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International audience; Microbial symbionts commonly protect their hosts from natural enemies, but it is unclear how protective symbionts influence the evolution of host immunity to pathogens. One possibility is that 'extrinsic' protection provided by symbionts allows hosts to reduce investment in 'intrinsic' immunological resistance mechanisms. We tested this idea using pea aphids (Acyrthosiphon pisum) and their facultative bacterial symbionts that increase host resistance to the fungal pathogen Pandora neoaphidis. The pea aphid taxon is composed of multiple host plant associated populations called biotypes, which harbour characteristic communities of symbionts. We found that biotypes that more frequently carry protective symbionts have higher, rather than lower, levels of intrinsic resistance. Within a biotype there was no difference in intrinsic resistance between clones that did and did not carry a protective symbiont. The host plant on which an aphid feeds did not strongly influence intrinsic resistance. We describe a simple conceptual model of the interaction between intrinsic and extrinsic resistance and suggest that our results may be explained by selection favouring both the acquisition of protective symbionts and enhanced intrinsic resistance in habitats with high pathogen pressure. Such combined protection is potentially more robust than intrinsic resistance alone. This article is protected by copyright. All rights reserved.

The current limitations of calcium phosphate cements (CPCs) used in the field of bone regeneration consist of their brittleness, low injectability, disintegration in body fluids and low biodegradability. Moreover, no method is currently available to measure the setting time of CPCs in correlation with the evolution of the setting reaction. The study proposes that it is possible to improve and tune the properties of CPCs via the addition of a thermosensitive, biodegradable, thixotropic copolymer based on poly(lactic acid), poly(glycolic acid) and poly(ethylene glycol) (PLGA&ndash, PEG&ndash, PLGA) which undergoes gelation under physiological conditions. The setting times of alpha-tricalcium phosphate (&alpha, TCP) mixed with aqueous solutions of PLGA&ndash, PLGA determined by means of time-sweep curves revealed a lag phase during the dissolution of the &alpha, TCP particles. The magnitude of the storage modulus at lag phase depends on the liquid to powder ratio, the copolymer concentration and temperature. A sharp increase in the storage modulus was observed at the time of the precipitation of calcium deficient hydroxyapatite (CDHA) crystals, representing the loss of paste workability. The PLGA&ndash, PLGA copolymer demonstrates the desired pseudoplastic rheological behaviour with a small decrease in shear stress and the rapid recovery of the viscous state once the shear is removed, thus preventing CPC phase separation and providing good cohesion. Preliminary cytocompatibility tests performed on human mesenchymal stem cells proved the suitability of the novel copolymer/&alpha, TCP for the purposes of mini-invasive surgery.

Aim: We used comparative phylogeography of two intestinal parasites of freshwater fish to test whether similarity in life cycle translates into concordant phylogeographical history. The thorny-headed worms Pomphorhynchus laevis and P. tereticollis (Acanthocephala) were formerly considered as a single species with a broad geographical and host range within the Western Palaearctic. Location: Central and eastern parts of Northern Mediterranean area, Western and Central Europe, Ponto-Caspian Europe. Methods: A mitochondrial marker (COI) was sequenced for 111 P. laevis and 50 P. tereticollis individuals and nuclear ITS1 and ITS2 sequences were obtained for 37 P. laevis and 21 P. tereticollis. Genetic divergence, phylogenetic relationships and divergence time were estimated for various lineages within each species, and their phylogeographical patterns were compared to known palaeogeographical events in Western Palaearctic. Biogeographical histories of each species were inferred. Results: The two species show very different phylogeographical patterns. Five lineages were identified in P. laevis, partially matching several major biogeographical regions defined in the European riverine fish fauna. The early stages of P. laevis diversification occurred in the peri-Mediterranean area, during the Late Miocene. Subsequent expansion across Western Europe and Russia was shaped by dispersal and vicariant events, from Middle Pliocene to Middle Pleistocene. By contrast, P. tereticollis has differentiated more recently within the Western and Central parts of Europe, and shows weak geographical and genetic structuring. Conclusion: Our study highlights weak to moderate similarity in the phylogeographical pattern of these acanthocephalan parasites compared to their amphipod and fish hosts. The observed differences in the timing of dispersion and migration routes taken may reflect the use of a range of final hosts with different ecologies and dispersal capabilities. By using a group underrepresented in phylogeographical studies, our study is a valuable contribution to revealing the biogeography of host–parasite interactions in continental freshwaters. © 2017 John Wiley & Sons Ltd