Melatonin,immune function and aging

Aging is associated with a decline in immune function (immunosenescence), a situation known to correlate with increased incidence of cancer, infectious and degenerative diseases. Innate, cellular and humoral immunity all exhibit increased deterioration with age. A decrease in functional competence of individual natural killer (NK) cells is found with advancing age. Macrophages and granulocytes show functional decline in aging as evidenced by their diminished phagocytic activity and impairment of superoxide generation. There is also marked shift in cytokine profile as age advances, e.g., CD3+ and CD4+ cells decline in number whereas CD8+ cells increase in elderly individuals. A decline in organ specific antibodies occurs causing reduced humoral responsiveness. Circulating melatonin decreases with age and in recent years much interest has been focused on its immunomodulatory effect. Melatonin stimulates the production of progenitor cells for granulocytes-macrophages. It also stimulates the production of NK cells and CD4+ cells and inhibits CD8+ cells. The production and release of various cytokines from NK cells and T-helper lymphocytes also are enhanced by melatonin. Melatonin presumably regulates immune function by acting on the immune-opioid network, by affecting G protein-cAMP signal pathway and by regulating intracellular glutathione levels. Melatonin has the potential therapeutic value to enhance immune function in aged individuals and in patients in an immunocompromised state.     

Hormonal Effects on Calcium Metabolism in Crustacea

Cyclic shifts of calcium in the exoskeleton and soft tissues,as they are related to the intermolt cycle in crayfish, arereviewed. Regulatory factors, derived from the eyestalk, influencelevels of exoskeletal calcium; eyestalk extracts prepared fromanimals in premolt decrease shell calcium, while reciprocallyextracts from animals in intermolt increase it when these hormonalsources are injected into animals in the premolt stage (D₀-D₄). In addition, premolt eyestalk extract results in an increasein gastrolith calcium. In the exchange of calcium between theanimal and its environment there is evidence for differentialdepositionof recently available calcium in the exoskeleton. Further, intermoltand early premolt animals maintained in Ca⁴⁵-labelled waterfor 15 days concentrate it 4 and 3—fold in the exoskeletonand stomach, respectively. However, removal of a molt-inhibitingfactor through ablation of eyestalks results in a 20 and 40—foldincrease in incorporation inthese same sites relative to environmentalconcentrations. Treatment with mammalian parathyroid extract mobilizes bothexoskeletal and gastric calciumand leads to a rise in bloodcalcium. However, there is little or no effect on levels ofexoskeletal citric acid. Further, citric acid is higher in thecrayfish carapace during stage C, the period of mineralization,than in stage D, the period of demineralization. There are both similarities and differences between the effectsof crustacean and mammalianregulating factors with respect tothe direction and extent of mineralization. Biochemical studiesshould elucidate the mechanisms regulated by these hormones.     

The partition matrix: exploring variable phylogenetic signals along nucleotide sequence alignments

The partition matrix is a graphical tool for comparative analysis of nucleotide sequences following alignment. It is particularly useful for investigating the divergent phylogenies of sequence regions undergoing reticulate evolution. A partition matrix is generated by determining the consistency of the parsimoniously informative sites in a set of aligned sequences with the binary partitions inferred from the sequences. Since the linear order of sites is maintained, the matrix can be used to assess whether the distribution of sites either supporting or conflicting with particular partitions changes along the length of the alignment. The usefulness of the matrix in allowing visual identification of differences in evolutionary history among regions depends on the order in which partitions are shown; several suitable ordering schemes are proposed. We demonstrate the use of the partition matrix in interpreting the evolution of the pseudoautosomal boundary region on the sex chromosome of catarrhine primates. Its routine use should help to avoid attempts to derive single phylogenies from sequences whose evolution has been reticulate and to identify the gene conversion or recombination events underlying the reticulation. The method is relatively fast. It is exploratory, and it can form the basis for more formal analysis, which we discuss.      

Positive selection and sequence rearrangements generate extensive polymorphism in the gamete recognition protein bindin

Bindin is a gamete recognition protein of sea urchins that mediates species-specific attachment of sperm to an egg-surface receptor during fertilization. Sequences of bindin from closely related urchins show fixed species-specific differences. Within species, highly polymorphic bindin alleles result from point substitution, insertion/deletion, and recombination. Since speciation, positive selection favoring allelic variants has generated diversity in bindin polypeptides. Intraspecific bindin variation can be tolerated by the egg receptor, which suggests functional parallels between this system and other flexible recognition systems, including immune recognition. These results show that polymorphism in mate recognition loci required for rapid evolution of sexual isolation can arise within natural populations.      

Foraging behaviour of Terek SandpipersXenus cinereus feeding on Sand-Bubbling CrabsScopimera globosa

Summary On the intertidal flats of the Nakdong Estuary in South Korea Terek Sandpipers foraged solitarily, and made 0.5–6 m long runs which ended with pecks on or into the sediment to capture Sand-bubbling Crabs. The birds foraged during low tide and spent about 80 % of their time foraging; the rest preening and resting. More than half of the recorded prey and over 80 % of the average energetic intake consisted of Sand-bubbling Crabs. As the size of captured crabs increased, a greater proportion was washed before ingestion. Small crabs were always swallowed, but of the larger crabs an increasing portion was eventually rejected after capture. When deep down in their burrows, only the smallest crabs were within the reach of the sandpipers' bills. Henceforth, the crabs were only available when outside their burrows, on the surface. This happened for only three hrs (or one third) of each diurnal low tide period. Early in the tidal cycle after the crabs came to the surface, Terek Sandpipers made many runs and pecks per unit time to capture them. When crabs were most abundant and easy to catch, the birds were apparently more selective in their prey choice: more captured crabs were washed before being eaten and more were eventually rejected. Suggestions are made to explain the behaviour of both the predator and the prey.

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Verhalten von Terekwasserläufern(Xenus cinereus) beim Erbeuten von Winkerkrabben(Scopimera globosa)

Zusammenfassung Im Watt der Nakdong-Mündung in Südkorea gingen Terekwasserläufer einzeln der Nahrungssuche nach; ihre Beute waren hauptsächlich Winkerkrabben. Nach einer Laufstrecke von 0.5–6 m pickten sie nach der Beute auf oder im Sediment. Die Vögel suchten während des Niedrigwassers nach Nahrung und verwendeten dafür etwa 80 % ihrer Zeit; den Rest verbrachten sie mit Putzen und Rasten. Mehr als die Hälfte der festgestellten Beute und über 80 % der mittleren Energieaufnahme bestand ausScopimera globosa. Mit steigender Beutegröße wurde ein größerer Anteil der Beute vor dem Verschlucken gewaschen. Kleine Krabben wurden immer verschluckt, während von den größeren ein zunehmender Anteil schließlich verworfen wurde. Wenn die Krabben tief unten in ihren Höhlen saßen, befanden sich nur die kleinsten in der Reichweite der Schnäbel. Daher waren die meisten Krabben nur außerhalb ihrer Höhlen an der Oberfläche erreichbar, und zwar lediglich während drei Stunden (oder einem Drittel) der täglichen Niedrigwasserperiode. Früh in der Tidenperiode, wenn die Krabben an die Erdoberfläche gekommen waren, liefen und pickten die Terekwasserläufer pro Zeiteinheit oft, um die Krabben zu fangen. Wenn die Krabben am häufigsten waren und sich am leichtesten fangen ließen, waren die Vögel anscheinend selektiver in ihrer Beuteauswahl: Mehr Krabben wurden vor dem Verzehr gewaschen und mehr wurden schließlich verworfen. Zur Erklärung des Verhaltens sowohl des Räubers als auch der Beute werden Hypothesen angeboten.

     

Phenotypic compromise in the face of conflicting ecological demands: an example in red knots Calidris canutus

Phenotypic flexibility is a phenomenon where physiological functions in animals are reversibly adjusted in response to ecological constraints. Research usually focuses on effects of single constraints, but under natural conditions animals face a multitude of restrictions acting simultaneously, and potentially generating conflicting demands on the phenotype. We investigated the conflicting demands of low temperatures and a low quality diet on the phenotype of a shorebird, the red knot Calidris canutus . We tested the effects of switching diet from a high quality trout food to low quality hard-shelled bivalves in captive birds acclimated to temperatures reflecting natural winter conditions. Feeding on bivalves generated a digestive constraint forcing the birds to increase the height and width of their gizzard by 66% and 71%, respectively, over 30 days. The change in gizzard size was associated with an initial 15% loss of body mass and a reduction in size of the pectoral muscles by 11%. Because pectoral muscle size determines summit metabolic rate (M_sum, an indicator of cold endurance), measured M_sum declined by 9%. Therefore, although the birds were acclimated to cold, gizzard growth led to a loss of cold endurance. We propose that cold-acclimated knots facing a digestive constraint made a phenotypic compromise by giving-up cold hardiness for digestive capacity. Field studies suggest that phenotypic compromises occur in free-living red knots as well and help improve survival.     

Cytogenetic studies in Eigenmannia virescens (Sternopygidae, Gymnotiformes) and new inferences on the origin of sex chromosomes in the Eigenmannia genus

Background

Previous studies suggested that multiple domestication events in South and South-East Asia (Yunnan and surrounding areas) and India have led to the genesis of modern domestic chickens. Ha Giang province is a northern Vietnamese region, where local chickens, such as the H'mong breed, and wild junglefowl coexist. The assumption was made that hybridisation between wild junglefowl and Ha Giang chickens may have occurred and led to the high genetic diversity previously observed. The objectives of this study were i) to clarify the genetic structure of the chicken population within the Ha Giang province and ii) to give evidence of admixture with G. gallus. A large survey of the molecular polymorphism for 18 microsatellite markers was conducted on 1082 chickens from 30 communes of the Ha Giang province (HG chickens). This dataset was combined with a previous dataset of Asian breeds, commercial lines and samples of Red junglefowl from Thailand and Vietnam (Ha Noï). Measurements of genetic diversity were estimated both within-population and between populations, and a step-by-step Bayesian approach was performed on the global data set.

Results

The highest value for expected heterozygosity (> 0.60) was found in HG chickens and in the wild junglefowl populations from Thailand. HG chickens exhibited the highest allelic richness (mean A = 2.9). No significant genetic subdivisions of the chicken population within the Ha Giang province were found. As compared to other breeds, HG chickens clustered with wild populations. Furthermore, the neighbornet tree and the Bayesian clustering analysis showed that chickens from 4 communes were closely related to the wild ones and showed an admixture pattern.

Conclusion

In the absence of any population structuring within the province, the H'mong chicken, identified from its black phenotype, shared a common gene pool with other chickens from the Ha Giang population. The large number of alleles shared exclusively between Ha Giang chickens and junglefowl, as well as the results of a Bayesian clustering analysis, suggest that gene flow has been taking place from junglefowl to Ha Giang chickens.     

Permanent female mimics in a lekking shorebird

Female mimics are known from many species, but permanent, non-conditional, alternative mating strategies are only known from an isopod, a fish, a lizard and a bird. The single bird example refers to lek-breeding ruffs Philomachus pugnax, a shorebird for which two strategies (independent and satellite) have been known for over 50 years. Ruffs also provided the single case of an animal with two, rather than three, permanent alternative mating strategies. Here, we describe a rare female-like morph of ruffs: the 'missing' third alternative mating strategy, which we have called 'faeder'. Faeders are slightly larger than females and in late April have testes 2.5 time the size of testes of normal males. On leks in aviaries and in the wild they appear to combine feminine and masculine behaviours. Faeders may represent the ancestral, care-giving, male strategy, but their relatively large testes suggest that currently they behave as sneakers.     

Small home ranges and high site fidelity in red knots (Calidris c. canutus) wintering on the Banc d’Arguin, Mauritania

Using automated and manual radio-telemetry and resightings of individual colour-ringed birds, we assessed the daily use of space of red knots Calidris canutus canutus at a tropical wintering area along the Sahara coast, the Banc d’Arguin in Mauritania. Confirming earlier suggestions, we found that birds were very faithful to their roosts and that the daily foraging range was small; in the course of several winter months birds used an area of only 2–16 km² of intertidal area. We found no differences between their movements in daylight and at night. Additionally, individuals seem to return to exactly the same locations in subsequent winters. This pattern is very different from red knots wintering in the temperate Wadden Sea. Here, they readily change roost sites and easily cover areas of about 800 km² in the course of weeks but, just as in Mauritania, no differences between day and night are apparent. In northern Patagonia and north-western Australia, red knots have range sizes closer to those on the Banc d’Arguin, but here they do show differences in space use between day and night. Ecological explanations for these contrasting patterns require further comparative data based on in-depth studies on the predictability of the food base and the presence of diurnal and nocturnal predators.