Description of a new species of Neoechinorhynchus (Acanthocephala: Neoechinorhynchidae) a parasite of Dormitator latifrons from Southwestern Mexico based on morphological and molecular characters

Phenotypic plasticity, genetic structure, and systematic position of Neoechinorhynchus emyditoides Fisher, 1960 (Acanthocephala: Neoechinorhynchidae) a parasite of emydid turtles from the Nearctic and Neotropical regions

The taxonomy of the 10 recognized Neoechinorhynchus species associated with emydid turtles is complex due to the morphological conservatism. In the present study, specimens of N. emyditoides from northern and southeastern Mexico exhibit great phenotypic plasticity on its diagnostic characteristics. We sequenced three molecular markers: the internal transcribed spacers ITS1, ITS2 and 5.8S gene, the D2 + D3 domains of the large subunit from nuclear DNA and cytochrome c oxidase subunit I (cox1 ) from mitochondrial DNA. Sequences of the nuclear molecular markers were aligned and compared with other congeneric species associated with emydids available in GenBank. Phylogenetic analyses supported the polyphyly of Neoechinorhynchus . The species from emydids formed a clade, which was subdivided into five subclades that correspond with each species analysed (N. pseudemydis , N. chrysemydis , N. emydis , N. schmidti and N. emyditoides ). To understand better the genetic structure of N. emyditoides a haplotype network was inferred with 29 cox1 sequences, revealing the presence of 13 haplotypes, two of which were shared and 11 were unique. The high values of fixation index, F st (0.4227–0.8925) detected between the two populations from southeastern and the two from northern Mexico indicated low genetic flow among the populations. Our data suggest that the Neoechinorhynchus species associated with emydid turtles diversified in the eastern USA and that of N. emyditoides expanded its distribution range reached southeastern Mexico.

Molecular characterisation and updated description of Neoechinorhynchus aldrichettae Edmonds, 1971 (Acanthocephala: Neoechinorhynchidae), based on material from Aldrichetta forsteri (Valenciennes) collected in Tasmania, Australia

We report on Neoechinorhynchus aldrichettae Edmonds, 1971 (Acanthocephala: Neoechinorhynchidae), obtained from yellow-eye mullet Aldrichetta forsteri (Valenciennes) (Mugiliformes: Mugilidae) from the Huon River, Tasmania, Australia. We provide new 18S and 28S rDNA gene sequence data for N. aldrichettae, assess its phylogenetic position relative to other species of Neoechinorhynchus and provide an updated morphological account of this species including detail of features omitted in the type-description, specifically of the apical organ, a collar at the base of the neck and a para-receptacle structure associated with the proboscis receptacle. We determine that eggs in this species are ovoid, without polar prolongations of fertilisation membrane, which permits assignment of N. aldrichettae to the subgenus Neoechinorhynchus. Our phylogenetic analyses place N. (N.) aldrichettae in a clade with other species of Neoechinorhynchus which parasitise mullets in marine and estuarine waters. We find that, in terms of monophyletic clades, the current subgeneric classification system for Neoechinorhynchus is not reflected in our phylogenetic analyses.

Morphological and molecular characterization of Neoechinorhynchus (N.) cephali n. sp. (Acanthocephala: Neoechinorhynchidae) Stiles and Hassall 1905 infecting the flathead grey mullet Mugil cephalus (Linnaeus, 1758) from the southwest coast of India

The present paper describes Neoechinorhynchus (Neoechinorhynchus) cephali n. sp., an acanthocephalan parasite infecting the intestine of the flathead grey mullet Mugil cephalus from the southwest coast of India. The parasite exhibited a prevalence of 7.40%, mean intensity of 18.5 and abundance of 18-19 worms/infected host. Morphologically, N. (N.) cephali n. sp. is sexually dimorphic, small, cylindrical, slightly curved and creamy white in colour. Females are larger than males, measured 8.87 × 0.88 mm and 5.65 × 0.66 mm, respectively. Proboscis is armed with three circles of six hooks each, which progressively decreases in size posteriorly. Hooks are backwardly curved and robust and tapering with a sharp, pointed tip, striations on the surface and a manubrium at its base. The body is aspinose, trunk surface with micropores and pits and proboscis surface with papilliform structures. The body wall is with five dorsal and two ventral hypodermal nuclei, along with lacunar canals connected by circular anastomoses. Lemnisci are subequal, small lemnisci are uninucleated, and large ones are binucleated. The cement gland is oval, with four giant nuclei; bursa is with many sensory cells. Eggs are elliptical, with concentric shells, and polar prolongation is absent. In the molecular and phylogenetic analyses based on the 18S ribosomal DNA region, the present species stands out with a high bootstrap value and is positioned as a sister branch of N. (N.) dimorphospinus. Based on the differences in morphology, morphometry and molecular and phylogenetic analyses, the present species of acanthocephalan infecting M. cephalus is considered as new, and the name Neoechinorhynchus (Neoechinorhynchus) cephali n. sp. is proposed.

The Molecular Profile of Rhadinorhynchus dorsoventrospinosus Amin, Heckmann, and Ha 2011 (Acanthocephala: Rhadinorhynchidae) from Vietnam

Of the 46 known species of Rhadinorhynchus Lühe, 1911, only 6 species, including Rhadinorhynchus dorsoventrospinosus Amin, Heckmann, and Ha, 2011, have dorsal and ventral, as well as lateral, trunk spines in the posterior field of trunk spines. The other 5 species are Rhadinorhynchus erumei Gupta and Fatima, 1981, Rhadinorhynchus adenati (Golvan and Houin, 1964) Golvan, 1969, Rhadinorhynchus lintoni Cable and Linderoth, 1963, Rhadinorhynchus pacificus Amin, Rubtsova, and Ha, 2019, and Rhadinorhynchus multispinosus Amin, Rubtsova, and Ha, 2019. These 5 species are distinguished from R. dorsoventrospinosus by differences in proboscis hook armature, trunk spine organization, and egg size. The distinction of R. dorsoventrospinosus is further demonstrated by its molecular description. We amplified the 18S and ITS1+5.8S+ITS2 rDNA region and cytochrome c oxidase subunit 1 (COI) gene for this study. Unfortunately, no ITS1+5.8S+ITS2 gene sequences are available for comparison with other species of the genus Rhadinorhynchus. Therefore, phylogenetic trees generated from sequences of the 18S nuclear region and COI gene were analyzed for the phylogenetic position of isolates of R. dorsoventrospinosus. Rhadinorhynchus dorsoventrospinosus has been validated as a species based on comparisons of morphological (original description) and molecular features (this paper). The additional genetic data will be useful as more species are described and as more genetic material becomes available to improve taxon sampling in the genetic analysis.

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.

Redescription of Acanthogyrus (Acanthosentis) maroccanus (Dollfus, 1951) (Acanthocephala: Quadrigyridae), a parasite of the Algerian barb Luciobarbus callensis (Valenciennes) (Cyprinidae) in Algeria, and first molecular data

Acanthogyrus (Acanthosentis) maroccanus (Dollfus, 1951), an insufficiently described quadrigyrid acanthocephalan of cyprinid fishes from Northwest Africa, is redescribed based on recently collected specimens from the Algerian barb Luciobarbus callensis (Valenciennes) in Algeria. Newly observed morphological features for A. (A.) maroccanus include the arrangement of proboscis hooks (not in regular circles), the male reproductive structures extending into the copulatory bursa and the presence of a para-receptacle structure and vaginal sleeve. The mechanism of copulation of this acanthocephalan is described based on several copulating pairs. The phylogenetic position of A. (A.) maroccanus within Eoacanthocephala was assessed based on partial 28S rDNA sequences. Maximum likelihood and Bayesian inference analyses placed A. (A.) maroccanus in a clade with Palliolisentis (Demidueterospinus) ophiocephalus (Thapar, 1931), both species included in the Quadrigyridae, the only family within the Gyracanthocephala.

Integrative taxonomy reveals a new species of Dollfusentis (Acanthocephala: Illiosentidae), in Orthopristis ruber (Osteichthyes: Haemulidae) from Rio de Janeiro, Brazil

The taxonomy of species of Dollfusentis is rather confused due to the overlap of morphological traits. The aim of this study was to follow an integrative taxonomy approach over the acanthocephalans collected from Orthopristis ruber in Brazil. Dollfusentis lenti n. sp. is described and is characterised by having an elongate trunk with spines sparsely distributed (largest 60-85 μm long) extending from the neck to almost reach the end of proboscis receptacle; additionally, the new species possesses a long proboscis with 12-14 longitudinal rows of 16-17 hooks each; 3-4 posterior hooks reduced in size, well-spaced from the eight ventrolateral crescent hooks, and lemnisci longer than proboscis receptacle. New sequences of 18S rDNA, ITS1, 5.8S and ITS2, 28S rDNA and COI mtDNA are provided. Dollfusentis bravoae is morphologically similar because it possesses the same number of proboscis hooks, although it differs by the size of testes and uterus and by having a higher number of trunk spines; additionally, new scanning electron micrographs and genetic data for both species support its distinction. Phylogenetic analysis obtained either with two nuclear genes or mitochondrial COI gene showed that Dollfusentis spp. belong to Illiosentidae, and the new species is yielded as the sister species of D. bravoae, with D. chandleri as the sister species of the latter two.

A closer look at the morphological and molecular diversity of Neoechinorhynchus (Acanthocephala) in Middle American cichlids (Osteichthyes: Cichlidae), with the description of a new species from Costa Rica

Neoechinorhynchus is one of the most speciose genera of acanthocephalans, with approximately 116 described species. A recent study, aimed at establishing the genetic diversity of Neoechinorhynchus in Middle American freshwater fishes, validated nine species molecularly and morphologically and revealed the existence of 10 putative candidate species. Neoechinorhynchus golvani, a parasite commonly found in cichlids throughout Middle America with an allegedly large intraspecific morphological variability, was found to represent a species complex; species delimitation methods uncovered three additional genetic lineages. Here, we re-analyse the morphological and molecular data for N. golvani species complex infecting cichlids in that geographical area. A multivariate analysis of variance (MANOVA) was conducted particularly for the length of apical, middle and posterior hooks of the species/lineages of Neoechinorhynchus in cichlids, revealing morphological variation in the length of apical hooks for Lineage 8, although no morphological distinction was observed for Lineages 9 and 10. A new concatenated phylogenetic analysis of one mitochondrial and two ribosomal DNA genes was used to further corroborate the species delimitation among lineages; Neoechinorhynchus Lineage 8 was found to be morphologically and genetically distinct from its sister taxa, N. golvani and other two undescribed genetic lineages, and is formally described as a new species. Neoechinorhynchus costarricense n. sp. is described from the intestines of eight species of cichlids in Costa Rica. The new species is distinguished from the other species/lineages of Neoechinorhynchus in cichlids mainly by the size of the apical hooks of the proboscis.

Molecular characterization ofNeoechinorhynchus cylindratusVan Cleave, 1913 (Acanthocephala: Neoechinorhynchidae), a parasite of the largemouth bass (Micropterus salmoides) in northern Mexico

Members of the genusNeoechinorhynchusStiles & Hassall, 1905 are endoparasites of freshwater fishes, brackish water fishes, and freshwater turtles distributed worldwide. In North America, 33 species have been described. One of the most widely distributed species in the eastern United States and Canada isNeoechinorhynchus (Neoechinorhynchus) cylindratus,a common acanthocephalan that infects centrarchid fishes. In the current study, adult specimens ofN. (N) cylindratuswere collected from largemouth bass (Micropterus salmoides) from the Purificación River in northern Mexico. In the same freshwater system, two additional congeneric species (Neoechinorhynchus (Neoechinorhynchus) emyditoidesandNeoechinorhynchus (Neoechinorhynchus) panucensis) were collected and analysed. Sequences of the large subunit, internal transcribed spacers ITS1 and ITS2, 5.8S from nuclear DNA, and sequences of the cytochromecoxidase subunit I (cox1) from mitochondrial DNA were generated and aligned with other sequences obtained from GenBank. Maximum likelihood and Bayesian inference analyses inferred for each dataset showed thatN. (N) panucensis,N. (N) emyditoidesandN. (N) cylindratuswere nested within several clades, indicating that these species do not share a common ancestor. Our phylogenies also revealed that the genusNeoechinorhynchusis paraphyletic, requiring further taxonomic revision using phylogenetic systematics and re-examination of morphological and ecological data. The presence of severalN. (N) cylindratusadults in northern Mexico allowed us to typify this species for the first time using a combination of morphological and molecular characteristics. The current record shows a wide distribution range ofN. (N) cylindratusacross Canada, the United States and Mexico in the Nearctic region.

A hyper-diverse genus of acanthocephalans revealed by tree-based and non-tree-based species delimitation methods: Ten cryptic species of Neoechinorhynchus in Middle American freshwater fishes

The genus Neoechinorhynchus represents a hyper-diverse group of acanthocephalans, parasites of fresh and brackish water fish and freshwater turtles, with approximately 116 species described worldwide. Forty-nine species have been recorded in the Americas, nine of them in Middle America. Even though species delimitation methods using DNA sequences have been rarely used for parasitic helminths, the genetic library for species of Neoechinorhynchus has grown in the past few years, enhancing the possibility of using these methods for inferring evolutionary relationships and for establishing more robust species boundaries. In this study, we used non-tree-based and tree-based methods through a coalescent approach to explore the species limits of specimens of Neoechinorhynchus collected in 57 localities across Middle America. We sequenced a large number of individuals to build a comprehensive dataset for three genes: the mitochondrial cytochrome c oxidase subunit I (352 individuals), the internal transcribed spacers (330 individuals), and the D2 + D3 domains of the large subunit (278 individuals). Several species delimitation methods were implemented, i.e., Automatic Barcode Gap Discovery (ABGD), General Mixed Yule-Coalescent Model (GMYC), Bayesian species delimitation (BPP) and species tree (∗BEAST). Additionally, we conducted a detailed morphological study of the diagnostic traits associated with the proboscis of 184 males and 169 females. Overall, our analyses allowed us to validate nine nominal species of Neoechinorhynchus and to identify 10 additional genetic lineages herein regarded as candidate species. This unexpected genetic diversity and the lack of reliable morphological traits show that the genus Neoechinorhynchus includes a group of cryptic species, at least in Middle America.

Morphological and molecular data for a new species of Pomphorhynchus Monticelli, 1905 (Acanthocephala: Pomphorhynchidae) in the Mexican redhorse Moxostoma austrinum Bean (Cypriniformes: Catostomidae) in central Mexico

Pomphorhynchus purhepechus n. sp. is described from the intestine of the Mexican redhorse Moxostoma austrinum Bean (Catostomidae) in central Mexico. The new species can be distinguished from the other seven described species of Pomphorhynchus Monticelli, 1905 in the Americas by a subspherical proboscis and 14 longitudinal rows with 16-18 hooks each; the third and the fourth row of hooks are alternately longest. Sequences of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene and the large subunit (LSU) rDNA (including the domains D2-D3) were used to corroborate the morphological distinction between the new species and Pomphorhynchus bulbocolli Linkins in Van Cleave, 1919, a species widely distributed in several freshwater fish species across Canada, USA, and Mexico. The genetic divergence estimated between the new species and the isolates of P. bulbocolli ranged between 13 and 14% for cox1, and between 0.6 and 0.8% for LSU. Maximum likelihood and Bayesian inference analyses of each dataset showed that the isolates of P. bulbocolli parasitising freshwater fishes from three families, the Catostomidae, Cyprinidae and Centrarchidae, represent a separate lineage, and that the acanthocephalans collected from two localities in central Mexico comprise an independent lineage. In addition, our analysis of the genetic variation of P. bulbocolli demonstrates that individuals of this acanthocephalan from different host species are conspecific. Finally, the distribution, host-association, and phylogenetic relationship of the new species, when placed in the context of the region's geological history, suggest that both host and parasite underwent speciation after their ancestors became isolated in Central Mexico.

Morphometric and molecular characterisation of Tenuiproboscis keralensis n. sp. infecting marine and brackish water fishes from the south-west coast of India with a note on morphological plasticity

A new species of acanthocephalan infecting marine and brackish water fishes from the south-west coast of India is described. The parasite belongs to the genus Tenuiproboscis, and the fish hosts include Lutjanus argentimaculatus, L. ehrenbergii, Siganus javus, Epinephelus malabaricus, E. coioides, Scatophagus argus, Parascolopsis aspinosa, Caranx ignobilis, Gerres filamentosus and Lates calcarifer. The parasite inhabits mid- and hindgut regions and is characterised by an elongated, cylindrical, bulbous and posteriorly tapering metasoma and a claviform proboscis having 14-15 rows of 14-15 hooks each. Females larger than males, measured 3898.16-10,318.00 μm (6430.00 ± 1417.30) in length and 458.93-1435.68 μm (929.81 ± 250.39) in width. Males measured 3234.89-8644.20 μm (5729.50 ± 1176.60) in length and 388.30-1584.61 μm (795.88 ± 184.12) in width. Parasites recovered from different host species showed morphological/morphometric variations. However, principal component analysis (PCA) revealed significant overlapping of characters indicating their similarities. Proboscis profiling based on variations in size and position of hooks also yielded similar results. Further, in molecular phylogenetic analysis, parasites from different fish hosts formed a monophyletic clade with strong bootstrap support, again indicating their conspecific nature. These morphological/morphometric variations can be ascribed to differences in host species. Morphology and morphometrics in combination with PCA, proboscis profiling and molecular analysis suggest the present acanthocephalan parasite is different from other described species of Tenuiproboscis. Hence, it is considered as a new species and named T. keralensis n. sp. Prevalence, intensity and abundance of the parasite in different hosts are also discussed.

Morphological and molecular evidence on the existence of a single estuarine and rocky intertidal acanthocephalan species of Profilicollis Meyer, 1931 (Acanthocephala: Polymorphidae) along the Atlantic and Pacific coasts of southern South America

Profilicollis chasmagnathi Holcman-Spector, Mañé-Garzón & Dei-Cas, 1977 (Acanthocephala: Polymorphidae) has been reported to parasitise different grapsid species as intermediate hosts along the South Atlantic shores, i.e. Cyrtograpsus angulatus (Dana) and Neohelice granulata (Dana) in Uruguay and Cyrtograpsus altimanus (Rathbun) in Argentina. Larvae of a similar acanthocephalan described as Profilicollis antarcticus Zdzitowiecki, 1985 were recorded in the crab Hemigrapsus crenulatus (Milne-Edwards) from an estuarine habitat on the Southeast Pacific shore in Chile. Earlier studies have questioned the specific assignation of the Chilean estuarine populations of Profilicollis Meyer, 1931. The aim of this study was to re-examine the identification of these acanthocephalans by means of morphological and molecular analyses of cystacanths of Profilicollis spp. gathered from C. angulatus, N. granulata, C. altimanus and H. crenulatus. Our analyses showed that a single species of Profilicollis, P. chasmagnathi, parasitises these four crab species. The assessment of specimens from the South Shetlands Islands, the type-locality of P. antarcticus, is needed before formally proposing that P. antarcticus is a junior subjective synonym of P. chasmagnathi.

Mayarhynchus karlae n. g., n. sp. (Acanthocephala: Neoechinorhynchidae), a parasite of cichlids (Perciformes: Cichlidae) in southeastern Mexico, with comments on the paraphyly of Neoechinorhynchus Stiles & Hassall, 1905

Mayarhynchus n. g. (Acanthocephala: Neoechinorhynchidae) is erected for Mayarhynchus karlae n. g, n. sp. described from the intestine of four species of cichlid fishes distributed from southeastern Mexico. The new genus placed in the family Neoechinorhynchidae (Ward, 1917) Van Cleave, 1928, is readily distinguished from the other 17 genera in the family by having a small proboscis armed with 45-46 relatively weak rooted hooks arranged in nine longitudinal rows of five hooks each. In addition, Mayarhynchus n. g., n. sp. is diagnosed by the presence of a short trunk, body wall with five dorsal and one ventral giant hypodermal nuclei, proboscis receptacle nearly cylindrical with single layered wall, lemnisci broad and flat with large nuclei, testes in tandem, cement gland with eight large nuclei, and eggs elongate to oval. Partial sequences of the cytochrome c oxidase subunit 1 (cox1), internal transcribed spacers (ITS1 + 5.8S + ITS2), and the D2-D3 domains of the large subunit rRNA gene (28S) were obtained for five specimens of the new species and other species belonging to the Neoechinorhynchidae. Phylogenetic analyses confirmed that the new genus belongs to the Neoechynorhynchidae and indicated that the genus Neoechynorhynchus Stiles & Hassall, 1905 is not monophyletic. Comparison between three populations of the new species yielded nine variable sites for cox1, 11 for ITS and four for 28S.

Classification of the acanthocephala

In 1985, Amin presented a new system for the classification of the Acanthocephala in Crompton and Nickol's (1985) book 'Biology of the Acanthocephala' and recognized the concepts of Meyer (1931, 1932, 1933) and Van Cleave (1936, 1941, 1947, 1948, 1949, 1951, 1952). This system became the standard for the taxonomy of this group and remains so to date. Many changes have taken place and many new genera and species, as well as higher taxa, have been described since. An updated version of the 1985 scheme incorporating new concepts in molecular taxonomy, gene sequencing and phylogenetic studies is presented. The hierarchy has undergone a total face lift with Amin's (1987) addition of a new class, Polyacanthocephala (and a new order and family) to remove inconsistencies in the class Palaeacanthocephala. Amin and Ha (2008) added a third order (and a new family) to the Palaeacanthocephala, Heteramorphida, which combines features from the palaeacanthocephalan families Polymorphidae and Heteracanthocephalidae. Other families and subfamilies have been added but some have been eliminated, e.g. the three subfamilies of Arythmacanthidae: Arhythmacanthinae Yamaguti, 1935; Neoacanthocephaloidinae Golvan, 1960; and Paracanthocephaloidinae Golvan, 1969. Amin (1985) listed 22 families, 122 genera and 903 species (4, 4 and 14 families; 13, 28 and 81 genera; 167, 167 and 569 species in Archiacanthocephala, Eoacanthocephala and Palaeacanthocephala, respectively). The number of taxa listed in the present treatment is 26 families (18% increase), 157 genera (29%), and 1298 species (44%) (4, 4 and 16; 18, 29 and 106; 189, 255 and 845, in the same order), which also includes 1 family, 1 genus and 4 species in the class Polyacanthocephala Amin, 1987, and 3 genera and 5 species in the fossil family Zhijinitidae.

A description ofNeoechinorhynchus(Neoechinorhynchus)veropesoin. sp. (Acanthocephala: Neoechinorhynchidae) from the intestine of the silver croaker fishPlagioscion squamosissimus(Heckel, 1840) (Osteichthyes: Sciaenidae) off the east coast of Brazil

Plagioscion squamosissimus(Heckel, 1840) (Osteichthyes: Sciaenidae) is considered piscivorous and is a generalist species endemic to the Amazon region. This fish is an important part of the natural ecosystems in which it occurs and provides basic functional components in the food web. The genusNeoechinorhynchusStiles & Hassall, 1905 is distributed worldwide and parasitizes fish and turtles, but there are few reports of parasites of this genus in South America, due to the high diversity of fish that can be found in this region. A new species of thorny-headed worm (Acanthocephala: Neoechinorhynchidae) is described fromP. squamosissimusfrom Guajará Bay, Belém, Pará, Brazil. In general, the unique characteristics of the hooks on the anterior end of the proboscis and the length-to-width ratio relationship separate this new species from other described species in the genusNeoechinorhynchus. Although the species in this genus are mostly found in North America, the dearth of species known from the neotropics may be due to the lack of studies in this region.

Molecular characterisation and infection dynamics of Dentitruncus truttae from trout (Salmo trutta and Oncorhynchus mykiss) in Krka River, Croatia

Dentitruncus truttae (Acanthocephala, Palaeacanthocephala) is an intestinal parasite of fish that can cause extensive damage to the host digestive tract, yet little is known about its epidemiology and genetic variability. It is a member of the Illiosentidae family with a worldwide distribution restricted to parts of southeast Europe. Its usual host is brown trout (Salmo trutta), but we report here the first detection in the intestine of rainbow trout (Oncorhynchus mykiss). We examined the physiology of D. truttae-infected S. trutta and O. mykiss, seasonal and spatial variability of D. truttae infections, and genetic variability of the parasite population in Krka River, Croatia. D. truttae was more abundant in both trout populations in the autumn, with no seasonal variation in prevalence. The parasite was more abundant in male than female trout (n=75, p<0.01). Analysis of the spatial distribution of the parasite across various sampling sites along the river showed the lowest prevalence and abundance of parasitic infections at the most downstream sampling site, which may reflect the predominance of female fish there and/or the smaller population of intermediate hosts. To provide the first molecular insights into D. truttae, we analysed sequences at three marker loci: the 18S rRNA gene, the cytochrome c oxidase subunit 1 (COI) gene and the internal transcribed spacer region. Phylogenetic analysis based on 18S rRNA confirmed the taxonomic grouping of D. truttae in the Illiosentidae family, first made more than 50 years ago based on morphology. The COI haplotype network did not show discrete genetic clusters corresponding to the different sampling sites, suggesting a stable population. These insights into D. truttae haplotype frequency distribution and intrapopulation genetic variation revealed minimal genetic variability, compared to the other acanthocephalan species.

First description of adults of the type species of the genus Glossocercus Chandler, 1935 (Cestoda: Gryporhynchidae)

The type species of the genus Glossocercus Chandler, 1935, G. cyprinodontis Chandler, 1935, was described as metacestode (larval stage) from the mesentery of the sheepshead minnow fish (Cyprinodon variegatus Lacépède) from Galveston Bay, Texas. The description was based on the morphology of the rostellar hooks; however, the features of the internal morphology of the proglottides could no be provided. In the present study we describe for the first time the features of the adult G. cyprinodontis from the intestine of Pelecanus occidentalis Linnaeus, Nycticorax nycticorax Linnaeus and Egretta rufescens Gmelin in Mexico. Glossocercus cyprinodontis possesses similar strobilar morphology with the two other congeneric species, both distributed in the Neartic and Neotropical regions, i.e. Glossocercus caribaensis (Rysavy et Macko, 1971) and Glossocercus auritus (Rudolphi, 1819). However, G. cyprinodontis differs mainly in the shape of the rostellar hooks (those of G. cyprinodontis possess the handle and the guard strongly sclerified compared to those of G. auritus and G. caribaensis) and their size (total length of 175-203 microm in G. cyprinodontis compared to 189-211 microm in G. caribaensis and 220-285 microm in G. auritus). Generic diagnosis of Glossocercus is emended: rostellar hooks in two rows with ten hooks of different shape and length in each, scolex large and globular, proglottides craspedote, wider than long, genital pores irregularly alternating, vagina transverse, surrounded by epithelial cells, ventral to cirrus-sac, uterus bar-shaped in mature proglottides, occupies all space between osmoregulatory ducts with eggs in gravid proglottides, ovary lobed in middle of proglottis, cirrus-sac elongate, between osmoregulatory canals, cirrus armed with spinitriches and apical tuft of slender spinitriches.