Pygidiopsoides spindalis Martin, 1951

Hechinger, Ryan F., 2019, Guide to the trematodes (Platyhelminthes) that infect the California horn snail (Cerithideopsis californica: Potamididae: Gastropoda) as first intermediate host, Zootaxa 4711 (3), pp. 459-494 : 481-482

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).

Figures

FIGURE 1. General characteristics of the parthenitae and cercariae of the trematodes infecting Cerithideopsis californica as first intermediate host. Species numbers and codes follow Table 1 and species accounts. Cercariae are all to scale, with additional magnified views of six small species (indicated by dashed lines). Note the oral stylets (presented in right lateral view) for Pruc and Smmi. Parthenitae are not to scale. Scale bars consistently indicate 100 µm.

FIGURES 53–56. Pygidiopsoides spindalis (Pysp). 53, Overview of a colony in a freshly deshelled, infected horn snail in sea water. Arrow indicates the colony, which is localized in the gonadal region. Scale bar = 1 cm. 54, Reproductive redia, live, with developing cercariae, under heavy coverslip pressure. Scale bar = 100 µm. 55, Soldier redia, live, under slight coverslip pressure. Scale bar = 50 µm. Base photo credit: Ana Garcia-Vedrenne. 56, Cercariae, live, under coverslip pressure. Scale bar = 100 µm. Base photo credit: Todd Huspeni.