| Kaonashia | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Stramenopiles |
| Family: | Kaonashiidae Weston, Eglit & Simpson 2023 |
| Genus: | Kaonashia Weston, Eglit & Simpson 2023 |
| Species: | K. insperata |
| Binomial name | |
| Kaonashia insperata Weston, Eglit & Simpson 2023 | |
Kaonashia insperata is aspecies ofsingle-celledphagotrophicstramenopiles. Described in 2023 from flagellates found in asoda lake, it is the sole species within the genusKaonashia and familyKaonashiidae. Cells of this organism have cortical alveoli, extrusomes, a ventral groove, a short anterior flagellum covered inmastigonemes, and a longer posterior flagellum covered in thinner hairs. The cells are most similar to those found indevelopayellids, but a molecular phylogenetic analysis found no well-supported affinity to any specific stramenopile group.
ThegenusKaonashia is named after the fictional ghost No-Face (Japanese:顔無し,Hepburn:Kaonashi) from theHayao Miyazaki filmSpirited Away. Thespecific epithetinsperata (from Latin insperata 'unexpected') references the unanticipated phylogenetic placement of this organism given its appearance.[1]
Kaonashia insperata is aspecies of free-livingphagotrophicflagellates. The cells are roughly ovoid or bean-shaped, 7–13 μm long, abundant in simpleextrusomes and flattenedcortical alveoli underlying much of thecell membrane, and with a conspicuous ventral groove. Themitochondria have tubularcristae. The cell shape and size is distorted when containingfood vacuoles and prey cells.[1]
Each cell has two flagella: a long,posterior flagellum (2.5 times the cell length) that lies inside the ventral groove and trails behind when swimming; and a shorter,anterior flagellum (1.5 times the cell length) that points forward in a rapid beating motion. Along the anterior flagellum are longmastigonemes (flagellar "hairs") arranged in two opposing rows. Each mastigoneme has two unequal terminal filaments. The mastigonemes appear near the insertion of the flagellum up until the distal portion where they are absent, not extending to the tip as is usual in other stramenopiles. The posterior flagellum sometimes anchors to the substrate through sparse, thinner hair-like filaments.[1]
The generalmorphology of their cells is consistent withstramenopiles, but their cellular structures are also found across other members of theSar clade and even more distantly related eukaryotes. The extrusomes ofK. insperata are smaller and simpler than most extrusomes in Sar species, and are most similar to those observed intelonemids and somerhizarians. The cortical alveoli are the unifying trait ofalveolates; among phagotrophic stramenopiles they have been identified indevelopayellids, although larger and more limited than those found inK. insperata. The ventral groove is observed in many distantly related eukaryotes such asexcavates; among stramenopiles, the highest similarity corresponds to developayellids. Regarding the flagella, a longer posterior flagellum is also seen in developayellids. The mastigonemes of the anterior flagellum are typical of stramenopiles, particularlyplacidideans andoomycetes due to the unequal terminal filaments, and the thinner hairs of the posterior one are similar to those used by some oomycetes to adhere to plant matter.[1]
The cells reproduce asexually throughbinary fission. The flagella are duplicated and positioned at opposite sides of the anterior end of the cell. Throughout thecell division, cells are still capable of movement, and appear two-lobed at the anterior end, frequently with a food vacuole located near the site ofcytokinesis.[1]
Kaonashia insperata is one of the few describedheterotrophicprotists found insoda lakes. It is a species of eukaryotrophicaerobes, meaning they consume other eukaryotes and breathe oxygen.[2] They feed on various species of unicellular algae, particularly those that are larger than 5 μm, such asGuillardia theta.[1]
Cells of this species were first obtained from thephotic zone ofSoap Lake,Washington, USA, initially under the name of isolate SC, together with residualGuillardia theta prey cells andbacteria. The flagellates werecultivated and studied under light and electron microscopy, which unveiled numerous morphological traits associated with theStramenopiles. A phylogenetic analysis performed with theSSU rDNA gene placed these flagellates within the Stramenopilesclade. Despite the close resemblance with developayellids, there is no well-supported affinity to any particular stramenopile subgroup. As a result, the organism was classified as a newgenus andspeciesKaonashia insperata in a new separatefamily Kaonashiidae, placed directly in the Stramenopiles. The description was published in 2023 in anarticle by protistologists Elizabeth J. Weston, Yana Eglit, and Alastair G. B. Simpson.[1]
Resin-embedded cells of isolate SC were assigned as thehapantotype ofKaonashia insperata and deposited in the Institute of Parasitology of theCzech Academy of Sciences under the code ICPAS_Pro_77.[1]
