Isospora formarum McQuistion &
Type host: Pitylus grossus
grossus (Slate-colored grosbeak)
Other Hosts: Pitylus grossus
Type locality: SOUTH AMERICA:
Ecuador, Provincia de Morona-Santiago, ca. 5 km SW of Taisha,
elev. 425 m.
Geographic distribution: SOUTH
AMERICA: Ecuador, Provincia de Morona-Santiago and Prov. de
Description of oocyst: Oocyst shape:
spheroid to subspheroid; number of walls: 2; wall thickness: ~1.5; wall
characteristics: smooth, colorless outer surface with darker, thinner
inner layer; L x W: 24.6 x 23.5 (20-25 x 21-27); L/W ratio: 1.1 (1.0-1.1);
M: absent; OR: absent; PG: absent. Distinctive features of oocyst: lack of
M, OR, and PG.
Description of sporocysts and
sporozoites: Sporocyst shape: ovoid; L x W: 15.7 x 11.3 (10-13 x
14-17); L/W ratio: 1.4 (1.2-1.5); SB: present as small, nipple-like
body; SSB: present, large and triangular-shaped or large and conical
with irregular lower edge; PSB: absent; SR: present; SR
characteristics: large, ~7 in diameter, nearly spheroid, composed of
fine, uniform granules; SP: elongate with oblong RB at 1
end and arranged randomly in sporocyst. Distinctive features of sporocyst:
SP and SR appear to be enclosed in a thin membrane within
Prevalence: 2 of 2 (100%).
Sporulation: Exogenous. Oocysts were
stored in 2.5% (w/v) aqueous potassium dichromate solution at
ambient temp. prior to examination.
Prepatent and patent periods:
Site of infection: Unknown.
Oocysts found in feces.
Materials deposited: None.
Remarks: This species has not been
reported since its original description.
Reference: McQuistion & Capparella