Discovery of a new animal parasitic euglenid species: Tsukuba-yadori-midorimushi

Tsukuba, Japan—Euglenids are known for their diverse nutritional methods, including photosynthesis, bacterial predation, and in some cases, animal parasitism. However, the documentation of parasitic euglenids is sparse and outdated, with no reliable information on their ecology or taxonomy.

In our study, we discovered flagellates within four animal species—including ostracods and rhabdocoels—collected from a rice field near the University of Tsukuba. These animals, which had flagellates in their bodies, died within days, indicating that the flagellate was a parasite. This flagellate displayed active metaboly without flagella inside the host body. However, upon leaving the host, it extended its flagella and began to swim. Using electron microscopy and other techniques, we examined the morphology of this flagellate and determined that it exhibited euglenid characteristics. In addition, DNA comparisons between flagellates isolated from all four animal species confirmed that they belonged to the same species. Phylogenetic analysis also revealed that this flagellate is a part of the photosynthetic euglenid group, suggesting that the flagellate lost its photosynthetic ability in the course of evolution to become an animal parasite. Comparing this to other previously reported parasitic euglenid flagellates, we deduced that our discovery is a new species. We have named it Euglenaformis parasitica (Japanese name: Tsukuba-yadori-midorimushi).

Euglenaformis parasitica exhibits a remarkably high infection rate in ostracods, a common species in rice fields. Elucidating the ecology of such parasitic organisms is anticipated to significantly enhance our understanding of rice-field ecosystems.
 

_{Original Paper}

Title of original paper:
Taxonomy of a New Parasitic Euglenid, Euglenaformis parasitica sp. nov. (Euglenales, Euglenaceae) in Ostracods and Rhabdocoels

Journal:
Protist

DOI:
10.1016/j.protis.2023.125967

_{Correspondence}

Associate Professor NAKAYAMA Takeshi
Institute of Life and Environmental Sciences, University of Tsukuba

KATO Koichiro
Aoyama Gakuin Junior High School

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Institute of Life and Environmental Sciences