New records of the colonial chrysophyte Urostipulosphaera articulata (Chrysophyceae, Ochromonadales) in China

Results of the polygenic phylogenetic tree, based on SSU, rbcL and ITS sequences, showed that the three samples were clustered with Urostipulosphaera articulata U5-5 from Czechia, with a high support rate of 100/1.00. Morphological observations further supported this result. Therefore, the three samples were identified as Urostipulosphaera articulata.

This is the first report in China and enriches the geographic diversity of this species. Moreover, we found the long flagellum with mastigonemes under the scanning electron microscope complementing the description of the morphological characteristics of this species. The ITS2 secondary structure of the specimens differed from that of Urostipulosphaera articulata U5-5, which exhibited a loop and five-arm structure.

A Bayesian relaxed clock analysis indicated that the genus Urostipulosphaera originated in the Early Cretaceous, approximately 109.85 million years ago (Ma) and diverged into two clades around 79.81 Ma.