Hooking the scientific community on thorny-headed worms: interesting and exciting facts, knowledge gaps and perspectives for research directions on Acanthocephala

Although interest in Acanthocephala seems to have reached only a small community of researchers worldwide, we show in this opinion article that this group of parasites is composed of excellent model organisms for studying key questions in parasite molecular biology and cytogenetics, evolutionary ecology, and ecotoxicology. Their shared ancestry with free-living rotifers makes them an ideal group to explore the origins of the parasitic lifestyle and evolutionary drivers of host shifts and environmental transitions. They also provide useful features in the quest to decipher the proximate mechanisms of parasite-induced phenotypic alterations and better understand the evolution of behavioral manipulation. From an applied perspective, acanthocephalans’ ability to accumulate contaminants offers useful opportunities to monitor the impacts – and evaluate the possible mitigation – of anthropogenic pollutants on aquatic fauna and develop the environmental parasitology framework. However, exploring these exciting research avenues will require connecting fragmentary knowledge by enlarging the taxonomic coverage of molecular and phenotypic data. In this opinion paper, we highlight the needs and opportunities of research on Acanthocephala in three main directions: (i) integrative taxonomy (including non-molecular tools) and phylogeny-based comparative analysis; (ii) ecology and evolution of life cycles, transmission strategies and host ranges; and (iii) environmental issues related to global changes, including ecotoxicology. In each section, the most promising ideas and developments are presented based on selected case studies, with the goal that the present and future generations of parasitologists further explore and increase knowledge of Acanthocephala

Patterns of diversity and host specificity in the cestodes of Neotropical freshwater stingrays

The rivers of South America are home to several animal groups of marine origin. These include freshwater stingrays (Potamotrygonidae), and their metazoan parasites such as cestodes, which were represented by 22 species prior to this project. This project was undertaken to (1) Investigate the diversity and host specificity of cestodes of freshwater stingrays, (2) Expand geographic ranges and stingray taxa examined for intestinal helminths, (3) Explore the phylogenetic relationships among species in the cestode genus Rhinebothrium. The intestinal helminth diversity of Paratrygon aiereba, Potamotrygon. motoro, and Potamotrygon cf castexi in Peru was found to include two digenean species, five nematode species, and 12 cestode species, six of which are new. Hyperparasitic larval cestodes found inside adult cestodes were identified as proteocephalideans based on histological and molecular sequence data. Sampling was conducted from ∼500 stingrays representing ∼29 (including 16 new) potamotrygonid species from multiple rivers in the Amazon and Rio de La Plata River Basins. Histological, light and scanning electron microscopic analyses revealed at least six new species of Rhinebothrium. Three were described and R. paratrygoni was redescribed. Rhinebothrium species varied in their host specificity, each parasitizing, on average, three host species. Rhinebothrium species in South America was found to be restricted to river basins, but not to individual rivers. Sequence data generated for portions of the LSU and CO I genes generally supported the species boundaries determined with discrete morphological characters. However, sequence data revealed little divergence between two pairs of species that had been distinguished with continuous morphological features. Phylogenetic analyses suggested that (1) Rhinebothrium species parasitizing potamotrygonids in South America are monophyletic, but the clade also includes the endemic genus Rhinebothroides, (2) The most basal lineage of Rhinebothrium in South America is represented by a new species that is restricted to the lower Amazon, (3) The identity of the marine sister taxon of Rhinebothrium species in South America remains unclear. Cestode diversity in potamotrygonids, and Rhinebothrium in particular, is greater than previously documented, and host specificity of Rhinebothrium species, while greater than previously documented, is more relaxed than that observed in marine tetraphyllidean cestodes. The number of cestode species parasitizing Neotropical freshwater stingrays now exceeds 30.

Diversification and Species Boundaries of Rhinebothrium (Cestoda; Rhinebothriidea) in South American Freshwater Stingrays (Batoidea; Potamotrygonidae)

Background: Neotropical freshwater stingrays (Batoidea: Potamotrygonidae) host a diverse parasite fauna, including cestodes. Both cestodes and their stingray hosts are marine-derived, but the taxonomy of this host/parasite system is poorly understood. Methodology: Morphological and molecular (Cytochrome oxidase I) data were used to investigate diversity in freshwater lineages of the cestode genus Rhinebothrium Linton, 1890. Results were based on a phylogenetic hypothesis for 74 COI sequences and morphological analysis of over 400 specimens. Cestodes studied were obtained from 888 individual potamotrygonids, representing 14 recognized and 18 potentially undescribed species from most river systems of South America. Results: Morphological species boundaries were based mainly on microthrix characters observed with scanning electron microscopy, and were supported by COI data. Four species were recognized, including two redescribed (Rhinebothrium copianullum and R. paratrygoni), and two newly described (R. brooksi n. sp. and R. fulbrighti n. sp.). Rhinebothrium paranaensis Menoret & Ivanov, 2009 is considered a junior synonym of R. paratrygoni because the morphological features of the two species overlap substantially. The diagnosis of Rhinebothrium Linton, 1890 is emended to accommodate the presence of marginal longitudinal septa observed in R. copianullum and R. brooksi n. sp. Patterns of host specificity and distribution ranged from use of few host species in few river basins, to use of as many as eight host species in multiple river basins. Significance: The level of intra-specific morphological variation observed in features such as total length and number of proglottids is unparalleled among other elasmobranch cestodes. This is attributed to the large representation of host and biogeographical samples. It is unclear whether the intra-specific morphological variation observed is unique to this freshwater system. Nonetheless, caution is urged when using morphological discontinuities to delimit elasmobranch cestode species because the amount of variation encountered is highly dependent on sample size and/or biogeographical representation.National Science Foundation (NSF)[9532943]National Science Foundation (NSF)[0118882]National Science Foundation (NSF)[0818696]National Science Foundation (NSF)[0818823]National Science Foundation (NSF)[0418932]University of ConnecticutHarvard Museum of Comparative Zoology, United States of AmericaFulbright AwardFundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Sao Paulo State Government, Brazil[2003/01816-2]Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Sao Paulo State Government, Brazil[2005/01299-3]Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Sao Paulo State Government, Brazil[2008/09436-8

REVISION OF SANGUINICOLA PLEHN, 1905 WITH REDESCRIPTION OF SANGUINICOLA VOLGENSIS (RAŠÍN, 1929) MCINTOSH, 1934, DESCRIPTION OF A NEW SPECIES, PROPOSAL OF A NEW GENUS, AND PHYLOGENETIC ANALYSIS

Sanguinicola Plehn, 1905 comprises 26 species that collectively infect fishes from 8 orders (Cypriniformes, Characiformes, Siluriformes, Esociformes, Salmoniformes, Labriformes, Centrarchiformes, and Perciformes). Its revision is warranted because several species assigned to the genus could represent new genera, nucleotide sequences are wanting, many species have incomplete descriptions, and types for most species are missing or of poor quality. Herein, we emend Sanguinicola based on morphology and the first nucleotide-based phylogenetic analysis that includes multiple sequences from morphologically identified adult specimens. We describe Sanguinicola plehnae Warren and Bullard n. sp. from the heart of northern pike, Esox lucius Linnaeus, 1758 from Russia; provide supplemental observations of Sanguinicola volgensis (Rašín, 1929) McIntosh, 1934 from the heart of sabrefish (type species), Pelecus cultratus (Linnaeus, 1758) Berg, 1949 from Russia; describe Sanguinicola cf. volgensis from the heart of ide, Leuciscus idus (Linnaeus, 1758) Berg, 1949 from Russia; and describe Pseudosanguinicola occidentalis (Van Cleave and Mueller, 1932) Warren and Bullard n. gen., n. comb. from the heart of walleye, Sander vitreus (Mitchill, 1818) Bailey, Latta, and Smith, 2004 from eastern North America. Sanguinicola plehnae differs from its congeners by having lateral tegumental spines that total 118–122, are small (3% of body width), and protrude 2–3 µm from the tegument (lacking associated conical protrusion) as well as by having a large testis (\u3e40% of body length). Sanguinicola volgensis differs from its congeners by having posteriorly directed lateral tegumental spines encased in a tegumental conical protrusion as well as by having an ovoid egg. Specimens of S. cf. volgensis differ from those of S. volgensis by having a body that is 5–6× longer than wide (vs. 2–3× in S. volgensis) and \u3c90 lateral tegumental spines (vs. \u3e95). Pseudosanguinicola Warren and Bullard n. gen. differs from Sanguinicola by having densely transverse rows of lateral tegumental spines (vs. a single column of large spines). The phylogenetic analysis utilizing the large subunit ribosomal DNA (28S) failed to reject monophyly of Sanguinicola.https://digitalcommons.snc.edu/faculty_staff_works/1060/thumbnail.jp

Global parasite trafficking:Asian Gyrodactylus (Monogenea) arrived to the U.S.A. via invasive fish Misgurnus anguillicaudatus as a threat to amphibians

Abstract A monogenean flatworm Gyrodactylus jennyae Paetow, Cone, Huyse, McLaughlin & Marcogliese, 2009 was previously described as a pathogen on bullfrog Lithobates catesbeianus Shaw, 1802, in a Canadian captive population originating in Missouri, U.S.A. The ITS barcoding of G. jennyae showed relatedness to Asian Gyrodactylus macracanthus Hukuda 1940, a parasite of the Asian loach Misgurnus anguillicaudatus Cantor, 1842. The resulting suggestion that the globally invasive pet-trade of fish may be a mechanism for arrival of Gyrodactylus species to North America provided the framework for the current study. The present study was undertaken following the discovery of two other species of Gyrodactylus in a population of illegally introduced M. anguillicaudatus in New York State. Here the invasion hypothesis was tested via DNA sequencing of the ITS of the two Gyrodactylus species obtained from M. anguillicaudatus from New York, termed Gyrodactylus sp. A and Gyrodactylus sp. B. Both Gyrodactylus sp. A and Gyrodactylus sp. B were closely related to G. jennyae and G. macracanthus, and all belong to a molecularly well-supported monophyletic Asian freshwater group. In conclusion, this invasive fish has trafficked at least three parasite species to the U.S.A., one of them also found on frog. This route from the Asian wetlands to other continents is similar to that of amphibian chytrid fungi of genus Batrachochytrium Longcore, Pessier & Nichols, 1999