Diverse new species and genera of Developea (Stramenopiles) displaying self-aggregation and multiflagellated stages

Developea is a poorly studied group of flagellated protists, with only seven species known to date. It is closely related to parasitic oomycetes, hyphochytriomycetes, Pirsoniales, and photosynthetic ochrophytes (e.g., diatoms and brown algae), altogether forming the large clade Gyrista within supergroup Stramenopiles. Due to their deep phylogenetic position and phagotrophic feeding mode, developeans might have preserved ancestral characteristics shared with related large and important sister groups. Despite their cosmopolitan distribution, only few environmental 18S rRNA gene sequences related to Developea are known. Here we describe 12 new strains which represent eight new species and two new genera, as well as the previously described species Developayella elegans. We provide feeding experiments on diverse eukaryotic prey, including red algae, diatoms, and heterotrophic flagellates. The ability of the new developean species to successfully consume red algae represents missing piece of the previously postulated developean-like phagoheterotrophic model for the symbiotic ancestor of photosynthetic stramenopiles. Three species, including D. elegans, are omnivorous, i.e. able to survive on either eukaryotic or prokaryotic prey. Finally, we observe new and rare morphological features for Developea, such as facultative multiflagellated life stages, cysts and self-aggregation. These features might have been present in the ancestor of Stramenopiles.