Revision of Leptorhynchoides thecatus (Acanthocephala: Illiosentidae), with morphometric analysis and description of six new species

ADULT THORNY-HEADED WORM (ACANTHOCEPHALA) PARASITES OF NORTH AMERICAN HERPETOFAUNA: CHECKLIST OF SPECIES AND IDENTIFICATION KEY TO FAMILIES AND GENERA

An updated checklist of adult thorny-headed worms (Acanthocephala) that parasitize wild North American amphibians and reptiles is presented: A total of 21 species grouped in 4 genera, 4 families, 2 orders, and 2 classes are registered; these infect a total of 19 species of reptiles and 17 species of amphibians in the region. An illustrated identification key for the families and genera listed is proposed.

Silver Shiner, Notropis photogenis, fecundity and parasite infections during the reproductive period

The reproductive period is a critical part of a species' life-history. Estimating species-specific fecundity can improve demographic models aimed at developing recovery targets for imperilled species. We provide egg diameter and fecundity estimates and develop a length-fecundity relationship for Silver Shiner, Notropis photogenis (Cope,1865), a small-bodied freshwater species listed as Threatened under Canada’s Species at Risk Act. Furthermore, we document the incidence of an acanthocephalan parasite (thorny-headed worm) Leptorhychoides thecatus (Linton, 1891), in the gastrointestinal tract of Silver Shiner, which is the first published record of the parasite in this species. Silver Shiner egg diameters (average ± standard deviation) were 0.61 ± 0.15 mm and ranged from 0.13-0.92 mm. Fecundity ranged from 311-2768 eggs and was significantly higher in age 2-3+ fish (1475 ± 570 eggs) compared to age 1+ fish (576 ± 270 eggs). We highlight that parasite infection negatively impacted the body condition of individuals and that additional work is needed to determine the impact of parasite infestation on reproductive output, recruitment, susceptibility to predation, and survival of Silver Shiner in Canada. The fecundity and egg diameter estimates for Canadian Silver Shiner provided here can be incorporated into future populations modelling for this threatened species.

Genetic diversification of acanthocephalans of the genus Floridosentis Ward 1953 (Acanthocephala: Neoechinorhynchidae), parasites of mullets from the Americas

Adult worms of the genus Floridosentis are endoparasites of marine fishes of the genus Mugil and are broadly distributed in the Americas. Currently, Floridosentis includes two species, F. mugilis, distributed in the Gulf of Mexico and along the Atlantic Ocean coast, and F. pacifica, restricted to the Pacific Ocean coast. The aim of this study was to explore the species limit of both species of the genus Floridosentis, collected in 37 localities in eight countries: Mexico, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Ecuador and Venezuela. We sequenced 253 specimens to build a comprehensive dataset for three genes: the cytochrome c oxidase subunit I (cox 1) from mitochondrial DNA, the internal transcribed spacers ITS1 and ITS2 including the 5.8S gene (ITS region), and the D2 + D3 domains of the large subunit (LSU) of nuclear DNA. Maximum likelihood and Bayesian analyses with the cox 1 and concatenated (cox 1 + ITS+LSU) datasets were conducted. Two species delimitation methods were implemented, the Automatic Barcode Gap Discovery (ABGD), and Bayesian species delimitation (BPP), plus a haplotype network inferred with 253 specimens, allowing us to validate two nominal species of Floridosentis., F. mugilis, plus one linage distributed in the Gulf of Mexico and along the Atlantic Ocean coast, and F. pacifica, plus two additional lineages distributed along the Pacific Ocean coast. All these lineages are shared by both species of mullet (Mugil curema and M. cephalus). The currents in the Atlantic Ocean, Pacific Ocean and Gulf of Mexico, in combination with the biology of the definitive hosts, have played a key role in the distribution of the two nominal species and of the three lineages of Floridosentis across the Americas.

The Molecular Profile of Paratrajectura Longcementglandatus Amin, Heckmann Et Ali, 2018 (Acanthocephala: Transvenidae) from Percid Fishes in the Marine Waters of Iran and Iraq

Paratrajectura longcementglandatus Amin, Heckmann et Ali, 2018 (Transvenidae) was recently described from two species of percid fishes collected from the marine territorial waters of Iraq and Iran in the Persian Gulf. The genus Paratrajectura Amin, Heckmann et Ali, 2018 is a close relative to transvenid genera Trajectura Pichelin et Crib, 2001 and Transvena Pichelin et Crib, 2001. Morphologically, Paratrajectura is characterised by having apical proboscis cone, long, tubular cement glands, short lemnisci, prominent roots on all proboscis hooks, subterminal female gonopore, and males with long pre-equatorial testes. Molecular studies of P. longcementglandatus using 18S rDNA and cox1 genes compared with available data of members of other families of Echinorhynchida showed that P. longcementglandatus is grouped with species of the genus Transvena forming a clade within the family Transvenidae.

A New Species of the Acanthocephalan Genus Filisoma (Cavisomidae) from Perciform Fishes in Rio de Janeiro, Brasil

BACKGROUND

Twelve species of Filisoma Van Cleave, 1928 are recognized parasitizing tropical and subtropical fish. Four of these species were described from kyphosid fish and it has been suggested that a co-speciation may have occurred among species of Kyphosus Lacepède, 1801 and Filisoma, which could provide valuable information about the evolution history of this host-parasite system.

PURPOSE

During a survey of the helminth fauna of Kyphosus sectatrix (Linnaeus, 1758) and Kyphosus incisor (Cuvier, 1831) (Kyphosidae Jordan, 1887) off Rio de Janeiro coast, a new species of Filisoma was found and is described herein based on morphological, genetic, and ultrastructural data.

METHODS

Fish were obtained off Rio de Janeiro coast, Brazil. The parasites found in the intestine were measured and drawings were made with a drawing tube. Type specimens were deposited at the Helminthological Collection of Oswaldo Cruz Institute (CHIOC). The ultrastructure was studied using scanning electron microscope. The genetic analysis included the study of the partial sequences of 18S, ITS1, 5.8S and 28S rDNA, and the mitochondrial cytochrome c oxidase 1 gene (cox 1), with phylogenetic reconstructions based on the maximum likelihood analysis.

RESULTS

Filisoma caudata n. sp. is characterized by a proboscis with 16‒18 longitudinal rows of 38‒45 hooks each. Hooks are uniform in shape dorsoventrally, gradually decreasing in size towards the base of the proboscis. Anterior hooks are 30‒45 μ long, middle hooks 30‒35 μ long and 5 basal transversal hooks 20‒30 μ long. The new species is differentiated from the closest species Filisoma filiformis Weaver and Smales, 2013 by the size and distribution of hooks, apart from having a subterminal vulva and a curved posterior trunk end (tail) measuring 500‒1,000 long. Phylogenetic analysis based on 18S, 28S rDNA and mtDNA-cox1 markers grouped the new species with Filisoma bucerium Van Cleave, 1940 and Filisoma rizalinum Tubangui and Masiluñgan, 1946 showing a close relationship between these species of Cavisomidae Meyer, 1932 and Echinorhynchidae Cobbold, 1879; the latter represented by species of Acanthocephalus Koelreuther, 1771. The new species can be differentiated from others on morphological and molecular basis. A key to the 13 species of Filisoma Van Cleave, 1928 is provided.

CONCLUSION

Filisoma caudata n. sp. is described herein based on morphological, genetic, and ultrastructural data. The topologies of obtained phylogenies suggest that species of Echinorhynchidae should be reevaluated since the family is considered paraphyletic in all analyses conducted.

Differential patterns of definitive host use by two fish acanthocephalans occurring in sympatry: Pomphorhynchus laevis and Pomphorhynchus tereticollis

Parasites with complex life-cycles and trophic transmission are expected to show low specificity towards final hosts. However, testing this hypothesis may be hampered by low taxonomic resolution, particularly in helminths. We investigated this issue using two intestinal fish parasites with similar life-cycles and occurring in sympatry, Pomphorhynchus laevis and Pomphorhynchus tereticollis (Acanthocephala). We used species-specific ITS1 length polymorphism to discriminate parasite species from 910 adult acanthocephalans collected in 174 individual hosts from 12 fish species. Both P. laevis and P. tereticollis exhibited restricted host range within the community of available fish host species, and transmission bias compared to their relative abundance in intermediate hosts. The two parasites also exhibited low niche overlap, primarily due to their contrasting use of bentho-pelagic (P. laevis) and benthic (P. tereticollis) fish. Furthermore, parasite prevalence in intermediate hosts appeared to increase with taxonomic specificity in definitive host use. Comparison of P. laevis and P. tereticollis adult size in the two main definitive hosts, barbel and chub, suggested lower compatibility towards the fish species with the lowest parasite abundance, in particular in P. laevis. The determinants of low niche overlap between these two sympatric acanthocephalan species, and the contribution of definitive host range diversity to parasite transmission success, are discussed.

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The fish acanthocephalans P. laevis and P. tereticollis show moderate specificity and low niche overlap.

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Transmission bias from shared intermediate hosts towards either benthic or bentho-pelagic fish is evidenced.

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Decreased taxonomic specificity towards fish hosts matches with lower prevalence in intermediate hosts.

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Lower worm size in the host with the lowest abundance calls for further investigation of compatibility filter.

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Low taxonomic resolution within some parasite species complex hinders accurate estimate of host use pattern.