Larval and adult digestive tract of the carrion beetle Oxelytrum discicolle (Brullé, 1840) (Coleoptera: Silphidae)

Oxelytrum discicolle is a necrophagous beetle occurring in Central and South America, with potential use in forensic entomology for investigations in the context of legal medicine. The present work aimed to describe the morphology of the digestive tract of larvae and adults and contributes to the knowledge about the digestion associated with necrophagy. In the three larval instars, the foregut is short and narrow, the midgut is a dilated tube, elongated with a smooth surface, and the hindgut is narrow and long, with small lateral projections and a dilated terminal region. The gut epithelium in the second and third instar larvae is vacuolated in the mid- and hindgut, with high production of apocrine secretions in the midgut lumen. In adults, the foregut is short, with small spines in the cuticular intima that covers the flattened epithelium. The midgut is dilated, with many short gastric caeca with regenerative cells in the blind portion, which differentiate in digestive columnar cells towards the midgut lumen. The hindgut is long and narrow, with an enlarged distal portion with folded epithelium lined by a thin cuticle. The histochemical tests reveal the absence of protein storage granules in the gut epithelium of larvae and adults. The gut characteristics of the carrion beetle O. discicolle are similar to those of other predatory and phytophagous Coleoptera, which may indicate that ancestry may influence the alimentary canal morphology more than the feeding habits.