Vicariance in a generalist fish parasite driven by climate and salinity tolerance of hosts.

Acanthocephalans are parasites with complex lifecycles that are important components of aquatic systems and are often model species for parasite-mediated host manipulation. Genetic characterization has recently resurrected Pomphorhynchus tereticollis as a distinct species from Pomphorhynchus laevis, with potential implications for fisheries management and host manipulation research. Morphological and molecular examinations of parasites from 7 English rivers across 9 fish species revealed that P. tereticollis was the only Pomphorhynchus parasite present in Britain, rather than P. laevis as previously recorded. Molecular analyses included two non-overlapping regions of the mitochondrial gene - cytochrome oxidase and generated 62 sequences for the shorter fragment (295 bp) and 74 for the larger fragment (583 bp). These were combined with 61 and 13 sequences respectively, from Genbank. A phylogenetic analysis using the two genetic regions and all the DNA sequences available for P. tereticollis identified two distinct genetic lineages in Britain. One lineage, possibly associated with cold water tolerant fish, potentially spread to the northern parts of Britain from the Baltic region via a northern route across the estuarine area of what is now the North Sea during the last Glaciation. The other lineage, associated with temperate freshwater fish, may have arrived later via the Rhine/Thames fluvial connection during the last glaciation or early Holocene when sea levels were low. These results raise important questions on this generalist parasite and its variously environmentally adapted hosts, and especially in relation to the consequences for parasite vicariance.

Invasive house mice facing a changing environment on the Sub-Antarctic Guillou Island (Kerguelen Archipelago).

Adaptation to new environments is a key feature in evolution promoting divergence in morphological structures under selection. The house mouse (Mus musculus domesticus) introduced on the Sub-Antarctic Guillou Island (Kerguelen Archipelago) had and still has to face environmental conditions that likely shaped the pattern and pace of its insular evolution. Since mouse arrival on the island, probably not more than two centuries ago, ecological conditions dramatically differed from those available to their Western European commensal source populations. In addition, over the last two decades, the plant and animal communities of Guillou Island were considerably modified by the eradication of rabbits, the effects of climate change and the spread of invasive species detrimental to native communities. Under such a changing habitat, the mouse response was investigated using a morphometric quantification of mandible and molar tooth, two morphological structures related to food processing. A marked differentiation of the insular mice compared with their relatives from Western Europe was documented for both mandibles and molar shapes. Moreover, these shapes changed through the 16 years of the record, in agreement with expectations of drift for the molar, but more than expected by chance for the mandible. These results suggest that mice responded to the recent changes in food resources, possibly with a part of plastic variation for the mandible prone to bone remodelling. This pattern exemplifies the intricate interplay of evolution, ecology and plasticity that is a probable key of the success of such an invasive rodent facing pronounced shifts in food resources exploitation under a changing environment.

Treatment of dystonic syndromes by chronic electrical stimulation of the internal globus pallidus.

AIM: Dystonia is a medically intractable condition causing twisting or myoclonic movements and abnormal postures. There is an important heterogeneity among etiologies of dystonia. The electrical stimulation of the globus pallidus has been used successfully in primary generalized dystonia. The aim of this study was to examine the long-term efficacy and safety of deep brain stimulation (DBS) in the treatment of primary and secondary generalized dystonia in children and adults. METHODS: Fifty-three patients were included. Electrodes were bilaterally implanted under stereotactic guidance and connected to neurostimulators, subcutaneously inserted. Efficacy was evaluated by comparing scores on the clinical and functional Burke-Marsden-Fahn dystonia rating scales (BMFDRS) before and after implantation. Patients were divided into 3 groups: group 1 comprised 15 patients with DYT1 dystonia; group 2, 17 patients with dystonia of unknown etiology and group 3, 21 patients with secondary dystonia. The mean follow-up was 26.6+/-12.3 months for primary dystonia and 23.1+/-11.8 for secondary dystonia. RESULTS: After 1 year, the improvement of the clinical score is 71% in group 1, 74% in group 2 and 31% in group 3. The functional score was improved by 63% in group 1, 49% in group 2 and 7% in group 3. We did not find any significant difference between children and adults. In secondary dystonia, efficacy of the stimulation is more limited. The efficacy of the stimulation improved with time for the 3 groups. COMCLUSION: Electrical stimulation of the internal globus pallidus proved to be an effective treatment for generalized dystonia and should be considered as first-line therapy.