Spermatodesmata of the Sawflies (Hymenoptera: Symphyta): Evidence for Multiple Increases in Sperm Bundle Size
We present the first survey of spermatodesmata (bundles of spermatozoa connected at the head by an extracellular 'gelatinous' matrix) across the sawfly superfamilies. Spermatodesmata occur in all examined taxa within the sawfly grade (Xyelidae-Orussidae inclusive), but are not found in the Apocrita. Using DAPI staining, the numbers of individual sperm per spermatodesm were calculated and the values obtained are mapped on to the current phylogenetic hypothesis. The plesiomorphic spermatodesm in the Hymenoptera, based on that observed in the putatively basal family Xyelidae, contains relatively few sperm, approximately 16. However, in the Tenthredinoidea and in the Siricidae, far larger numbers are found, reaching up to 256 in the Cimbicidae.