We report a novel nanoflagellate, Ophirina amphinema n. gen. n. sp., isolated from a lagoon of the Solomon Islands. The flagellate displays ‘typical excavate’ morphological characteristics, such as the presence of a ventral feeding groove with vanes on the posterior flagellum. The cell is ca. 4 µm in length, bears two flagella, and has a single mitochondrion with flat to discoid cristae. The flagellate exists in two morphotypes: a suspension-feeder, which bears flagella that are about the length of the cell, and a swimmer, which has longer flagella. In a tree based on the analysis of 156 proteins, Ophirina is sister to jakobids, with moderate bootstrap support. Ophirina has some ultrastructural (e.g. B-fibre associated with the posterior basal body) and mtDNA (e.g. rpoA–D) features in common with jakobids. Yet, other morphological features, including the crista morphology and presence of two flagellar vanes, rather connect Ophirina to non-jakobid or non-discobid excavates. Ophirina amphinema has some unique features, such as an unusual segmented core structure within the basal bodies and a rightward-oriented dorsal fan. Thus, Ophirina represents a new deeply-branching member of Discoba, and its mosaic morphological characteristics may illuminate aspects of the ancestral eukaryotic cellular body plan.
Bibliographical noteFunding Information:
We thank Dr. Akihiro Tame (Marine Work Japan Ltd.) for technical help with electron microscopy; Mses Chiho Kusaka and Kaoru Ito for technical help with molecular experiments; Ms. Ashley Yang for assistance with culture maintenance and shipping; Dr. Christopher Filardi for assistance with field sampling; Dr. Filardi and Dr. Simon Albert for discussions about naming of the collection site; Dr. Alexandros Pittis for assistance with RNA-seq data assembly; Dr. Andrew J. Roger (Halifax University) for technical help with phylogenyetic analysis; and Dr. Alastair G. B. Simpson (Halifax University) for helpful discussions on the ultrastructural observations. This study was supported by a grant from the Japan Society for the Promotion of Science (17K19434) awarded to AY, and by the Simons Foundation (#382790) awarded to EK.
© 2018, The Author(s).