Partial co-option of the appendage patterning pathway in the development of abdominal appendages in the sepsid fly Themira biloba
- 270 Downloads
The abdominal appendages on male Themira biloba (Diptera: Sepsidae) are complex novel structures used during mating. These abdominal appendages superficially resemble the serially homologous insect appendages in that they have a joint and a short segment that can be rotated. Non-genital appendages do not occur in adult pterygote insects, so these abdominal appendages are novel structures with no obvious ancestry. We investigated whether the genes that pattern the serially homologous insect appendages have been co-opted to pattern these novel abdominal appendages. Immunohistochemistry was used to determine the expression patterns of the genes extradenticle (exd), Distal-less (Dll), engrailed (en), Notch, and the Bithorax Complex in the appendages of T. biloba during pupation. The expression patterns of Exd, En, and Notch were consistent with the hypothesis that a portion of the patterning pathway that establishes the coxopodite has been co-opted to pattern the developing abdominal appendages. However, Dll was only expressed in the bristles of the developing appendages and not the proximal–distal axis of the appendage itself. The lack of Dll expression indicates the absence of a distal domain of the appendage suggesting that sepsid abdominal appendages only use genes that normally pattern the base of segmental appendages.
KeywordsAppendage Sepsidae Abdomen Innovation Co-option
We would like to thank Rudolf Meier for sharing his culture of T. biloba, and Bill Eberhard for sharing his knowledge of sepsid behavior and rearing. Thank you to Rob White, Nipam Patel, and Sean Carroll for providing antibodies. We would like to thank Lisa Nagy, Yui Suzuki, Robin Smith, and two anonymous reviewers for their comments on the manuscript. Laura Grunert provided critical technical assistance. We would also like to thank Maple View Farm in Chapel Hill, NC and the University of Arizona Agricultural Center for providing cow dung. This work was funded by the Department of Biology at Duke University (JHB and HFN), National Science Foundation grant IBN-0315897 (HFN), and the Center for Insect Science at the University of Arizona through the National Institute of Health Training Grant 1K12 GM000708 (JHB).
- Abouheif E (1997) Developmental genetics and homology: a hierarchical approach. TREE 12:405–408Google Scholar
- Hennig W (1949) Sepsidae. In Lindner E (ed) Die Fliegen der Palaearktischen Region. E Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany, pp 1–91Google Scholar
- Lachmann A (1991) Vergleichende Untersuchung zum Lebenszyklus der kuhdungbewohnenden Sphaeroceridenarten Chaetopodella scutellaris (Haliday, 1836) und Coproica lugubris (Haliday, 1836). Deutsche Entomologische Zeitschrift 38:197–210Google Scholar
- Mayr E (1960) The emergence of evolutionary novelties. In: Tax S (ed) Evolution after Darwin. University of Chicago Press, Chicago, pp 349–380Google Scholar
- Meier R (1996) Larval morphology of the Sepsidae (Diptera: Sciomyziodea), with a cladistic analysis using adult and larval characters. Bulletin of the AMNH 228:1–147Google Scholar
- Pont AC (1979) Sepsidae: Diptera, Cyclorrhapha, Acalyptrata. In: Fitton MG (ed) Handbooks for the identification of British insects. Royal Entomological Society of London, London, pp 1–35Google Scholar
- Roth VL (1988) The biological basis of homology. In: Humphries CJ (ed) Ontogeny and systematics. Columbia University Press, New York, pp 1–26Google Scholar
- Snodgrass RE (1935) Principles of insect morphology. McGraw-Hill Book Company, New YorkGoogle Scholar