Sublittoral hard substrate communities off Helgoland

In the Helgoland region eight sublittoral hard substrate communities occur. These communities were stationary in time during the years 1987–1989. The major governing parameters are the available amount of daylight and the degree of exposure to water movement. In the photic zone, three communities are met with, one of which is widespread and appears to be independent of the exposure to water movement. Under exposed conditions, at the lower border of the photic zone, a second community is observed. A third community is established on erosive muschelkalk substrates. In the aphotic zone also, three communities are found. The distribution of these communities is related to the rate of water movement. One community is divided into three variants, with different preferences regarding the angle of inclination and nature of the substrates. In the artificially constructed harbours, where sedimentation exceeds erosion, two different communities have settled. In the community under moderately sheltered conditions many species are found which also occur in the natural photic zone. Under extremely sheltered conditions a group of species has become dominant which is very rare in the Helgoland region outside the quay-walls but which has been described as being characteristic for sheltered localities elsewhere.     

Evidence on ecotone concepts from switch,environmental and anthropogenic ecotones

Abstract. Four contrasting ecotones were sampled to address three questions: (1) Are there ‘ecotonal’ species, (2) Do ecotones possess higher (or lower) species richness than the adjacent communities? and (3) Are exotic species more likely to occur in ecotones? One ecotone was edaphic, one was apparently caused by a positive‐feedback switch, one was environmental/anthropogenic and one was entirely anthropogenic. The exact position of each ecotone was established from the spatial change in ordination scores. Ecotonal species, in the sense of species mainly restricted to the ecotone at the site, were present in all four ecotones. All but one of the ecotonal species were native. The switch ecotone and the purely anthropogenic ecotone also contained native species that were significantly more frequent in the ecotone than in either adjacent community. Species richness was intermediate between that of the two adjacent communities in three of the ecotones. In the environmental/anthropogenic ecotone, species richness was higher than in adjacent communities, but not significantly so. There were appreciable numbers of exotic species in the two ecotones with anthropogenic influence, one of which had a proportion of exotic species intermediate between the two adjacent communities. Contrary to theory, the proportion of exotic species in the second ecotone was significantly lower than in either adjacent community. We conclude that all three features we examined depend on the particular ecological conditions and the ecology of the species present; they are not intrinsic properties of ecotones.     

Bacterial Communities in Central European Bumblebees: Low Diversity and High Specificity

Recent studies on the microbial flora of the honeybee gut have revealed an apparently highly specific community of resident bacteria that might play a role in immune defence and food preservation for their hosts. However, at present, very little is known about the diversity and ecology of bacteria occurring in non-domesticated bees like bumblebees, which are of similar importance as honeybees for the pollination of agricultural and wild flowers. To fill this gap in knowledge, we examined six of the most common bumblebee species in Central Europe from three locations in Germany and Switzerland for their bacterial communities. We used a culture-independent molecular approach based on sequencing the 16S rRNA gene from a selection of individuals and examining a larger number of samples by terminal restriction fragment length polymorphism profiles. The gut flora was dominated by very few and mostly undescribed groups of bacteria belonging to the Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria. This core set of bacteria was present in all of the examined bumblebee species. These bacteria are similar to, but distinct from, bacteria previously described from the honeybee gut. Significant differences were observed between the communities of bacteria in the different bumblebee species; the effect of sampling location was less strong. A novel group of Betaproteobacteria additionally shows evidence for host species-specific genotypes. The gut flora of bumblebees therefore is apparently composed of relatively few highly specialized bacteria, indicating a strong interaction and possibly important functions with their hosts.     

The role of waves in the colonisation of terrestrial sediments deposited in the marine environment

Elevated rates of sediment run-off, as a result of changes in land-use and climate, are a significant threat to marine coastal communities, with a potential to cause broad-scale, long-term alteration of habitats. Individual sedimentation events can smother estuarine flats with terrigenous sediments, creating a significant disturbance to local benthic communities. Variations in the degree to which a habitat is altered, the rate at which mixing occurs, and species-specific dispersal and responses to the altered habitat, suggest that colonisation of terrestrial sediment depositions will vary with location, both between and within estuaries. This study was designed to explore the effect that variations in wave-induced hydrodynamics would have on long-term colonisation of terrestrial sediment depositions on intertidal flats. Sites for the experimental deposition of terrestrial sediment were located along a gradient in wave exposure, with only limited variation in immersion times (30 min) and ambient sediment particle sizes (predominantly fine sand). Over 20 months, periodic measurements were made of factors predicted to affect colonisation: the sediment characteristics of the deposited sediment; local-scale wave climate; bioturbation of the deposited sediment; and local populations of benthic invertebrates. Neither opportunistic use of the new resource, progressive recovery or facilitation by colonising macrofauna was observed. Little vertical mixing of the deposited and existing sediment by either waves or bioturbators occurred; instead bedload transport was the dominant process. Local differences in hydrodynamic conditions and macrobenthic communities resulted in site-specific colonisation of the experimental plots. The strength and duration of the macrofaunal response to deposited sediment observed in this study suggest that chronic small-scale (m's) patchy deposition of terrestrial sediment in the intertidal marine environment has a strong potential to alter both habitats and communities.     

Nitrogen economy of endolithic microbial communities in hot and cold deserts

The source of combined nitrogen in endolithic microbial communities was studied in samples from desert localities in North and South America, the Middle East, South Africa, and Antarctica. Nitrogen fixation (acetylene reduction) seems to occur only exceptionally. Evidence suggests that, in general, the nitrogen source for endolithic microorganisms in deserts is abiotically fixed nitrogen produced by atmospheric electric discharges (lightning or aurorae), conveyed to the rock by atmospheric precipitation. Nitrogen is apparently not a limiting factor in these low-productivity communities. An incomplete nitrogen cycle seems to be present which includes the following pathways: supply of nitrates and ammonia from the atmosphere; decomposition of organic matter to ammonia; reassimilation of ammonia; ammonia volatilization; loss of organic matter through weathering (only in certain Antarctic rocks); biological nitrogen fixation (exceptional).     

A new species of Eriopeltis Signoret (Homoptera: Coccidae) from Britain

Abstract. Eriopeltis varleyi from Wytham in Britain is described as new. The adult female and male are described and all stages are illustrated. Keys are provided for the identification of all known species of Eriopeltis, and to the males of the three species known from Britain. E. varleyi is univoltine and apparently specific to Brachypodiumpinnatum (L.) Beauv. Males and females occur in equal proportions, but many more males were produced when populations were reared under very warm dry conditions in the laboratory. The population studied at Wytham was parasitized by a number of species of chalcid wasps and a chamaemyid fly egg predator.     

Basal lamina glycoproteins laminin and type IV collagen are assembled into a fine-fibered matrix in cultures of a teratocarcinoma-derived endodermal cell line

Extracellular matrix glycoproteins synthesized and deposited by a mouse teratocarcinoma-derived endodermal cell line (PYS-2) in culture were analysed by metabolic labelling and immunochemical methods, and the matrix structure was studied by immunofluorescence and electron microscopy. PYS-2 cells secreted two major high-molecular weight glycoproteins, laminin and type IV collagen, which were deposited in apparently unprocessed form under the cells into a lamellar matrix composed of a loose network of fine fibrils and attached dense grains. The cells did not synthesize detectable amounts of fibronectin, but the matrix was found to bind fibronectin from the culture medium. The matrix structure was sensitive to bacterial collagenase indicating a role for type IV collagen in matrix integrity. The PYS-2 matrix which contains defined basal lamina glycoproteins provides possibilities for in vitro studies on the organization of deposited basal lamina components.     

Conservation of Borneo biodiversity: do small lowland parks have a role,or are big inland sanctuaries sufficient? Brunei as an example

Borneo, the World’s fourth largest island, represents a continental mass sandwiched between volcanic arcs. Patterns of tree species richness, here proposed as proxy for overall biodiversity, and endemism within the island are described and interpreted with special reference to Dipterocarpaceae. Most of Borneo’s surface is sedimentary shales, mostly inland, and sandstones, mostly coastal, deposited in past epicontinental seas. The shales mainly support the regional West Malesian (Sundaland) tree flora, while the Neogene coastal hills, especially in the north-west, support the richest communities which are also richest in endemics. The forests of these hills, which include the richest tree communities in the Old World and are therefore of global significance, are accessible and critically endangered. Priorities for their future management are outlined.     

红树植物多样性及其研究进展

红树植物是分布于热带、亚热带海岸潮间的木本植物群落。因因适应海岸带和作的生长环境形成了独特的形态结构和生理生态特性。红树林是海岸有重要价值的湿地。论述了红树植物的物 多样性、适应多样性、物侯多样性以及分子水平的多样性及其研究进展。     

The occurrence of tumors in the minnow Phoxinus phoxinus (L.), their influence upon the parasite fauna, component community of parasites, and organism of the host

The occurrence of tumors, their influence upon the organism of Phoxinus phoxinus (L.), its parasite fauna, and parasite component community were investigated in the upstream of the Pechora River. According to the data obtained, tumors could occur in the fishes of every age group, but one-year (0+) or two-year (1+) old minnow is affected by tumors more frequently. The tumors lesion extensiveness ranges from 0.02 to 3 %. From 1 to 3 tumors were recorded on one fish specimen. The investigated tumors were in progressive stage (Georgiev, 2000), since the vascular ingrowth and dissemination (in few cases) of the tumors were observed. Tumors are colored in intensive-black and taupe. The taupe tumors usually have a compact capsule at its peripheries, which isolates affected tissue from muscle fibers. In the intensive-black tumors the invasion of tumor cells to the adjacent transversal striated musculature is observed. Distinct symptoms of necrosis are revealed in all slides of the new growths. Blood vessels are formed in most tumors, and the blood flow is recorded before the completion of the vessels forming, that apparently supplies the tumors feeding. Metastases in different organs revealed in several minnow specimens. Tumor affected individuals of the minnow has parasite species complex practically identical (by species list and quantity) with the same of the even-aged unaffected fishes. However, the parasite component communities of the affected individuals are characterized by 4 groups of species, while the parasite component communities of the intact individuals--by 3 groups. The parasite communities of affected and unaffected one-year fishes are similar by the number of the groups of species, but differ in the number of species.     

Vegetation of the woodland‐steppe transition at the southeastern edge of the Inner Mongolian Plateau

Abstract. The vegetation of the woodland‐steppe transition in southeastern Inner Mongolia, where the East Asian monsoon climate reaches its northwestern edge, is described and analysed in this paper. The communities are classified in a phytocoenological way. 12 major types of woodland, shrubland, meadow, fen, open woodland and steppe are differentiated and described on the basis of 133 phytosociological relevés. Detrended Correspondence Analysis shows that precipitation plays a crucial role in the distribution of grassland communities while woodland and shrubland communities are controlled by both warmth and humidity conditions. Four vegetation zones can be distinguished. From the woodland to the woodland‐grassland zone, the temperature decreases and the precipitation increases with increasing altitude, which leads to the conditions suitable for the meadow and fen communities. In the direction of the woodland‐steppe zone the temperature increases while the precipitation decreases with the gradual lowering of the altitude; the steppe communities form a matrix while the woodlands have a patchy distribution. From the woodland‐steppe to the steppe zone, the precipitation rather than temperature decreases; as a result the woodland communities disappear gradually. On a local scale, geomorphologic conditions determine the vegetation pattern of the study area. Due to the existence of a sandy substrate different woodland types occur together in the woodland‐steppe transition. The local distribution of woodland and steppe communities is dependent on slope conditions. In addition, human disturbance has also influenced the composition of plant communities.     

Biomicrospheres Generate Ooids in the Laboratory

Precipitation of calcium carbonate is widespread in microbial communities (biofilms, microbial mats, etc.) and plays an important role in the nucleation and formation of stromatolites, onkolites and oolites. Here we report carbonate precipitation under laboratory conditions in defined spherical microbial communities. These microbial communities represent a symbiosis of cyanobacteria, diatoms and heterotrophic bacteria. Calcification structures always reflect the shape of microbial aggregates resulting from the formation of coalescent grains in chains. Position of the single carbonate crystals follows the spherical arrangement of the filamentous cyanobacteria and results in hollow spheres. The structure of the spherical biofilm determines the form of the carbonate layer. Tiny calcite scleres, deposited by spherical microbial communities in concentric arrangement are observed continuously, documented and described in the laboratory cultures. They may represent the precursors of oolites and are the first reproducible laboratory system generating ooids without a hard nucleus within an otherwise laminated microbial mat community.     

A large arthropod from the Lower Old Red Sandstone (Early Devonian) of Tredomen Quarry,south Wales

Abstract: A large arthropod from the Lower Old Red Sandstone of Tredomen Quarry, near Brecon, Powys, southeast Wales is described as Bennettarthra annwnensis gen. et sp. nov. The animal is incomplete, preserved to a length of 30 cm, and displays a trunk of at least ten, non‐diplopodous segments. The trunk may be delineated into two distinct tagmata: the anterior three somites (as preserved in the fossil) appearing ornamented and apparently bearing robust, ornamented, segmented walking legs; the posterior somites appearing relatively smooth, of which at least the anterior five somites bear simple, sclerotized rudimentary appendages. Unfortunately, diagnostic features such as detailed appendage arrangement for the anterior tagma and the head and tail region are largely missing, frustrating detailed classification. However, the delineation of the non‐diplopodous trunk into two tagmata, each displaying apparently distinct appendage morphology, together with the large size of the fossil, is a feature hitherto unknown in any arthropods from terrestrial/freshwater fossil assemblages of this age. In terms of taxonomic placement, based on the currently limited morphological evidence, a malacostracan or hexapodan affinity for Bennettarthra appears most likely. The animal is preserved in laminated sandstone with plant debris, osteostracan fish and abundant thin irregularly shaped carbonaceous sheets. The sandstone was deposited from a river flood that buried and preserved articulated fish and Bennettarthra. These animals were probably buried alive and suffocated in sediment. Trace fossils including Diplichnites trackways and Beaconites burrows occur in close stratigraphic proximity to the flood deposit, and it is possible that this arthropod was the maker of one or both of these traces.     

Species-diversity patterns in some middle ordovician communities from California - Nevada

Certain fossil communities may be recognized in collections from Early—mid-Middle Ordovician age rock units in the Inyo Mountains, California, and the Bare and Ranger Mountains in adjacent Nevada. These dominantly brachiopod—tribolite communities lived in several different, shallow shelf-sea environments. The communities appear to have maintained their diversity and evenness within relatively narrow limits for as long as the major aspects of the environments in which they lived, remained little changed (periods of about 1–2 m.y.). Some taxa occur in several communities (and are called wide-niched), and some occur in only a single community (and are called narrow-niched). Certain taxa that occur in large numbers in a single community appear to have been far more tolerant of particular environmental conditions than were associated taxa in the same community that are represented by few individuals. Counts of such abundant taxa that are restricted to a single community (and are thus considered narrow-niched) compared with counts of the individuals of those taxa found in several communities (and thus are considered wide-niched) indicate that the taxa highly tolerant of particular environmental conditions may be represented by more individuals than are the wide-niched taxa.     

Phytosociology of terricolous lichen vegetation in the Cairngorm Mountains,Scotland

Abstract:The results of an investigation into the lichen vegetation associated with vascular plant communities in the Scottish Highlands are presented. Most lichen species rarely occur in homogeneous stands of vascular plant vegetation, either occurring around the edges of recognized National Vegetation Classification (NVC) communities or in small-scale mosaics with them. However, some lichen species have a high fidelity to the more open NVC communities. The problems associated with applying NVC survey techniques to lichen assemblages are described and discussed.     

CYTOLOGICAL STUDIES OF OEDOGONIUM. I. OOSPORE GERMINATION IN O. FOVEOLATUM

Details of oospore germination, including meiosis, are described and illustrated as they appear in the homothallic Oedogonium foveolatum. Unequivocal meiotic division is demonstrated to occur within 12 hr prior to the liberation of the motile tetrad cells. The development and liberation of the meiotic products are described as are instances of anomalous oospore germination. In some cases, meiosis apparently fails to occur, and a single, diploid germling invariably results. Various factors influencing oospore germination are discussed, including an apparent absolute light requirement.     

Surgical repair of the lacerated cervix in the mare

Surgery was performed to repair lacerations which prevented cervical closure in thirteen mares. All lacerations involved the portion of the cervix that protrudes into the vagina. There did not appear to be a predisposition for lacerations to occur in any one position about the perimeter of the cervix. Nine mares had one laceration and four mares had two lacerations. Although the lacerations were presumed to have occurred at parturition, they apparently were not associated with dystocia. The method of surgical repair is described. Eight mares were bred after surgery, and five conceived.