sensillum of sacculus chamber III obsolete grooved sensillum https://github.com/FlyBase/drosophila-anatomy-developmental-ontology/issues/1312 true FBbt:00005191 fly_anatomy.ontology Obsoleted as these only seem to exist in the sacculus, making this term equivalent to FBbt:00004180 'sensillum of sacculus chamber III'. Sensillum that is double-walled, containing an open slit channel system. For three-fourths of its length from the tip, the cuticular surface bears alternating longitudinal grooves and ridges. In cross-section, the cuticle is hollow and looks like a ring of spheres, each with a small solid cuticular ridge on its external surface. In the groove, between two ridges, there is a small slit, exposing the interior of the sensillum to the outside. Proximally, the lateral walls of adjacent cuticular ridges fuse. The inner wall surrounds the lumen of the hair, which contains a thin, loosely scattered, electron-lucent homogeneous material. It is innervated by two sensory neurons. There are 2 types of grooved sensillum, both found in chamber III of the sacculus.