Molecular data reveal high diversity of Uvulifer (Trematoda: Diplostomidae) in Middle America, with the description of a new species

First insights into the ectoparasitic helminth fauna of freshwater fish on an Adriatic island

Surface flow of freshwater on Adriatic islands is rare due to the extreme permeability of the karst terrain. Hence, most helminthological studies of freshwater fishes in the Adriatic drainage have focused on mainland freshwater systems, while data from islands are scarce. We collected minnow, Phoxinus lumaireul (Schinz, 1840), specimens in the Suha Ričina stream on Krk Island and screened them for helminth ectoparasites. Identification of metacercariae cysts (black spots) was carried out by sequencing part of the 28S rDNA gene, and a single monogenean worm was identified by sequencing part of the internal transcribed spacer 2 (ITS2). To estimate the level of infection, the number of black spots was counted to calculate prevalence, mean abundance, and mean intensity. Phylogenetic inference based on maximum likelihood and Bayesian inference revealed a rare black spot disease taxon, genus Uvulifer, which represents one of the first records in Europe on fish (second intermediate host), a first record from a Phoxinus host, a first record for the Adriatic drainage and Croatia, and a first record for Southern Europe in general. Furthermore, the monogenean was identified as Gyrodactylus sp., potentially representing a new species.

Unravelling the diversity of Posthodiplostomum Dubois, 1936 (Trematoda: Diplostomidae) in fish-eating birds from the Neotropical region of Mexico, with the description of a new species

Adults of the genus Posthodiplostomum, Dubois, 1936 are parasites of fish-eating birds, mainly of the family Ardeidae, and are globally distributed. The genus currently comprises 35 species, although recent molecular evidence has shown that the diversity of the genus is underestimated since several candidate species have been recognized. In the Neotropical region of Mexico, at least 6 Posthodiplostomum lineages have been detected with metacercaria stages recovered from unrelated fish hosts. Here, we obtained adult specimens of Posthodiplostomum from 6 fish-eating birds representing 2 families (Butorides virescens, Ardea herodias, Nycticorax nycticorax, Tigrisoma mexicanum – Ardeidae, and Rynchops niger and Leucophaeus atricilla – Lariidae) from 4 localities in southern Mexico. Specimens were sequenced for 2 nuclear (28S and ITS1–5.8S–ITS2) and 1 mitochondrial (cox1) molecular marker. Phylogenetic analyses allowed us to link metacercariae and adult specimens and recognized a lineage, which was described morphologically. The new species can be distinguished from its congeners by its prosoma morphology and body size; this is the first described species in the Neotropical region of Mexico. Additionally, new host and locality records for P. macrocotyle and P. pricei are presented, expanding their geographical distribution range in the Americas.

Description and Phylogenetic Relationships of Anhingatrema n. gen. (Digenea: Diplostomidae) with Two New Species from New World Anhingas (Aves: Anhingidae)

PURPOSE

The Diplostomidae is a globally distributed family of digeneans that parasitize a wide variety of tetrapod definitive hosts. Recent molecular phylogenetic studies have revealed unknown diplostomid diversity in avian hosts throughout the New World. Herein, we provide descriptions of a novel genus of diplostomids with two new species.

METHODS

Two species of diplostomids belonging to the new genus were collected from anhinga birds in Mississippi (USA) and Brazil. Partial nuclear 28S ribosomal and mitochondrial cox1 genes were sequenced. Ribosomal data were used for phylogenetic inference.

RESULTS

Both species of Anhingatrema n. gen. were positioned in a 100% supported, monophyletic clade in the phylogenetic tree. The molecular phylogenetic position and a combination of morphological features (e.g., presence of pseudosuckers, testes shape and orientation) supported erection of the new genus. Anhingatrema overstreeti n. sp. and Anhingatrema cararai n. sp. are morphologically similar, but differ in size of and ratios associated with pseudosuckers. The two species differ by 2% of 28S sequences and 13.8% of cox1 sequences. Comparison of DNA sequences revealed that Diplostomidae gen. sp. in GenBank (MZ314151) is conspecific with An. overstreeti n. sp.

CONCLUSION

Anhingatrema n. gen. is the sixth genus of diplostomids known from anhingas worldwide. Anhingatrema cararai n. sp. is the first diplostomid to be reported from anhingas in South America. Combined with previous studies, the molecular phylogenies revealed at least two host switches to anhingas from other birds during the evolutionary history of the Diplostomidae.

Phylogenetic relationships and further unknown diversity of diplostomids (Diplostomida: Diplostomidae) parasitic in kingfishers

Kingfishers (Alcedinidae Rafinesque) are common inhabitants of wetlands and are known to be definitive hosts to a wide range of digeneans that parasitize fish as second intermediate hosts. Among these digeneans, members of the Diplostomidae Poirier, 1886 (diplostomids) are particularly common. Recent studies of diplostomids collected from kingfishers have revealed that they are probably more diverse than currently known. This particularly concerns the genera Crassiphiala Van Haitsma, 1925 and Uvulifer Yamaguti, 1934. In the present work, we studied seven diplostomid taxa from kingfishers in Brazil, the USA and the Philippines. Partial DNA sequences of the nuclear large ribosomal subunit (28S) and mitochondrial cytochrome c oxidase I (cox1) genes were obtained, and 28S sequences were used to study the phylogenetic interrelationships of these diplostomids. We provide the first DNA sequences from Uvulifer semicircumcisus Dubois et Rausch, 1950 and a member of Subuvulifer Dubois, 1952. Pseudocrassiphiala n. gen. is erected for a previously recognized species-level lineage of Crassiphiala and a new generic diagnosis of Crassiphiala is provided. Crassiphiala jeffreybelli n. sp., Crassiphiala wecksteini n. sp. and Pseudocrassiphiala tulipifera n. sp. are described, and a description of newly collected, high-quality specimens of Crassiphiala bulboglossa Van Haitsma, 1925 (the type-species of the genus) is provided.

TESTING THE ENEMY RELEASE HYPOTHESIS IN THE INVASIVE FISH <i>AMATITLANIA NIGROFASCIATA</i> (PERCIFORMES: CICHLIDAE) IN MEXICO

The enemy release hypothesis (ERH) posits that invasive species are released from their natural enemies in their introduced range, which promotes their successful invasion. In this study, we tested the ERH in a population of the convict cichlid Amatitlania nigrofasciata , an invasive species in Mexico. The ERH predicts that the convict cichlid: a) is not infected by specialist helminth parasites in the introduced range; b) has lower infection parameter values, as measured through richness, prevalence, abundance and diversity of helminths, than a native species-the redside cichlid Cichlasoma istlanum ; and c) is not affected in its condition factor by the abundance of helminths it carries. The convict cichlid was infected by two (33%) specialist helminths relative to the six specialist helminths that infect the cichlid in its native range. The convict cichlid had lower helminth richness and diversity than the redside cichlid. However, the prevalence and abundance of the parasite species varied between the host fish. While the prevalence and abundance of the nematode Rhabdochona kidderi was higher in the redside cichlid, the prevalence and abundance of the trematode Uvulifer sp. was higher in the convict cichlid. The condition factor in both host fish was not correlated with helminth abundance. Our results do not agree with the prediction that the convict cichlid is completely released from specialist parasites, nor with the prediction that this invasive species has lower infection parameter values than the native redside cichlid. However, our results agree with the prediction that the abundance of parasite helminths do not affect the cichlid’s condition factor. More studies are necessary to determine the advantages that the convict cichlid could have in the introduced range when it is infected with a low richness and diversity of helminths.

Filling the knowledge gap of Middle American freshwater fish parasite biodiversity: metazoan parasite fauna of Nicaragua

The heterogeneous landscape of Nicaragua harbours a large diversity of freshwater fishes. The great Nicaraguan lakes, Managua and Nicaragua, and several adjacent crater lakes harbour numerous endemic fish species. However, information about their parasite fauna is still fragmentary. Here, we surveyed the great Nicaraguan lakes and four crater lakes and provide data for 17 metazoan parasite taxa infecting seven fish host species. We also gathered all the published records from the literature on the parasites reported from Nicaraguan freshwater fishes, as well as those for Costa Rica and Panama to discuss the region of Lower Central America as a whole. With this information we built a parasite-host and a host-parasite checklist. With data from near 50% of the native and endemic freshwater fishes in Nicaragua, the parasite fauna comprises 101 taxa in 51 fish species allocated in 11 families. Cichlids are the most diverse group of fishes in this region and have been the most extensively surveyed for their metazoan parasites. Helminths are the best-represented groups of metazoan parasites, with 42 trematodes, five cestodes, 24 monogeneans, two acanthocephalans, 20 nematodes and one hirudinean. Additionally, freshwater fishes are parasitized by copepods, branchiurans and oribatid mites. Even though the inventory is not yet complete, the patterns of diversity uncovered revealed promising information about the origin, biogeography and evolutionary history of the Nicaraguan freshwater fish parasite fauna. More studies are necessary to complete our knowledge about the diversity, host association and distribution of metazoan parasites in Nicaragua and other Central American countries.

The macroparasite fauna of cichlid fish from Nicaraguan lakes, a model system for understanding host-parasite diversification and speciation

The Nicaraguan lakes represent an ideal continent-island-like setting to study the colonization patterns of both fish and their parasites. The dominant fish fauna are cichlids, particularly the Midas cichlid species complex Amphilophus spp., a well-studied model for recent sympatric speciation. Here, we characterized the Midas cichlid macroparasite diversity in Nicaraguan lakes. We evaluated patterns of parasite diversity across host populations. Morphological and molecular analyses were conducted, revealing a macroparasite fauna composed by 37 taxa, including platyhelminths, nematodes, copepods, branchiurans, hirudineans and oribatids. Three invasive species are reported for the first time. The Midas cichlid was infected by 22 parasite taxa, 18 shared with other cichlids. Eight taxa conformed the core parasite fauna of the Midas cichlid. The large lakes had higher parasite diversity than the smaller and isolated crater lakes, although parasite infracommunity diversity was lower. Environmental factors along with the differential distribution of intermediate hosts, the potential resistance gained by their hosts after colonization of new lakes, competitive exclusion among parasites, or the introduction of exotic fish, may determine the observed pattern of parasite heterogeneous distribution. Our study provides a ground to explore the evolutionary history of both, hosts and parasites within the context of speciation and diversification processes.

Assessing the genetic diversity of the metacercariae of Posthodiplostomum minimum (Trematoda: Diplostomidae) in Middle American freshwater fishes: one species or more?

Trematode taxonomy is mainly based on the morphological traits of adults. The identification of metacercariae is challenging because such traits are not developed in larval forms, and they even may show some level of morphological variability. Studies testing the potential correspondence between morphological differences and genetic variation of parasites are still lacking. The metacercariae of Posthodiplostomum minimum are probably the diplostomids more widely distributed in North and Middle American freshwater fish, and their intraspecific morphological variability has been attributed to the effect exerted by the host. Here, we tested the hypothesis whether they represent a single species, or a species complex by assessing the genetic divergence and phylogenetic relationships of metacercariae sampled from several host species in a wide geographical range across Middle America. The internal transcribed spacers (ITS1-5.8S-ITS2), and the mitochondrial COI gene were sequenced for 124 and 55 metacercariae, respectively. Phylogenetic analysis inferred from ITS sequences uncovered six well-supported monophyletic lineages. The six lineages show no correspondence to any Posthodiplostomum species for which sequences are available thus far in GenBank. Lineages exhibit some degree of host specificity; Lineages I, II, IV and V are primarily parasites of cyprinodontiforms of the families Poeciliidae, Goodeidae, Profundulidae and Fundulidae. In poeciliids there are at least four candidate species of Posthodiplostomum, some of them occurring in sympatry; instead, Lineages II and VI are exclusively parasites of cichlids. This study contributes to our understanding of the diversity of larval forms of diplostomids and provides an opportunity to further study their life cycles.

Identification of the avian tracheal trematode Typhlocoelum cucumerinum (Trematoda: Cyclocoelidae) in a host-parasite-environment system: diagnosis, life cycle and molecular phylogeny

Typhlocoelum cucumerinum is a tracheal parasite of birds widely distributed across the globe. Nevertheless, aspects of the biology of this cyclocoelid are still poorly understood. Herein, we report the finding of T. cucumerinum in definitive and intermediate hosts from an urban waterbody of Brazil. The parasite was initially detected during the necropsy of domestic Muscovy ducks (Cairina moschata) found dead in the locality. Coproparasitological tests in live animals revealed that 12/47 (25.53%) Muscovy ducks and 2/8 (25%) mallards (Anas platyrhynchos platyrhynchos) were infected with T. cucumerinum. Moreover, rediae and metacercariae morphologically similar to T. cucumerinum were found in 3/248 (1.33%) Biomphalaria straminea collected in the same waterbody frequented by the birds. The conspecificity between the adult and the larval stages was confirmed molecularly (100% similarity in Cox-1). Moreover, the phylogenetic position of T. cucumerinum was determined for the first time based on partial fragments of the 28S, Cox-1 and Nad-1 genes. The species grouped with other members of the subfamily Typhlocoelinae with sequences available, but the data obtained do not support the distinctiveness of the genera Typhlocoelum and Tracheophilus. Further studies involving a broader range of species can result in taxonomic rearrangements in Typhlocoelinae.

Phylogenetic position of Sphincterodiplostomum Dubois, 1936 (Digenea: Diplostomoidea) with description of a second species from Pantanal, Brazil

Sphincterodiplostomum is a monotypic genus of diplostomid digeneans that parasitize fish-eating birds in the neotropics. The type species Sphincterodiplostomum musculosum has a unique, dorsal, tubular invagination in the opisthosoma with a muscular sphincter. Whereas larvae of S. musculosum are relatively commonly reported in Neotropical fish helminth surveys, adult specimens from birds are rarely collected. Prior to our study, no DNA sequence data for S. musculosum were available. Our molecular and morphological study of mature and immature adult Sphincterodiplostomum specimens from three species of birds and one species of crocodilian revealed the presence of at least two species of Sphincterodiplostomum in the neotropics. We provide the first molecular phylogeny of the Diplostomoidea that includes Sphincterodiplostomum. In addition, this is the first record of S. musculosum from caimans, along with the first record of fully mature adult S. musculosum from green kingfisher Chloroceryle americana. The new species of Sphincterodiplostomum (Sphincterodiplostomum joaopinhoi n. sp.) can be morphologically distinguished from S. musculosum based on the anterior extent of vitelline follicles, narrower prosoma, substantially smaller holdfast organ and structure of tegumental spines. Our data revealed 0.7% interspecific divergence in 28S and 10.6-11.7% divergence in cox1 sequences between the two Sphincterodiplostomum species.

Phylogenetic Relationships of Cardiocephaloides spp. (Digenea, Diplostomoidea) and the Genetic Characterization of Cardiocephaloides physalis from Magellanic Penguin, Spheniscus magellanicus, in Chile

PURPOSE

Cardiocephaloides is a small genus of strigeid digeneans with an essentially cosmopolitan distribution. Most members of Cardiocephaloides are found in larid birds, however, Cardiocephaloides physalis is an exception and parasitizes penguins in some coastal regions of South America and South Africa. No prior molecular phylogenetic studies have included DNA sequence data of C. physalis. Herein, we provide molecular phylogenetic analyses of Cardiocephaloides using DNA sequences from five species of these strigeids.

METHODS

Adult Cardiocephaloides spp. were obtained from larid birds and penguins collected from 3 biogeographical realms (Palearctic, Nearctic and Neotropics). We have generated sequences of the complete ITS region and partial 28S gene of the nuclear ribosomal DNA, along with partial sequences of the mitochondrial CO1 gene for C. physalis, C. medioconiger and the type species of the genus, C. longicollis and used them for phylogenetic inference.

RESULTS

Cardiocephaloides spp. appeared as a 100% supported clade in the phylogenetic tree based on 28S sequences. The position of C. physalis varied between the phylogenetic trees based on the relatively conservative 28S gene on one hand, and variable ITS1 and COI sequences on the other. Cardiocephaloides physalis was nested within the clade of Cardiocephaloides spp. in the 28S tree and appeared as the sister group to the remaining members of the genus in the ITS1 region and COI trees. We detected 0.4-1.6% interspecific divergence in 28S, 1.9-6.9% in the ITS region and 8.7-11.8% in CO1 sequences of Cardiocephaloides spp. Our 28S sequence of C. physalis from South America and a shorter sequence from Africa available in the GenBank were identical.

CONCLUSION

Cardiocephaloides as represented in the currently available dataset is monophyletic with C. physalis parasitism in penguins likely resulting from a secondary host-switching event. Identical 28S sequences of C. physalis from South America and Africa cautiously confirm the broad distribution of this species, although comparison of faster mutating genes (e. g., CO1) is recommended for a better substantiated conclusion.

Phylogenetic Affinities of Uvulifer Spp. (Digenea: Diplostomidae) in the Americas with Description of Two New Species from Peruvian Amazon

Uvulifer Yamaguti, 1934, is a genus of diplostomoidean digeneans that parasitizes kingfishers worldwide. Species have a Neascus-type metacercaria that encysts in or on fish intermediate hosts, often causing black spot disease. Only 3 prior studies published DNA sequence data for Uvulifer species with only 1 including a single named species (Uvulifer spinatus López-Jiménez, Pérez-Ponce de León, & García-Varela, 2018). Herein we describe 2 new species of Uvulifer from the green-and-rufous kingfisher, Chloroceryle inda (Linnaeus), collected in Peru ( Uvulifer batesi n. sp. and Uvulifer pequenae n. sp.). Both new species are readily differentiated from their New World congeners by a combination of morphological characters including distribution of vitelline follicles and prosoma:opisthosoma length ratios. In addition, we used newly generated nuclear 28S rRNA and mitochondrial COI gene sequence data to differentiate among species and examine phylogenetic affinities of Uvulifer. This includes the 2 new species and Uvulifer ambloplitis (Hughes, 1927), as well as Uvulifer elongatus Dubois, 1988 , Uvulifer prosocotyle (Lutz, 1928), and Uvulifer weberi Dubois, 1985 , none of which have been part of prior molecular phylogenetic studies. Our data on Uvulifer revealed 0.1-2.2% interspecific divergence in 28S sequences and 9.3-15.3% in COI sequences. Our 28S phylogeny revealed at least 6 well-supported clades within the genus. In contrast, the branch topology in the COI phylogenetic tree was overall less supported, indicating that although COI sequences are a great tool for species differentiation, they should be used with caution for phylogenetic inference at higher taxonomic levels. Our 28S phylogeny did not reveal any clear patterns of host association between Uvulifer and particular species of kingfishers; however, it identified 2 well-supported clades uniting Uvulifer species from distant geographical locations and more than 1 biogeographic realm, indicating at least 2 independent dispersal events in the evolutionary history of the New World Uvulifer. Our results clearly demonstrate that the diversity of Uvulifer in the New World has been underestimated.

Paraphyly of Conodiplostomum Dubois, 1937

Adult trematodes of the genera Conodiplostomum Dubois, 1937 and Neodiplostomum Railliet, 1919 (Trematoda: Diplostomidae) parasitize the intestines of birds of prey, owls and, rarely, passeriform birds. Although the family is taxonomically unsettled, molecular phylogenetics have not been applied to analyze Conodiplostomum and Neodiplostomum and the reference DNA sequences from adult Diplostomidae are scarce and limit studies of their indistinct larval forms. We analyze the Conodiplostomum and Neodiplostomum spp. found during the examination of Czech birds performed from 1962 to 2017, and we provide comparative measurements and host spectra, including prevalence and intensity; we also provide and analyze the sequences of four DNA loci from eight diplostomid species. Molecular phylogenetic analysis suggested that Conodiplostomum spathula (Creplin, 1829), the type species of this genus, is nested in Neodiplostomum. Thus, we suggest the rejection of Conodiplostomum spathula (Creplin, 1829) and the resurrection of Neodiplostomum spathula (Creplin, 1829) La Rue, 1926 and reclassification of all species of Conodiplostomum with the neodiplostomulum type of metacercariae to Neodiplostomum as well. Conodiplostomum canaliculatum (Nicoll, 1914) is reclassified as Neodiplostomum spathulaeforme (Brandes, 1888). The molecular analysis suggested that Conodiplostomum perlatum (Ciurea, 1911), the species with the neascus type of metacercariae, belongs to Crassiphialinae Sudarikov, 1960. We erect the genus Ciureatrema gen. nov. Heneberg & Sitko and reclassify Conodiplostomum perlatum (Ciurea, 1911) as Ciureatrema perlatum (Ciurea, 1911) and establish it as a type species of Ciureatrema gen. nov. Further research should focus on the evolution of the neascus and neodiplostomulum types of metacercariae, as well as the evolution of the genital cone and pseudosuckers in Diplostomidae.

Phylogenetic relationships, expanded diversity and distribution of Crassiphiala spp. (Digenea, Diplostomidae), agents of black spot disease in fish

Crassiphiala is a monotypic genus of diplostomid digeneans and is the type genus of the subfamily Crassiphialinae. The type species Crassiphiala bulboglossa parasitizes kingfishers in the Nearctic and has a Neascus-type metacercaria that encysts on fish intermediate hosts, often causing black spot disease. While recent molecular phylogenetic studies included some members of the Crassiphialinae, no DNA sequence data of Crassiphiala is currently available. Our molecular and morphological study of adult and larval crassiphialines from the Americas revealed the presence of at least three lineages of Crassiphiala from the Nearctic and two lineages from the Neotropics. This is the first record of Crassiphiala from the Neotropics. Herein, we provide the first molecular phylogeny of the Diplostomoidea that includes Crassiphiala. Our data revealed 0.2-2.4% divergence among 28S sequences and 11-19.8% among CO1 sequences of lineages of Crassiphiala. The results of our analyses did not support the monophyly of Crassiphialinae. Our results clearly demonstrated that the diversity of Crassiphiala has been underestimated.

Validity of the Diplostomoidea and Diplostomida (Digenea, Platyhelminthes) upheld in phylogenomic analysis

Higher systematics within the Digenea, Carus 1863 have been relatively stable since a phylogenetic analysis of partial nuclear ribosomal markers (rDNA) led to the erection of the Diplostomida Olson, Cribb, Tkach, Bray, and Littlewood, 2003. However, recent mitochondrial (mt) genome phylogenies suggest this order might be paraphyletic. These analyses show members of two diplostomidan superfamilies are more closely related to the Plagiorchiida La Rue, 1957 than to other members of the Diplostomida. A recent phylogeny based on partial cytochrome c oxidase I also indicates one of the groups implicated, the Diplostomoidea Poirier, 1886, is non-monophyletic. To determine if these results were robust to additional taxon sampling, we analyzed mt genomes from seven diplostomoids in three families. To choose between phylogenetic alternatives based on mt genomes and the prior rDNA-based topology, we analyzed hundreds of ultra-conserved genomic elements assembled from shotgun sequencing. The Diplostomida was paraphyletic in the mt genome phylogeny but supported in the ultra-conserved genomic element phylogeny. We speculate this mitonuclear discordance is related to ancient, rapid radiation in the Digenea. Both ultra-conserved genomic elements and mt genomes support the monophyly of the Diplostomoidea and show congruent relationships within it. The Cyathocotylidae Mühling, 1898 are early diverging descendants of a paraphyletic clade of Diplostomidae Poirier, 1886, in which are nested members of the Strigeidae Railliet, 1919; the results support prior suggestions that the Crassiphialinae Sudarikov, 1960 will rise to the family level. Morphological traits of diplostomoid metacercariae appear to be more useful for differentiating clades than those of adults. We describe a new species of Cotylurus Szidat, 1928, resurrect a species of Hysteromorpha Lutz, 1931, and find support for a species of Alaria Schrank, 1788 of contested validity. Complete rDNA operons from seven diplostomoid species are provided as a resource for future studies.