NEW SPECIES OF BACCIGEROIDES (DIGENEA: GYMNOPHALLOIDEA) INFECTING INTESTINAL MUCOSA OF GULF MENHADEN, BREVOORTIA PATRONUS GOODE, 1878 (CLUPEIFORMES: ALOSIDAE) FROM THE NORTHERN GULF OF MEXICO.

Abstract

We describe Baccigeroides currani n. sp. (Digenea: Gymnophalloidea) infecting the intestinal mucosa of the Gulf menhaden, Brevoortia patronus Goode, 1878 (Clupeiformes: Alosidae) from the Gulf of Mexico. The new species differs from its congeners by the combination of having an oral sucker that is more narrow than (vs. equal to or larger than) the ventral sucker, ceca that extend posteriad to the middle of the post-testicular space (vs. to the level of the testes), a cirrus sac that extends posteriad to the middle of or beyond the posterior margin of the ventral sucker (vs. wholly confined to the forebody or slightly overlapping the anterior margin of the ventral sucker), a bipartite (vs. unipartite) seminal vesicle, and a post-testicular (vs. pre-testicular) ovary. We emend Baccigeroides Dutta, 1995 to include features of the new species and its congeners: ceca that extend posteriad to the middle of the post-testicular space, a cirrus sac that extends posteriad to the middle of or beyond the posterior margin of the ventral sucker, a bipartite seminal vesicle, a median genital pore, a post-testicular ovary, a dorsal Laurer's canal pore opening near the posterior body end, and an excretory system with arms merging anteriorly at the level of the pharynx. The ITS2 and 28S sequences of the new species were most similar to those of Bacciger bacciger (Rudolphi, 1819) Nicoll, 1914 (type species) and Pseudobacciger cheneyae Sun, Bray, Yong, Cutmore, and Cribb, 2014. Phylogenetic analyses of the 28S and ITS2 sequences each recovered species of Bacciger Nicoll, 1914, Baccigeroides, and Pseudobacciger Nahhas and Cable, 1964 as closely related taxa and sister to the gymnophalloids of Tandanicolidae Johnston, 1927. Bacciger was polyphyletic (B. currani, Cercaria rangiae Wardle, 1983, and P. cheneyae nested in the clade of Bacciger spp.) and requires revision. We reject the synonymy of Baccigeroides opisthonemae (Nahhas and Cable, 1964) n. comb. and Baccigeroides ovatus (Price, 1934) Cutmore, Bray, and Cribb, 2018 because they are morphologically distinct; however, both species require redescription based on the types and new specimens collected from the type host and type locality. The present study comprises the first phylogenetic analysis that includes a sequence of Baccigeroides and the first report of species of Baccigeroides infecting an alosid from the northern Gulf of Mexico.