Pirsonia guinardiae

Super Group: 
Schnepf, Drebes & Elbrächter 1990


Diagnosis_Genus: Pirsonia Schnepf, Drebes & Elbrächter. Parasites of diatoms. Free-swimming stages are coloufless, small flagellates, laterally flattened with oblique cell apex and two subapically inserted flagella, a long anteriorly oriented one and a very long posteriorly oriented: one. The cytoplasm contains many refractive granules. The flagellate attaches to a host celt and becomes a trophont, differentiating into an auxosome and a trophosome. The trophosome is situated inside the diatom shell; it includes a digestion vacuole and has small pseudopodia which phagocytise host cytoplasm. The auxosome remains outside the frustule; it does not contain vacuoles. Auxosome and trophosome are connected ,by a thin cytoplasmic strand. The auxosome detaches and divides thereafter or divides still attached to the host cell, giving rise to many offspring. The trophosome persists a short time after the detachment of the auxosome or its derivatives. Mastigophora incertae sedis.
Diagnosis_Species: Pirsonia guinardiae Schnepf, Drebes & Elbrächter. Structure as described for the genus. Flagellates laterally flattened, about 10 µm long and 6 µm wide. Auxosome remains flagellated. Mature auxosomes apple-shaped, about 15 µm in diameter, generally detaching before division, giving rise to 4 (to 8) daughter cells which are infectious without a longer resting phase. Thick-walled cysts present.
Body_spores_length: 7-12 µm
Body_spores_wide: 5-7 µm


Pirsonia: was established in honor of Prof. Dr. A. Pirson, Göttingen
guinardiae: Type host for the species Pirsonia guinardiae

Type species

This is the type species of the genus.

Type illustration / Type locality / Type specimen

Type illustration: Figs 1-26.
Type locality: North Sea, near List/Sylt
Type host: Guinardia flaccida



Substrate: epiphytic
Salinity: marine

Life cycle

Generation: <1 month
Reproduction_mode: asexual
Symbiont: horizontal

Feeding behaviour


Mode of locomotion


Identification criteria

Observation site(s)


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