Morphology of the midgut and hindgut and pollen-feeding ecology of Eulasia arctos anatolica (Reitter, 1903) (Coleoptera: Glaphyridae)

This study aims to investigate the morphological structure of the midgut and hindgut of Eulasia arctos anatolica (Reitter, 1903) and to reveal, for the first time, the relationship between the pollen grains found in the digestive system and the feeding of E. arctos anatolica. According to the results obtained, the longest section of the digestive system of E. arctos anatolica, the midgut, has a single layer of columnar epithelial cells with a striated border and secretory vesicles, indicating apocrine secretion. Regenerative cells were found at the base of epithelial folds, and Scrophulariaceae pollen grains were present in the midgut lumen. The hindgut consists of the ileum, colon, and rectum. SEM and LM analyses showed that a cuticular intima, a single-layered cuboidal epithelium, and a muscle layer surround these sections. Spore-like granular structures and crystals were observed in the lumens of the ileum and colon. In the rectum, six rectal pads were identified, along with pollen grains from the Scrophulariaceae and Compositae families, as well as spore-like structures and crystals. The most important finding of the study is the direct observation of pollen grains in both the midgut and rectum lumens. This provides the first morphological evidence that E. arctos anatolica actively feeds on plants from the Scrophulariaceae and Compositae families. The results reveal not only the structural features of the digestive system but also functional adaptations to a diet based on pollen. Therefore, this study offers original contributions to the morphological and ecological understanding of the species’ feeding relationships.