Study in Royal Society journal on world's only horned rodent

July 12, 2005

Biology Letters

MHC-assortative facial preferences in humans by Dr SC Roberts, Dr AC Little, Professor L Gosling, Mr BC Jones, Professor DI Perrett, Mr V Carter and Professor M Petrie

As choosing a genetically dissimilar mate is possible using smell, we tested whether faces display the same information. We asked women to rate attractiveness of male photographs (some genetically similar, some dissimilar). To our surprise, genetically similar faces were rated more attractive, especially when we compared scores given to particular male faces by genetically similar or dissimilar women. Although unexpected, this like-prefers-like (assortative) preference is consistent with other human mate preference studies. It suggests, for the first time, that immune (MHC) genes are linked to visible (facial) traits and that smell and face information are integrated to choose the optimal mate.
Contact: Dr S. Craig Roberts, School of Biological Sciences, University of Liverpool, Biosciences Building, LIVERPOOL, L69 7ZB, United Kingdom

Migrating locusts can detect polarized reflections to avoid flying over the sea by Dr. N Shashar, Mr S Sabbah and Ms N Aharoni
Locust (Schistocerca gregaria) migration are well known and often feared over Africa, the Middle East and the south of Europe. Though the swarms are generally dispersed with the wind, the insects do have partial control over the direction towards which they fly. For example, on occasion, they may avoid flying over the sea. Behavioral experiments showed that the animals use their sensitivity to polarized light (a quality of light largely unseen by humans) and avoid surfaces that reflect strong linear polarization. Indeed, sea surfaces can serve as such polarization reflectors and therefore deter locust swarms from crossing them at low flight.
Contact: Dr Nadav Shashar, University of Maryland Baltimore County, Department of Biological Sciences, Baltimore MD 21228, USA

Cyclicity in the fossil record mirrors rock outcrop area by Dr AB Smith and Dr AJ McGowan
It has recently been shown that there is a 62-million year cyclicity to the history of marine diversity through the geological record. Why fossil diversity should rise and fall regularly over time unexplained and could either represent a biological pattern of repeated 'boom and bust' cycles, or an artefact of preservation reflecting variations in the nature of the fossil record. We show that there is a correlation between marine diversity and the amount of marine sedimentary rock exposed. This suggests that the 62-million year cyclicity originates from long-term changes in sedimentary depositional and erosional regimes, and raises the strong possibility that it is not a biological signal but a sampling signal.
Contact: Dr AB Smith (FRS), Palaeontology, The Natural History Museum, Cromwell Road, LONDON, SW7 5BD, United Kingdom

Expression of uncoupling protein and alternative oxidase depends on lipid or carbohydrate substrates in thermogenic plants by Dr K Ito and Dr RS Seymour
Thermogenesis has been believed to require mitochondrial uncoupling protein (UCP) in mammals and alternative oxidase (AOX) in plants. In the present study, we have found that the genes for both proteins are expressed in thermogenic plants, but the type correlates with the respiratory substrate; that is, AOX for carbohydrates and UCP for lipids. Our findings thus clearly undermine the common dichotomy that thermogenesis depends on UCPs in mammals and AOXs in plants, and further suggest that cellular metabolism is a major determinant in selective expression of appropriate thermogenic genes in plants.
Contact: Dr K Ito, Cryobiosystem Research Centre, Faculty of Agriculture, Iwate University, Ueda, 3-18-8, MORIOKA, IWATE, 020-8550, Japan

Correlated evolution of maternally-derived yolk testosterone and early developmental traits in passerine birds by Ms. KB Gorman and Professor TD Williams
Female birds allocate steroid hormones to the yolk of their eggs during reproduction which subsequently influence early developmental traits of the offspring. In theory, genetic differences in these maternal and offspring hormonal traits can provide a basis for the co-evolution of these phenotypes. Thus, we tested for evolutionary associations between maternally-derived yolk testosterone (T) concentration and early developmental traits in passerine birds via a comparative, phylogenetic analysis. We provide evidence for the correlated evolution of maternal yolk T concentration and length of the prenatal developmental period; higher yolk T is associated with shorter prenatal development. Our results highlight the need for more studies investigating the role of yolk hormones in evolutionary processes concerning maternal effects.
Contact: Ms. KB Gorman, Biological Sciences, Simon Fraser University, 8888 University Dr., BURNABY, BRITISH COLUMBIA, V5A 1S6, Canada

Spatial Encoding in Mountain Chickadees: Features Overshadow Geometry by Ms. ER Gray, Ms L L Laurie, Ms. A Ferrey, Dr. CB Sturdy and Professor ML Spetch
To get their bearings, humans and other animals attend to the geometrical shape of their environment. This has been observed in every species tested even when features alone could be used, suggesting that animals are predisposed to attend to geometry. All prior studies, however, tested animals reared in human-made enclosures, rich in right-angled structures. We tested mountain chickadees, raised in a forested environment. Although able to learn geometry, chickadees differed from all previously tested animals by ignoring geometry when a useful feature was present. These findings suggest the importance of nurture in the expression of a basic navigational strategy.
Contact: Professor ML Spetch, Psychology, University of Alberta, BSP-217, EDMONTON, T6G 2E9, Canada

Costly parasite resistance - a genotype-dependent handicap in sand lizards? By Dr M Olsson, Dr E Wapstra, Prof T Madsen, Dr B Ujvari and Mr C Rugfelt
Recent work in evolutionary immunology has shown that elevation of an adaptive immune response can be costly and result in loss in body condition and even reduced chances of survival. In the present study, we look at such costs in sand lizard (Lacerta agilis) males of a genotype that allows them to better combat ectoparasites early in the season, and verifies that these males loose body condition much more rapidly than males that are poorer at such immune defence. Furthermore, these males seem to be more susceptible to secondary infections by blood parasites, but still have higher reproductive success.
Contact: Dr M Olsson, School of Biological Sciences, University of Wollongong, WOLLONGONG, 2522, Australia

Infection density of Wolbachia endosymbiont affected by co-infection and host genotype by Dr N Kondo, Prof M Shimada and Dr T Fukatsu
Endosymbiotic associations with multiple microorganisms are commonly found in a wide array of insect groups, which provides a model system for investigating the mechanisms that regulate the infection density of coexisting symbionts. We investigated the adzuki bean beetles, Callosobruchus chinensis, infected with both or either of two distinct Wolbachia strains, and identified previously unknown aspects of symbiont density regulation: (i) intra-specific host genotypes that differently affect Wolbachia density and (ii) suppression of Wolbachia density by co-infecting Wolbachia strain. These findings suggest that symbiont density is determined through complex interplay between host genotype, symbiont genotype and other factors.
Contact: Dr T Fukatsu, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, TSUKUBA, 305-8566, Japan

Proceedings of the Royal Society B: Biological Sciences

Evolution of fossoriality and the adaptive role of horms in the Mylagaulidae (Mammalia : Rodentia) by Ms. SSB Hopkins (rspb.2005.3171)

Ceratogaulus, the fossil "horned gopher" of the North American Great Plains, has long puzzled paleontologists. This extinct mammal, related to the living sewellel, is the only known horned rodent and the smallest horned mammal. The ancestors of Ceratogaulus evolved a burrowing lifestyle, but a rigorous test of adaptation reveals that the horns in this animal were not evolved for digging. The pattern of evolution and the biomechanics of the horns are best explained as adaptations for defense against predation. Increasing body size and the appearance of new predators 17 million years ago drove Ceratogaulus to evolve these defensive weapons.
Contacts : Ms. SSB Hopkins, Integrative Biology, University of California, Berkeley, 3060 VLSB, BERKELEY, 94720, USA

Ravens, Corvus corax, differentiate between knowledgeable and ignorant competitors by Thomas Bugnyar, Bernd Heinrich (rspb.2005.3144)
We here tested whether ravens treat competitors according to their possible knowledge about the location of food. Birds were confronted with conspecifics that could, or could not, observe the making of caches and thus would likely, or unlikely, pilfer those caches. Irrespective of whether they acted as a food-storer or pilferer, ravens instantly responded to former observers but not to non-observers, suggesting that they discriminated on the inferred view of those competitors. This raises the intriguing possibility that ravens may appreciate elements of mental states in others.
Contact: Dr T Bugnyar, University of Vermont, BURLINGTON, VT, 05405, United States

Alternative life-histories shape different brain gene expression profiles in males of the same population by Dr N Aubin-Horth, Dr C Landry, Dr BH Letcher and Dr HA Hofmann
Atlantic salmon are known for spectacular marine migrations before homing to spawn in native rivers. However, some males become reproductively active sneakers at greatly reduced sizes without leaving freshwater. We monitored activity of thousands of genes in wild Atlantic salmon brains and demonstrate that these profound life-cycle differences are accompanied by change in expression of 15% of these genes. Unexpectedly, gene expression patterns in immature males were different both from immature females and sneakers, indicating that sea migration and delayed maturation by immature males, which is seen as the default life-cycle, may actually result from an active inhibition of development into a sneaker.
Contact: Nadia Aubin-Horth, Bauer Center for Genomics research, Harvard University, 7 Divinity Ave. Cambridge, MA 02138, USA

Gene essentiality and the topology of protein interaction networks. By Mr S Coulomb, Dr M Bauer, Dr D Bernard and Dr MC Marsolier-Kergoat (rspb.2005.3128)
Protein interactions can be modelled as non-oriented links connecting the nodes of a network. Several authors have proposed that the essentiality of a gene (the fact that a gene is required for the survival of an organism in a given environment) is related to the topological characteristics of the corresponding protein in its interaction network. We have reassessed systematically these conclusions because many of these studies had overlooked important biases present in interaction databases. Our results suggest that the topology of protein interaction networks has little influence on gene essentiality and more generally on cell resistance against mutations.
Contact : Dr MC Marsolier-Kergoat, SBGM, CEA, CEA/Saclay, GIF-SUR-YVETTE, 91191, France

The hidden cost of information in collective foraging by Dr FX Dechaume-Moncharmont, Dr A Dornhaus, Professor AI Houston, Professor JM McNamara, Dr EJ Collins and Professor NR Franks (rspb.2005.3137)
Impatience can be a virtue. Social insects are famous for their ability to communicate with one another. Examples include the waggle dances of honeybees and the pheromone trails of ants. These communication systems allow social insect colonies to focus their foraging efforts rapidly on newly discovered food sources. Such information transfer can clearly be beneficial. But here we ask, is such information always valuable? That is, does it always improve a colony's net energy gain? Our mathematical model reveals a surprising result. There is a hidden cost to potentially valuable information. Sometimes, it is not worth waiting for. Under certain natural conditions, the optimum strategy is totally independent foraging because the costs of waiting for information outweigh the benefits of being better informed. This counter-intuitive outcome is remarkably robust over a wide range of parameters. It occurs because food sources are only available for a limited period. It seems that sometimes impatience is a virtue.
Contact : Dr FX Dechaume-Moncharmont, School of Biological Sciences, University of Bristol, Woodland road, BRISTOL, BS8 1UG

Females solicit sneakers to improve fertilisation success in the bitterling (Rhodeus sericeus) by Dr C Smith and Dr M Reichard (rspb.2005.3140)
It is generally thought that female fertility in animals is not limited by the availability of sperm. In the bitterling, a fish that lays its eggs on the gills of freshwater mussels, we showed that when females spawn with a single male fewer of their eggs were fertilised than those mating with groups of males. We also showed that females perform conspicuous behaviours before spawning that appear to signal to males that they are about to spawn, thereby encouraging additional males to participate. Our results suggest a battle between the sexes over the ideal number of mating partners.
Contact: Dr C Smith, University of Leicester, University Road, LEICESTER, LE1 7RH

Geographical variation in sound production in the anemonefish Amphiprion akallopisos by Dr ES Parmentier, Dr JP Lagardere, Professor P Vandewalle and Professor ML Fine (rspb.2005.3146)
Amphiprion akallopisos is a clownfish that uses sound production notably to defend its anemone territory. In this study, we compared sounds produced by these fish from populations in Madagascar and Indonesia, a distance of 6,500 km. Differentiation of agonistic calls into distinct types indicates a complexity not previously recorded in fish communication. Moreover, various acoustic parameters, including peak frequency, pulse duration, number of peaks per pulse, differed between the two populations. The geographic comparison is the first to demonstrate dialects in a marine fish species. These results highlight the possible approach for investigating the role of sounds in reproductive divergence and speciation.
Contact: Dr ES Parmentier, Sciences et Gestion de l'Environnement, Universite de Liege, Labo. Morphologie Fonctionnelle et Evol, LIEGE, 4000, Belgium

The loss of anti-predator behaviour following isolation on islands by Dr DT Blumstein and Ms JC Daniel (rspb.2005.3147)
Predator naiveté is often pronounced on islands, where species are found with few or no predators, and we generally expect the loss of predators to lead to a loss of antipredator behaviour. We found that kangaroos and wallabies isolated on islands indeed lost some antipredator behaviors. Remarkably, however, we found no evidence that isolation from all predators, per se, was responsible for this loss. Other random processes associated with insularity may be responsible for the loss of antipredator behavior on islands. Identifying the mechanism underlying loss is important because insular populations are more vulnerable to human exploitation and the introduction of exotic predators than those found on the mainland.
Contact : Dr DT Blumstein, UCLA, 621 Young Drive South, LOS ANGELES, CA, 90095-1606, USA

Dynamic games with imitation predict vaccinating behaviour by Dr C.T. Bauch (rspb.2005.3153)
The literature on vaccine scares generally focuses on individual perception of vaccine risks. However parents also take into account the current level of disease prevalence in the population, and the opinions of medical authorities and other parents. The present study takes this context into account by applying game theory and epidemic modelling to predict the time evolution of vaccine uptake. The study obtains qualitative agreement with the persussis vaccine scare in Britain during the 1970s. The study also illustrates how voluntary vaccination programmes are essentially victims of their own success and the nonvaccinating behaviour of 'free-riders'.
Contact: Dr C.T. Bauch, Mathematics and Statistics, University of Guelph, Dept. of Mathematics and Statistics, GUELPH, Canada

Royal Society of Chemistry

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