Microsatellite discovery in an insular amphibian (Grandisonia alternans) with comments on cross-species utility and the accuracy of locus identification from unassembled Illumina data

The Seychelles archipelago is unique among isolated oceanic islands because it features an endemic radiation of caecilian amphibians (Gymnophiona). In order to develop population genetics resources for this system, we identified microsatellite loci using unassembled Illumina MiSeq data generated from a genomic library of Grandisonia alternans, a species that occurs on multiple islands in the archipelago. Applying a recently described method (PALFINDER) we identified 8001 microsatellite loci that were potentially informative for population genetics analyses. Of these markers, we screened 60 loci using five individuals, directly sequenced several amplicons to confirm their identity, and then used eight loci to score allele sizes in 64 G. alternans individuals originating from five islands. A number of these individuals were sampled using non-lethal methods, demonstrating the efficacy of non-destructive molecular sampling in amphibian research. Although two loci satisfied our criteria as diploid, neutrally evolving loci with the statistical power to detect population structure, our success in identifying reliable loci was very low. Additionally, we discovered some issues with primer redundancy and differences between Illumina and Sanger sequences that suggest some Illumina-inferred loci are invalid. We investigated cross-species utility for eight loci and found most could be successfully amplified, sequenced and aligned across other species and genera of caecilians from the Seychelles. Thus, our study in part supported the validity of using PALFINDER with unassembled reads for microsatellite discovery within and across species, but importantly identified major limitations to applying this approach to small datasets (ca. 1 million reads) and loci with small tandem repeat sizes

Spatial ecology and habitat use of two-spined blackfish Gadopsis bispinosus in an upland reservoir

The scale and patterns of movement and habitat use are primary considerations in the conservation and management of threatened species. Movement, activity and habitat use of the threatened two-spined blackfish Gadopsis bispinosus were assessed in a small upland reservoir in south-eastern Australia using manual and remote radio-telemetry. Movements and activity of two-spined blackfish (n = 19) were studied over a 28-day period and exhibited proportionately large directional crepuscular movement and activity with heightened activity continuing throughout the night (although movement was subdued). Two daily movement strategies were observed: movements from diurnal home-shelter habitats (predominantly rock) to macrophytes at night (14 individuals), and occupation of macrophytes during the entire diel period and restricted movement (five individuals). Daily movement strategies were fixed (not plastic) among all individuals, with one exception, for the duration of the study period. Rock, fallen timber and macrophytes were the most commonly used daytime shelter habitat (in order of preference). Although some information exists on movements and habitat use of this species and the congeneric river blackfish G. Marmoratus in lotic environments, we present the first study of movements and habitat use for either species in lentic environments. Given the occupation of lentic environments by this threatened species, the data presented in this study provide insight into the habitat requirements for this species, and offer opportunities for habitat enhancement in existing reservoirs within the species' geographic range

Effects of medial temporal lobe degeneration on brain perfusion in amnestic MCI of AD type: deafferentation and functional compensation?

International audiencePURPOSE: Cortical atrophy is correlated with the progression of neuropathological lesions within the medial temporal lobes (MTL) in Alzheimer's disease (AD). Our aim was to determine which local and remote functional changes result from MTL volume loss at the predementia stage. METHODS: We studied the relationship between entorhinal and hippocampal MR volumes and whole-brain SPECT perfusion via a voxel-based correlative analysis in 19 patients with amnestic mild cognitive impairment with a memory profile suggestive of early AD. RESULTS: Right MTL volumes were positively correlated with remote posterior perfusion of the posterior cingulate cortex, and negatively correlated with remote anterior perfusion of the right medial and dorsolateral prefrontal cortex. There was no local correlation between volumes and perfusion within the MTL. CONCLUSION: These findings provide further insight into functional changes that result from MTL volume loss during the predementia stage of AD. The positive correlation between MTL volumes and posterior cingulate perfusion may reflect the deafferentation of a temporocingulate network due to mediotemporal degeneration. The paradoxical negative correlation between MTL volumes and prefrontal perfusion may result from recruitment of an alternative anterior temporofrontal network. It remains to be investigated how the "net sum" of this perfusion modulation affects memory and other cognitive domains through a possible compensatory perspective