Euduboscquella aspida

Super Group: 


Diagnosis_Genus: Euduboscquella Coats & Bachvaroff 2012. Euduboscquellidae with trophont episome as disc-shaped shield bordered by a perinematic ring. Lamina pharyngea extending from perinematic ring into trophont cytoplasm. Food vacuole formed as trophont emerges from host giving rise to extracellular tomont. Multiple spore morphotypes possible, including dinokont and non-dinokont cells. Individual infections producing only one type of spore.
Diagnosis_Species: Trophont morphology/development: Ovoid, ≤ 80 µm diam. with flattened episome; elliptical shield is underlain by a fibrillar lattice; sagittal furrow conspicuous and bisects the shield; perinema forms an open circle with overlapping ends; lamina pharyngea well developed; nucleus spherical ~40 µm diam.; nucleolus is large in young trophonts, but absent in parasites ≥ 30 µm diam.; a substantial amount of host cytoplasm is ingested during the phagotrophic phase. Infection occurs in the host cytoplasm. During its developmentn the trophont remains uninucleate (synenergid nuclear structures).
Sporogenesis: Sporogenesis occurs outside the host (palintomic divisions); cytokinesis is perpendicular to a row of basal bodies positioned along the saggital furrow; sporocytes remain connected and form long beaded strands; food vacuole does not divide.
Spore morphology: Microspores (~50,000) measure 2 x 3 µm and have two short (~1 µm) flagella; macrospores (~1000) are 6-7 µm long and have a trailing and transverse flagellum each ~12 µm in length; microspores comma-shaped with bulbous episome; macrospores bean-shaped. Macrospores remain attached during sporogenesis forming long filament of cells, while microspores are released immediatly after division. The swimming behaviour of both type of spores is different, macrospores actively swimming (and they remain active longer than microspores), while microspores goes down and have kind of erratic swimming.
The host can survive to the infection. When followed in the laboratory, the transition of the parasite from intracellular to extracellular phase did not kill the host. The ability of Favella panamensis to survive infections was also evident in plankton samples, where sporogenic stages were frequently observed in the loricae of actively swimming hosts that, aside from being small, had a normal appearance (Coats et al. 1994).

Body_trophont: ≤ 80 µm µm
Body_macrospores_length: 6 – 7 µm
Body_microspores_length: 2 – 3 µm


Genus name is derived from the Greek eu- (= well, normal) and the genus name Duboscquella.


Multiple infections are frequent but immature trophont generally degenerates. As example, multiple infections were common in Favella panamensis collected from two North American estuaries with as many as 53% of infected hosts containing more than one parasite (mean =20+2.9%, n=34). (Coats et al. 1994).

Sociability_trophont: solitary
Sociability_trophont: sometime gregarious
Substrate_trophont: endozoic (endoparasite)
Substrate_tomont: extracellular
Substrate_spores: planktonic
Salinity: marine
Salinity: brackish
Salinity: variable

Life cycle

Live cycle of the parasite: Because most of young trophont are localised close to the host cytopharynx, Cachon (1964) proposed that infections start by the ingestion of the spores (passive infestation). The intracellular trophont feeds by osmotrophy (during 3-4 days) and increases in size. The cell membrane of the hyposome has considerable pinocytotic acitivity (Cachon and Cachon 1987). When leaving the host, the parasite becomes phagotrophic by ingesting most of the host cytoplasm (the phagotrophic stage). The sporogenesis starts at this moment and yields to the production of spores. Macrospores and microspores are formed by different trophonts, no fusion was observed between both.

Parasitism did not appear to prevent reproduction of the host, as cytological preparations revealed that all stages of the ciliate's cell cycle including mitosis could harbor well developed infections. Interestingly, food vacuoles of postphagotrophic parasites sometimes contained one of the host's macronuclei. The reproductive competency of individual Favella panamensis that have lost one or, more macronuclei is unknown. (Coats et al. 1994).

Phases_alternance: haplontic
Generation: <1 month
Reproduction_mode: asexual

Symbiont: horizontal_ingestion

Feeding behaviour


Mode of locomotion


Observation site(s)


Displaying 1 - 2 of 2
Association with... Region origin Name of site In reference...
Favella panamensis Florida Indian River
Favella panamensis Maryland Chesapeake Bay