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Alteration of sex ratio at high temperature in insects and its causes 修士課程1年 等百合佳

2015/12/08 1:32 に Yurika Hitoshi が投稿

Although each insect has an appropriate sex ratio to maximize its fitness(1), abiotic factors sometimes alter the ratio. In this seminar, I will introduce examples where sex ratio was altered by high temperature.


Since 1970, 141 papers were published on the sex ratio when insects were reared at different constant temperatures. Among them, 70 were about parasitoid wasps.

Parasitoid wasps alter their progeny’s sex ratio according to factors such as host size and maternal age(2). When reared at high temperatures, the sex ratio biases to males in general including Trichogramma euproctidis.

Because of their haplo-diploid sex determination system, females of parasitoid wasps are able to control the progeny’s sex by fertilizing the egg or not. By observing the oviposition behavior, it was discovered that T. euproctidis actively oviposit more males than females at high temperature(3).


Among the 71 papers studying on insects other than parasitoid wasps, only 5 papers reported that the sex ratio changed significantly at different rearing temperatures. Two of them were related to the infection of Wolbachia.

Wolbachia is an endosymbiotic bacterium that infects a wide range of species, and known to manipulate the host sex ratio for their own fitness towards female by killing males in species such as Ostrinia scapulalis(4, 5). Heat treatment eliminated Wolbachia and returned the sex ratio to the original state(6).


The remaining 3 papers each studied on different insects. Bessa parallela, a species of the parasitoid fly(7), and the thrip Scolothrips longicornis(8) biased its sex ratio to males at high temperature, whereas the lady beetle Propylea dissecta(9) biased its sex ratio to females.

The mechanism is unknown in either of these studies. Since the degree and the direction of the alteration of the sex ratio by high temperatures differ among species, more studies are necessary to understand this phenomenon.



1.         Hamilton WD (1967) EXTRAORDINARY SEX RATIOS. Science 156(3774):477-488.

2.         King BH (1987) OFFSPRING SEX-RATIOS IN PARASITOID WASPS. Quarterly Review of Biology 62(4):367-396.

3.         Moiroux J, Brodeur J, & Boivin G (2014) Sex ratio variations with temperature in an egg parasitoid: behavioural adjustment and physiological constraint. Animal Behaviour 91:61-66.

4.         Werren JH, Baldo L, & Clark ME (2008) Wolbachia: master manipulators of invertebrate biology. Nature Reviews Microbiology 6(10):741-751.

5.         Fukui T, et al. (2015) The Endosymbiotic Bacterium Wolbachia Selectively Kills Male Hosts by Targeting the Masculinizing Gene. Plos Pathogens 11(7).

6.         Sugimoto TN, Kayukawa T, Matsuo T, Tsuchida T, & Ishikawa Y (2015) A short, high-temperature treatment of host larvae to analyze Wolbachia-host interactions in the moth Ostrinia scapulalis. Journal of Insect Physiology 81:48-51.

7.         Ichiki R, Takasu K, & Shima H (2003) Effects of temperature on immature development of the parasitic fly Bessa parallela (Meigen) (Diptera : Tachinidae). Applied Entomology and Zoology 38(4):435-439.

8.         Pakyari H, Fathipour Y, & Enkegaard A (2011) Effect of Temperature on Life Table Parameters of Predatory Thrips Scolothrips longicornis (Thysanoptera: Thripidae) Fed on Twospotted Spider Mites (Acari: Tetranychidae). Journal of Economic Entomology 104(3):799-805.

9.         Omkar & Pervez A (2004) Temperature-dependent development and immature survival of an aphidophagous ladybeetle, Propylea dissecta (Mulsant). Journal of Applied Entomology 128(7):510-514.