A New Webbing Aberoptus Species from South Africa Provides Insight in Silk Production in Gall Mites (Eriophyoidea)

Abstract

Arthropods include a high diversity of lineages adapted for silk production. Several species of microscopic phytophagous mites of the hyperdiverse superfamily Eriophyoidea spin web; however, the origin of their silk is unknown. We described a new web-spinning mite, Aberoptus schotiae n. sp., collected from leaves of Schotia brachypetala (Fabaceae) in South Africa and showed that it has a complex life cycle, including two morphotypes of adults and nymphs. Molecular phylogenetic analyses and 28S sequence comparison showed conspecificity of heteromorphic females and rejected synonymy of Aberoptus and Aceria proposed by previous authors. For the first time, we provided SEM images of the web nests and, using a set of different microscopic techniques, described the silk-producing anal secretory apparatus (ASA) of Aberoptus. It comprises two pairs of anal glands (hypertrophied in web-spinning females), three cuticular sacs and a rectal tube leading to the anal opening. This is a unique case (analogy) of anal silk secretion in Chelicerata previously reported only in Serianus (Pseudoscorpiones). Recent findings of rudimentary ASA in distant eriophyoid lineages and the results of this study transform the current paradigm of exoticism of web-spinning eriophyoid taxa into the concept of synapomorphic specialization of the hindgut for excreting the anal gland secretions in Eriophyoidea.