives of 13 of the 14 genera and three out-group taxa. The subfamily Orphninae is a strongly supported monophyletic group (bootstrap support 88-90%) with respect to the chosen out-group. Characters that support the Orphninae are: mandibles not sickle shaped, molar surface on the mandibles present, lacinia present, and stridulatory comb present. Separate Old and New World lineages are also supported by the phylogeny, when two genera, Goniorphnus Arrow and Stenosternus Karsch, are excluded from the analysis. The new species described are: Aegidinus cornutus Colby, A. crypticus Colby, A. howdenorum Colby, A. howeae Colby, A. oreibates Colby, A. petrovi Colby, A. simulatus Colby, A. sunidgea Colby, A. teamscaraborum Colby, A. tricornis Colby, A. unicus Colby, and A. venezuelensis Colby.
The E4 allele of the ApoE gene has consistently been shown to be related to an increased risk of Alzheimer's disease (AD). The E4 allele is also associated with functional and structural grey matter (GM) changes in healthy young, middle-aged and older subjects. Here, we assess volumes of deep grey matter structures of 22 healthy younger ApoE4 carriers and 22 non-carriers (20–38 years). Volumes of the nucleus accumbens, amygdala, caudate nucleus, hippocampus, pallidum, putamen, thalamus and brain stem were calculated by FMRIB's Integrated Registration and Segmentation Tool (FIRST) algorithm. A significant drop in volume was found in the right hippocampus of ApoE4 carriers (ApoE4+) relative to non-carriers (ApoE4−), while there was a borderline significant decrease in the volume of the left hippocampus of ApoE4 carriers. The volumes of no other structures were found to be significantly affected by genotype. Atrophy has been found to be a sensitive marker of neurodegenerative changes, and our results show that within a healthy young population, the presence of the ApoE4+ carrier gene leads to volume reduction in a structure that is vitally important for memory formation. Our results suggest that the hippocampus may be particularly vulnerable to further degeneration in ApoE4 carriers as they enter middle and old age. Although volume reductions were noted bilaterally in the hippocampus, atrophy was more pronounced in the right hippocampus. This finding relates to previous work which has noted a compensatory increase in right hemisphere activity in ApoE4 carriers in response to preclinical declines in memory function. Possession of the ApoE4 allele may lead to greater predilection for right hemisphere atrophy even in healthy young subjects in their twenties.