Ultrastructural Architecture and Morphological Examination of <i>Hirudo verbana</i> (Annelida, Hirudinea)

In this study, the morphological characteristics of the medicinal leech Hirudo verbana (Annelida, Hirudinea) were examined. Mitochondrial CO1 gene sequences of representative specimens were recorded in GenBank, and macroscopic, histological, and SEM analyses of remaining representatives were made. The species had trignathous jaws, each half-moon in shape. There were 75-80 denticles on the left jaw with their tips medially, while the right jaw had 30-34 equilateral triangular denticles, all arranged in a single row. The anterior jaw had 35-40 blunt-tipped denticles similarly arranged in a single row. Salivary papillae of varying sizes were scattered along the edges of the jaws, with salivary pores appearing as irregularly distributed round openings. Five pairs of dorsal eyes appeared round under a stereomicroscope but oval under SEM. Seventeen pairs of round nephridial pores were symmetrically located on every fifth annulus of the ventral side. Grape-cluster-like cells containing granules were observed between the crop and the muscle layer. Bean-shaped testisacs and coiled vas deferens canals were bilaterally arranged near the crop. Thread-like extensions and sensilla were identified across the ventral annuli. Beneath the epidermis, circular, oblique, and longitudinal muscle layers and three types of secretory cells between them were identified. As a result, this study has identified differences in the denticle morphology of H. verbana and has contributed these findings to the literature. Additionally, it was found that there are differences in the shape of the examined structures between stereomicroscope and SEM images in small and complexly structured organisms.