DESCRIPTION, REDESCRIPTION, AND LIFE CYCLES OF PARORCHIS LAFFERTYI N. SP. AND PARORCHIS CATOPTROPHORI (TREMATODA:...

We describe Parorchis laffertyi n. sp., a trematode infecting the California horn snail, Cerithideopsis californica (Haldeman, 1840), as a first intermediate host. The first intermediate host stages of this species were previously cryptic with Parorchis catoptrophori Dronen & Blend, 2008, which also infects C. californica. For both species, we describe the parthenita colonies, soldier rediae, reproductive rediae, cercariae, metacercariae, and sexual adults by using DNA sequencing and material from natural and experimental infections. Our study of all life stages was conducted with material originating from naturally infected, lab-maintained horn snails from San Diego, California. Cercariae that were repeatedly shed from specific, labeled snails were used as material for experimental infections, developmental studies, and DNA sequencing. In all cases, data were tracked to their source individual first intermediate host colonies. These same colonies were dissected to describe the morphology, behavior, and demographics of reproductive and soldier rediae. Metacercaria descriptions came from cercariae shed and encysted in the laboratory; we also document a metacercaria developmental time series. We experimentally exposed final host chickens (Gallus gallus domesticus Linnaeus, 1758) and ducks (Anas platyrhynchos domesticus Linnaeus, 1758) to metacercariae per cloaca and successfully obtained and described the sexual adults of P. catoptrophori and an immature adult of P. laffertyi from the chickens. Both cytochrome c oxidase subunit I (COI) and 28S rDNA phylogenetic analyses supported the hypothesis that P. catoptrophori and P. laffertyi are 2 species of Parorchis Nicoll, 1907. As indicated in its original description, adults of P. catoptrophori can be readily distinguished from adults of other Parorchis species by their possession of a greater number of collar spines (∼80 vs. ∼60 in most other species); a bipartite pharynx; a pharynx to oral sucker ratio of ∼1:2; presence of esophageal diverticula; and deeply lobed testes. The immature adult of P. laffertyi can be distinguished from adults of other Parorchis species by the collar spine number (∼55); bipartite pharynx; a pharynx to oral sucker ratio of ∼1:2; presence of esophageal diverticula; and distinct COI and 28S sequence data. Mature adult specimens of P. laffertyi are needed to parse additional morphological characteristics. We used our morphometric data and additional published information to provide an emended diagnosis for the genus Parorchis. There are now 18 formally named Parorchis species, 4 of which have had their first intermediate host stages described and 4 of which have available DNA sequence information.