Prey depletion and foraging strategy in the Oystercatcher Haematopus ostralegus

Summary The responses of a population of Oystercatchers to their own depletion of their prey, the edible cockle Cerastoderma edule, have been examined in Strangford Lough, Northern Ireland., Cockle stocks were severely depleted each winter as a result of predation by Oystercatchers and about half the birds present in October in the main study area had left by March: the reduction was greater when the initial population of Oystercatchers was high than when it was low. Oystercatchers were initially widespread around the Lough but tended to aggregate by January into a few good sites. Within each site annual differences in the location of feeding effort were correlated with year to year variation in the location of second winter cockles.Within the feeding areas in a bay the birds apparently hunted in the short-term on the basis of expectation, ceasing to crop, the densest cockle beds once an average yield for the area has been removed; this yield was apparently estimated from the local density of the anvils on which captured cockles were broken open. This effect led to marginal areas being depleted of cockles more rapidly than high density areas, so that the birds gradually concentrated their hunting onto an increasingly restricted area of the bay. The birds initially took only second winter and larger cockles but by late winter cockle densities had fallen so much that smaller cockles were accepted: areas previously abandoned or unused for hunting were then economically viable because of the reduced expectations of the birds and were incorporated into the feeding areas.These results are seen as consistent with Royama's profitability theory.     

Anatomical observations on the bill of the Oystercatcher (Haematopus ostralegus occidentalis) in relation to feeding behaviour

Oystercatchers have recently increased as inland breeders in Northern Britain. Concurrently, they have been observed feeding in coastal fields in winter. It is suggested that the bill of this species possesses dual characteristics enabling them to feed on shellfish adn also to probe in the soil for terrestrial invertebrates.
The gross internal morphology of the bills of adults and young is described. A bony core contains large nerves running the length of the bill. These break up towards the tip where numerous sensory corpuscles are seen. It is concluded that the possession of a strong bone core together with numerous sense organs at the tip has been of considerable importance in enabling the Oystercatcher to exploit inland situations.     

Individual and age differences in the feeding ecology of Oystercatchers Haematopus ostralegus wintering on the Exe Estuary, Devon

The habitats and foods used by a sample of marked individuals and by the whole population of Oystercatchers Haematopus ostralegus wintering on the Exe estuary, South Devon, are described. In the spring and early summer, only a few hundred immatures were present. Two thousand adults and several hundred juveniles arrived in late summer from the breeding grounds and remained until the following spring. The majority of the birds were then adults. At low water, most adults fed on the mussel Mytilus edulis beds and ate mussels. Most individuals specialised on this prey and ate little else. Some adults fed on mud-flats and sandflats within the estuary and along the coast, and specialised on a mixture of Nereis diversicolor and Scrobicularia plana or on Cerastoderma edule or Littorina spp. Though some juveniles ate mussels from the time they arrived, most did not. In winter, they took Scrobicularia on mudflats, earthworms Lumbricidae and leatherjackets Tipulidae larvae in fields and Spisula and mussels along the coast. At other times of year they mainly ate Nereis. However, as they grew older, more birds began to specialise on mussels, especially in their second, third and fourth summers when the adults were away. At high water, most birds roosted at the mouth of the estuary or along the coast. However, several hundred fed in the fields in winter with more doing so late in the winter on warm days on Neap tides when less time was available for feeding on the estuary in daylight. Birds feeding on Nereis and Scrobicularia at low water were most often seen in the fields, irrespective of age. Birds feeding on Mytilus and Littorina occurred there rarely, but no bird eating Cerastoderma was seen there. The findings are discussed in relation to age differences in feeding skills and ability to compete successfully with other birds.     

A silver spoon for a golden future: long-term effects of natal origin on fitness prospects of oystercatchers (Haematopus ostralegus)

1. Long-term effects of conditions during early development on fitness are important for life history evolution and population ecology. Using multistrata mark-recapture models on 20 years of data, we quantified the relation between rearing conditions and lifetime fitness in a long-lived shorebird, the oystercatcher (Haematopus ostralegus). We addressed specifically the relative contribution of short- and long-term effects of rearing conditions to overall fitness consequences. 2. Rearing conditions were defined by differences in natal habitat quality, in which there is a clear dichotomy in our study population. In the first year of life, fledglings from high-quality natal origin had a 1.3 times higher juvenile survival. Later in life (age 3-11), individuals of high-quality natal origin had a 1.6 times higher adult prebreeder survival. The most striking effect of natal habitat quality was that birds that were reared on high-quality territories had a higher probability of settling in high-quality habitat (44% vs. 6%). Lifetime reproductive success of individuals born in high-quality habitat was 2.2 times higher than that of individuals born in low-quality habitat. This difference increased further when fitness was calculated over several generations, due to a correlation between the quality of rearing conditions of parents and their offspring. 3. Long-term effects of early conditions contributed more to overall fitness differences as short-term consequences, contrary to common conceptions on this issue. 4. This study illustrates that investigating only short-term effects of early conditions can lead to the large underestimation of fitness consequences. We discuss how long-term consequences of early conditions may affect settlement decisions and source-sink population interactions.     

Muscle relaxants; effects on respiratory and circulatory dynamics

There are exceptions and variations to the general clinical rule that muscle relaxants depress respiration and have no effect on circulation. Variation may be attributed to differences in animal species, in individual response, in muscle affected, in drug used and in dose employed. Conclusions about muscle relaxants derived from animal experiments cannot always be assumed to apply to man. The "respiratory sparing" action of a muscle relaxant cannot be relied upon in any individual patient. Facilities for adequate artificial respiration must always be available when any dose of any muscle relaxant drug is administered. Muscle relaxants affect circulation by inhibition of parasympathetic and sympathetic ganglia, by anticholinesterase activity and by release of histamine.     

The effects of nitrogen application on growth and nitrogen distribution within the potato canopy

The effect of applying nitrogen (N) fertiliser on the growth and distribution of N within the potato canopy was studied in 1983 and 1984. In both years N was applied either in excess of that required to produce maximum tuber yields, or not at all. The large application of N changed the pattern of canopy growth - stimulating growth of leaves at the top of the stem, particularly lateral branches, for longer during the season, and accelerating the death of (shaded) leaves at the base of the canopy. The pattern of canopy senescence was, therefore, changed from a synchronous to a progressive type. Application of nitrogen fertiliser at supra-optimal rates increased the N contents of leaves, stems and tubers. The extra N in the leaves of these plants was present as reduced N in all leaf positions, and as nitrate (NO^-₃) in the lowermost leaves. In addition, substantial quantities of NO^-₃ were also stored in the stems. Part of this extra N in the canopy was redistributed during subsequent growth, especially to the lateral branches as crop N uptake slowed towards the end of the season. In addition, substantial quantities of N were also potentially available for redistribution to the growing tubers. There was little redistribution of N from the leaves of N-deficient plants. It is suggested that redistribution of N in the canopy of N-replete plants allowed the growth of lateral branches towards the end of the season, thereby maintaining photosynthetically active leaves for longer than N-deficient plants.     

Identifying from recent sediment records the effects of nutrients and climate on diatom dynamics in Loch Leven

1. Changes in nutrients and climate have occurred over approximately the same timescales in many European lake catchments. Here, we attempt to interpret the sedimentary diatom record of a large shallow lake, Loch Leven, in relation to these pressures using information gained from analysis of long‐term data sets of water quality, climate and planktonic diatoms. 2. The core data indicate the enrichment of Loch Leven starting in c. 1800–1850, most likely from agricultural practices in the catchment, with a more marked phase since c. 1940–1950 caused by increased phosphorus inputs from sewage treatment works, land drainage and a woollen mill. 3. While the recent diatom plankton remains are dominated by taxa associated with nutrient‐rich conditions, an increase in Aulacoseira subarctica relative to Stephanodiscus taxa since the mid‐1980s suggests that reductions in external catchment sources of nutrients (since 1985) may have resulted in partial recovery. This observation accords well with the long‐term monitoring series of water chemistry and phytoplankton. 4. On a decadal‐centennial scale, the eutrophication signal in the sediment record outweighs any evidence of climate as a control on the diatom community. However, at an inter‐annual scale, while the diatom data exhibit high variability, there are several changes in species composition in the recent fossil record that may be attributed to climatic controls. 5. The study highlights the value of a palaeolimnological approach, particularly when coupled with long‐term data sets, for developing our understanding of environmental change at a range of temporal scales. The diatom record in the sediment can be used effectively to track recovery from eutrophication, but requires greater understanding of contemporary ecology to fully interpret climate impacts. 6. The study illustrates the complexity of ecosystem response to synchronous changes in nutrients and climate, and the difficulty of disentangling the effects of these multiple, interacting pressures.     

Chorionic gonadotropin has a recent origin within primates and an evolutionary history of selection

Chorionic gonadotropin (CG) is a critical signal in establishing pregnancy in humans and some other primates, but this placentally expressed hormone has not been found in other mammalian orders. The gene for one of its two subunits (CG beta subunit [CGbeta]) arose by duplication from the luteinizing hormone beta subunit gene (LHbeta), present in all mammals tested. In this study, 14 primate and related mammalian species were examined by Southern blotting and DNA sequencing to determine where in mammalian phylogeny the CGbeta gene originated. Bats (order Chiroptera), flying lemur (order Dermoptera), strepsirrhine primates, and tarsiers do not have a CGbeta gene, although they possess one copy of the LHbeta gene. The CGbeta gene first arose in the common ancestor of the anthropoid primates (New World monkeys, Old World monkeys, apes, and humans), after the anthropoids diverged from tarsiers. At least two subsequent duplication events occurred in the catarrhine primates, all of which possess multiple CGbeta copies. The LHbeta-CGbeta family of genes has undergone frequent gene conversion among the catarrhines, as well as periods of strong positive selection in the New World monkeys (platyrrhines). In addition, newly generated DNA sequences from the promoter of the CG alpha subunit gene indicate that platyrrhine monkeys use a different mechanism of alpha gene expression control than that found in catarrhines.     

Effects of a recent founding event and intrinsic population dynamics on genetic diversity in an ungulate population

Maintenance of genetic diversity has recently become a management goal for a number of species, due to its importance for present and future population viability. Genetic drift, primarily through differential reproductive success and inbreeding, can accelerate the loss of genetic diversity in recently recovered populations. We attempt to quantify the consequences of these factors on the genetic diversity contained in a small, recently founded wood bison (Bison bison athabascae) population by examining the genetic variation in this conservation herd, the calves born therein, and its large source population. The Hook Lake Wood Bison Recovery Project was initiated to found a disease-free herd of wood bison containing a representative amount of the genetic diversity present in the Wood Buffalo National Park metapopulation. Levels of diversity in the Hook Lake Wood Bison Recovery Project founders are higher than in previous salvage attempts. To examine the effects of differential reproductive success on this population, we monitored parentage of the calves born in the Hook Lake Wood Bison Recovery Project for 3 years since the founders reached sexual maturity. Two of the male founders sired over 90% of the offspring born in this population, which has led to a reduction in diversity in their calves. Monitoring of reproductive success, and incorporation of selective breeding strategies will be required to reduce the rate at which genetic diversity is lost from this small, isolated population. These steps should occur in other recovery projects, particularly when a small number of individuals are capable of dominating reproduction.     

Mechanobiology of low-density lipoprotein transport within an arterial wall—Impact of hyperthermia and coupling effects

The effects of hyperthermia, coupling attributes and property variations on Low-density lipoprotein (LDL) transport within a multi-layered wall while accounting for the fluid structure interaction (FSI) is analyzed in this work. To understand the potential impact of the hyperthermia process, thermo-induced attributes are incorporated, accounting for the plasma flow, mass transfer, as well as the elastic wall structure. The coupling effect of osmotic pressure, Soret and Dufour diffusion is discussed and their influence on LDL transport is examined, demonstrating that only the Soret effect needs to be accounted for. The effect of thermal expansion on changing the behavior of flow, mass transport, and elastic structure is illustrated and analyzed while incorporating the variations in the effective LDL diffusivity and consumption rate, as well as other dominating parameters. It is shown that hyperthermia results in an enhancement in LDL transport by increasing the concentration levels within the arterial wall.     

Trophic dynamics within a hybrid zone – interactions between an abundant cyprinid hybrid and sympatric parental species

1. Recent proliferation of hybridisation in response to anthropogenic ecosystem change, coupled with increasing evidence of the importance of ancient hybridisation events in the formation of many species, has moved hybridisation to the forefront of evolutionary theory. 2. In spite of this, the mechanisms (e.g. differences in trophic ecology) by which hybrids co‐exist with parental taxa are poorly understood. A unique hybrid zone exists in Irish freshwater systems, whereby hybrid offspring off two non‐native cyprinid fishes often outnumber both parental species. 3. Using stable isotope and gut content analyses, we determined the trophic interactions between sympatric populations of roach (Rutilus rutilus), bream (Abramis brama) and their hybrid in lacustrine habitats. 4. The diet of all three groups displayed little variation across the study systems, and dietary overlap was observed between both parental species and hybrids. Hybrids displayed diet, niche breadth and trophic position that were intermediate between the two parental species while also exhibiting greater flexibility in diet across systems.     

Diet and alcohol effects on the manifestation of hepatic porphyrias

Porphyria cutanea tarda (PCT) is the most frequently reported type of porphyria. The average patient is male more than 40 years old with a history of alcohol consumption. In women the incidence of PCT has increased with use of estrogens for birth control. The cutaneous features are those of chronic porphyrin photosensitivity on the light-exposed area of the skin: pigmentation, hirsuitism and fragility, and vesiculobullae, which has prompted the expression bullosa actinica et mechanica. One-third of the patients have glucose intolerance. PCT has been reported frequently among the Bantu people in South Africa as resulting from combinations of alcohol and cooking in ironware. The average patient has a higher than normal hematocrit, which is used as a guide to treatment by phlebotomy ranging from 8 to 14 units removed every 2-4 wk. Chemically induced PCT has been reported with chlorinated hydrocarbons, the best-known of which is hexachlorobenzene (HCB). Porphyria was noted in more than 3,000 patients in southeast Turkey between 1955 and 1961, because of consumption of seed wheat treated with HCB. In addition, more than 1,000 children under the age of 1 year died because HCB was transferred from the mother, either via the placenta or through breast milk.     

Population dynamics of American horseshoe crabs—historic climatic events and recent anthropogenic pressures

Populations of the American horseshoe crab, Limulus polyphemus, have declined, but neither the causes nor the magnitude are fully understood. In order to evaluate historic demography, variation at 12 microsatellite DNA loci surveyed in 1218 L. polyphemus sampled from 28 localities was analysed with Bayesian coalescent‐based methods. The analysis showed strong declines in population sizes throughout the species’ distribution except in the geographically isolated southern‐most population in Mexico, where a strong increase in population size was inferred. Analyses suggested that demographic changes in the core of the distribution occurred in association with the recolonization after the Ice Age and also by anthropogenic effects, such as the past overharvest of the species for fertilizer or the current use of the animals as bait for American eel (Anguilla rostrata) and whelk (Busycon spp.) fisheries. This study highlights the importance of considering both climatic changes and anthropogenic effects in efforts to understand population dynamics—a topic which is highly relevant in the ongoing assessments of the effects of climate change and overharvest.     

The distribution of SCEs within and between the genomes of an interspecific hybrid

The distribution of sister chromatid exchanges has been examined in the chromosomes of a hybrid male wallaby (Macropus rufogriseus x Wallabia bicolor ), and in the X chromosomes of M. parryi and M. rufus. Comparisons were made of SCE frequency between the two genomes of the hybrid, only one of which has an appreciable amount of constitutive heterochromatin, and between the euchromatic and heterochromatic regions of the M. rufogriseus genome. The frequency of SCEs is closely correlated with the DNA content of the individual chromosomes. The distribution of the SCEs between the euchromatin and heterochromatin in the M. rufogriseus genome showed a deficiency of SCEs observed in the heterochromatin compared with the euchromatin. —A substantial excess of SCEs occurred at the nucleolar organiser region of the M. rufogriseus X chromosome. This excess was absent from the nucleolar organiser region of the X chromosome of the two other macropodine species studied and is accounted for by the presence of an adjacent euchromatin-heterochromatin junction.     

The complex evolutionary dynamics of ancient and recent polyploidy in Leucaena (Leguminosae; Mimosoideae)

? Premise of the study: The evolutionary history of Leucaena has been impacted by polyploidy, hybridization, and divergent allopatric species diversification, suggesting that this is an ideal group to investigate the evolutionary tempo of polyploidy and the complexities of reticulation and divergence in plant diversification. ? Methods: Parsimony- and ML-based phylogenetic approaches were applied to 105 accessions sequenced for six sequence characterized amplified region-based nuclear encoded loci, nrDNA ITS, and four cpDNA regions. Hypotheses for the origin of tetraploid species were inferred using results derived from a novel species tree and established gene tree methods and from data on genome sizes and geographic distributions. ? Results: The combination of comprehensively sampled multilocus DNA sequence data sets and a novel methodology provide strong resolution and support for the origins of all five tetraploid species. A minimum of four allopolyploidization events are required to explain the origins of these species. The origin(s) of one tetraploid pair (L. involucrata/L. pallida) can be equally explained by two unique allopolyploidizations or a single event followed by divergent speciation. ? Conclusions: Alongside other recent findings, a comprehensive picture of the complex evolutionary dynamics of polyploidy in Leucaena is emerging that includes paleotetraploidization, diploidization of the last common ancestor to Leucaena, allopatric divergence among diploids, and recent allopolyploid origins for tetraploid species likely associated with human translocation of seed. These results provide insights into the role of divergence and reticulation in a well-characterized angiosperm lineage and into traits of diploid parents and derived tetraploids (particularly self-compatibility and year-round flowering) favoring the formation and establishment of novel tetraploids combinations.