A Molecular Phylogenetic Study of the Genus Ribeiroia (Digenea): Trematodes Known to Cause Limb Malformations in Amphibians

Abstract

Species of Ribeiroia (Trematoda: Psilostomidae) are known to cause severe limb malformations and elevated mortality in amphibians. However, little is known regarding the number of species in this genus or its relation to other taxa. Species of Ribeiroia have historically been differentiated by slight differences among their larval stages. To better understand the systematics and biogeography of this genus and their potential relevance to the distribution of malformed amphibians, specimens identified as Ribeiroia were collected across much of the known range, including samples from 5 states in the United States (8 sites) and 2 islands in the Caribbean (Puerto Rico and Guadeloupe). A cercaria from East Africa identified as Cercaria lileta (Fain, 1953), with attributes suggestive of Ribeiroia (possibly R. congolensis), was also examined. The intertranscribed spacer region 2 (ITS-2) of the ribosomal gene complex was sequenced and found to consist of 429 nucleotides (nt) for R. ondatrae (United States) and 427 nt for R. marini (Caribbean), with only 6 base differences noted between the 2 species. The ITS-2 region of C. lileta (429 nt) aligned closely with those of the 2 other Ribeiroia species in a phylogenetic analysis that included related trematode genera. This evidence suggests that a third Ribeiroia species exists in tropical Africa. Variation in ITS-2 within R. ondatrae was nonexistent among the 8 populations from North America. Our study further suggests that Ribeiroia spp. originally parasitized Biomphalaria sp., and that a host switch to a closely related snail, Helisoma sp., may have occurred in the lineage represented by R. ondatrae. However, relationships within the Echinostomatidae are not understood well enough to make any robust conclusions at this time.

Histopathological effects of the intramolluscan stages of Zygocotyle lunata, Echinostoma trivolvis, and Ribeiroia ondatrae on Helisoma trivolvis and observations on keratin in the trematode larvae

“…BioEdit Sequence Alignment Editor was used to directly compare the project sequences to R. ondatrae ITS-2 sequences from GenBank (Hall 1999). The sequences were found to be identical to the ITS-2 region of R. ondatrae (Wilson et al 2005).…”

“…Cercariae of E. trivolvis and Z. lunata were identified by one of us (BF), who has worked with these cercariae for many years. The gymnocephalus cercaria was identified as R. ondatrae by its unique morphological characteristics (Johnson et al 2004) and by molecular analysis (Wilson et al 2005). DNA was extracted from the cercariae using the MoBio Ultraclean Tissue DNA Isolation Kit (MoBio Laboratories Inc., Carlsbad, CA, USA).…”

“…DNA was extracted from the cercariae using the MoBio Ultraclean Tissue DNA Isolation Kit (MoBio Laboratories Inc., Carlsbad, CA, USA). The intertranscribed spacer region 2 (ITS-2) of the ribosomal gene complex was targeted using the primer set 3 S (5′ GGT ACC GGT GGA TCA CGT GGC TAG TG 3′; Bowles et al 1995) and ITS2.2 (5′ CCT GGT TAG TTT CTT TTC CTC CGC 3′ Hugall et al 1999) as described in Wilson et al (2005). Promega Master Mix (Promega Corporation, Madison WI, USA) was used for all polymerase chain reactions (PCR) at 25-µl reaction volume with template and primer concentrations based on manufacturer's recommendations.…”

A review on the molecular characterization of digenean parasites using molecular markers with special reference to ITS region

“…Wilson et al (2005) studied the systematics and biogeography of Ribeiroia sp. from amphibians using the ITS-1 and ITS-2 region sequences.…”

Parasites of the Mink Frog (Rana septentrionalis) from Minnesota, U.S.A

“…[Bain and Prod'hon, 1974]) in the blood. Sutherland (2005) and Wilson et al (2005) also reported mink frogs as hosts for the metacercariae of Ribeioria ondatrae, which have been implicated in causing limb deformities in amphibians in North America (Johnson et al, 1999;Johnson et al, 2002) and, indeed, Sutherland (2005 found infections associated with limb deformities in mink frog populations of Minnesota. Conn et al (2002) also reported mink frogs from upstate New York as hosts for echinostomatid metacercariae.…”