Evidence that two species of aphid ingest food through an open stylet sheath

Zusammenfassung Myzus persicae undAcyrthosiphon pisum nehmen beim Saugen an Saccharoselösungen Kohlenstoffteilchen bis zu einem Durchmesser von 0,5–1 auf (ungefähre Weite des Nahrungskanals der Stechborsten). Demnach muss die um die Stechborsten ausgebildete Speichelscheide am Ende offen sein. BeiA. pisum konnte beobachtet werden, dass grössere Kohlenstoffteilchen an der Stechborstenspitze das Saugen deutlich behindern, was durch Bewegungen der Stechborsten und erneute Speichelabgabe behoben werden konnte.

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The contribution of this author was made while on sabbatical leave from the Waite Institute, University of Adelaide (South Australia), and supported in part by Public Health Service Training Grant No. 5T1-AI-218, from the National Institute of Allergy and Infectious Diseases (USA).     

Protection of a hermit crab by its symbiotic sea anemoneCalliactis tricolor

Zusammenfassung Experimenteller Nachweis, dass Einsiedlerkrebse,Pagurus pollicaris, mit symbiontischer Seeanemone,Calliactis tricolor, anf ihrer Schale vom natürlichen Feind der Krabbe,Calappa flammea, weitgehend gemieden werden.

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The authors wish to thankGeorce Kirvin of Quality Sea Foods, Port St. Joe, Florida, for providing boat time, and Ross McWilliams for help in collecting the experimental animals.     

A dioestrous increase in thymocyte proliferation during the oestrous cycle

Summary Coitus, which precedes internal fertilisation, is a unique physiological event which allows motile allogeneic spermatozoa to enter the female host and invade her tissues. The cyclic cellular proliferation observed in the thymus of the female rat may be an important preparation of her immune system for this event.     

Possible demographic consequences of AIDS in developing countries

Simple mathematical models of the transmission dynamics of HIV that incorporate demographic and epidemiological processes to assess the potential impact of AIDS on human population growth and structure in developing countries suggest that AIDS is capable of changing population growth rates from positive to negative values over timescales of a few decades. The disease is predicted to have little if any impact on the dependency ratio of a population, defined as the number of children below age 15 years and elderly people over 64 years, divided by the number of adults between 15 to 64 years.     

An infrared flash contemporaneous with the gamma-rays of GRB 041219a

The explosion that results in a cosmic gamma-ray burst (GRB) is thought to produce emission from two physical processes: the central engine gives rise to the high-energy emission of the burst through internal shocking, and the subsequent interaction of the flow with the external environment produces long-wavelength afterglows. Although observations of afterglows continue to refine our understanding of GRB progenitors and relativistic shocks, gamma-ray observations alone have not yielded a clear picture of the origin of the prompt emission nor details of the central engine. Only one concurrent visible-light transient has been found and it was associated with emission from an external shock. Here we report the discovery of infrared emission contemporaneous with a GRB, beginning 7.2 minutes after the onset of GRB 041219a (ref. 8). We acquired 21 images during the active phase of the burst, yielding early multi-colour observations. Our analysis of the initial infrared pulse suggests an origin consistent with internal shocks.