Effects of starvation on reproduction of the predacious mite <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> (Acari: Phytoseiidae) |
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Authors: | Shingo Toyoshima Peter Michalik Giovanni Talarico Anja E Klann Gerd Alberti |
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Institution: | (1) National Institute of Fruit Tree Science, Morioka 020-0123, Japan;(2) Zoological Institute and Museum, Ernst-Moritz-Arndt-University Greifswald, Johann-Sebastian-Bach-Strasse 11/12, 17489 Greifswald, Germany |
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Abstract: | Effects of starvation on gravid females of Neoseiulus californicus were investigated at 20°C and 85% RH. When females that had been reared with abundant prey were swapped, just after laying
their first egg, to conditions without any prey and water, they laid 1.8 eggs and survived for 4.3 days. In the body of well-fed
females, an egg with eggshell and/or two oocytes were observed in the ventral and dorsal regions, respectively. The larger
oocyte had two roundish nuclei and abundant yolk granules, and was enveloped with a vitelline membrane. These two nuclei were
not fused but were just close to each other. The smaller oocyte had a nucleus, but had not yet formed yolk granules and vitelline
membrane. Females after 12 h starvation had an egg in the ventral region and an oocyte in the dorsal region of the body. After
more than 24 h starvation females maintained an oocyte in the dorsal region of the body, but had no egg in the ventral region.
The oocyte was filled with abundant yolk granules and contained two irregular nuclei when females were starved for 24 h, but
when starved for more than 36 h it contained one irregular nucleus. These findings suggest that (1) gravid females maintained
an oocyte in the dorsal region after laying two eggs during starvation, (2) the oocyte was not absorbed during starvation,
(3) the oocyte advanced vitellogenesis and the fusion of two nuclei, and (4) the vitellogenic oocyte was not enveloped with
an eggshell and had not started embryogenesis. |
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Keywords: | Neoseiulus californicus Starvation Survival Oogenesis Sex ratio |
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