Anatomie des Pterothorax der Phasmatodea, Mantophasmatodea und Embioptera und seine Bedeutung für die Phylogenie der Polyneoptera (Insecta)

Abstract

The phylogenetic relationships within Polyneoptera and between several taxa of Phasmatodea were analysed based on 60 characters of the thorax and the wing base. Anatomy of the meso- and metathorax of a representative of Embioptera (Antipaluria caribbeana) and for the first time of a representative of Mantophasmatodea (Austrophasma caledonensis) are included. Monophyly of Pliconeoptera is supported by the absence of the pleuro-pleural muscles IIppm2 and IIIppm2. Furthermore, in Pliconeoptera a new lateral nerve is present which innervates the intrasegmental lateral tergosternal muscle bundles of the pregenital abdominal segments. The dorsal nerve innervating the dorsal longitudinal muscles originates from its ganglion and not in front of it as it is the case in Plecoptera. Anatomical features of the meso- and metathorax of Austrophasma (Mantophasmatodea) compared with data of Grylloblatta (Grylloblattodea) indicate a sister group relationship of Mantophasmatodea and Grylloblattodea. Austrophasma and Grylloblatta both posses a sterno coxal muscle (IIIscm5), which is absent in other Polyneoptera. Furthermore, four muscles probably were lost in Austrophasma and Grylloblatta. The following muscles are missing in both taxa: the dorso ventral muscle IIdvm6, the sterno coxal muscle IIscm2, the dorso ventral muscle IIIdvm6 and the sterno coxal muscle IIIscm6. A sister group relationship between Embioptera and Phasmatodea is supported by two additional characters: presence of paratergo-sternal lateral muscles, which are subdivided in at least two bundles and presence of two lateral tergo-sternal muscles, which are each subdivided in several parallel bundles. Whithin Phasmatodea, the basal splitting in Timema + (Agathemera + Neophasmatidae) receives further support. The Euphasmatodea (Agathemera + Neophasmatidae) are characterised by the loss of the ventral longitudinal muscle IIvlm3 and the loss of the internal ventral longitudinal muscles of the pregenital abdomen. All Neophasmatidae possess a ventral longitudinal muscle IIvlm1, which connects both arms of the furca. Within Phasmatodea Medauroidea, Ramulus and Carausius have an anastomosis between Nervus anterior and Nervus lateralis 2 of the mesothoracic ganglion in common. In Sungaya, Haaniella, Heteropteryx, Sipyloidea, Pseudophasma, Medauroidea, Ramulus, Carausius, Eurycantha, Phaenopharos, Sceptrophasma and Extatosoma the transversal nerve and Nervus anterior of the first abdominal ganglion are separated and are connected by an anastomosis. In Medauroidea, Ramulus, Carausius, Eurycantha, Phaenopharos, Sceptrophasma, Extatosoma, Agathemera, Haaniella, Heropteryx and Sungaya the muscle IIIdlm 2 is reduced. This reduction likely appeared independently in Agathemera. The traditional phasmatodean subfamilies Phasmatinae, Pseudophasmatinae and Pachymorphinae are probably not monophyletic. The investigation of postembryonic development of the musculature especially of the metathorax of the winged phasmid Sipyloidea sipylus contributes to the discussion about the probability of wing loss within Phasmatodea. Especially the muscles involved in flight become functional only late during the lifespan of the juvenile animal. They are ready for use only after the adult molt. When the animal is old and finishes the egg depositing period, the wing muscles degenerate first. During development structures which mean high energetical costs for the indvidual such as the musculature of the flight apparatus, function only during the reproductive period and are degenerated quite fast thereafter. These observations indicate a repeated loss of wings and special flight muscles within Phasmatodea.