UV-C radiation-induced changes in the legs and trichoid sensilla of the red flour beetle Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)

Abstract

Since various kind of receptors in insects are mainly located on their legs. We estimate the influence of ultraviolet-C on the leg morphology and trichoid sensilla of Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae), zero-day-old pupae were irradiated with UV-C at a distance of 35 cm for 1, 2, 4, 8, 16, 32, and 64 min. Changes in leg morphologies and trichoid sensilla were determined using light and scanning electron microscopes. UV-C radiation caused the abnormalities of an adult’s legs that were classified into three levels; mild, moderate, and strong. Legs of the resulting adults were developed into malformed structures that lacked clear segmental identity. The severity of leg abnormalities was recorded in a dose-dependent manner. UV-C significantly decreased the length and width of the femur, tibia, and tarsus. In the strongly affected level, the femur was reduced in size while the tibia and tarsus were completely deleted, and there was no evidence of claws. Scanning electron microscopy showed the wrinkled cuticle on the leg segment, and the sensilla of the resulting adults appeared less in number. After UV-C radiation, the trichoid sensilla on the femur became longer and wider, but the trichoid sensilla on the tibia were shorter and narrower. Taken together, UV-C irradiation during pupal stage interfered development of legs and brought about specific malformation features.