New insights into the coevolutionary history of termites and their gut flagellates: Description of Retractinympha glossotermitis gen. nov. sp. nov. (Retractinymphidae fam. nov.)

Lower termites harbor diverse consortia of symbiotic gut flagellates. Despite numerous evidence for co-cladogenesis, the evolutionary history these associations remains unclear. Here, we present Retractinymphidae fam. nov., a monogeneric lineage Trichonymphida from Serritermitidae. Although Retractinympha glossotermitis gen. nov. sp. morphologically resembles members genus Pseudotrichonympha , phylogenetic analysis identified it as sister group Teranymphidae. We compared morphology and ultrastructure R . to that other Teranymphidae, including so-far undescribed solitaria Termitogeton planus (Rhinotermitidae). Like all is large, elongated flagellate with bilaterally symmetric rostrum, an anterior, flagella-free operculum, internal rostral tube. However, readily distinguished by length its flagella, which never exceeds postrostral retractable anterior end. Inclusion hitherto unstudied Stylotermes halumicus (Stylotermitidae) in our survey trichonymphid flagellates Neoisoptera confirmed combined presence Heliconympha absence unique The close relatedness Serritermitidae spirotrichosomid Stolotermitidae provides strong support their acquisition horizontal transmission.