Txikispora philomaios n. sp., n. g., a micro-eukaryotic pathogen of amphipods, reveals parasitism and hidden diversity in Class Filasterea

This study provides a morphological, ultrastructural, and phylogenetic characterization of a novel micro-eukaryotic parasite (2.3–2.6 µm) infecting amphipod genera Echinogammarus and Orchestia. Longitudinal studies across two years revealed that infection prevalence peaked in late April and May, reaching 64% in Echinogammarus sp. and 15% in Orchestia sp., but was seldom detected during the rest of the year. The parasite infected predominantly hemolymph, connective tissue, tegument, and gonad, although hepatopancreas and nervous tissue were affected in heavier infections, eliciting melanization and granuloma formation. Cell division occurred inside walled parasitic cysts, often within host hemocytes, resulting in hemolymph congestion. Small subunit (18S) rRNA gene phylogenies including related environmental sequences placed the novel parasite as a highly divergent lineage within Class Filasterea, which together with Choanoflagellatea represent the closest protistan relatives of Metazoa. We describe the new parasite as Txikispora philomaios n. sp. n. g., the first confirmed parasitic filasterean lineage, which otherwise comprises four free-living flagellates and a rarely observed endosymbiont of snails. Lineage-specific PCR probing of other hosts and surrounding environments only detected T. philomaios in the platyhelminth Procerodes sp. We expand the known diversity of Filasterea by targeted searches of metagenomic datasets, resulting in 13 previously unknown lineages from environmental samples.

Bibliographic Details

Main Authors:	Urrutia, A., Mitsi, Konstantina, Foster, Rachel A., Ross, Stuart, Carr, M., Ward, Georgia M., Aerle, Ronny van, Marigómez, Ionan, Leger, Michelle M., Ruiz-Trillo, Iñaki, Feist, Stephen W., Bass, David
Other Authors:	Ministerio de Economía y Competitividad (España)
Format:	artículo biblioteca
Published:	John Wiley & Sons 2022-11-02
Subjects:	Echinogammarus, Environmental DNA, Hemolymph congestion, Histopathology, Holozoa, Intracellular parasite, Orchestia,
Online Access:	http://hdl.handle.net/10261/271630 http://dx.doi.org/10.13039/501100011033 http://dx.doi.org/10.13039/501100000780 http://dx.doi.org/10.13039/501100003329
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