The history continues: From Steringotrema microacetabularis (Fellodistomidae) to Bacciger microacetabularis (Baccigeridae) genetic evidence reveals a new genus of Cryptogonimidae.

Abstract

Steringotrema microacetabularis Suriano & Martorelli, 1983 (Fellodistomidae) was described from the flounder Paralichthys orbignyanus. Later, it was redescribed, based on new material from the same host and type locality, and reconsidered as Bacciger microacetabularis (Baccigeridae). The main difference noted in the redescription was the presence of spines on the body. However, the lack of DNA data made confirming the true affiliation of this digenean challenging. New specimens sampled from P. orbignyanus allowed us to sequence the 28S, ITS, and COI genes. Fresh specimens were stained to compare their morphology with the holotype and voucher specimens. The digeneans found correspond with those reported from Mar Chiquita, described as B. microacetabularis (=S. microacetabularis). Genetic analyses clustered the newly sequenced individuals within the Cryptogonimidae, showing relationships with Oligogonotylus manteri, Tabascotrema verai, and Caecincola parvulus (28S); T. verai, Lobosorchis spp., Euryakaina manilensis, and Metadena marina (ITS); and Siphoderina spp. (COI). After comparing the species with cryptogonimids lacking spines in the oral sucker, a new genus, Surianotrema n. gen., is described. This genus increases the number of cryptogonimid genera known in South America to seven - three in freshwater and four in marine environments - with Surianotrema n. gen. being the first to be sequenced. New sequences from other South American cryptogonimids are necessary to better understand the phylogenetic relationships between genera within this family, particularly in South America.