Euduboscquella sp. (Dinoflagellata, Syndinea), an intracellular parasite of the ciliate Helicostomella longa (Brandt, 1906) Kofoid & Campbell, 1929: Morphology and molecular phylogeny

Abstract

Syndinean dinoflagellates that infect tintinnid ciliates cause host mortality which can lead to the decline of blooms and promote species succession. We provide data on parasitism of the tintinnid, Helicostomella longa, for weekly samples collect from the southern coast of Korea over a two-year period. Parasite morphology was examined using material and specimens processed by quantitative protargol staining (QPS). Molecular phylogeny of the parasite was inferred using nuclear 18S ribosomal RNA gene sequences. The intracellular parasite develops in the host cytoplasm. At the end of vegetative growth cycle, the mature trophont emerges from the host and undergoes sporogenesis with early separation of the sporocytes. Sporogenesis produces three different types of spores: (1) about 80 dinospores (ca. 8 μm in length), (2) about 450 non-motile spherical spores (ca. 2 μm in diameter), (3) about 320 triangular spores (ca. 7 μm in length). Infected H. longa showed 100% mortality rate. Based on the morphological and molecular analyses, the intracellular parasite was identified as a new species of Euduboscquella (Dinoflagellata, Syndinea). Further investigations will estimate parasite prevalence in natural host assemblages and examine relationships between infections and environmental conditions.ollect from the southern coast of Korea over a two-year period. Parasite morphology was examined using material and specimens processed by quantitative protargol staining (QPS). Molecular phylogeny of the parasite was inferred using nuclear 18S ribosomal RNA gene sequences. The intracellular parasite develops in the host cytoplasm. At the end of vegetative growth cycle, the mature trophont emerges from the host and undergoes sporogenesis with early separation of the sporocytes. Sporogenesis produces three different types of spores: (1) about 80 dinospores (ca. 8 μm in length), (2) about 450 non-motile spherical spores (ca. 2 μm in diameter), (3) about 320 triangular spores (ca. 7 μm in length). Infected H. longa showed 100% mortality rate. Based on the morphological and molecular analyses, the intracellular parasite was identified as a new species of Euduboscquella (Dinoflagellata, Syndinea). Further investigations will estimate parasite prevalence in natural host assemblages and examine relationships between infections and environmental conditions.