title: Giant stick insects reveal unique ontogenetic changes in biological attachment devices.
abstract: A strong modification of tarsal and pretarsal attachment pads during the postembryonic development is described for the first time. In the exceptionally large thorny devil stick insect Eurycantha calcarata a functional arolium is only present in the immature instars, enabling them to climb on smooth surfaces, especially leaves. Nymphs are also characterized by greyish and hairy euplantulae on tarsomeres 1-4. The gradual modifications of the arolium and the euplantula of tarsomere 5 in the nymphal development are probably mainly related to increased weight. The distinct switch in the life style between the leaf-dwelling nymphal stages and the ground-dwelling adults results in the final abrupt change of the adhesive devices, resulting in a far-reaching reduction of the arolium, the presence of a fully-developed, elongated euplantula on tarsomere 5, and white and smooth euplantulae on tarsomeres 1-4. The developmental remodelling of attachment pads also reflects a phylogenetic pattern. The attachment devices of the earlier instars are similar to those found in the basalmost lineage of extant stick insects, Timema, which is characterized by a very large pan-shaped arolium and a hairy surface of the tarsal and pretarsal attachment pads.
authors.affiliation: Department of Life Sciences, University of Siena, Via A. Moro 4, 53100 Siena, Italy. Electronic address: gottardo@unisi.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Gottardo
authors.affiliation: Via Cici 26/M, 30038 Spinea, VE, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Vallotto
authors.affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Ebertstrasse 1, D-07743 Jena, Germany.
authors.forename: Rolf G
authors.initials: RG
authors.lastname: Beutel
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D017753:Ecosystem; D007313:Insecta / Q000033:anatomy & histology* / Q000254:growth & development*; D009512:New Guinea; D009758:Nymph
keywords: Adaptive developmental plasticity; Attachment pads; Insect cuticle; Phasmatodea; Ultrastructure