Structure and evolution of spiracular gills in pupae of net-winged midges (Nematocera; Blephariceridae). Part I.PaulianinaandEdwardsina(subfamily Edwardsininae)

Abstract

The pupae of Blephariceridae develop in streams and respire by means of spiracular gills. Our knowledge about the morphology of these organs is limited, and no scanning electron microscopic analyses of their fine structure have been carried out. Therefore, ca. 30 representative species from all continents and all main taxa of the Blephariceridae have been comparatively investigated with respect to their pupal gills. This first part of a series of publications on the theme deals with the ground plan of the spiracular gills in the subfamily Edwardsininae, with special attention paid to the fine structure of the plastron and atrium. For this purpose, one or two species from the three geographically isolated subpopulations of the Edwardsininae (Madagascar, South America, Australia) have been examined and compared with a pupa from the Deuterophlebiidae, the sister-group of the Blephariceridae. The results are discussed with regard to phylogeny and agree well with recent studies on the systematics of the Nematocera. The gills of the Edwardsininae have a primitive construction compared with those of the other subfamily, the Blepharicerinae, which has a worldwide distribution. The supposed functional advantages of spiracular gills and the reason for their evolution are critically considered. The findings cast some doubts on the usual interpretation that the felt inside the atrium serves as a sealant.