Phylogenetic Placement of a Schistosome from an Unusual Marine Snail Host, the False Limpet (Siphonaria lessoni) and Gulls (Larus dominicanus) from Argentina with a Brief Review of Marine Schistosomes from Snails

Abstract

In the blood fluke family Schistosomatidae, marine snails are well known as intermediate hosts. Eight families of marine snails have thus far been reported to host schistosomes across the world, most of which have been implicated in human cercarial dermatitis (HCD) outbreaks. As part of our larger effort to define the species diversity and biology of schistosomes in Argentina, in particular their role in causing HCD, we searched in the marine pulmonate snail (Siphonaria lessoni) for a schistosome species described previously from S. lessoni from southern Argentina. Additionally, gulls (Larus dominicanus) collected from a different project locality (inland) were examined, because they are known to spend time in the intertidal regions. Schistosome sporocysts were found in S. lessoni, and a small worm fragment was retrieved from a gull. Molecular phylogenies for 28S, ITS1-5.8S-ITS2, and cox1 genes revealed that the specimens from the gull and S. lessoni grouped closely together, suggesting they are conspecifics. Also, ITS1-5.8S-ITS2 sequences suggested one of the schistosomes from S. lessoni and a schistosome from a South African penguin were also conspecifics. Further study is needed to verify if these specimens comprise a distinct marine clade within the larger avian schistosome clade that is comprised mostly of species using freshwater snail hosts. Thus far, it appears this group of marine schistosomes may be more likely found in the southern hemisphere. It is unclear if the observed distribution pattern of schistosomes in Siphonaria is a result of sampling bias and/or indicative of a specific bird-snail-schistosome association. It is clear they are sharply differentiated from the basal marine clade of avian schistosomes that includes Austrobilharzia.

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

“…Freshwater TBFs infect snails of Planorbidae, Physidae, and Ampullariidae, whereas marine TBFs infect those of Fissurellidae (limpets) and Vermetidae (worm snails) as well as polychaetes (De Buron et al, 2018). Schistosomes have thus far been found only to utilize aquatic snails and have secondarily colonized marine habitats at least once (Brant et al, 2017). The use of a wide range of snail family diversity in the schistosomes has likely contributed to their diversification (Brant and Loker, 2013).…”

Swimmer’s itch in Canada: a look at the past and a survey of the present to plan for the future

“…Other reports from the literature tend to find higher prevalence of schistosomes among snails, although in general less snails are collected and examined, and reports are from a single time point (e.g. 1.24–1.8% in Poland, 3456 and 299 snails examined, respectively [ 40 , 41 ]; 0.9–1.3% in Argentina, 402 snails examined [ 28 ]; 2.6% in Belgium, 270 snails examined [ 42 ]). Nevertheless, if the rate of prevalence for schistosomes in snails uncovered through this study is indicative of that for lakes across Alberta, or elsewhere, this holds significance for control measures.…”

Morphological, Behavioral, and Molecular Characterization of Avian Schistosomes (Digenea: Schistosomatidae) in the Native Snail Chilina dombeyana (Chilinidae) from Southern Chile

“…The systematics of Neotropical schistosomes is poorly understood both for freshwater and marine schistosomes [4,[12][13][14][15]17]. So far, five genera and seven species have been recorded in the Neotropics [4,12], although most correspond to older records with no molecular data.…”