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Sperm competition and variation in zebra mating behavior (1990)

Ginsberg, J. R. ; Rubenstein, D. I.

Springer

Behavioral ecology and sociobiology 26 (1990), S. 427-434

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ISSN: 1432-0762

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Data are presented on the breeding behavior of two zebra species to test whether intra- and interspecific variation in male reproductive behavior and physiology are correlated with differences in female promiscuity. In one species, plains zebra (Equus burchelli) females live in closed membership single male groups and mate monandrously. In the other species, the Grevy's zebra (E. grevyi) females live in groups whose membership is much more temporary. Typically, associations with individual males are brief and mating is polyandrous. However, some females - those having just given birth — reside with one male for long periods, mating monandrously. These differences in female mating behavior generate variability in the potential for sperm competition. We show that behavioral differences in male investment in reproductive activities correlate with the potential for sperm competition. When mating with promiscuous mares, Grevy's zebra stallions made a greater investment in reproductive behavior (calling, mounting, ejaculations) than did stallions of either species when mating with monandrous females. The evolution of large testes size in the Grevy's zebra, when compared to the congeneric plains zebra, horse, and mountain zebra, allows for this increased investment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00170901

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Mehrlagige galvanische Chromschichten unter mechanischen und tribologischen Beanspruchungen (1990)

Ginsberg, J. ; Gahr, K.-H. Zum

Weinheim : Wiley-Blackwell

Materialwissenschaft und Werkstofftechnik 21 (1990), S. 274-280

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ISSN: 0933-5137

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Das Verhalten ein- und mehrlagiger Chromschichten wurde unter statischer und schwingender Biegebeanspruchung sowie unter Bedingungen des Abrasivverschleißes untersucht Ergänzend wurden die Eigenspannungen der verschiedenen Schichtsysteme ermittelt und licht-und rasterelektronenmikroskopische Analysen der Bildung und Ausbreitung von Rissen vorgenommen. Die Ergebnisse zeigen, daß durch einen optimierten mehrlagigen Schichtaufbau das Eigenschaftsprofil der Verbundkörper unter kombinierter mechanischer und tribologischer Beanspruchung verbessert wird.

Additional Material: 9 Ill.