Rhinebothrium jaimei sp. n. (Eucestoda: Rhinebothriidea: Rhinebothriidae): a new species from Neotropical freshwater stingrays (Potamotrygonidae)

Abstract

Neotropical freshwater stingrays (Batoidea: Potamotrygonidae) host a diversity of parasites, including some, like their hosts, that are marine-derived. Among the parasites of potamotrygonids, the cestode fauna is the most diverse, with multiple genera having been reported, including genera endemic to the freshwaters of the Neotropics and genera that have cosmopolitan distributions. Recent efforts have been made to document the diversity of cestodes of this host-parasite system and to refine the taxonomy of parasite lineages. The present study contributes to our knowledge of Rhinebothrium Linton, 1890, a diverse cosmopolitan genus of rhinebothriidean cestode, with 37 species reported from marine batoids, one species from a freshwater stingray in Borneo and six species from potamotrygonids. Rhinebothrium jaimei sp. n. is described from two species of potamotrygonids, Potamotrygon orbignyi (Castelnau) (type host) and Potamotrygon scobina Garman, from Bahía de Marajó of the lower Amazon region. It can be distinguished from most of its marine congeners via multiple attributes, including its possession of two, rather than one, posteriormost loculi on its bothridia and the lomeniform shape of its bothridium that is wider anteriorly. In addition, R. jaimei sp. n. can be distinguished from the six Rhinebothrium species described previously from potamotrygonids based on a unique combination of morphological features. Despite extensive stingray cestode sampling efforts throughout all major Neotropical river systems, we found that unlike most species of potamotrygonid Rhinebothrium species, which are widespread, R. jaimei sp. n. is restricted to the Bahía de Marajó. The discovery of this new species of Rhinebothrium in Bahía de Marajó, an area in which potamotrygonids occur sympatrically with some species of euryhaline batoids (e.g. Dasyatis spp.) and share some trophic resources, suggest that modern ecological processes may be contributing to the distribution patterns of cestodes infecting potamotrygonids.

Species diversity of Rhinebothrium Linton, 1890 (Eucestoda: Rhinebothriidea) from Styracura (Myliobatiformes: Potamotrygonidae), including the description of a new species

“…In addition, since members of Rhinebothrium are commonly found in batoids (Linton 1890;Brooks 1977;Friggens & Duszynski 2005;Reyda & Marques 2011;Marques & Reyda 2015;Golestaninasab & Malek 2016), we assume that the lack of members of this genus in this host could be an artifact of sample size and/or biogeographical representation. Therefore, we expect that future studies with new samples from the eastern Pacific Ocean will reveal the existence of at least one member of Rhinebothrium infecting S. pacifica.…”

Acanthobothrium Blanchard, 1948 from the northwest Atlantic and their phylogenetic relationships with freshwater lineages

“…a few cestode genera, including Acanthobothrium, Rhinebothroides and Rhinebothrium, have been studied in estuarine areas (Bueno, 2010;Cardoso Jr., 2010;Machado, 2012;Marques & Reyda, 2015). From these, Acanthobothrium is a good candidate for analyzing species sharing and the relationships between marine and freshwater cestodes, and with their hosts.…”

“…In the recent years, the documentation of that cestodes parasites of Neotropical freshwater stingrays (Myliobatiformes: Potamotrygonidae) has challenged the current paradigm of host specificity attributed to most cestode genera hosted by elasmobranchs (Cardoso Jr., 2010;Marques & Reyda, 2015;Reyda & Marques, 2011;. The paradigm of specific cestodes species to a single host species, and exclusively to their occurrence area, has been questioned.…”

“…These examples, provide some evidence that cross infections may occur in areas where the distribution of marine and freshwater rays overlap. In addition, a species of Rhinebothrium, R. jaimei Marques & Reyda, 2015, putatively related to marine species of Rhinebothrium, was described from Potamotrygon orbignyi Castelnau in the Bay of Marajó, the mouth of the Amazon basin. These findings make it difficult to assess if the cestode distribution and specificity in marine/estuarine environments are in fact different from the patterns observed in freshwater or if they are simply the result of poor sampling of estuarine regions.…”

“…The tides and salinity levels are controlled by the discharge of the Amazonian rivers, which fluctuates according to annual rainfall variation (Almeida et al, 2009). In this area, freshwater potamotrygonids co-occur with tree marine species of dasyatids -H. guttatus, Fontitrygon colarensis (Santos, Gomes & Charvet-Almeida) and Fontitrygon geijskesi Boeseman (Last et al, 2016;Marques & Reyda, 2015;. Although the cestode fauna of the freshwater potamotrigonids species reported from this area are relatively well known (Bueno, 2010;Cardoso Jr., 2010;Marques & Reyda, 2015;Reyda & Marques, 2011), there is no documentation of the cestodes parasitizing the marine stingrays species, especially the dasyatids (Cardoso Jr., 2010;Machado, 2012;Marques & Reyda, 2015).…”