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Gregarious vs. solitary Desert Locusts: variation in progeny size, number, and starvation physiology and resistance

Maeno K.O., Piou C., Babah Ebbe M.A.O., Nakamura S.. 2013. In : Zhang, Long. ; Zhang, Liwei. ; You, Yinwei. ; Gao, Qiang. ; Yin, Xuewei. Metaleptea Special conference Issue of the 11th International congress of orthopterology "Orthoptera in scientific progress and human culture", Kunming, China, 11th-15th August 2013. Kunming : Orthoprerists society, p. 128-128. International congress of orthopterology "Orthoptera in scientific progress and human culture". 11, 2013-08-11/2013-08-15, Kunming (Chine).

Female desert locusts, Schistocerca gregaria, epigenetically modify their progeny quality and quantity in response to crowding. Gregarious (crowd-reared) adult females produce larger but fewer progeny than do solitarious (isolated-reared) females. Hatchlings from gregarious females also show better survival. The reasons for these differences are unclear. This study investigated 1) the effects of rearing density on the variation in egg size within single egg pods; 2) the starvation tolerance of hatchlings from mothers with different phases and 3) physiological differences in hatchling energy reserves. Our results confirmed that isolated-reared females produce smaller but more eggs than crowd-reared females, and that the variation in egg size within single egg pods was greater for crowd-reared females than for isolated females. A trade-off (negative relationship) between egg size and number of eggs per individual egg pod was observed for both crowded and isolated groups. When starved, gregarious hatchlings (from crowd-reared females) survived significantly longer than solitarious ones (from isolated-reared females). For solitarious hatchlings, survival time was longer as hatchling body size increased, but for gregarious hatchlings, relatively small individuals survived as long as larger hatchlings. The percentage of water content per fresh body weight was almost equal between the two phases, both before and after starvation. In contrast, the percentage of lipid content per dry body weight was significantly higher in gregarious hatchlings than in solitarious ones before starvation, but became almost equal after starvation. These results demonstrated that crowded female adults not only trade-off to modify their progeny size and quantity, and also increase variability in progeny size and variability in energy reserves of these progeny. We hypothesize that gregarious females enhance their fitness by producing progeny differently adapted to high environmental variability and particularly to starvation conditions. (Texte intégral)

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