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See detailThe scent of inbreeding: male sex pheromones betray inbred males
van Bergen, Erik; Brakefield, Paul M.; Heuskin, Stéphanie ULg et al

in Proceedings of the Royal Society B : Biological Sciences (2013)

Inbreeding depression results from mating among genetically related individuals and impairs reproductive success. The decrease in male mating success is usually attributed to an impact on multiple fitness ... [more ▼]

Inbreeding depression results from mating among genetically related individuals and impairs reproductive success. The decrease in male mating success is usually attributed to an impact on multiple fitness-related traits that reduce the general condition of inbred males. Here, we find that the production of the male sex pheromone is reduced significantly by inbreeding in the butterfly Bicyclus anynana. Other traits indicative of the general condition, including flight performance, are also negatively affected in male butterflies by inbreeding. Yet, we unambiguously show that only the production of male pheromones affects mating success. Thus, this pheromone signal informs females about the inbreeding status of their mating partners. We also identify the specific chemical component, hexadecanal, probably responsible for the decrease in male mating success. Our results advocate giving increased attention to olfactory communication as a major causal factor of mate-choice decisions and sexual selection. [less ▲]

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See detailGenetic and historic evidence for climate-driven population fragmentation in a top cetacean predator: the harbour porpoises in European water.
Fontaine, Michaël C. ULg; Tolley, Krystal A.; Michaux, Johan ULg et al

in Proceedings of the Royal Society B : Biological Sciences (2010), 277(1695), 2829-37

Recent climate change has triggered profound reorganization in northeast Atlantic ecosystems, with substantial impact on the distribution of marine assemblages from plankton to fishes. However, assessing ... [more ▼]

Recent climate change has triggered profound reorganization in northeast Atlantic ecosystems, with substantial impact on the distribution of marine assemblages from plankton to fishes. However, assessing the repercussions on apex marine predators remains a challenging issue, especially for pelagic species. In this study, we use Bayesian coalescent modelling of microsatellite variation to track the population demographic history of one of the smallest temperate cetaceans, the harbour porpoise (Phocoena phocoena) in European waters. Combining genetic inferences with palaeo-oceanographic and historical records provides strong evidence that populations of harbour porpoises have responded markedly to the recent climate-driven reorganization in the eastern North Atlantic food web. This response includes the isolation of porpoises in Iberian waters from those further north only approximately 300 years ago with a predominant northward migration, contemporaneous with the warming trend underway since the 'Little Ice Age' period and with the ongoing retreat of cold-water fishes from the Bay of Biscay. The extinction or exodus of harbour porpoises from the Mediterranean Sea (leaving an isolated relict population in the Black Sea) has lacked a coherent explanation. The present results suggest that the fragmentation of harbour distribution range in the Mediterranean Sea was triggered during the warm 'Mid-Holocene Optimum' period (approx. 5000 years ago), by the end of the post-glacial nutrient-rich 'Sapropel' conditions that prevailed before that time. [less ▲]

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See detailQuantifying lymphocyte kinetics in vivo using carboxyfluorescein diacetate succinimidyl ester (CFSE).
Asquith, Becca; Debacq, Christophe; Florins, Arnaud-Francois ULg et al

in Proceedings of the Royal Society B : Biological Sciences (2006), 273(1590), 1165-71

The cytoplasmic dye carboxyfluorescein diacetate succinimidyl ester (CFSE) is used to quantify cell kinetics. It is particularly important in studies of lymphocyte homeostasis where its labelling of cells ... [more ▼]

The cytoplasmic dye carboxyfluorescein diacetate succinimidyl ester (CFSE) is used to quantify cell kinetics. It is particularly important in studies of lymphocyte homeostasis where its labelling of cells irrespective of their stage in the cell cycle makes it preferable to deuterated glucose and BrdU, which only label dividing cells and thus produce unrepresentative results. In the past, experiments have been limited by the need to obtain a clear separation of CFSE peaks forcing scientists to adopt a strategy of in vitro labelling of cells followed by their injection into the host. Here we develop a framework for analysis of in vivo CFSE labelling data. This enables us to estimate the rate of proliferation and death of lymphocytes in situ, and thus represents a considerable advance over current procedures. We illustrate this approach using in vivo CFSE labelling of B lymphocytes in sheep. [less ▲]

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See detailSocially induced and rapid increases in aggression are inversely related to brain aromatase activity in a sex-changing fish, Lythrypnus dalli
Black, M. P.; Balthazart, Jacques ULg; Baillien, M. et al

in Proceedings of the Royal Society B : Biological Sciences (2005), 272(1579), 2435-2440

Social interactions can generate rapid and dramatic changes in behaviour and neuroendocrine activity. We investigated the effects of a changing social environment on aggressive behaviour and brain ... [more ▼]

Social interactions can generate rapid and dramatic changes in behaviour and neuroendocrine activity. We investigated the effects of a changing social environment on aggressive behaviour and brain aromatase activity (bAA) in a sex-changing fish, Lythrypnus dalli. Aromatase is responsible for the conversion of androgen into oestradiol. Male removal from a socially stable group resulted in rapid and dramatic (>= 200%) increases in aggression in the dominant female, which will become male usually 7-10 days later. These dominant females and recently sex-changed individuals had lower bAA but similar gonadal aromatase activity (gAA) compared to control females, while established males had lower bAA than all groups and lower gAA than all groups except dominant females. Within hours of male removal, dominant females' aggressive behaviour was inversely related to bAA but not gAA. These results are novel because they are the first to: (i) demonstrate socially induced decreases in bAA levels corresponding with increased aggression, (ii) identify this process as a possible neurochemical mechanism regulating the induction of behavioural, and subsequently gonadal, sex change and (iii) show differential regulation of bAA versus gAA resulting from social manipulations. Combined with other studies, this suggests that aromatase activity may modulate fast changes in vertebrate social behaviour. [less ▲]

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See detailA parasite reveals cryptic phylogeographic history of its host.
Nieberding, C.; Morand, S.; Libois, Roland ULg et al

in Proceedings of the Royal Society B : Biological Sciences (2004), 271(1557), 2559-68

This study compares the continental phylogeographic patterns of two wild European species linked by a host-parasite relationship: the field mouse Apodemus sylvaticus and one of its specific parasites, the ... [more ▼]

This study compares the continental phylogeographic patterns of two wild European species linked by a host-parasite relationship: the field mouse Apodemus sylvaticus and one of its specific parasites, the nematode Heligmosomoides polygyrus. A total of 740 base pairs (bp) of the mitochondrial cytochrome b (cyt b) gene were sequenced in 122 specimens of H. polygyrus and compared with 94 cyt b gene sequences (974 bp) previously acquired for A. sylvaticus. The results reveal partial spatial and temporal congruences in the differentiation of both species' lineages: the parasite and its host present three similar genetic and geographical lineages, i.e. Western European, Italian and Sicilian, and both species recolonized northwestern Europe from the Iberian refuge at the end of the Pleistocene. However, H. polygyrus presents three particular differentiation events. The relative rate of molecular evolution of the cyt b gene was estimated to be 1.5-fold higher in the parasite than in its host. Therefore, the use of H. polygyrus as a biological magnifying glass is discussed as this parasite may highlight previously undetected historical events of its host. The results show how incorporating phylogeographic information of an obligate associate can help to better understand the phylogeographic pattern of its host. [less ▲]

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See detailCharacterization of the primary sonic muscles in Carapus acus (Carapidae): a multidisciplinary approach
Parmentier, Eric ULg; Gennotte, Vincent ULg; Focant, Bruno et al

in Proceedings of the Royal Society B : Biological Sciences (2003), 270(1530), 2301-2308

Sound production in carapid fishes results from the action of extrinsic muscles that insert into the swim bladder. Biochemical, histochemical and morphological techniques were used to examine the sonic ... [more ▼]

Sound production in carapid fishes results from the action of extrinsic muscles that insert into the swim bladder. Biochemical, histochemical and morphological techniques were used to examine the sonic muscles and compare them with epaxial muscles in Carapus acus. Sonic fibres are thicker than red and thinner than white epaxial fibres, and sonic fibres and myofibrils exhibit an unusual helicoidal organization: the myofibrils of the centre are in a straight line whereas they are more and more twisted towards the periphery. Sonic muscles have both features of red (numerous mitochondria, high glycogen content) and white (alkali-stable ATPase) fibres. They differ also in the isoforms of the light chain (LC3) and heavy chain (HC), in having T tubules at both the Z-line and the A–I junction and in a unique parvalbumin isoform (PAI) that may aid relaxation. All these features lead to the expression of two assumptions about sound generation: the sonic muscle should be able to perform fast and powerful contractions that provoke the forward movement of the forepart of the swim bladder and the stretching and ‘flapping’ of the swim bladder fenestra; the helicoidal organization allows progressive drawing of the swim bladder fenestra which emits a sound when rapidly released in a spring-like manner. [less ▲]

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See detailNeoteny and progenesis as two heterochronic processes involved in paedomorphosis in Triturus alpestris (Amphibia: Caudata)
Denoël, Mathieu ULg; Joly, Pierre

in Proceedings of the Royal Society B : Biological Sciences (2000), 267(1451), 1481-1485

Current theories on the evolution of paedomorphosis suppose that several ontogenetic pathways have appeared according to different selective pressures. The aim of this study was to find out whether two ... [more ▼]

Current theories on the evolution of paedomorphosis suppose that several ontogenetic pathways have appeared according to different selective pressures. The aim of this study was to find out whether two distinct processes can lead to paedomorphosis in the Alpine newt, Triturus alpestris. In this respect, we compared age structures of paedomorphic and metamorphic individuals in two newt populations where the two forms lived syntopically. Whereas paedomorphosis resulted in a slower rate of somatic development in one population, it resulted in an acceleration of sexual maturation in the other population. These processes correspond to neoteny and progenesis, respectively. These results suggest that phenotypic plasticity can result from contrasted ontogenetic pathways between two populations of the same species. They give support to models that consider gonadic development as the target of selection under different environmental pressures. [less ▲]

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