FUNCTIONAL-MORPHOLOGY OF THE SUBGENUAL ORGAN OF THE CARPENTER ANT

Using light microscopy, confocal microscopy, electron microscopy and h istochemistry, the subgenual organ (SGO) of an ant, Camponotus lignipe rda, is investigated. Sensory units and attachment cells together encl ose a large extracellular cavity, which is filled by acid mucopolysacc harides, as revealed by staining with ruthenium red. Due to this cavit y, the whole SGO has the shape of a deformed sphere and the scolopidia exhibit a distribution of angles between 0 degrees and 60 degrees wit h the tibial long axis (as is shown by phalloidin-rhodamin staining of the actin filaments of the scolopale, viewed in situ by laser scannin g confocal microscopy). The subgenual organ is innervated by a branch of the tibial nerve, which splits within or shortly distal to the femu r-tibia joint. The other features of the SGO of Camponotus ligniperda are similar as in other insects: the SGO of Camponotus ligniperda cont ains about 35 scolpidial sensilla; it is fixed to the subgenual nerve on its proximal end, by its attachment cells to the opposite part of t he cuticle; the fixation by the attachment cells is accomplished by a vast quantity of cytoplasmic microtubules; the construction of the sen sory units is the same as in other mononematic scolopidial organs. The role of the extracellular lumen inside the organ and the special shap e of the SGO of Camponotus ligniperda in mechanical transmission is di scussed.