Why are there so many species of bumble bees at Dungeness?

WILLIAMS, P. H., 1989. Why are there so many species of bumble bees at Dungeness? Dungeness is unique in the British Isles in that it has more species of bumble bees than any other locality. Three ideas about what governs the number of species at a locality are examined by locking at patterns of flower visits at Dungeness in comparison with those at Shoreham, a species-poor locality also in Kent. The species of bumble bees that are present at Dungeness but absent from Shoreham show no association in their distributions among 2 km grid-squares in Kent with the species of food-plants that they prefer at Dungeness, nor is there any correlation between the diversity of bees and diversity of food-plants at Dungeness and Shoreham. From the information available, Dungeness is most likely to have more species of bumble bees because it has a particularly high density of the more nectar-rich flowers that bumble bees can use. Bumble bees feed most profitably from deep flowers because these contain more nectar than shallow flowers, although direct access to deeper flowers is ultimately limited by the length of each bee's proboscis. The distribution of worker proboscis lengths among species in the species-pool in Kent is clumped about a median of 7.9 mm. The best foraging conditions for the maximum number of species should be provided when flowers of similar depths are present in sufficiently large numbers for all foragers to make near-optimal flower choices. Although there is no difference in median between the distributions of the bees' proboscis lengths and the depths of the flowers they use at Dungeness, at Shoreham the flower depths used are shorter than the proboscis lengths. Among the food-plants at Dungeness, high densities of Teucrium scorodonia and Echium vulgare are likely to be especially important.     

The competitive and predatory impacts of the nonindigenous crab Carcinus maenas (L.) on early benthic phase Dungeness crab Cancer magister Dana

We evaluate the potential competitive and predatory impacts of nonindigenous European green crab Carcinus maenas on native Dungeness crab Cancer magister in the northeast Pacific. The coastal estuaries of Washington State, USA, provide appropriate habitat for recently introduced green crab, yet these areas are important nursery grounds for Dungeness crab and contribute greatly to the coastal crab fishery. Juvenile Dungeness crabs are dependent on limited intertidal epibenthic shell for refuge habitat during early benthic life and experience increased mortality on open sand and mud as a result of predation by fish and birds. Early juveniles throughout the subtidal are similarly at risk due to predation by fish and especially adult conspecifics. Laboratory experiments and infrared video observations revealed that juvenile green crab displace Dungeness crab of equal size from shelters during one-on-one competition. Green crab also consistently win nocturnal foraging trials in which the species compete for fresh, damaged clams. Field and laboratory enclosure experiments show that juvenile Dungeness crab emigrate from oyster shell habitat as a result of competition and predation by adult green crab. Depending on the extent to which the two species overlap, interactions with the dominant nonindigenous species could have a negative influence on juvenile Dungeness crab survival and could conceivably impact recruitment to the fishery. However, current evidence indicates that the distribution of green crab in Washington State is far removed from nursery areas of Dungeness crab.     

Orfordness and Dungeness: a comparative study

FULLER, R. M., 1989. Orfordness and Dungeness: a comparative study . Dungeness originally developed as a shingle spit from Winchelsea, across the bay which now forms the Romney Marshes and, 700–800 years ago, probably had its distal end between New Romney and Hythe. The structure seems to have been very similar to present-day Orfordness. Then a breach at the spit's origin produced an abrupt change in accretion and erosion patterns with the eventual development of the present-day cuspate foreland. It would seem that Orfordness is on the verge of such a breach, which is prevented by coastal defence works. Much can be learned by comparing physiographic and ecological processes at Orfordness with those at Dungeness, using Orfordness as an historical model for early Dungeness. This paper considers some of the evidence for these conclusions, examines the structures which survive to the present-day and discusses the ecological significance of the features, especially in terms of plant successional developments.     

Migration studies at Dungeness Bird Observatory

McMINN, S., 1989. Migration studies at Dungeness Bird Observatory . The part played in the study of bird migration by the Dungeness Bird Observatory is outlined. Information concerning blackbird ( Tardus merula ) and robin ( Erithacus rubecula ) migration is presented as well as notes on migration over the sea.     

The medicinal leech, Hirudo medicinalis (L.) (Hirudinea: Gnathobdellae), at Dungeness, Kent

WILKIN, P. J., 1989. The medicinal leech, Hirudo medicinalis (L.) (Hirudinea: Gnathobdellae), at Dungeness, Kent . An account of the ecology and conservation of the medicinal leech ( Hirudo medicinalis (L.)) at Dungeness, Kent, is presented.     

The shingle ridge succession at Dungeness

FERRY, B. W., BARLOW, S. L. & WATERS, S. J. P., 1989. The shingle ridge succession at Dungeness . The range of plant communities which have colonized both intact shingle ridges and areas of disturbed shingle on Denge Beach, Dungeness, are described. An attempt is made to place these communities into categories of the National Vegetation Classification scheme, and further to relate them to physical and chemical gradients and variations in the shingle substrate.     

Management plan for the Royal Society for the Protection of Birds reserve at Dungeness, Kent

THOMAS, G. J., GLOVER, J. & MAKEPEACE, P., 1989. Management plan for the Royal Society for the Protection of Birds reserve at Dungeness, Kent . A synopsis of a new management plan for RSPB Dungeness reserve is presented.     

Lichens at Dungeness

LAUNDON, J. R., 1989. Lichens at Dungeness . The lichen vegetation at Dungeness is reviewed. The most important lichen communities are of three types. Firstly, there are the crustose lichens which colonize the bare pebbles. Secondly, the tracts of rich Cladonia turf which form the lichen heath and which play a major role in the vegetation cycle. Thirdly, there are the epiphytes on Prunus scrub. In addition, lichens on artificial substrates, especially wooden fences, are noteworthy. About 150 species occur, amongst the most interesting being Cladonia mitis, Lecanora helicopis, Lecidea insidiosa, Parmelia soredians, Rinodina aspersa and Umea glabrata. A new combination is made in the genus Porpidia. The term 'bird farming' is published. The fragmentation of the vegetation by building and gravel extraction receives critical comment.     

Shingle-based wetlands at Dungeness

WATERS, S. J. P. & FERRY, B. W., 1989. Shingle-based wetlands at Dungeness . At Dungeness, a unique development of open water and natural wetland has occurred on the shingle beaches. Over 700–1000 years, low-lying areas have changed from saline lagoons into freshwater lakes which are now largely infilled by reedswamp and sallow carr. Since about 1970, the water-table has been lowered, by a combination of water abstraction and hydrological changes associated with gravel extraction. Water-table lowering has accelerated colonization by reedswamp and sallow carr, and has caused loss of sedge-rich marshland. Possible methods are suggested for promoting development of such marshland in artificial excavations.     

A trematode metacercaria encysted in the nerves of the dungeness crab, Cancer magister

Of 188 Dungeness crabs, Cancer magister, 8 contained unidentified trematode metacercariae encysted in various components of the nervous system, including the thoracic ganglion, brain, lamina ganglionaris of the eyestalk, and major nerves arising from the thoracic ganglion. A single cyst was present in the available tissue sections of 7 of the crabs and no behavioral abnormalities were exhibited. One crab with multiple cysts in major nerves near the thoracic ganglion was markedly ataxic. The cysts and included worms distorted, compacted, and destroyed nervous tissue, and occupied most of the nerves where present. Host response was minimal, but some cysts invoked massive hemocytic accumulations near the infection site. Infections probably seriously affect nerve impulse transmission and accounts for the lethargic behavior of the crab with multiple cysts in major nerves. The present report is the first record of digenetic trematode infections in the Dungeness crab and the apparent restriction of the worm to nervous tissue is unusual if not unique in the Digenea. Because of the absence of grossly recognizable lesions and the small samples excised at necropsy, both the incidence and intensity of infection in Dungeness crab populations are almost certainly higher than indicted by our data.     

Seasonal and site specific variation in the component community structure of intestinal helminths in Apodemus sylvaticus from three contrasting habitats in south-east England

Seasonal fluctuations in the prevalence and abundance of infection with intestinal helminths were studied in Apodemus sylvaticus (wood mouse, n = 399), from three contrasting habitats in southern England, to test the hypothesis that both intrinsic (host sex, age) and extrinsic (season, site) factors influence parasite species richness and abundance. Five species of helminths were recovered but only one of these (Capillaria murissylvatici) was site-specific (Dungeness). Total species richness was therefore 5 at Dungeness and 4 at the other two sites. Mean species richness was 1.4, but in adult mice there was a pronounced difference between the sites, and an independent highly significant effect of season. Syphacia stroma and Corrigia vitta both showed marked differences between sites in respect of prevalence and abundance of infection. Capillaria murissylvatici was encountered at Dungeness mostly in the spring whereas seasonal changes in abundance of S. stroma were consistent across all three sites. Seasonal fluctuations in the abundance of Catenotaenia pusilla were compounded by differences between sites. Host sex was not a significant factor in any species, although a posteriori analysis of S. stroma worm burdens for the Isle of Wight site revealed a moderate local sex effect. Overall the principal determinants of variation in helminth burdens were the extrinsic factors, site and season.     

Population dynamics of lichenicolous mites at Dungeness

BARLOW, S. L. & FERRY, B. W., 1989. Population dynamics of lichenicolous mites at Dungeness . A quantitative and, to a degree qualitative, assessment of mite populations was made on seven lichen species of the late succession communities at Dungeness.
No specific mite numbers/lichen species association was found, but a cyclic, bi-modal response curve was obtained for general mite numbers on all seven lichen species samples (F = 25.01, P <0.001).
A range of climatic parameters were assessed in relation to the mite population on lichens. Only temperature was shown to be correlated (negatively) with mite numbers (F = 6.3, P <0.05), whilst rainfall and humidity were not significantly correlated (F = 3.99, P £0.05, and F = 0.52, P £0.4 respectively).     

A comparison of realised niche relations of species in New Zealand and Britain

Summary Many plant species prominent in the native vegetation of the dry shingle banks at Dungeness (Britain) are also prominent as exotics in the dry Upper Clutha catchment (New Zealand). To examine the realised niche relations of these species, vegetation was sampled in the two areas. Inverse classification and ordination were used to determine the relative beta niches of the species in the two areas. There was little agreement; it seems that the exotic species in the Upper Clutha were pre-adapted to different niches from those in their native range.     

Kinship analysis of Pacific salmon: insights into mating, homing, and timing of reproduction

Multilocus microsatellite genotypes were used to infer kinship and relatedness in two species of Pacific salmon from three populations in Washington State. Even in the absence of direct genetic data from parents, clustering of individuals according to allele sharing and reconstruction of parental genotypes allowed resolution of full- and half-sib relationships among 135 chinook salmon (Oncorhynchus tshawytscha) sampled as preemergent juveniles from 14 redds in the Dungeness River. Inferred reproductive behaviors included single-pair matings, polyandry in which females mated with two to three males at a single redd, polygyny in which males mated with two females at different redds, use of two redds by a single female, and use of one redd site by two females. Greater average relatedness (rxy) in the upper reach of the Dungeness River implied within-reach homing of returning adults. In steelhead trout (O. mykiss), the frequency of related pairs (dyads) of mature individuals that migrated up Snow Creek less than a week apart was greater than expected for randomly chosen dyads, as was the frequency of steelhead dyads that were spawned on the same day in the Forks Creek hatchery. These results imply a heritable basis for upstream migration date and maturation date in steelhead trout.     

Responses of bender apodeme tension receptors in the Dungeness crab,Cancer magister

Receptors monitoring tension are located on the apodemes of the bender (productor propoditis) muscle of walking legs and chelipeds of the Dungeness crab, Cancer magister. The bipolar neurons form a nerve, the bender apodeme sensory nerve (BASN), which joins the CP1 chordotonal organ nerve proximally, BASN units exhibit spontaneous activity at rest, and fire bursts of action potentials to rapid passive reduction of the carpopodite-propodite joint. Isometric contraction of the bender muscle results in BASN output that is directly related to force. Afferent activity ceases upon quick release of isometric tension, when tension drops to zero, and the unloaded muscle contracts isotonically.     

Uptake of DOM by Nemertean Worms: Association of Worms with Arthrodial Membranes

SYNOPSIS. Carcinonemertes errans is a nemertean worm, the juvenilesof which are found as epibionts on the Dungeness crab, Cancermagister, in close association with the arthrodial membranesof the crabs. The juvenile nemerteans appear to have no meansof taking in particulate food but survive for many months onthe surface of the host. We show that the juvenile C. erransare capable of removing amino acids from dilute solution insea water, that the water near the arthrodial membranes wherethe worms are found contains high concentrations of primaryamines, and that there is a low resistance pathway for low molecularweight amino acids across the arthrodial membrane examined invitro.     

A ciliate infection (Paranophrys sp.) in laboratory-held Dungeness crabs,Cancer magister

A ciliate infection ascribed to the genus Paranophrys was found in early adult Dungeness crabs, Cancer magister, held in laboratory bioassay facilities, and in outdoor flow-through tanks in Newport, Oregon. Infections proved lethal as ciliates multiplied to high densities in the blood and tissues causing degeneration and necrosis of musculature. All infected crabs had recent wounds through the exoskeleton which probably provided a portal of entry, and the elapsed time between infliction of a wound and gross symptoms of stress was estimated at 9 days although animals died as late as 26 days. The nature of Paranophrys infections in C. magister, i.e., as an opportunistic pathogen of cultured animals and/or a disease in wild populations of this crab is discussed.