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Study in Royal Society journal on first evidence for magnetic field detection in sharks

15.12.2004


Journal of The Royal Society Interface

Sharks can detect changes in the geomagnetic field by Dr G Meyer, Dr N Holland and Mr P Papastamatiou

Scientists have long suspected that sharks are able to use the earth’s magnetic field to navigate across seemingly featureless oceans but until now evidence of this ’compass sense’ has been circumstantial. We showed that captive sharks can be trained to swim over a target whenever an artificial magnetic field is activated thereby clearly demonstrating that sharks can sense magnetic fields. This significant advance in demonstrating the existence of a compass sense should now make it possible to investigate exactly how this sense works and how sensitive sharks are to the earth’s magnetic field. Contact: Dr Carl Meyer, Hawaii Institute of Marine Biology, University of Hawaii, 46-007 Lilipuna Road, KANEOHE, HI96744, United States



Proceedings of The Royal Society B: Biological Sciences

Homing pigeons develop local route stereotypy by Dr J Meade, Dr D Biro and Dr T Guilford

The navigational feats of birds have fascinated humans for centuries. Much has now been discovered about the mechanisms birds use to navigate over unknown territory. How birds develop a map of their familiar environment however, remains unsolved. We investigated local navigation by homing pigeons, by using recently available GPS tracking technology, which provides details of a bird’s route over the landscape with extraordinary precision. We find that birds develop and stick to individually distinctive routes home, which remain surprisingly indirect, repeating these routes precisely. Our results call into question the established view that pigeons use only their compasses from familiar locations, suggesting instead that their familiar area map is based on the use of visual landmarks. Contact: Dr Jessica Meade, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS

Automimicry destabilises aposematism: predator sample-and-reject behaviour may provide a solution by Dr G Gamberale Stille and Dr T Guilford

Many unpalatable prey animals signal their distastefulness with conspicuous colours to deter attack. These warning colours are often the basis for mimicry by other species. Further, "automimicry" occur within species where the signal copying is perfect, and we show that this cheating strategy of avoiding the cost of toxicity but cashing in on the protection should destabilise warning coloration. We offer a solution, and show that birds offered a mixture of nasty prey and mimics can "sample-and-reject" the truly nasty prey, leaving them relatively unharmed, and eating only the cheats instead. Thus, paradoxically, it is not avoidance signalling that stabilises the warning signals, but the actions of predators who are invited to taste the prey. Contact: Dr Gabriella Gamberale Stille, Department of Zoology, Stockholm University, 106 91 Stockholm, SWEDEN

Ancient DNA by Dr E Willerslev and Professor A Cooper

Since 1984 ancient DNA has progressed from the retrieval of a few fragments of DNA from recent specimens, to large-scale studies of mammal populations from before the last Ice Age. Issues of contamination continue to plague reports of ancient human and bacterial DNA, but an improved understanding of the processes involved in sample contamination and DNA damage provide a more robust platform for ancient DNA to assume a central role in evolutionary research. New approaches include the study of how key genes have been selected during the process of domestication, and how climate change has effected the diversity and distribution of mammals. The future promises studies of DNA in polar caps, deep earth environments and even on Mars and other planets. Contact: Professor Alan Cooper, Henry Wellcome Ancient Biomolecules Centre, University of Oxford, South Parks Road, OXFORD, OX1 3PS

Escalation and trophic specialization drive adaptive radiation of freshwater gastropods in ancient lakes on Sulawesi, Indonesia by Dr T von Rintelen, Dr M Glaubrecht, Dr AB Wilson and Professor A Meyer

Two ancient lake systems on the Indonesian island Sulawesi harbour a species flock of live-bearing freshwater snails. A molecular genetic analysis of the 33 species in the lakes has revealed four independent colonizations of the lakes, followed in each case by a radiation and considerable morphological diversification. Strikingly stronger shells in the lake species, coupled with the occurence of large crabs with crusher claws, suggest a unique role for coevolution in this new model system for the study of adaptive radiation. In addition, highly diverse radulae (snail rasping organ) in the lakes indicates that the development of feeding specialization likely is a driving force in speciation. Contact: Dr von Rintelen, Museum of Natural History, Institute of Systematic Zoology, Invaldienstr. 43, Berlin, D-10115, Germany

Neuro-evolutionary patterning of sociality by Dr JL Goodson

Although birds and mammals have not shared a common ancestor for almost 300 million years, new findings show that the brain areas that activate during social interactions in birds are strikingly similar to those in mammals. This suggests that fundamental features of the "social brain" remained constant during the evolution of mammals, dinosaurs and birds. Furthermore, by comparing gregarious and asocial songbird species, researchers have shown that social interactions activate brain areas in a manner proportional to the species’ typical group sizes. Thus, activity of specific brain areas may determine how many other individuals an animal would like to be with. Contact: Dr Jim Goodson, Psychology Dept., 0109, 9500 Gilman Drive, University of California, San Diego, La Jolla, CA 92093-0109, USA

State-dependent foraging rules for social animals in selfish herds by Dr SA Rands, Dr R A Pettifor, Dr J M Rowcliffe and Dr G Cowlishaw

When individual animals form groups, they benefit from a reduction in predation risk. However, joining a group can also reduce the amount of food the animal receives. Animals have to weigh the advantages and disadvantages of staying in a group, meaning that groups change over time as their members become hungry or find food. We describe a simple, realistic rule for animals to follow, based upon their energy reserves and what their neighbours are doing. This rule affects the size of groups formed, and shows that the complex behaviours of herds can emerge from simple rules followed by each group-member. Contact: Dr Sean Rands, Department of Zoology, University of Cambridge, Downing Street, CAMBRIDGE, CB2 3EJ

Why do multiple traits determine mating success? Differential use in female choice and male competition in a water boatman by Dr U Candolin

Why multiple traits determine mating success is generally unknown. One possible explanation is that different traits serve different functions in female choice and male-male competition. In a water boatman Sigara falleni, traits determined at distinct life history stages differed in their importance in female choice and male competition. Juvenile diet determined traits that influenced mating success under female choice, whereas adult diet determined traits that influenced mating success under male competition. This differential use of traits could result from a conflict of interest between the sexes, or from constraints forcing the sexes to pay attention to different traits. Contact: Dr Ulrika Candolin

Group-beneficial traits, frequency-dependent selection and genotypic diversity: an antibiotic resistance paradigm by Dr LA Dugatkin, Dr M Perlin, Dr J Scott Lucas and Dr R Atlas

How traits that benefit others evolve has been a perennial mystery for evolutionary biology. We chose antibiotic resistance as a test case for looking at the evolution of group-beneficial traits. We constructed strains of bacteria that secrete an enzyme into their environment that breaks down the antibiotic ampicillin, thereby protecting nearby cells. Our findings demonstrate that cells that would normally die in the presence of ampicillin can maintain themselves at low frequencies when in the presence of cells that produce the ampicillin-destroying enzyme (ie the group-beneficial trait). Our results suggest that understanding the evolution of certain group-beneficial traits may have implications for the medical sciences. Contact: Dr. Lee Alan Dugatkin, Department of Biology, University of Louisville, Louisville, KY, 40208, USA

The three-dimensional flight of red-footed boobies: adaptations to foraging in a tropical environment? by Dr H Weimerskirch and Dr M Le Corre

By using high precision miniaturised loggers (GPS, accelerometers-time depth recorders, activity recorders, altimeters) we studied for the first time the three-dimensional flight and diving behaviour of a seabird. Red-footed Boobies make an extensive use of wind conditions, using a flap-glide flight, with extensive gliding periods that reduce travelling costs. Travelling phases were regularly interrupted by active foraging periods with series of landing, and shallow plunge diving or surface diving that are used to chase for very mobile prey like flying fishes associated with sub surface predators such as tunas. To spot prey patches at distance birds climb regularly to altitudes of 20-50m and when returning to the colony they climb to altitudes up to 500m to avoid attacks by frigatebirds along the coasts. Thus, boobies use a series of very specific flight and activity patterns that have been selected as adaptations to the particular conditions of tropical waters. Contact: Dr Henri Weimerskirch, CEBC, CNRS, VILLIERS EN BOIS, 79360, France

Juvenile immune system activation induces a costly upregulation of adult immunity in field crickets Gryllus campestris by Dr A Jacot, Mr H Scheuber, Dr J Kurtz and Dr MWG Brinkhof

In contrast to vertebrates that show specific immune memory, invertebrates’ primary mode of enhancing future parasitic resistance is probably through systemic up-regulation of relatively unspecific immune components. In field crickets, we conducted a study to investigate the effects of a bacterial infection at the juvenile stage on adult immunity. Following the bacterial infection, crickets showed elevated levels of specific immune parameters as adults, at the cost of a reduced physiological condition. Our data thus suggest the long-term up-regulation of immunity in response to antigenic cues as an adaptive, yet costly, invertebrate strategy to improve resistance to future parasitism. Contact: Dr Alain Jacot, Institute for Ornithology, Max Planck Society, Postfach 1564, STARNBERG (SEEWIESEN), 82305, Germany

Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences

The effect of cavitation on glacier sliding by Dr C Schoof
The response of a glacier to climate change depends on the rate at which the glacier flows, which often occurs as a result of the glacier sliding over the underlying bedrock. In this study, we show that the equation which is most widely used to represent sliding in numerical models of glaciers is not consistent with the physics involved, and generally overestimates friction at the glacier bed. Based on a mathematical model of the sliding process, we present a corrected description of sliding for use in numerical models of glacier flow. Contact: Dr Christian Schoof, Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, VANCOUVER, V6T 1Z4, Canada

Transformed multipole theory of the response fields D and H to electric octopole–magnetic quadrupole order by Professor RE Raab and Dr OL De Lange

The electromagnetic response of matter to the electric and magnetic fields of a light wave depends on these fields and on the properties of the substance. For a linear dependence on the fields these properties must satisfy certain conditions. In addition, for long wavelengths these properties can be expressed as a series of decreasing contributions. The leading two contributions are able to explain a range of optical effects. However, there are yet other effects which require the next order in the series. The relevant terms, satisfying the theoretical conditions, are determined in the present paper. Contact: Professor Roger Raab, Department of Physics, University of Kwazulu-Natal, Private Bag X01, Scottsville, NATAL, SW1, South Africa

Tim Watson | EurekAlert!
Further information:
http://www.royalsoc.ac.uk

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