Behavioral evidence of oxidative stress by hematophagy in the ocellar system of Rhodnius prolixus Stål, 1859 red-eyed mutants.

The photonegative response to light stimulation in Rhodnius prolixus (Reduviidae, Triatominae) is modulated by compound eyes and ocelli. Screening pigments in the visual system have been shown to protect the cellular structures from the oxidative stress damage produced by blood ingestion and light stimulation. Red-eyed mutants of Rhodnius prolixus lack screening pigments in their compound eyes and ocelli and are exposed to more oxidative stress. Experiments with Rhodnius prolixus and Triatoma infestans red-eyed mutants reared from the first nymphal stage show damage in the retinas of the compound eyes and a decrease in photonegative responses due to light stimulation. Because ocelli are only present during the imaginal stages, we designed a group of experiments to assess the possible damage to the ocelli by oxidative stress mediated by blood ingestion in Rhodnius prolixus red-eyed mutants and wild-type insects. To test our hypothesis, we carried out behavioral experiments to evaluate the photonegative responses in adults exposed to different treatments, including coverage of either the compound eyes or ocelli, and different blood feeding regimens. Our results show that the ocelli in Rhodnius prolixus adults can modulate photonegative responses in red-eyed mutants better than the compound eyes can. In addition, a decrease in photonegative responses was evident when the red-eyed mutants were fed blood continuously for four weeks. Our results confirm that ocelli in Rhodnius prolixus can be considered a parallel pathway that intersects with information from the compound eyes regarding light stimulation and that their screening pigments play important roles in preventing the damage caused by oxidative stress due to blood ingestion.