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Distance Migration (distance + migration)
Kinds of Distance Migration Selected AbstractsNucleotides and epidermal growth factor induce parallel cytoskeletal rearrangements and migration in cultured adult murine neural stem cellsACTA PHYSIOLOGICA, Issue 2 2010I. Grimm Abstract Aim:, The adult subventricular zone (SVZ) contains neural stem cells that generate neuroblasts migrating to the olfactory bulb (OB) and differentiating into interneurones. The molecular cues controlling essential functions within the neurogenesis pathway such as proliferation, short and long distance migration, functional integration and cell survival are poorly understood. We have previously shown that cultured adult neural stem cells express a considerable variety of nucleotide receptors and that nucleotides and epidermal growth factor (EGF) induce converging intracellular signalling pathways that carry potential for synergism in the control of neural stem cell proliferation and cell survival. Here we investigate the role of EGF and the nucleotides ATP, ADP,S and UTP in neural stem cell migration. Methods:, Neural stem cells were prepared from adult mice and subjected to adherent culture. Labelling of F-actin was performed with tetramethylrhodamine isothiocyanate-phalloidin. Images were processed for quantitative evaluation of fluorescence labelling. Agonist-induced phosphorylation of AKT and focal adhesion kinase was analysed by quantitative Western blotting. Agonist-dependent cell migration was assayed using 48-well microchemotaxis chambers. Results:, Nucleotides and EGF induce the formation of stress fibres, an increase in the cortical actin cytoskeleton and in cell spreading. This is associated with increased phosphorylation of AKT and focal adhesion kinase. Using microchemotaxis chambers we demonstrate a parallel increase in cell migration. Conclusion:, Our results suggest that nucleotides and EGF acting as paracrine or autocrine signalling substances can be of relevance for structuring and maintaining the cytoarchitecture of the SVZ and the stream of neuroblasts migrating to the OB. [source] Differential migration of chiffchaffs Phylloscopus collybita and P. ibericus in Europe and AfricaJOURNAL OF AVIAN BIOLOGY, Issue 3 2005Paulo Catry Differential migration is a widespread, but poorly understood, phenomenon in birds. In this paper, we present the first detailed field study of differential migration in the Old World warbler (Sylviidae) family. We studied two chiffchaff Phylloscopus [collybita] semispecies: the common chiffchaff P. [c.] collybita and the Iberian chiffchaff P. [c.] ibericus. Using data collected at several latitudes in Europe and Africa, we present convincing evidence for differential distance migration of sexes in chiffchaffs, with females moving further than males. Interestingly, while there was a pronounced gradient in the sex-ratios in Europe and North Africa (with an increasing proportion of females with declining latitude), no clear pattern was found south of the Sahara, where sex-ratios were more male-biased than predicted by a simple latitude model. This suggests that, amongst the chiffchaffs wintering in West Africa, a large proportion is composed by Iberian birds, and provides support to previous suggestions that Iberian chiffchaffs are long distance migrants. Results from detailed studies in Senegal also show that chiffchaffs display differential timing of spring migration, with males leaving the winter quarters considerably earlier than females. The results are discussed in the framework of the three main (non-mutually exclusive) hypotheses attempting to explain the latitudinal segregation of the sexes. Given the relative failure of standard comparative studies to discriminate between competing single-factor hypotheses to explain differential migration, it is argued that the chiffchaff species complex might be particularly suited to study this issue using a new approach suggested by Cristol et al. (1999): detailed (further) comparisons between closely related species (such as the common and the Iberian chiffchaffs) could help identifying the key factors to be incorporated into optimality models that can predict relative distance of migration of different sex or age classes. [source] Long distance migration and marine habitation in the tropical Asian catfish, Pangasius krempfiJOURNAL OF FISH BIOLOGY, Issue 3 2007Z. Hogan A synthesis of catch data from southern Laos and life-history information indicate that adult Pangasius krempfi, an important Asian catfish, migrates up the Mekong River from the South China Sea in Vietnam past Cambodia, arriving in southern Laos each year in May. Strontium concentrations in the otoliths of river-caught P. krempfi are, on average, three to four times higher than the levels of strontium in the otoliths of related freshwater species, indicating marine and estuary habitation for fish caught in southern Laos. Pangasius krempfi muscle tissue samples from the same fish also exhibit stable isotope (,15N and ,13C) values characteristic of marine environments. The results of this investigation support the conclusion that P. krempfi is anadromous, spending a part of its life at sea and in the brackish water of the Mekong Delta before returning to spawn in fresh water. The fish travels at least 720 km to the Khone Falls in southern Laos, and possibly further. Spawning probably occurs in fresh water from June to August at which time young fish move down the Mekong River to the Mekong Delta. The data answer a previously unresolved question (the long-distance migratory behaviour of P. krempfi) and have important implications for the management and conservation of Mekong River fishes. [source] THE PALEOCENE SANDY SIRI FAIRWAY: AN EFFICIENT "PIPELINE" DRAINING THE PROLIFIC CENTRAL GRABEN?JOURNAL OF PETROLEUM GEOLOGY, Issue 1 2006S.E. Ohm A new petroleum charge model is presented for the sand-dominated Paleocene channel system known as the Siri Fairway in the Central Graben of the North Sea. The Siri Fairway is located in the platform area along the Danish - Norwegian border and extends from the Norwegian palaeo shelf into the Tail-End Graben and Søgne Basin. The nearest known expelling source rocks are located in the Central Graben. The discovery of the Siri oilfield and later the Cecilie and the Nini fields proves that petroleum has migrated through these Paleocene sandstones for up to 70 km, which is a considerable distance in the North Sea. If the Siri Fairway has acted as a "pipeline" for petroleum migrating from the Graben to the platform area, the chemical composition of the hydrocarbons discovered in the Graben and within the Fairway itself should be similar in terms of maturity and organic facies signature. This study shows this not to be the case. The Graben oils have a mature signature, whereas the oils from the Siri field have an early mature signature and are mixed with biogenic gas generated in situ. The biogenic gas "signature", which was inherited from gas which accumulated in the trap before the arrival of the oil charge, should have disappeared if petroleum had continuously been introduced to the Fairway. It therefore appears that hydrocarbon charging to the Fairway ceased for some reason before the source rocks in the Graben entered the main oil window; the Siri Fairway therefore represents an aborted migration route, and limited charging of the Paleocene sandstone deposits in the platform has occurred. The chemical composition of the oils from the Siri field indicates that the Fairway was charged from two different basins with different subsidence histories. The Siri-2 trap is thus interpreted to have been filled with the same oil as that found in Siri-1 and Siri-3, but this oil was later partly displaced by oil generated in a shallower sub-basin. The sandstones in the Siri Fairway were deposited as turbidites and/or gravity slides in the Late Paleocene, and consist of stacked interfingering sandstone lobes which are encased to varying degrees in fine-grained sediments. Although long distance migration through the sandstones has been proved to occur, connectivity between individual sandlobes may be problematic. The number of dry wells drilled in the Fairway and the early-mature character of the analysed oils, together with the general absence of more mature later petroleum, indicate that migration routes in this region are limited and difficult to predict. [source] Frequency of fault bars in feathers of birds and susceptibility to predationBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009ANDERS PAPE MØLLER Fault bars are transparent bands in the feathers of birds produced under stressful and adverse conditions. The frequency of feathers with fault bars is highly heterogeneous among species. We predicted that prey had a higher frequency of fault bars than individuals from the general population, and that a high susceptibility to predation would be associated with a low frequency of fault bars among species of birds because such species would suffer particularly high costs of producing fault bars. The frequency of fault bars in prey was almost three-fold higher than in the general population, based on a database on the frequency of fault bars and susceptibility to predation by the goshawk Accipiter gentilis L., implying intense natural selection against fault bars. A high susceptibility to predation by the sparrowhawk Accipiter nisus L. and the goshawk, relative to what would be expected from their abundance, was associated with a low frequency of fault bars across species, with long distance migration also being negatively associated with frequency of fault bars. Feathers with fault bars were more likely to break than feathers without fault bars, thereby potentially affecting the flight ability of individuals. These findings are consistent with the hypothesis that susceptibility to factors that cause production of fault bars can be modified by natural selection, as illustrated by the impact of predation on the frequency of fault bars. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 334,345. [source] Inferring colonization history and dispersal patterns of a long-lived seabird by combining genetic and empirical dataJOURNAL OF ZOOLOGY, Issue 4 2010L. C. Young Abstract Identifying biological trends and threats to organisms that make long distance migrations are often the limiting factors in their conservation. Indeed, Laysan albatross Phoebastria immutabilis are highly vagile seabirds, foraging throughout the North Pacific Ocean. Despite mark,recapture data indicating natal philopatry, Laysan albatross recently re-colonized several anthropogenically extirpated breeding locations. At the same time, a breeding population in the north-western Hawaiian Islands was lost to erosion and it was hypothesized that the colonization events were due to displacement rather than dispersal. Nuclear and mitochondrial markers were used in a range wide survey to test whether natal philopatry corresponded to population structure in Laysan albatross, and to determine whether recent colonization events were a result of displacement from vanishing breeding habitat. Five microsatellite loci found little population structure (FST=0.01, P=0.001), and sequences from the mitochondrial control region revealed low population structure (,ST=0.05, P<0.001). The results were consistent with male-mediated dispersal and strong, but not absolute, philopatry by females. Mixed stock analyses and banding records from the newly colonized sites indicated contributions from multiple source populations, which contradicted the displacement hypothesis of a single source population and instead supported species-wide dispersal from all source colonies. High genetic diversity (,=0.045, h=0.989), rapid colonization, and great dispersal potential bode well for the conservation of Laysan albatross. However, it may be necessary to protect high-island nesting sites, preserve genetic diversity and maintain breeding populations in the face of projected sea level rises and persistent bycatch. [source] | |||||||||||||