78.3  Tuesday, Jan. 6  Chromosomal inversion effects on aridity tolerance in the mosquito Anopheles gambiae GRAY, Emilie M*; ROCCA, Kyle AC; BESANSKY, Nora J; Univ. of Notre Dame djemilie@gmail.com

The malaria vector Anopheles gambiae is endowed with a large number of chromosomal inversions, apparently allowing the species to inhabit a wide variety of habitats. Inversion frequencies vary both geographically and seasonally, yet the phenotypic nuances resulting from this mosaic of genotypes are unknown. This ecological flexibility is exemplified by the 2La inversion, whose frequency co-varies with aridity. We have selected two colonies of A. gambiae differing in only the 2La inversion in order to characterize distinguishing traits of the inversion. This paper presents our findings regarding the inversions effect on adult aridity tolerance. An accompanying paper (Rocca, Gray and Besansky) explores larval thermotolerance.
We established that carriers of the 2La inversion resist desiccation longer than their standard conspecifics. In teneral adults this difference is due to variation in water loss rate (WLR) whereas at later ages it is due to variation in desiccation tolerance (DT). We analyzed mass, water, lipid, trehalose and glycogen content and found only trehalose to differ, being higher in 2La than in 2L+. We also tested the effect of dry season acclimation (8 adult days at lower humidity and higher temperature) on desiccation resistance and found that both colonies increased resistance by reducing their WLR. The amplitude of change, however, was similar in both populations.
In conclusion, our results suggest that 2La enhances aridity tolerance by acting on DT and WLR. The first is possibly associated with higher trehalose levels. The second may be linked to variations in cuticular characteristics; interestingly many cuticular protein genes have been identified within the 2La inversion. Possible modes of action of the inversion on the phenotype will be discussed.