Gamma radiation-induced changes in the Caribbean fruit fly, Anastrepha suspensa (Loew)

The Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), has been targeted for control using the Sterile Insect Technique (SIT) in which males are sterilized by radiation. Studies of other species have shown that mating and flight behaviors are altered by radiation. Although behavior is influenced by physiology, little is known about radiation impacts on the developmental physiology and immunity. Our working hypothesis is that hemolymph physiology is altered by radiation. Our objectives were to evaluate changes in (1) hemolymph protein expression, (2) hemocyte population, and (3) melanization rates in larvae/pupae at different times post treatment. Hemolymph proteins from treated and untreated A. suspensa late 3rd instars and 0-2 day prepupae were fractionated by 1D SDS-PAGE. Total numbers of hemocytes were determined using a hemocytometer and melanization of whole hemolymph was photographed at predetermined time intervals under the light microscope. Two unique proteins (~105 kDa and 25 kDa) were upregulated in treated samples but were absent from the controls. Conversely, a 23kDa band that was in the controls disappeared from the treated samples. Hemocyte counts decreased by ~ 50% after treatment (515.4 x 10⁴ to 226.7 x 10⁴ cells/mL) in late 3rd instars but returned to control levels in 0-1- (368.4 x 10⁴ to 363.4 x 10⁴cells/mL) and 1-2- (371.1 x 10⁴ to 414.7 x 10⁴ cells/mL) day- old prepupae. However, melanization rate was > 3x faster in the controls than in treated hemolymph samples. Thus, gamma radiation treatment could influence essential physiological processes such as immune responses in A. suspensa larvae.