TISSUE AND CELL. lYY4 26 (2) 249-2.57 0 1994 Longman Group UK Ltd. DUSAN DEVETAK” and MARIA ANNA PABSTt STRUCTURE OF THE SUBGENUAL ORGAN IN THE GREEN LACEWING, CHRYSOPERLA CARNEA Keywords: Subgcnual organ. scolopidium, cell ]unctlon\. ultra~tructurc, C‘hw.wper/~ c mwo ABSTRACT. REM and TEM studies of the suhgcnual organ m zyxwvutsrqponmlkjihgfedcb Chr~w perla CUNICU (Ncur- optcra: Chrybopidae) show that it is composed of three acolopidia. each with one wnsory. one scolopalc and one cap cell. The distal part of the dendntc shows a cilium with a ‘Y + 0’ structure The cross-banding pattern of the ciliary root has a periodictty of bands of ahout hl nm The acolopale material in a certain part of the scolopalc cell is organized into five rods. The ccl1 bodies of all three cap cells form il Icns-like structure. the vclum. which is fixed to zyxwvutsrqponmlkjihgfe the leg uall and the trachea with an cxtracellular material. The importance of the vclum is discucscd Four types of intcrccllular junction arc found; bpot desmosomcs. hclt de\mosomcs, wptatc Iunction\ and gap junctions. Introduction The chordotonal organ or scolopidial organ is an arthropod sensory organ composed of one or more structural units called scolopidia (Debaisieux, 1938; Moulins, 1976; McIver. 1985). The term ‘chordotonal organs’ was introduced by Graber (1882). The first description of the ultrastructure of a scolo- pidium was given by Gray and Pumphrey (1958) and Gray (1960) for the tympanal organ of Locusta. The scolopidium is a struc- tural unit consisting of one or more bipolar sensory cell(s) and two accessory cells-the scolopale cell and the cap (=attachment) cell. The scolopale cell envelops the distal region of the sensory-cell dendrite(s). The cap cell (sensu Schmidt, 1969, 1973) (= attachment cell sensu Gray, 1960; McIver. 1985) connects the scolopidium with an attachment point. The general structure of *Department of Biology, Faculty of Education, Uni- versity of Maribor, KoroSka 160, Sl-62000 Maribor, Slo- venia. tDepartment of Histology and Embryology, University of Graz, Harrachgasse 21, A-8010 Graz, Austria. Received 9 November 1993 Accepted 10 December 1993 scolopidium was described in detail and reviewed by Moulins (1976) and Mclver (1985). All scolopidial organs that have been investigated electrophysiologically have been shown to be mechanotransducers. An organ of this type may function as a proprio- ceptor-a detector of movements in interseg- mental joints (in legs: tarso-pretarsal organ. tibia1 distal chordotonal organ, femoral chor- dotonal organ), a substrate vibration recep- tor (subgenual organ; tarso-pretarsal organ in Notonecta). a receptor of air-borne sounds (tympanal organ), or a detector of antenna1 movement (Johnston’s organ) (for review see Howse, 1968; Wright, 1976; McIver. 1985). The leg chordotonal organs which monitor the movement and position of the joints or detect substrate vibrations have been studied with the light microscope in orthopterans by Schwabe (1906). in a variety of insects by Debaisieux (1934, 1938), in honeybees and ants by Schiin (1911). in locusts by Friedrich (1927, 1928) and Usherwood et al. (1968). in termites and Periplaneta americana b! Howse (1965, 1968). in Periplaneta amen- cana by Schnorbus (1971), in Gr):llus assi- milk by Friedman (1972), in Bombus lapidarius by Friihlich (1974). in Nrzara r,ir- 249