Molecular developmental evidence for a subcoxal origin of pleurites in insects and identity of the subcoxa in the gnathal appendages.
Pleurites are chitinous plates in the body wall of insects and myriapods. They are believed to be an adaptation to locomotion on land but their developmental and evolutionary origins are unclear. A widely endorsed explanation for their origin is through toughening pre-existing parts of the body wall; in contrast, the subcoxal theory suggests pleurites derive from a redeployment of the proximal-most section of the leg, the subcoxa. Here, by studying expression of appendage patterning genes in embryos and larvae of the beetle Tribolium castaneum, we provide the first molecular evidence for the existence of a cryptic subcoxal segment in developing legs. We follow this structure during development and show that the embryonic subcoxa later forms the pleurites of the larva as predicted by the subcoxal theory. Our data also demonstrate that subcoxal segments are present in all post-antennal appendages, including the first molecular evidence of a two-segmented mandible with a subcoxal segment in insects.
Laboratoire de Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique de Banyuls, Avenue du Fontaulé, 66650 Banyuls-sur-mer, France.
Joshua F
JF
Coulcher
Department of Earth Sciences, The Natural History Museum, London SW7 5BD, United Kingdom.
Gregory D
GD
Edgecombe
Department of Genetics, Evolution and Environment, Darwin Building, Gower St, London WC1E 6BT, United Kingdom.
Maximilian J
MJ
Telford
D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000196:embryology; D005121:Extremities / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D007814:Larva / Q000201:enzymology; D014231:Tribolium / Q000235:genetics*