Allobodo chlorophagus n. gen. n. sp., a Kinetoplastid that Infiltrates and Feeds on the Invasive Alga Codium fragile

• Published in: Protist 2018-12, Vol.169 (6), p.911-925
• Main Authors: Goodwin, Joshua D., Lee, Thomas F., Kugrens, Paul, Simpson, Alastair G.B.
• Format: Article
• Language: English
• Subjects: Algae; invasive; kinetoplastid; parasite; phylogeny; protozoa
• ISSN: 1434-4610; 1618-0941
• DOI: 10.1016/j.protis.2018.07.001

A novel biflagellate protist that consumed chloroplasts inside material of the invasive marine green alga Codium fragile was reported from the U.S. east coast in 2003. We observed a similar association in C. fragile from five sites in Nova Scotia, Canada during 2013 and 2014. After incubating Codium fragments for 2–3 days, some utricles and filaments contained numerous chloroplast-consuming cells. Transmission electron microscopy (TEM) confirmed that these were kinetoplastids with a pankinetoplast, large electron-dense droplets in the cytoplasm and a connective between the paraxonemal rod bases, but no conspicuous para-cytopharyngeal rod, all consistent with U.S. material observed in 2003. The ITS1-5.8S rRNA-ITS2 sequences from 13 Nova Scotia isolates were identical. SSU rRNA gene phylogenies placed the Codium-associated kinetoplastid in neobodonid clade ‘1E’. Clade 1E likely contains no previously described species, and branches outside all other major neobodonid groups, either as their sister or as a separate lineage, depending on rooting. These results indicate that the kinetoplastid represents a single species that merits a new genus (and family), and we describe it as Allobodo chlorophagus n. gen., n. sp. The lack of evidence for food sources other than Codium is consistent with a parasitic association, but other possibilities exist (e.g. necrotrophy).