a–e The ctenidium of Benthomodiolus erebus sp. n. a gross anatomy, b SEM of whole filament, c SEM of tip of a single filament, d SEM of inter filamental junction, e SEM of polygonal surface of microvilli. f–h The ctenidium of B. geikotsucola. f gross anatomy, g SEM of a whole filament, h SEM of the polygonal surface.