Mechanisms of species‐sorting: effect of habitat occupancy on aphids' host plant selection

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Ecological adaptations of grassland‐inhabiting flightless Orthoptera: Fulvoscirtes and Acanthoscirtes,two new genera of African Karniellina (Orthoptera,Tettigoniidae, Conocephalinae,Conocephalini)

Two new genera, Fulvoscirtes n.gen. and Acanthoscirtes n.gen. , are established within the subtribe Karniellina of Conocephalini. Fulvoscirtes is based on Xiphidion kilimandjaricum Sjöstedt, 1909 and Acanthoscirtes on Phlesirtes kevani Chopard from northern Kenya. The majority of Fulvoscirtes spp. are confined to open grasslands in the submontane zone of mountains. Fulvoscirtes contains eight species, seven of which are newly described in this paper. Three species and one subspecies occur on Mt Kilimanjaro. These are F. kilimandjaricum (Sjöstedt) constricted to the southern slopes, F. legumishera n.sp. confined to the northern side and F. sylvaticus n.sp. occurring on the western side of Kilimanjaro and on the eastern slopes of Mt Meru. Fulvoscirtes fulvus n.sp. is divided into two subspecies, F. fulvus fulvus n.ssp. found in the submontane zone of east Kilimanjaro and F. fulvus parensis n.ssp. in submontane to montane localities of the North and South Pare mountains. Fulvoscirtes fulvotaitensis n.sp. occurs in the Taita Hills of southern Kenya. Fulvoscirtes viridis n.sp. is described from savannah habitats between Mts Longido and Meru. Fulvoscirtes laticercus n.sp. is found in the Kenyan highlands, while the most southerly occurring species, Fulvoscirtes manyara n.sp. , is found on Mt Hanang and the Mbulu highlands of northwestern Tanzania. Acanthoscirtes contains three species, of which A. albostriatus n.sp. is described newly from savannah habitas of eastern Kilimanjaro. Information is given on the ecology and the acoustic behaviour of some of the species together with keys to the genera of the Karniellina and the species of Fulvoscirtes and Acanthoscirtes. The genera of Karniellina probably evolved at a time when grasslands spread in East Africa due to an increasing aridification of the climate. The earliest lineage, the genus Karniella, is adapted to more forested habitats while the majority of the genera of Karniellina prefer open grasslands. Major splits within Karniellina probably occurred with the emergence of savannah grasslands due to the ongoing fragmentation of forest habitats several millions years ago, but most species within the genera are geologically young, their radiation being boosted by climatic fluctuations of the past 1–2 Ma.     

Morphology and Morphogenesis of Strobilidium caudatum (Fromentel), Meseres corlissi N. Sp., Halteria grandinella (Müller), and Strombidium rehwaldi N. Sp., and a Proposed Phylogenetic System for Oligotrich Ciliates (Protozoa,Ciliophora)1

ABSTRACT. The morphology and morphogenesis of some oligotrichs were investigated using protargol impregnation, silver carbonate impregnation and scanning electron microscopy. The somatic kineties of Strobilidium caudatum form a spiral at the posterior pole. Strobilidiids without such a spiral are transferred to the genus Rimostrombidium. Fourteen new combinations and a nomen novum, Strobilidium kahli, are necessary, Meseres corlissi n. sp. is characterized by eight somatic kineties composed of long cilia which are not fused to “bristles” as they are in Halteria. Strombidium oblongum shows similar characteristics and is thus combined with Meseres. Strombidium rehwaldi n. sp. has an anterior and an equatorial girdle of extrusomes. The morphogenesis of Meseres and Halteria is very similar, i.e. the entire somatic ciliature and the oral primordium originate apokinetally on the cell surface; the parental somatic ciliature is resorbed. In strobilidiids and tintinnids, the oral anlagen develop in a subsurface pouch and the parental somatic kineties, which are not resorbed, elongate by intrakinetal proliferation of basal bodies. In strombidiids, the oral primordium develops in an intracellular sac or tube. These morphogenetic peculiarities and distinct morphologic characters (e.g. arrangement of adoral membranelles) were applied in constructing a phylogenetic system for oligotrichs using hypotrichs as outgroup. This shows that halteriids are more closely related to hypotrichs than they are to other oligotrichs. The Halteriidae are thus raised to ordinal and subclass ranks, Halteriida n. ord., Halteriia n. subcl.     

THERAPEUTIC STRATEGIES FOR THE INHIBITION OF INDUCIBLE NITRIC OXIDE SYNTHASE—POTENTIAL FOR A NOVEL CLASS OF ANTI-INFLAMMATORY AGENTS

In recent years, NO, a gas previously considered a potentially toxic chemical, has become established as a diffusible universal messenger mediating cell—cell communication throughout the body. In mammals, NO is a recognized mediator of blood vessel relaxation that helps to maintain blood pressure. In the central nervous system NO acts as a non-conventional neurotransmitter and participates in the establishment of long-term plasticity required for memory formation. In addition, NO is responsible for some parts of the host response to sepsis and inflammation and contributes to certain disease states. A number of strategies have emerged with regard to a pharmacological control of pathological NO overproductions. This review will discuss these novel therapeutic approaches that may provide new means for clinical medicine.     

A Marine Euplotes (Ciliophora, Hypotrichida) with Reduced Number of Prezygotic Micronuclear Divisions

In contradistinction to the pattern of 3 prezygotic micronuclear divisions found in 10 species of Euplotes, a marine species resembling Euplotes crassus in structure, has only 2 divisions. This atypical division pattern was observed in all matings involving the 4 available mating types. The critical stages of the nuclear events are demonstrated by using special strains having the micronuclear DNA content and chromosome number only 1/2 the normal values. The employment of such strains facilitates differentiation between the stationary and migratory pronuclei in a given conjugant and determination of the times of conclusion of prezygotic divisions and of the pronuclear exchange.     

A new genus of African Karniellina (Orthoptera,Tettigoniidae, Conocephalinae,Conocephalini): integrating morphological,molecular and bioacoustical data

Melanoscirtes gen.n. is established within Karniellina. The members of this subtribe are small conocephaline bush crickets, confined to Africa. Melanoscirtes is erected on Phlesirtes kibonotensis, a species restricted to forest clearings and forest edge in the submontane and montane zones of Mt. Kilimanjaro. A subspecies, M. kibonotensis uguenoensis, is described from the North Pare mountains, a mountain range of the Eastern Arc adjacent to Mt. Kilimanjaro. Further species of Melanoscirtes occur on other mountain ranges of the northern branch of the Eastern Arc mountains of northern Tanzania and southern Kenya. The South Pare mountains harbour M. shengenae; the West Usambaras, M. usambarensis, and the Taita Hills, M. taitensis. All species and subspecies of Melanoscirtes exhibit a similar morphology and occupy analogous habitats on the respective mountains. The song patterns for all species found within this genus are very similar, and this, together with evidence from molecular data, suggests that allopatric speciation is the reason for the biogeographic pattern found in this genus. A key for the subspecies and species of Melanoscirtes is provided.     

Long‐term trends in the diatom composition of the spring bloom of a German reservoir: is Aulacoseira subarctica favoured by warm winters?

1. Long‐term data on the meteorology, hydrology, physicochemistry and plankton of a reservoir and its tributaries in SE Germany run from 1976 until now. This dimictic reservoir changed from mesotrophic to eutrophic in the 1970s, remained eutrophic in the 1980s and returned to the mesotrophic state after a sharp reduction in P loading in 1990. 2. Phytoplankton biomass reaches an annual maximum in spring and consists almost entirely of diatoms. While Asterionella formosa was dominant until 1990, Aulacoseira subarctica became more frequent at the end of the 1990s and was particularly abundant in years with short winters. 3. Statistical analyses suggested that these changes were triggered primarily by the mild winters that were frequent after 1988. Climate‐related hydrophysical variables and the initial biomass of the diatoms at the beginning of the year, considered as an ‘inoculum’, were identified as most important. These variables explained 39% of the total variance of the relative abundance, whereas the change in trophic conditions was responsible for about 20%. 4. The absolute and relative abundance of A. subarctica was positively related to short ice cover, early ice‐out and a long‐lasting spring circulation. Owing to its physiological traits, and particularly its ability to survive under low‐light conditions, A. subarctica benefitted from short, mild winters. Under such conditions, it could sustain or establish a high initial biomass, whereas the concentrations of the other diatoms decreased over winter. However, this advantage may be lost if further warming causes an early onset of summer stratification. Because of its low population growth rate and requirement for high turbulence, A. subarctica needs long, cold springs to exploit the improved starting conditions and to become abundant. 5. In contrast to A. subarctica, A. formosa required a substantial soluble reactive phosphorus supply to compete successfully. The eutrophic conditions until 1990 were the prerequisite for its mass growth under low‐light and low‐temperature conditions during the spring. After reduction in P concentration from 1990, A. formosa declined and other diatom species became more abundant. 6. These other diatoms may be viewed as ‘stopgaps’ when conditions were not favourable for A. subarctica or A. formosa. Diatoma elongatum exploited brief circulation periods in years with low P loading. Synedra acus and Fragilaria crotonensis, because of their poor competitive ability at low light intensity, reached high density in the upper water column in the transitional period between spring circulation and summer stratification. 7. Our study suggests that climate‐related variables have crucial impacts on the spring phytoplankton dynamics of deep stratified waterbodies. They can mask the consequences of changes in the trophic conditions and, corresponding to the functional traits of the different phytoplankton species, also decisively control their relative abundances. In this reservoir, the warmer winters and prolonged spring circulations did not only lead to high phytoplankton biomass (despite considerably reduced nutrient loads) but also cause a marked shift in the diatom assemblage during the spring bloom.     

Gnathostomulida from Hawaii

As thc second in a series on Gnathostomulida from the Pacific Ocean this paper describes an additional eight species from Hawaii of which four are new to science. All are accommodated within existing genera: Haplognathia asymmetrica sp.n., Haplognathia ruberrima (Sterrer, 1966), Haplognathia rufa sp.n., Cosmognathia arcus Sterrer, 1991, Cosmognathia manubrium sp.n., Pterognathia ctenifera Sterrer, 1970, Pterognathia hawaiiensis sp.n., and Austrognathia novaeze landiae Sterrer, 1991.     

Strategies of passerine migration across the Mediterranean Sea and the Sahara Desert: a radar study

Radar observations of the diurnal timing of bird migration in the Sahara Desert are presented for autumn migration. Study sites were on a transect along the north-south migratory direction. Three groups of birds migrating either during day, evening or night in the northern part of the Western desert in Egypt were identified. The maximum of day and night groups occurred later the further south the study sites were. Based on the distance between sites and the timing of peak migration, birds were flying at an estimated ground speed of about 20 m/s. The maximum of the evening group was at about 21:00 h at all sites. The three groups were classified according to three different strategies of migration across the Mediterranean Sea and the Sahara Desert: (1) the day group of birds performed a non-stop flight across the sea and at least the northern part of the desert; [2] the night group performed an intermittent migratory strategy with stopover at the coast of Egypt to continue migration the next evening; (3) the evening group birds were also intermittent migratory fliers, but they stopped somewhere in the desert after a continuous flight across the sea and part of the desert. About 20% of all migrants are involved in non-stop migration and 80% in intermittent migration with stopover at the coast (70%) or with stopover in the desert (10%). It is argued that any species of small passerine has the option to use any of the three strategies.     

Ostracode fauna, stratigraphy and definition of the Beyrichienkalk sequence

An essential clue to the uppermost Silurian in the submarine Baltic arca is the Beyrichienkalk. According to recent investigations it constitutes a glacial drift boulder sequence characterized by four ostracode associations with about sixty species. In the correlation of ostracode zones of Baltoscandia these associations form a connecting link and thus are also of biozonal character. In the terms of regional stratigraphic units (East Baltic arca). the lower stratigraphic boundary of this sequence lies approximately at the beginning of the Kuressaare beds and the top in the upper Ohesaare beds. The term Beyrichienkalk should be used for those glacial erratics that are characterized by typical ostracodes of the four associations defined here.