Distress calls may honestly signal bird quality to predators.
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In predator-prey interactions, both interactors may benefit from sharing information about prey vulnerability. We examined the relationship between calls used to discourage close predators (distress calls) and the health condition of the caller to test whether these signals are reliable indicators of prey quality. The structure of calls from captured lesser short-toed larks Calandrella rufescens was related to their body condition and T-cell-mediated immunocompetence. Birds in better nutritional and immunological condition utter harsher calls (i.e. they spread the call energy over a wider range of frequency) than birds in poorer conditions. Hence, the harshness of distress calls seems honestly to signal the health status of prey and thus their ability to escape, on which the predator might base its optimal foraging choice. Previous studies have investigated the honesty of songs that have evolved via sexual selection, but this is the first study, to our knowledge, the demonstrates a relationship between individual quality and a vocalization primarily shaped by natural selection. (+info)
The dynamics of genetic and morphological variation on volcanic islands.
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Oceanic archipelagos of volcanic origin have been important in the study of evolution because they provide repeated natural experiments allowing rigorous tests of evolutionary hypotheses. Ongoing volcanism on these islands may, however, affect the evolutionary diversification of species. Analysis of population structure and phylogeographic patterns in island populations can provide insight into evolutionary dynamics on volcanic islands. We analysed genetic and morphological variation in the gecko Tarentola boettgeri on the island of Gran Canaria and compared it with Tarentola delalandii on Tenerife, a neighbouring volcanic island of similar age but distinctly different geological past. Intraspecific divergence of mitochondrial haplotypes indicates long-term persistence of Tarentola on each island, with a phylogeographic signal left by older volcanic events. More recent volcanic eruptions (approximately 0.2 million years ago on Tenerife, approximately 2.2 million years ago on Gran Canaria) have left a signature of population expansion in the population genetic structure, the strength of which depends on the time since the last major volcanic eruption on each island. While these stochastic events have left traces in morphological variation in Tenerife, in Gran Canaria geographical variation was solely associated with environmental variables. This suggests that historically caused patterns in morphology may be overwritten by natural selection within 2 million years. (+info)
Do seasonal changes in metabolic rate facilitate changes in diving behaviour?
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Macaroni penguins were implanted with data loggers to record heart rate (fH), abdominal temperature (Tab) and diving depth during their pre-moult trip (summer) and winter migration. The penguins showed substantial differences in diving behaviour between the seasons. During winter, mean and maximum dive duration and dive depth were significantly greater than during summer, but the proportion of dives within the calculated aerobic dive limit (cADL) did not change. Rates of oxygen consumption were estimated from fH. As winter progressed, the rate of oxygen consumption during dive cycles (sVO2DC)) declined significantly and mirrored the pattern of increase in maximum duration and depth. The decline in sVO2DC) was matched by a decline in minimum rate of oxygen consumption (sVO2min)). When sVO2min) was subtracted from sVO2DC), the net cost of diving was unchanged between summer and winter. We suggest that the increased diving capacity demonstrated during the winter was facilitated by the decrease in sVO2min). Abdominal temperature declined during winter but this was not sufficient to explain the decline in sVO2min). A simple model of the interactions between sVO2min), thermal conductance and water temperature shows how a change in the distribution of fat stores and therefore a change in insulation and/or a difference in foraging location during winter could account for the observed reduction in sVO2min) and hence sVO2DC). (+info)
Umbilical cord mercury concentration as biomarker of prenatal exposure to methylmercury.
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Biomarkers are often applied to assess prenatal exposure to methylmercury in research and surveillance. In a prospective study in the Faroe Islands, the main exposure biomarkers were the mercury concentrations in cord blood and maternal hair obtained at parturition. We have now supplemented these exposure biomarkers with mercury analyses of umbilical cord tissue from 447 births. In particular, when expressed in relation to the dry weight of the tissue, the cord mercury concentration correlated very well with that in cord blood. Structural equation model analysis showed that these two biomarkers have average total imprecision of about 30%, which is much higher than the laboratory error. The imprecision of the dry-weight-based concentration was lower than that of the wet-weight-based parameter, and it was intermediate between those of the cord blood and the hair biomarkers. In agreement with this finding, regression analyses showed that the dry-weight cord mercury concentration was almost as good a predictor of methylmercury-associated neuropsychologic deficits at 7 years of age as was the cord-blood mercury concentration. Cord mercury analysis can therefore be used as a valid measure of prenatal methylmercury exposure, but appropriate adjustment for the imprecision should be considered. (+info)
Does kin selection influence fostering behaviour in Antarctic fur seals (Arctocephalus gazella)?
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A recent observation that female Antarctic fur seals foster pups born to related females raises the fascinating possibility that kin selection may promote altruistic behaviour even on a crowded breeding beach, where individual interactions are frequent and complex. However, the use of genetic markers to identify small numbers of unusually highly related individuals is fraught with difficulty due to the likely presence of genotyping errors and related problems. Consequently, we examined an enlarged dataset where errors had been reduced to an absolute minimum by a combination of close scrutiny and repeat genotyping. We find no support for the idea that females preferentially suckle pups born to female relatives. Instead, the previously reported pattern can be explained by a combination of genotyping errors and de novo mutations. Our study emphasizes the need for caution when interpreting rare events that occur at a rate approaching that expected for normal genotyping errors. (+info)
Patterns of prescription of hypoglycaemic drugs in Gran Canaria (Canary islands, Spain) and estimation of the prevalence of diabetes mellitus.
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OBJECTIVE: To study the patterns of hypoglycaemic treatment in our community and to estimate the prevalence of known and drug-treated diabetes mellitus. METHODS: From all the diabetic patients who attended the Healthcare Centers of the National Health Service in Gran Canaria in 1999, a random sample of 2924 diabetic patients > 20 years old was selected. Data on age, gender, clinical onset of diabetes, and hypoglycaemic treatment were obtained. Data on drug consumption were supplied by the National Health Service. RESULTS: Of the DM-2 patients 4.4% (3.65-5.14) 84.2% (82.7785.42), 9.4% (8.34-10.45) and 2.1% (1.58-2.61) received diet only, oral drugs, insulin or combination. The duration of DM-2 was associated with more oral drugs and more insulin treatment, but the duration of DM-1 was not associated with intensive insulin therapy;<50% of the type 1 patients had >or=3 daily injections. The prescriptions of biguanides were scarce; over 1/3 of them were of buformin. DM-1 and DM-2 patients were treated with similar doses of insulin, but DM-1 patients had more insulin injections (2.56 vs 2.07, P<0.001), and more fast-acting insulins (65.2% vs 38.0%, P<0.001). The estimated prevalences of known and drug-treated diabetes in the Gran Canaria island were 5.95% (95% CI: 5.096.80%) and 5.73% (4.88-6.57%). CONCLUSIONS: Our prevalences of known and drug-treated diabetes is among the highest reported in European populations. The prescriptions of metformin and of combined therapy in DM-2, and of intensive insulin therapy in DM-1 are less frequent than expected, but nonetheless insulin therapy in DM-1 is more intensive and uses more fast-acting insulin than in DM-2. (+info)
Evaluation of Acanthamoeba isolates from environmental sources in Tenerife, Canary Islands, Spain.
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Tests for potentially pathogenic amoebae were carried out in order to determine the presence of free-living amoebae of genus Acanthamoeba in soil and beach sand sources related to human environments in Tenerife, Canary Islands, Spain. Acanthamoeba identification was based on the morphology of cyst and trophozoite forms and PCR amplification with a genus specific primer pair. The pathogenical potential of Acanthamoeba isolates was characterized by temperature and osmotolerance assays and PCR reactions with two primer pairs related to Acanthamoeba pathogenesis. The results demonstrate the presence of potential pathogenic strain in both sources. Thus, some of the amoebae found in these habitats could act as opportunistic pathogens and may present a risk to human health. (+info)
Efficient high-resolution deletion discovery in Caenorhabditis elegans by array comparative genomic hybridization.
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We have developed array Comparative Genomic Hybridization for Caenorhabditis elegans as a means of screening for novel induced deletions in this organism. We designed three microarrays consisting of overlapping 50-mer probes to annotated exons and micro-RNAs, the first with probes to chromosomes X and II, the second with probes to chromosome II alone, and a third to the entire genome. These arrays were used to reliably detect both a large (50 kb) multigene deletion and a small (1 kb) single-gene deletion in homozygous and heterozygous samples. In one case, a deletion breakpoint was resolved to fewer than 50 bp. In an experiment designed to identify new mutations we used the X:II and II arrays to detect deletions associated with lethal mutants on chromosome II. One is an 8-kb deletion targeting the ast-1 gene on chromosome II and another is a 141-bp deletion in the gene C06A8.1. Others span large sections of the chromosome, up to >750 kb. As a further application of array Comparative Genomic Hybridization in C. elegans we used the whole-genome array to detect the extensive natural gene content variation (almost 2%) between the N2 Bristol strain and the strain CB4856, a strain isolated in Hawaii and JU258, a strain isolated in Madeira. (+info)