External structure of the sensillum capitulum, a hygro- and thermoreceptive sensillum of the cockroach, Periplaneta americana.
The antennal hygro- and thermoreceptive sensillum (sensillum capitulum) of the cockroach, Periplaneta americana, has been identified electrophysiologically and examined by scanning electron microscopy. It appears basiconic and has a characteristic cuticular apparatus; a mushroom-shaped inner stem and a non-perforated outer wall. The head of the inner stem, which is a cap of about 0.5 micrometer diameter, protrudes from the distal margin of the outer wall. The inner stem is not perforated, though in some cases a tiny hollow is observed in the apex of the cap. This kind of cuticular apparatus is not found in other sensilla and may be modality-specific to hygro- and/or thermoreception. The sensillum capitulum occurs singly on the distal part of each alternating segment of the flagellum and on each segment of some distal meristal segments.
D000818:Animals; D003058:Cockroaches / Q000033:anatomy & histology*; D006813:Humidity; D008855:Microscopy, Electron, Scanning; D010526:Periplaneta / Q000033:anatomy & histology*; D012679:Sense Organs / Q000648:ultrastructure*; D011984:Sensory Receptor Cells / Q000502:physiology / Q000648:ultrastructure*; D013823:Thermoreceptors / Q000648:ultrastructure*