Haltere morphology and campaniform sensilla arrangement across Diptera

• Published in: Arthropod structure & development 2017-03, Vol.46 (2), p.215-229
• Main Authors: Agrawal, Sweta, Grimaldi, David, Fox, Jessica L.
• Format: Article
• Language: English
• Subjects: Animals; Campaniform sensilla; Diptera; Diptera - classification; Diptera - ultrastructure; Halteres; Hicks papillae; Mechanoreceptors; Mechanoreceptors - ultrastructure; Microscopy, Electron, Scanning; Phylogeny; Sensilla; Sensilla - ultrastructure; Wings, Animal - ultrastructure
• ISSN: 1467-8039; 1873-5495
• DOI: 10.1016/j.asd.2017.01.005

One of the primary specializations of true flies (order Diptera) is the modification of the hind wings into club-shaped halteres. Halteres are complex mechanosensory structures that provide sensory feedback essential for stable flight control via an array of campaniform sensilla at the haltere base. The morphology of these sensilla has previously been described in a small number of dipteran species, but little is known about how they vary across fly taxa. Using a synoptic set of specimens representing 42 families from all of the major infraorders of Diptera, we used scanning electron microscopy to map the gross and fine structures of halteres, including sensillum shape and arrangement. We found that several features of haltere morphology correspond with dipteran phylogeny: Schizophora generally have smaller halteres with stereotyped and highly organized sensilla compared to nematoceran flies. We also found a previously undocumented high variation of haltere sensillum shape in nematoceran dipterans, as well as the absence of a dorsal sensillum field in multiple families. Overall, variation in haltere sensillar morphology across the dipteran phylogeny provides insight into the evolution of a highly specialized proprioceptive organ and a basis for future studies on haltere sensory function. •We used scanning electron microscopy to map gross and fine features of halteres of 150 flies from 42 families across Diptera.•Schizophora generally have smaller halteres with stereotyped and highly organized sensilla compared to nematoceran flies.•The sensilla of nematoceran dipterans were highly variable in shape, and multiple families lacked a dorsal sensilla field.•Linearity of sensilla arrangement and gross haltere shape both correspond with dipteran phylogeny.