| 1. |
- Eeva, T, et al.
(författare)
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Pollution related effects on immune function and stress in a free-living population of pied flycatcher Ficedula hypoleuca
- 2005
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 36:5, s. 405-412
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Tidskriftsartikel (refereegranskat)abstract
- We investigated whether exposure to heavy metal pollution affected the immune function of individuals in a free living population of a small insectivorous passerine bird, the pied flycatcher Ficedula hypoleuca. We measured humoral immune responses in two study areas: a polluted area in the vicinity of a copper smelter and a control area far from the smelter. Plasma corticosterone level and blood heterophil/lymphocyte ratio (H/L) were used as more general physiological measures of stress. The immune response of F hypoleuca was not suppressed by pollution stress. In contrast, we found that F hypoleuca males showed stronger Immoral immune responses to a novel antigen (tetanus toxoid) in the polluted environment than in the unpolluted one. After the immunization of males, numbers of lymphocytes rose significantly more in the polluted area, leading to a smaller H/L ratio than in males from the control area. Females showed no pollution related effects on their immune responses. Corticosterone levels of males and nestlings were not related to pollution levels. Nestlings showed somewhat higher H/L ratios and lower fledging success in the polluted area, both factors indicating increased stress levels in a polluted area. Our results suggest that Immoral immune response of male F hypoleuca may be enhanced under moderate levels of heavy metal Pollution. Enhanced immune function may, however, also be costly for birds and the higher humoral immune responses in polluted areas may thus have negative effects on the birds' breeding performance and survival.
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| 2. |
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| 3. |
- Hansson, Maria, et al.
(författare)
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The Baltic salmon in battle with pollutants and disease. / Östersjölaxen i kamp mot miljögifter och sjukdom.
- 2001
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Ingår i: Fauna och Flora: populär tidskrift för biologi. - 0014-8903. ; 96:2, s. 91-96
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Baltic salmon has during the latter part of the 20th century been subjected to several threats. Most notable have been the high levels of contaminant release and a disease that causes early life mortality of the young. Ever since utilization of water power from the Swedish rivers began in the 1940ies, thus deminishing the natural breeding areas for the salmons, an extensive hatchery program has compensated for the loss and, generally, increased the salmon populations in the Baltic Sea but simultanously decreased the genetic variation. In the 70ies a disease appeared in the hatcheries, causing high mortality (up to 95%) of the salmon fry. The explanation for this devastating syndrome, known today as M74, has not been found but it has been suggested that the high load of persistent environmental pollutants like PCB and dioxin that historically has been released into the water systems, have contributed to the problem. Since these chemicals strongly resemble endogenous signalling substances -hormones- exposed individuals experience altered cellular signalling which eventually results in cell death. This signalling is mediated by a receptor protein known as the aryl hydrocarbon (Ah) receptor which during recent years has been subjected to much interest because of its role in mediating toxicity of several environmental pollutants. Further research on the Ah receptor may in the future bring greater understanding of some the problems that the Baltic salmons presently are suffering from.
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| 4. |
- Ilmonen, P, et al.
(författare)
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Stress, immunocompetence and leukocyte profiles of pied flycatchers in relation to brood size manipulation
- 2003
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 1432-1939 .- 0029-8549. ; 136:1, s. 148-154
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Tidskriftsartikel (refereegranskat)abstract
- The two main trade-offs considered determining reproductive patterns in iteroparous organisms are the one between current and future reproduction, and the one between the number and quality of offspring. Recently, it has been suggested that these trade-offs may be mediated by stress-induced reduction in immunocompetence. To test the hypothesis that stress reduces immune function, we investigated the effects of brood size manipulation on stress hormone levels, leukocyte profiles and immune responses against challenge with novel antigens in nestling and parent male pied flycatchers (Ficedula hypoleuca). In male parents, heterophil (H) and lymphocyte (L) numbers, as well as H/L ratio increased with experimentally enlarged brood size, and corticosterone levels tended to do so, indicating that high parental work load altered their stress level and physiological state. Despite this, we found no effects on humoral immune responsiveness, measured as antibody production against diphtheria-tetanus vaccine. In nestlings, heterophil numbers and H/L ratio increased in enlarged broods, whereas T-cell-mediated immune responsiveness, measured against phytohemagglutinin (PHA), decreased in enlarged broods. The results support the view that growth-stress-induced immunosuppression may be an important physiological pathway mediating the trade-off between the number and viability of offspring. The difference in the observed immune-related responses between nestlings and males may be because we measured different aspects of the immune system (cellular vs humoral). However, it may also be a result of males lowering their own costs by feeding less, (and their mate possibly compensate by feeding more), whereas nestlings cannot escape the costs of increased intra-brood competition.
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| 5. |
- Kurtz, Joachim, et al.
(författare)
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An experimental test of the immunocompetence handicap hypothesis in a teleost fish: 11-ketotestosterone suppresses innate immunity in three-spined sticklebacks
- 2007
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 170:4, s. 509-519
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Tidskriftsartikel (refereegranskat)abstract
- The immunocompetence handicap hypothesis (ICHH) provides a functional explanation for how sexual ornaments can provide honest signals of male quality. A key aspect of this hypothesis is that testosterone (T) has a bimodal effect: a higher T level enhances the expression of ornaments (increasing mating success and, ultimately, fitness); however, at the same time, it suppresses immune function. Tests of the latter assumption, which have focused mainly on aspects of adaptive immunity in birds, led to equivocal results. We performed a hormone‐implant experiment in male three‐spined sticklebacks (Gasterosteus aculeatus) to test the key assumptions of the ICHH in a fish, where the dominant circulating androgen is 11‐ketotestosterone (11kT) rather than T. Males were implanted with 11‐ketoandrostenedione, which is a natural precursor of 11kT. Each individual's circulating 11kT level, ornamentation, and immunocompetence were measured 2 weeks later. In addition, we quantified oxidative tissue damage because the ICHH has been hypothesized to work via oxidative stress. We found that the males' 11kT levels correlated positively with ornamentation but negatively with immunocompetence, in particular, measures of innate immunity. Moreover, there was a trend for fish with high 11kT levels to suffer more from oxidative stress. Thus, our data provide support for the ICHH.
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| 6. |
- Langefors, Åsa
(författare)
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Adaptive and Neutral Genetic Variation and Colonization History of Atlantic Salmon, Salmo salar
- 2005
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Ingår i: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 74:3-4, s. 297-308
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Tidskriftsartikel (refereegranskat)abstract
- I combined neutral microsatellite markers with the major histocompatibility complex (MHC) class IIB to study genetic differentiation and colonization history in Atlantic salmon, Salmo salar, in the Baltic Sea and in the north-eastern Atlantic. Baltic salmon populations have lower levels of microsatellite genetic variation, in terms of heterozygosity and allelic richness than Atlantic populations, confirming earlier findings with other genetic markers, suggesting that the Baltic Sea populations have been exposed to genetic bottlenecks, most likely at a founding event. On the other hand, the level of MHC variation was similar in the Baltic and in the north-eastern Atlantic, indicating that positive balancing selection has increased the level of MHC-variation. Both microsatellite and MHC class IIB genetic variation give strong support to the hypothesis that the Baltic salmon are of a biphyletic origin, the southern population in this study is strongly differentiated from both the northern Baltic salmon populations and from the north-eastern Atlantic populations. Salmon may have colonized the northern Baltic Sea either from the south, via the so called “Närke strait” or from the north, via a proposed historical connection between the White Sea and the northern Baltic. At microsatellites, no significant isolation-by distance was found at either colonization route. At the MHC, populations were significantly isolated by distance when assuming that colonization occurred via the “Närke strait”.
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| 7. |
- Langefors, Åsa, et al.
(författare)
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Allelic polymorphism in MHC class IIB in four populations of Atlantic salmon (Salmo salar)
- 2001
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Ingår i: Immunogenetics. - : Springer Science and Business Media LLC. - 1432-1211 .- 0093-7711. ; 53:4, s. 329-336
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Tidskriftsartikel (refereegranskat)abstract
- We sequenced exon 2 of the MHC class II B gene in Atlantic salmon from the Baltic Sea and identified 17 different exon 2 alleles among 22 different restriction fragment length polymorphism haplotypes. The sequences differed at between I and 34 bases. Two different tests were used to estimate the importance of recombination in the generation of new alleles. Recombination events appear to have occurred between three and nine times. Only two pairs of sequences differed by less than five nucleotides', minimizing the importance of point mutations for generating new alleles. Phylogenetic analysis showed that sequences did not cluster according to populations, and genetic distances between populations were small compared to those obtained by allele frequency data. These results, together with the similarity found between exon 2 sequences from Baltic salmon and Norwegian salmon, indicate that all of the identified alleles were present in the ancient salmon population colonizing the Baltic rivers after the last glaciation.
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| 8. |
- Langefors, Åsa, et al.
(författare)
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Allelic variation of Mhc class II in Atlantic salmon; a population genetic analysis
- 1998
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 1365-2540 .- 0018-067X. ; 80:5, s. 568-575
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the degree of genetic variation at a variable Mhc class II beta gene in four populations of Atlantic salmon Salmo salar by using RFLPs. The class II beta gene encodes the part of the Mhc class II molecule that contains the antigen binding region and is therefore essential for disease resistance. There was extensive genetic variation in all four populations; the expected heterozygosity (H-si) varied between 0.50 and 0.81. Heterozygosity tended to be higher in broods surviving a syndrome causing high mortalities (60-95%) in Swedish salmon hatcheries. Populations that had experienced more incidences of genetic bottlenecks (years when fewer than 60 adults had been used for breeding) and had a lower average effective population size (N-e), had a lower degree of heterozygosity. The four populations differed significantly in allele frequencies as measured by F-ST = 0.13 and Nei's genetic distance (D = 0.09 - infinity). Pairwise F-ST values varied between 0.01 and 0.23, all but one being highly significant, indicating a differentiation between the populations in Mhc class II beta. This study shows that the four populations of Atlantic salmon have a high degree of polymorphism in the Mhc class II beta gene. However, there was great variation between different hatcheries, both in heterozygosity levels and allele frequencies.
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| 9. |
- Langefors, Åsa, et al.
(författare)
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Association between major histocompatibility complex class IIB alleles and resistance to Aeromonas salmonicida in Atlantic salmon
- 2001
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954 .- 0962-8452. ; 268:1466, s. 479-485
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Tidskriftsartikel (refereegranskat)abstract
- We have tested the importance of genetic variation in the major histocompatibility complex (MHC) class IIB in Atlantic salmon (Salmo salar) for survival after challenge with a highly virulent bacterial pathogen. Forty juvenile full siblings from each of 120 families were infected with the bacterium Aeromonas salmonicida, which causes high mortality in salmon due to furunculosis. Fishes from high-resistance (HR, < 35% mortality) and low-resistance (LR, > 80% mortality) families were screened for their MHC class IIB genotypes using the denaturing gradient gel electrophoresis (DGGE) technique. The exon 2 sequences, encoding the major part of the peptide-binding region, were established far each DGGE fragment. One allele, e, containing a missense single base substitution was significantly more prevalent in HR families than in LR families. An odds-ratio test showed that broods carrying this allele had a 12-fold higher chance of being HR than broods without the e allele. A second allele, i, showed significantly higher frequencies in uninfected and surviving individuals than in infected dead individuals. A third allele, j, tended to be more prevalent both in LR families and in individuals that had died of the infection. There was no correlation between MHC heterozygosity and resistance to A. salmonicida. Our results support the hypothesis that MHC polymorphism is maintained through pathogen-driven selection acting by means of frequency-dependent selection rather than heterozygous advantage.
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| 10. |
- Langefors, Åsa, et al.
(författare)
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Extra-pair fertilizations in the Sedge Warbler
- 1998
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Ingår i: Journal of Avian Biology. - 0908-8857. ; 29:2, s. 134-144
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Tidskriftsartikel (refereegranskat)abstract
- Parentage of 201 young (from 44 broods) in a population of Sedge Warblers Acrocephalus schoenobaenus in South Central Sweden, 1990-1992, was determined by using multilocus DNA fingerprinting. The frequency of extra-pair young (EPY) was 7.5% and they occurred in 23% of the broods. For 11 out of 15 extra-pair young we could identify the true father; in all of the cases he was a close neighbour. Among ten broods with extra-pair young, nine contained only one extra-pair sire and the remaining brood two extra-pair sires. The frequency of EPF varied among years (1.8-11.8%). The seasonal timing of broods with and without extra-pair young did not differ, and the occurrence of extra-pair fertilizations (EPF) was not related to the length of the pair male's mate-guarding period. EPF were not related to breeding synchrony (estimated as the mean number of fertile females per day during a female's fertile period). Pairs whose nests contained extra-pair young had more territories within 100 m of their nest than pairs without extra-pair young. Females that engaged in EPF had fewer attractive (i.e. singing) males to choose among the day before and at the day they formed their pair bend. Moreover, in all but one case the extra-pair male was not singing (i.e. not available as pair mate) the day the EPF-female settled. Males that fertilized extra-pair young tended to arrive earlier and to have higher pairing success than both males that were cuckolded and other males. Hence, female Sedge Warblers engaged in extra-pair fertilizations with attractive male neighbours. These results are consistent with the hypotheses that females participating in EPF are seeking genetic benefits to their offspring, but we cannot exclude the alternative explanation that attractive males are more efficient in forcing females to accept EPF.
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