Pygidiopsoides spindalis Martin, 1951

This parasite, Pygidiopsoides (Pygidiopsis-like) along with spindalis (referring to the spindle-shaped body), was described from adults recovered from the small intestines of cats and chicks fed metacercariae from fish in southern California, USA. Because this parasite has only one testis, it has been placed by some in the subfamily Haplorchiinae; however, based on larval morphology, it appears more related to members of the Centrocestinae (Martin, 1964). This worm is distinguished from the other members of the Centrocestinae by the presence of a common muscular genital ejector. Unlike specimens of Pygidiopsis, this trematode has a single testis and two gonotyls.

Pygidiopsoidesspindalis adults are 0.22 to 0.43 mm long and 0.06 to 0.10 mm wide. The body is covered with small spines, and 14 spines surround the mouth. The eggs are 26 to 28 µm long by 13 to 15 µm wide.

LIFE CYCLE: The life cycle has been examined by Martin (1951 and 1964). The miracidia develop in snails, Certhidea californica, that live in intertidal areas. The cercariae have simple tails without fins and two large eye spots. The cercariae penetrate the gills of brackish-water fish, Fundulus parvipinnis, and they work their way to the body process of the gill where they encyst. The adult trematodes were recovered from fish 4 to 6 days after being fed infected fish.


Martin WE. 1951. Pygidiopsoidesspindalis n. gen., n. sp., (Heterophyidae; Trematoda), and its second intermediate host. J Parasitol 37:297-300.

Martin WE. 1964. Life cycle of Pygidiopsoidesspindalis Martin, 1951 (Heterophyidae: Trematoda) Tr Am Mic Soc 83:270-272.