New insights on basivenal sclerites using 3D tools and homology of wing veins in Odonatoptera (Insecta)

Abstract

Being implied in flight, mimetism, communication, and protection, the insect wings were crucial organs for the mega diversification of this clade. Despite several attempts, the problem of wing evolution remains unresolved because the basal parts of the veins essential for vein identification are hidden in the basivenal sclerites. The homologies between wing characters thus cannot be accurately verified, while they are of primary importance to solve long-standing problems, such as the monophyly of the Palaeoptera, viz. Odonatoptera, Panephemeroptera, and Palaeozoic Palaeodictyopterida mainly known by their wings. Hitherto the tools to homologize venation were suffering several cases of exceptions, rendering them unreliable. Here we reconstruct the odonatopteran venation using fossils and a new 3D imaging tool, resulting congruent with the concept of Riek and Kukalová-Peck, with important novelties, viz. median anterior vein fused to radius and radius posterior nearly as convex as radius anterior (putative synapomorphies of Odonatoptera); subcostal anterior (ScA) fused to costal vein and most basal primary antenodal crossvein being a modified posterior branch of ScA (putative synapomorphies of Palaeoptera). These findings may reveal critical for future analyses of the relationships between fossil and extant Palaeoptera, helping to solve the evolutionary history of the insects as a whole.

To be or not to be: postcubital vein in insects revealed by microtomography

“…Three‐dimensional X‐ray tomography and reconstructions are very efficient in helping to determine the homologies of wing venation among insects, as has already been shown in recent studies (Desutter‐Grandcolas et al ., ; Jacquelin et al ., ). Here, it allowed us to demonstrate the existence of a PCu vein in most insect orders, and suggest that this structure most probably originated only once in insects.…”

“…The absence of the particular PCu structure could be explained, however, by the reduced 'anal'/posterior area of the wing. In the Odonata there is also no particular convex and curved bulla posterior of the cubital veins; however, we observed a vein forked into an anterior convex branch and a posterior concave branch that emerges from a bulla that is in a very basal position (Jacquelin et al ., ); posterior to this vein, there is only a membranule (a small membrane at the posterobasal angle of the wing) with very weak veinlets (in some fossil Isophlebioidea) or no vein at all. This forked vein corresponds to the anal vein followed by the 'jugal' area of the Polyneoptera.…”

“…Recently, the advent of X-ray microtomography methods (e.g. μCT scan, Synchrotron) overcame a technological lock to answering problems of insect venation (Desutter-Grandcolas et al, 2017;Jacquelin et al, 2018). After these studies, a main vein is considered as independent of the other main veins if its own base, i.e.…”

“…Indeed, as the best‐preserved structures of fossil insects, wing veins are critical to better understand the deep‐past evolution of insects – as recently shown for some orders (e.g. Nel et al ., ; Prokop et al ., , ; Jacquelin et al ., ). Yet, despite two centuries of efforts, the homologies of wing veins remain an open question.…”

“…Nel et al, 2012;Prokop et al, 2014Prokop et al, , 2018 Correspondence: Andre Nel, Institut Systématique Évolution Biodiversité (ISYEB), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, 57 rue Cuvier, CP 50, 75005 Paris, France. E-mail: anel@mnhn.fr Jacquelin et al, 2018). Yet, despite two centuries of efforts, the homologies of wing veins remain an open question.…”