Where are the South American freshwater turtle blood flukes (Trematoda: Spirorchiidae)? The first morphological and molecular analysis of spirorchiid cercariae from freshwater snails in Brazil

Abstract

Trematodes belonging to the family Spirorchiidae are blood parasites mainly of turtles with a worldwide distribution. These flukes were recently reported in some marine turtles from South America, where the occurrence of spirorchiids in freshwater definitive and intermediate hosts is so far unknown. In the present study, three morphotypes of brevifurcate apharyngeate distome cercariae found in freshwater molluscs from an urban reservoir in Brazil were used for morphological and molecular (nuclear 28S rDNA) evaluation. Two morphotypes of cercariae, probably congeneric species, were found in 12/17,465 specimens of Biomphalaria spp. and differ from each other by body size and sequences (0.1%). They present morphology similar to North American freshwater spirorchiids (Spirorchis spp.), however surprisingly molecular data reveals that these lineages are more closely related to marine spirorchiids. A third species found in 2/777 Pomacea sp. differs morphologically from all previously described spirorchiid cercariae and genetically from spirorchiids with available sequences (16-19%), grouping in the phylogenetic tree with freshwater North American species. This is the first report of freshwater spirorchiids in South America and the first molecular confirmation of the involvement of a caenogastropod in the life cycle of spirorchiids.

Neotropical Turtle Blood Flukes: Two New Genera and Species from the Amazon River Basin with a Key to Genera and Comments on a Marine-Derived Parasite Lineage in South America

“…The 28S trees (Figs. 37, 38), like others published previously (e.g., Pinto et al, 2015;Roberts et al, 2016c), each hinted at a monophyletic Spirorchiinae Stunkard, 1921(sensu Platt [1992) because they recovered paraphyletic Spirhapalum and monophyletic Spirorchis in the same clade (no 28S sequence data are available for Monticellius nor Plasmiorchis). Platt (1992) hypothesized that Spirhapalum was a stem lineage (pleisiomorphic member) of the Spirorchinae; however, the recovered 28S phylogeny and that of Tkach et al (2009) indicate that Spirhapalum is paraphyletic with the Spirorchis crown group (Fig.…”

“…In contrast, and perhaps owing to the difficulty in extracting taxonomically useful specimens from turtle blood, the blood parasites of freshwater turtles in South America remain unsampled. To our knowledge from South America, there is no published record of a blood parasite (of any phylum) infecting a freshwater turtle, and no freshwater turtle has been confirmed as a TBF host (Pinto et al, 2015). Platt (1992), who first drew attention to this gap in our knowledge of TBF biodiversity, placed a bold question mark over the figure of the continent of South America to make his point.…”

“…Twenty-three years later, relatively little progress had been made along these lines when compared to the taxonomic exploration of TBFs in North America and Southeast Asia. Pinto et al (2015) sequenced 3 innominate cercariae (W810 Spirorchiidae sp. 3 ex.…”

“…A morphological comparison between Uterotrema and the new genera is below. Pinto et al (2015) presented a 28S phylogeny that recovered Uterotrema sp. sister to Vasotrema þ Spirorchiinae.…”

Editorial: The biodiversity of trematodes of fishes

“…It is striking that, in almost every instance in which groups of trematodes are subjected to molecular phylogenetic analysis, unexpected but plausible changes in our understanding of relationships emerge (e.g. Choudhury et al, 2007;Bray et al, 2009;Cutmore et al, 2013;Pulis et al, 2014;Pinto et al, 2015). Despite this, the field can be considered to be in its infancy with the vast majority of genera and species not yet subjected to molecular phylogenetic analysis.…”