Phylogenetic position of rhyacophiloid caddisflies (Insecta, Trichoptera): a spermatological analysis of Rhyacophilidae and Glossosomatidae

Most caddisflies (Insecta, Trichoptera) are classified into two suborders, Annulipalpia and Integripalpia. However, the use of the derived characters that are regularly applied in systematic and phylogenetic analyses of Trichoptera is insufficient to determine with certainty the position of the families belonging to Rhyacophiloidea, which are considered by different authors to be either Annulipalpia, or Integripalpia, or even a separate suborder. Rhyacophiloidea comprise four overall similar families: free-living Rhyacophilidae and Hydrobiosidae, saddle-case making Glossosomatidae, and purse-case making Hydroptilidae. It was previously found that Annulipalpia spermatozoa have aberrant axonemes while Integripalpia spermatozoa display the plesiomorph 9 + 2 axoneme. The present spermatological analysis of the families Rhyacophilidae and Glossosomatidae shows that both have spermatozoa with aberrant axonemes lacking the two central microtubules found in the typical axoneme of insect spermatozoa. This is an apomorphic character shared with the superfamily Hydropsychoidea, indicating that from this point of view, Rhyacophiloidae are more closely related to Annulipalpia than to Integripalpia.