A taxonomic study of thePoa macrocalyx complex,with particular reference to the populations in eastern Hokkaido

An attempt was made to investigate some populations of thePoa macrocalyx complex in eastern Hokkaido in relation to the taxonomy of this complex. Individual specimens preserved in TI, KYO and TNS were also studied. Chromosome counts of 2n=42 were obtained in the majority of a total of 84 collections, and counts of 2n=63 (incl. ca. 63), ca. 70 and 84 were also made in a few collections. High percentages of viable pollen were observed. The morphological features which were designated by previous authors to be significant in separatingPoa sachalinensis fromP. macrocalyx and in discriminating between the varieties ofP. macrocalyx were critically examined with emphasis on the observations of infra-population variation. It was confirmed that (1) the populations of thePoa macrocalyx complex in eastern Hokkaido are greatly variable morphologically and are also in a dynamic state cytogenetically, (2) plants of this complex in eastern Hokkaido belong to one and the same species,P. macrocalyx, and the varietiesfallax, scabriflora andtatewakiana may be merely morphs, and (3) some plants which are somewhat different from the plants in eastern Hokkaido with respect to glume features are distributed in Sakhalin, and northern and central Hokkaido. Some problems which should be subjected to further studies are pointed out.     

Biogeography of limno-terrestrial Tardigrada, with particular reference to the Antarctic fauna

The Tardigrada is a cosmopolitan phylum of pre-Pangaean origin, yet tardigrade families and genera show distinct biogeographic components isolated by two major geological events. Separate Laurasian and Gondwanan familial clusters correlate with the Triassic disintegration of Pangaea, while discrete Antarctic, Australian and New Zealand familial/generic clusters relate to the subsequent Jurassic/Cretaceous disintegration of Gondwana.     

Evolutionary ecology of colonial reef-organisms, with particular reference to corals

Sedentary reef-organisms such as sponges, colonial coelenterates, bryozoans and compound ascidians produce repeated modules (aquiferous systems, polyps, zooids) as they grow. Modular construction alleviates constraints on biomass imposed by mechanical and energetic factors that are functions of the surface area to volume ratio. Colonies thus may grow large whilst preserving optimal modular dimensions. Among corals, optimal polyp size is smaller in the more autotrophic than in the more heterotrophic species. Modular construction allows flexibility of growth form, which can adapt to factors such as water currents, silting, light intensity and proximity of competitors. Modular colonies have great regenerative capacities, even separated fragments may survive and grow into new colonies. All fragments from a parental colony are genetically identical and large branching corals frequently undergo clonal propagation through fragmentation during storms. Soft corals can also fragment endogenously. By spreading the risk of mortality among independent units, the generation and dispersal of fragments lessens the likelihood of clonal extinction. In spite of their ability to propagate asexually, most benthic colonial animals also reproduce asexually. The selective advantages of the genetic diversity among sexually produced offspring seem not to be linked with dispersal, but probably lie in the biological interactions with competitors, predators and pathogens in the parental habitat. Age at first sexual maturity and the proportional investment of resources in sexual reproduction are related to colonial survivorship. Small branching corals on reef flats grow quickly, attain sexual maturity within 1–4 years, planulate extensively, but reach only small sizes before dying. Massive corals are longer lived and have the opposite characteristics of growth and reproduction. Most sessile reef organisms compete for space, food or light. Faster growers can potentially outcompete slower growers, but are often prevented from doing so by several forms of aggression from competitors and by the damage inflicted by storms. Competitive interactions among sedentary organisms on coral reefs are unlikely to be linear or deterministic, and so the co-existence of diverse species is possible.     

Molecular cytogenetics and taxonomy of insects,with particular reference to the coleoptera

We assess and review the impact of the new cytogenetic techniques in insects for their roles in taxonomy and for a better knowledge of their chromosomal structure. Particular emphasis is given to molecular cytogenetics by fluorescent in situ hybridization, localization of AT- or GC-rich regions with fluorochromes, and restriction endonuclease banding in beetle chromosomes. The main features of the cytogenetics of Coleoptera are treated in detail, taking into account the range of variation in chromosome number and genome size, and our in-depth findings on the constitutive heterochromatin and satellite DNAs of tenebrionid beetles. Some other topics of interest for insect cytogenetics, such as the meiotic association of sex chromosomes, the nucleolar organizing regions (NORs), and the molecular constitution of telomeres, are also discussed from the taxonomic and structural viewpoints.     

The effects of land use on freshwater fish in South Africa,with particular reference to Natal

Summary Freshwater fish live in an environment that is liable to modification by human activities. Instability of South African rivers makes them particularly vulnerable to changes brought about by settlement of the land.Indigenous species number 89, of which 47 belong to the Cyprinidae; eight exotic species are also established in South African natural fresh waters. These fish vary considerably in their tolerances, but the habitat of most species has undergone deterioration as a result of agriculture, pollution or water abstraction.Agricultural land-use effects are mainly (i) an increase in soil erosion leading to higher silt loads, which adversely affect the habitat, both for fish and for fish food and (ii) reduced low flows and higher flood-crests.Domestic and industrial pollution are liable to have disastrous effects, but fortunately serious pollution has so far been of localized occurrence and has affected mainly smaller streams.Dam building has had a major impact on fish populations. Below the dams some natural habitats have been impaired and migratory movements curtailed. The impoundments themselves on the other hand, have provided an enlarged and stable environment leading to population increases. Many of the larger impoundments carry indigenous fish, other dams have provided a habitat for exotic species.Progressive development of the land makes changes in natural waterways inevitable but conservation of mountain catchments and the building of dams are likely to prevent decimation of the more economically important species. Special steps may be needed to maintain the habitats of certain rare endemic species.Progressive development of the land makes changes in natural waterways inevitable but conservation of mountain catchments and the building of dams are likely to prevent decimation of the more economically important species. Special steps may be needed to maintain the habitats of certain rare endemic species.

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Zusammenfassung Süwasserfische leben in einer Umwelt, die infolge menschlicher Tätigkeiten leicht geändert werden kann. Die südafrikanischen Flüsse sind im allgemeinen unbeständig und daher besonders empfindlich gegen die Veränderungen, die die Besiedlung des Landes mit sich bringt.Es gibt 89 einheimische Fischarten, wovon 47 zu den Cypriniden gehören; 8 exotische Arten sind auch in natürlichen Gewässern eingebürgert worden. Trotz der ganz verschiedenen Toleranzen dieser Arten haben die Umweltsbedingungen für die meisten jedoch infolge von Landwirtschaft, Wasserverunreinigung oder Wasserabstraktion eine Verschlechterung erfahren.Die hauptsächlichsten Folgen landwirtschaftlicher Bodennutzung sind (i) eine Zunahme der Bodenerosion und die damit verbundene Verschlammung, die auf das Habitat ungünstig einwirkt, sowohl für die Fische als auch für das Fischfutter, und (ii) verringerter Durchflu bei niedrigem Wasserstand und höhere Wasserstände zu Flutzeiten.Die Verunreinigung, sei sie haushältlicher oder industrieller Herkunft, hat gewöhnlich katastrophale Auswirkungen. Glücklicherweise sind ernsthafte Verunreinigungen bis jetzt örtlich beschränkt geblieben und haben hauptsächlich kleinere Flüsse betroffen.Der Bau von Talsperren hat einen besonderen Einflu auf die Fischpopulationen gehabt. Unterhalb der Talsperren sind die Lebensbedingugen zu Ungunsten einiger Arten geändert worden, und Zugbewegungen sind eingeschränkt worden. Die entstandenen Stauseen an sich haben anderseits eine vergröerter und stabile Umgebung beschafft, die zu Populationszunahmen führte. Viele der gröeren Staussen sind von einheimischen Fischen bevölkert, andere beschaffen Lebensbedingugen für exotische Arten.Die fortschreitende Entwicklung der Bodennutzung bringt unvermeidliche Veränderungen der natürlichen Wasserwege mit sich. Der Schutz der Wasserauffangsgebiete in den Bergen und der Bau von Talsperren werden jedoch wahrscheinlich das Fortbestehen der wirtschaftlich wichtigen Fischarten sichern. Besondere Vorkehrungen mögen jedoch nötig sein, um die Lebensbedingugen seltener einheimischer Arten zu erhalten.

     

An HRP study in the cat of brainstem projections to the spinal cord, with particular reference to sacral afferents

Cells of origin of the spinal projections from the brainstem of the cat have been studied by means of retrograde axonal transport of horseradish peroxidase (HRP). Following injections of HRP into various levels of the spinal cord, many labeled cells were found in several structures in the brainstem. The labeled cells occurred in the raphe nuclei, reticular formation, vestibular complex, and nuclei of the dorsolateral pontine tegmentum. In the dorsolateral pontine tegmentum, many labeled cells were found in the nuclei of locus coeruleus, subcoeruleus and K?lliker-Fuse. In the coeruleus and subcoeruleus, the greatest number of labeled cells were found, when HRP was injected into the sacral cord. No difference emerged, however, in the number of labeled cells appearing in the K?lliker-Fuse nucleus after injection of the enzyme into different levels of the spinal cord. It appears that neurons in the lateral vestibular nucleus which project to different levels of the spinal cord are located in different parts of this nucleus.