Different forms of Tetranychus urticae Koch (Acari: Tetranychidae) and their plasticity in retaining eggs in the presence of predatory mites Amblyseius swirskii (Acari: Phytoseiidae).
عنوان دوره: اولین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Organisms would reduce the predation risk of their offspring through Parental care. Searching safe ovipositing sites, females should spent lots of energy so that sometimes they prefer to keep the eggs inside body and deposit them in a more appropriate time. In such situations, the predator (or any other risky factor) might induced the egg retention phenomena in prey (the ovipositing female). We used females of two (green and red) forms of Tetranychus urticae to study whether they could retain eggs inside their body when encountered the predatory mites,, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) were reared under controlled conditions (25±5°C, 16:8 (L:D) hours photoperiod and 65±5% RH.). Spider mites were reared on bean pots under controlled conditions (25±5°C, complete photoperiod (sodium lamp) and 65±10% RH). The treatment and control Petri dishes (6 cm) were consisted of 2.5×2.5cm2 detached bean leaf (put upside down) on water saturated cotton wool. Ten same-aged spider mite females and two same-aged predator females were added into the treatment dish and ten same-aged spider mite females were added into the Control for 24 hours. After 24 hours the survived spider mites oviposited in the presence of two predatory mites The spider mite ovipositing behavior was monitored for five hours. The eggs were hatched within three days. The experiment was replicated 20 times with each of the spider mite form. The egg incubation time were compared between the treatment (predator presence) and Control (predator absence). The results showed when T. urticae green form females oviposited on patches in the presence of predator (75/87±2.87), their eggs did not hatch significantly earlier than those laid by females exposed to no predators (78/77±0.82)(P> 0.05), whereas when T. urticae red form females oviposited on patches in the presence of predator A. swirskii, the females retained the eggs in their body (74/66±1/15)(P< 0.05). Retaining eggs inside the body for decreasing the risk of predators for prey eggs has little been studied. To our knowledge, the present research is the first studies on the probable ability of a tetranychid prey to retain eggs in the presence of predators.
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