Pygidiopsoides spindalis Martin

(13. Pysp; Figs. 1, 53–56)

Diagnosis: Parthenitae. Colony comprised of active rediae, densely concentrated in snail gonad region. Rediae almost opaque white to translucent white or grey; ~ 300–400 µm long, oblong to elongate (length:width ~3:1 to 8:1), sausage-shaped.

Cercaria . Body mostly translucent colorless; oculate; with oral sucker and no ventral sucker; body ~ 100 µm long, ~equal in length to tail; tail simple.

Cercaria behavior: Fresh, emerged cercariae remain in water column, swim ~continuously.

Similar species: Pysp is readily separable from the other heterophyids by the lack of a cercaria tail fin, in addition to its relatively short tail, blunt anterior, and small size.

Remarks: Martin (1951) described this species from adults obtained by feeding metacercariae from naturally infected Fundulus parvipinnis to chicks and cats. He later documented the life cycle, and described rediae and cercariae from naturally infected California horn snails and metacercariae from experimentally infected second intermediate hosts (Martin 1964). This species likely corresponds to the “small opisthorchioidea” in Martin (1955).

Garcia-Vedrenne et al. (2017) presents several lines of evidence indicating that this species has a caste of soldier rediae (however, the in vitro attack trials had limited success).