Effects of gamma‐irradiation on midgut proteolytic activity of the mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae)

Abstract

The Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), is a key pest of citrus in Spain because of significant yield losses and to quarantine restrictions. Biologically based control methods, such as the Sterile Insect Technique (SIT), which relies on the sterilization by irradiation of large numbers of insects, is gaining an increasing role in the control of medfly in Mediterranean areas. However, gamma-irradiation might damage the midgut epithelium cells, causing a lowering of nutritive assimilation that can negatively affect adult performance. Irradiation effects on digestive physiology are well established for a number of insect pests, but there is no information on medfly. Our aim was to determine the effects of gamma-irradiation on C. capitata digestive protease activity. Both larvae and adults were found to use a similar proteolytic system based on aspartyl-, trypsin-, chymotrypsin-, amino peptidase-, and carboxypeptidase A- and B-like activities. Pupae of the Vienna-7 (tsl) strain were irradiated at 70 or 140 Gy, two days before emergence, and the adults fed during 5 days on sugar-protein (4:1) diets. Protease activity was measured in midgut extracts and compared with males non-irradiated reared in the same conditions. The results showed that the irradiation doses tested had no effect on the digestive proteolytic activities of medfly adults. Moreover, the longevity of irradiated medflies at the highest dose (140 Gy) was similar to that of controls.

Feeding on yeast hydrolysate enhances attraction to cue‐lure in Queensland fruit flies, Bactrocera tryoni

“…Few studies have attempted to define the physiological mechanisms underlying reduced response to food lures in these species, so it is difficult to speculate why γ -irradiation had no effect on response to cue-lure by Q-flies in our study. A recent study on Mediterranean fruit fly midgut proteolytic activity found no effect of sterilization (San Andres et al, 2007). The results from our study suggest that the ability of Q-flies to digest and absorb sources of nitrogen is unaffected by sterilization, leading to rates of sexual maturation (and attraction to cue-lure) similar to fertile (un-irradiated) flies.…”

“…Sterile Q-flies used in SIT programmes are released as adults 24 -48 h after emergence (Meats et al, 2006). A recent study on Mediterranean fruit fly midgut proteolytic activity found no effect of sterilization (San Andres et al, 2007). This would improve estimates of sterile male abundance in the field derived from trap recaptures.…”

Description of the irradiated and nonirradiated midgut of Ceratitis capitata Wiedemann (Diptera: Tephritidae) and Anastrepha ludens Loew (Diptera: Tephritidae) used for sterile insect technique

“…Metabolic and physiological abnormalities in sterile medflies and mexflies may be difficult to measure, and intricate studies are likely warranted. To this end, San Andres et al (2007) reported that radiation does not have an effect on digestive proteolytic activity in the medfly midgut, however, no regional analysis of the midgut was undertaken nor was the age of the medflies stated in that study. Stiles et al (1989) showed that radiation effects on the midgut of Glossina palpalis Vanderplank were indeed regional.…”

Artificial selection, pre‐release diet, and gut symbiont inoculation effects on sterile male longevity for area‐wide fruit‐fly management

“…Symbiotic bacteria have been identified in the gut of several species of Tephritidae (Rubio & McFadden, ; Fitt & O'Brien, ; Lauzon et al., ; Kuzina et al., ; Marchini et al., ) and play a key role in protein absorption (Behar et al., ; San Andres et al., ). By adding symbionts to probiotic pre‐release diets, damage to the gut lining of irradiated medflies may have reverted and nutrient absorption capacity restored.…”