DESCRIPTION OF FEMALE DENDRITOBILHARZIA PULVERULENTA (BRAUN, 1901) SKRJABIN, 1924 FROM TWO NEW AVIAN HOSTS IN NAMIBIA WITH PHYLOGENETIC ANALYSES AND COMMENTS ON SEVERAL TAXONOMICALLY UNCERTAIN AVIAN SCHISTOSOME SEQUENCES.

During a 2021 parasitological survey of birds in the Nyae Nyae-Khaudum Dispersal Area (Kavango-Zambezi Transfrontier Conservation Area, Namibia), we collected 9 specimens of Dendritobilharzia pulverulenta (Braun, 1901) Skrjabin, 1924 infecting the blood (heart lumen) of a white-backed duck, Thalassornis leuconotus (Eyton, 1838) (Anseriformes: Anatidae), and a fulvous whistling duck, Dendrocygna bicolor (Vieillot, 1816) (Anatidae). These flukes were fixed for morphology and preserved for DNA extraction. We assigned our specimens to DendritobilharziaSkrjabin and Zakharow, 1920 because they were strongly dorso-ventrally flattened in both sexes and had an intestinal cyclocoel with a zig-zag common cecum with lateral dendritic ramifications, numerous testes posterior to the cyclocoel and flanking the dendritic ramifications, and a tightly compacted convoluted ovary as well as lacking an oral sucker, ventral sucker, and gynaecophoric canal. Further, our specimens were morphologically identical to previously published descriptions of D. pulverulenta. Sequences of the 28S from our specimens were nearly identical to those identified as D. pulverulenta from North America (New Mexico), and our 28S phylogenetic analysis recovered D. pulverulenta within a polytomy of other Gigantobilharziinae spp. The CO1 phylogenetic analysis recovered a monophyletic Dendritobilharzia and, with low taxon sampling, a monophyletic Gigantobilharzia. This is the first record of a species of Dendritobilharzia infecting these ducks as well as the first record of an adult Dendritobilharzia from sub-Saharan Africa. The original description of adult D. pulverulenta (type locality: northern Sudan) was based on 2 males only, and hence the present study is the first description of female D. pulverulenta from Africa (the continent of the type locality). We reassign 2 Gigantobilharziinae spp. based on morphology and nucleotide evidence: Gigantobilharzia ensenadense (Lorenti, Brant, Gilardoni, Diaz, and Cremonte, 2022) Dutton and Bullard, n. comb., and Gigantobilharzia patagonense (Lorenti, Brant, Gilardoni, Diaz, and Cremonte, 2022) Dutton and Bullard, n. comb. We also comment on several avian schistosome sequences whose identities need confirmation or that likely have been misidentified.

DULCITRANSVERSOTREMA N. GEN. (DIGENEA: TRANSVERSOTREMATIDAE) AND FIRST MORPHOLOGICAL AND NUCLEOTIDE-BASED CONFIRMATION OF THE LIFE CYCLE OF A TRANSVERSOTREMATID IN NORTH AMERICA.

We propose Dulcitransversotrema n. gen. for the freshwater transversotrematids Dulcitransversotrema patialense (Soparkar, 1924) n. comb. and Dulcitransversotrema chauhani (Agrawal and Singh, 1960) n. comb. Dulcitransversotrema is unique by the combination of lacking an oral sucker and an extensively coiled uterus as well as having testes that are not deeply lobed and that abut or nearly abut the inner posterolateral margins of the digestive tract (vs. deeply lobed testes that abut the cyclocoel region of the digestive tract only or that do not abut the ceca), a pre-oral genital pore (vs. post-oral genital pore), an ovary that is anterior to and abuts or nearly abuts the sinistral testis (vs. an ovary that is separated from the sinistral testis by some distance or having an ovary that is median and immediately pre-testicular), non-embryonated eggs (vs. embryonated eggs), typically having none or sparse vitelline follicles between the testes and ceca (vs. having a wholly inter-cecal vitellarium comprising a pair of highly compacted clusters of vitelline follicles anterolateral to the testes or having numerous vitelline follicles between the testes and ceca), an oblong, median, and primarily inter-testicular vitelline reservoir (vs. an extensively elongate, pre-testicular vitelline reservoir that arches anteriorly around the sinistral testis), and a subterminal excretory pore opening on the dorsal body surface between the level of the cyclocoel and posterior body end (vs. a terminal excretory pore). We describe the redia and cercaria of Dulcitransversotrema cf. patialense from the red-rimmed melania snail, Melanoides tuberculata (Müller, 1774) (Cerithioidea: Thiaridae), and their corresponding adult from beneath the scales of the zebrafish, Danio rerio (Hamilton, 1822) (Cypriniformes: Danionidae). All hosts were sampled from a spring-fed earthen pond at a private aquaculture facility near Ruskin, Florida. No transversotrematid life cycle was known from North America previously. The large subunit ribosomal DNA and ribosomal internal transcribed spacer 2 sequences of D. cf. patialense from Florida were most similar to those from D. patialense infecting red-rimmed melania from Mayagüez, Puerto Rico and differed by 134 and 69 nucleotides, respectively. Both phylogenetic analyses recovered Dulcitransversotrema as monophyletic and sister to a clade comprising Transversotrema spp. plus Crusziella formosa Cribb, Bray, and Barker, 1992.

First report of a fish blood fluke from sub-Saharan Africa: Nomasanguinicola dentata (Paperna, 1964) Warren and Bullard, 2023 infecting African sharptooth catfish, Clarias gariepinus (Burchell, 1822) Teugles, 1982 in the Kavango River, Namibia, and a revised phylogeny for Sanguinicolidae Poche, 1926.

We herein provide a supplemental description of Nomasanguinicola dentata (Paperna, 1964) Warren and Bullard, 2023 (Digenea: Sanguinicolidae) and provide a revised 28S phylogeny to test relationships among freshwater fish blood flukes. We examined the heart of three African sharptooth catfish, Clarias gariepinus (Burchell, 1822) Teugles, 1982 from the Kavango River (northeastern Namibia) that was infected with adults of N. dentata. This blood fluke differs from N. canthoensis by having a body 5.3-6.7 longer than wide (vs. 3.5-4.6), an anterior esophageal swelling 7-8% (vs. 14-24%) of total esophageal length, a posterior esophageal swelling 3-5% (vs. 8-10%) of total esophageal length, a pre-cecal (vs. wholly post-cecal) testis, and an ovary that does not extend laterally beyond the nerve cords. The 28S sequence for N. dentata differed from that of N. canthoensis by 144 bp (9% difference). The phylogenetic analysis recovered these species as sister taxa and Sanguinicolidae as monophyletic. This is the first report of a fish blood fluke from sub-Saharan Africa, and the first report of a species of Nomasanguinicola from Africa in ∼40 yrs.

First report of Myxobolus neurofontinalis (Bivalvulida: Myxobolidae) infecting anadromous Brook Trout from Prince Edward Island, Canada.

OBJECTIVE: During routine histological examination of tissues from mortality events of anadromous Brook Trout Salvelinus fontinalis from Prince Edward Island (PEI), Canada, myxospores consistent with Myxobolus were observed infecting the central nervous system. The objective of this study was to identify the species of Myxobolus infecting the nervous system of anadromous Brook Trout from PEI, Canada. METHODS: Myxospore morphology, small subunit (SSU) ribosomal DNA (rDNA) sequence data, and histology were used to identify myxospores isolated from infected Brook Trout. RESULT: Myxospore measurements from the PEI samples matched those reported in the description of Myxobolus neurofontinalis from North Carolina. A 1057-bp fragment of the SSU rDNA from myxospores collected from Brook Trout in PEI was identical to an isolate of M. neurofontinalis (MN191598) collected previously from the type locality, New River basin, North Carolina. Histological sections confirmed infections were intercellular in the central nervous system. Minimal host response was observed, with only sparse mononuclear inflammatory infiltrates present at the periphery of and within dispersed myxospores, suggesting that infections are not pathogenic to Brook Trout. CONCLUSION: Myxospores were identified as M. neurofontinalis, which was previously described from the central nervous system of Brook Trout from the New River basin, North Carolina, USA. This constitutes the first time M. neurofontinalis has been documented outside of the New River basin in North Carolina.

Description, life cycle, and phylogenetics of Proterometra wigglewomble n. sp. (Digenea: Azygiidae) from the Cahaba River, Alabama, U.S.A.

We herein describe Proterometra wigglewomble n. sp. (Digenea: Azygiidae: Azygiinae) from the Cahaba River, Alabama, USA, which asexually reproduces in the compact elimia, Elimia showalteri (Lea, 1860) (Cerithioidea: Pleuroceridae) and matures in the oesophagus of the blackbanded darter, Percina nigrofasciata (Agassiz, 1854) (Perciformes: Percidae). Adults of the new species differ from congeners by having a small body and eggs having a wholly fimbriated surface that appears as a cilia-like brush border. Live naturally-shed cercariae of the new species differ from those of its congeners by having a strongly claviform tail stem bearing aspinose mammillae, a single furca, excretory pores that open on the posterior margin of the single furca, and few eggs in the cercarial distome. The behaviour of the cercaria further differentiates the new species. Naturally-shed cercariae of P. wigglewomble secrete a jelly-like adhesive that coats the surface of the furca and evidently facilitates attachment to the surface of glass, plastic, and snail shell. Attached cercariae vigorously wiggle and thrash about once attached, as if mimicking the larva of a stream insect so as to lure the blackbanded darter to eat it. Phylogenetic analyses recovered monophyletic Azygiidae, comprising monophyletic Leuceruthrinae Goldberger, 1911 and polyphyletic Azygiinae Lühe, 1909. The present study is the largest taxon sampling for Azygiidae and the first to include 28S sequences of Leuceruthrus. Compact elimia and blackbanded darter are new host records for Proterometra. The new species is the 3rd congener reported from the Cahaba River, a region renowned for its fish and snail endemic biodiversity.

A new species of Ellipsomyxa Køie, 2003 (Bivalvulida) infecting the gall bladder of Pangasius macronema Bleeker (Siluriformes: Pangasiidae) from the Mekong River Delta, Vietnam.

During a parasitological survey of freshwater fishes in the Mekong River Delta, Vietnam, disporic plasmodia containing myxospores morphologically consistent with Ellipsomyxa Køie, 2003 (Bivalvulida) were observed infecting the gall bladder of Pangasius macronema Bleeker (Siluriformes: Pangasiidae). Herein, we use morphology and small subunit ribosomal DNA (SSU rDNA, 18S) sequence data to describe Ellipsomyxa intravesica Ksepka & Bullard n. sp. and relate it to other myxozoans. The new species resembles Ellipsomyxa adlardi Whipps & Font, 2013, which infects the naked goby, Gobiosoma bosc (Lacepede) (Gobiiformes: Gobiidae) in Lake Pontchartrain, Louisiana, but differs from it by having a longer myxospore (mean = 13.3; range = 12.0-15.0 vs. 12.4; 11.3-14.4) and shorter polar capsules (3.7; 3.0-4.0 vs. 4.3; 3.9-4.9). The 18S phylogenetic analysis recovered the sequence of the new species sister to those ascribed to Ellipsomyxa ariusi Chandran, Zacharia, Sathianandan & Sanil, 2020 and Ellipsomyxa sp. (MK561979); both of which infect the gall bladder of the threadfin sea catfish, Arius arius (Hamilton) (Siluriformes: Ariidiae) from the southwest coast of India. Consistent with previous phylogenetic analyses of Ellipsomyxa spp., Ellipsomyxa was recovered as monophyletic. The new species is the first species of Ellipsomyxa reported from a freshwater fish in Asia and the first myxozoan reported from P. macronema.

NEW GENUS AND SPECIES OF CYCLOCOELIDAE STOSSICH, 1902 (PLATYHELMINTHES: DIGENEA) INFECTING THE NASOPHARYNGEAL CAVITY OF CANADA GOOSE, BRANTA CANADENSIS (ANSERIFORMES: ANATIDAE) FROM WESTERN ALABAMA.

While surveying the parasites of birds associated with western Alabama aquaculture ponds, we collected several specimens of Anativermis normdroneni n. gen., n. sp. (Digenea: Cyclocoelidae) from the nasopharyngeal cavity of a Canada goose, Branta canadensis (Linnaeus, 1758) (Anseriformes: Anatidae). These flukes were heat killed and fixed in neutral buffered formalin for morphology or preserved in 95% ethanol for DNA extraction. Anativermis resembles Morishitium (Witenberg, 1928) by having testes that are spheroid with smooth margins and located in the posterior quarter of the body, an anterior testis that is lateral to the midline and abuts the respective cecum, a posterior testis that is medial (testes diagonal) and abuts the cyclocoel, a genital pore that is immediately postpharyngeal, and a vitellarium that is discontinuous posteriorly. The new genus differs from Morishitium and is unique among all other cyclocoelid genera by having the combination of a body that is broadest in the anterior body half, a posterior body end that is more sharply tapered than the anterior body end, an ovary that nearly abuts the posterior testis, a vitellarium that is asymmetrical and distributes from the area immediately posterior to the cecal bifurcation posteriad to approximately the level of the ovary, and uterine loops extending dorsolateral to the ceca and filling the space between the ceca and the respective body margin for nearly the entire body length. The new genus was recovered as a distinct lineage in separate 28S, 18S, and ITS2 phylogenetic analyses. This is the first report of a cyclocoelid infecting the Canada goose and of a cyclocoelid from Alabama.

REVISION OF SANGUINICOLA PLEHN, 1905 WITH REDESCRIPTION OF SANGUINICOLA VOLGENSIS (RASÍN, 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 (Rasín, 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 (>40% 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 <90 lateral tegumental spines (vs. >95). 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.

SYSTEMATIC REVISION OF THE FISH BLOOD FLUKES WITH DIAGNOSES OF CHIMAEROHEMECIDAE YAMAGUTI, 1971, ACIPENSERICOLIDAE N. FAM., SANGUINICOLIDAE POCHE, 1926, ELOPICOLIDAE N. FAM., AND APOROCOTYLIDAE ODHNER, 1912.

We herein morphologically diagnose the 5 natural groups of fish blood flukes and name them. Species of Chimaerohemecidae Yamaguti, 1971 infect chimeras, sharks, and rays (Chondrichthyes) and have C-shaped lateral tegumental spines and a non-sinusoidal testis or lack spines and have a sinusoidal testis. Species of Acipensericolidae n. fam. infect sturgeons and paddlefish (Acipenseriformes) and have a robust, bowl-shaped, pedunculate anterior sucker, lateral tegumental spines that are spike-like (not C shaped), an inverse U-shaped intestine (anterior ceca absent) with posterior ceca terminating near the excretory bladder, 6 testes (inter-cecal ovoid or oblong, lacking deep lobes; including 1 post-ovarian testis), a Laurer's canal, and a dextral common genital pore. Species of Sanguinicolidae Poche, 1926 infect primarily later-branching freshwater ray-finned fishes (Teleostei) and have a diminutive anterior sucker, a medial esophageal swelling (pouch), short, radial ceca of approximately equal length or short anterior ceca plus an elongate, dendritic posterior cecum, testis with appendix-like lateral lobes, no Laurer's canal, and separate or common genital pores. Species of Elopicolidae n. fam. infect ladyfishes, tarpons, and catadromous eels (Elopomorpha) and have a robust, bowl-shaped, pedunculate anterior sucker, lateral tegumental spines that are spike-like (can be lost in adult), short or indistinct anterior ceca, posterior ceca that terminate at level of the testis(es), a single testis or 2 testes, a Laurer's canal present or absent, and a sinistral common genital pore and atrium. Species of Aporocotylidae Odhner, 1912 primarily infect later-branching marine and estuarine ray-finned fishes (Teleostei) and have a spheroid anterior sucker with concentric rows of circumferential spines or the spheroid anterior sucker is lost in adults or adults have a diminutive anterior sucker, a sinuous esophagus lacking a pouch, an X- or H-shaped intestine having 4 ceca, long anterior ceca (or secondarily lost), smooth posterior ceca that extend posteriad in parallel with respective body margin and terminate near the posterior body end, testis(es) that lack appendix-like lateral lobes, no Laurer's canal, and a sinistral common genital pore or separate genital pores that are sinistral. Our 28S phylogeny recovered the fish blood flukes as monophyletic and each of the morphologically diagnosed families as monophyletic and sister to the remaining blood flukes infecting turtles and homeotherms. Acipensericolidae was recovered sister to the clade comprising Chimaerohemecidae + Sanguinicolidae and Elopicolidae + Aporocotylidae. The branching order and interrelationships of these families remains unsettled perhaps because of low taxon sampling among non-aporocotylids and extinction of intermediate taxa.

FIRST RECORD OF A PARASITE, DACTYLOGYRUS CF. SKRJABINI (MONOGENOIDEA: DACTYLOGYRIDAE), INFECTING INVASIVE SILVER CARP, HYPOPHTHALMICHTHYS MOLITRIX (VALENCIENNES, 1844) (CYPRINIFORMES: XENOCYPRIDIDAE) IN NORTH AMERICA.

The parasites infecting invasive carps in North America (all Cypriniformes: Xenocyprididae: grass carp, Ctenopharyngodon idella [Valenciennes, 1844]; silver carp, Hypophthalmichthys molitrix [Valenciennes, 1844]; bighead carp, Hypophthalmichthys nobilis [Richardson, 1845]; and black carp, Mylopharyngodon piceus [Richardson, 1846]) are little studied, and no parasite has been reported from silver carp there. We herein surveyed silver carp from Barkley Reservoir and Cheatham Reservoir (Cumberland River, Tennessee; June and December 2021) and the White River (Arkansas; May 2022) and collected numerous monogenoid specimens infecting the pores on the outer face of the gill raker plate. We heat-killed, formalin-fixed, and routinely stained some specimens for morphology and preserved others in 95% ethanol for DNA extraction and sequencing of the large subunit ribosomal DNA (28S). We identified our specimens as Dactylogyrus cf. skrjabini because they had a dorsal anchor deep root that is much longer than the superficial root, an approximately parallel penis and accessory piece, and a relatively large marginal hook pair V. No type specimen of Dactylogyrus skrjabiniAkhmerov, 1954 (type host and locality is silver carp, Amur River, Russia) is publicly available, but we borrowed several vouchers (NSMT-Pl 6393) that infected the gill rakers of silver carp captured in the Watarase River, Japan. The original description of D. skrjabini was highly stylized and diagrammatical, differing from the specimens we studied from North America and Japan by the dorsal anchor having a superficial root and shaft that comprise a strongly C-shaped hook (the superficial root curves toward the dorsal anchor point) (vs. superficial root straight, at ∼45° angle to deep root and directed away from the dorsal anchor point), a single, much reduced transverse bar that is narrow for its entire breadth (vs. dorsal and ventral transverse bars robust and broad, having an irregular outline), an accessory piece that lacks digitiform projections (vs. accessory piece with 4 digitiform projections), and an accessory piece that lacks a half cardioid-shaped process (vs. accessory piece having a half cardioid-shaped process). Our 28S sequences (generated from 4 specimens of D. cf. skrjabini: 2 from Tennessee [763 base pairs (bp)] and 2 from Arkansas [776 bp]) were identical to 1 ascribed to D. skrjabini from Japan. The present study is the first verifiable and credible report of a parasite from silver carp in North America and the first nucleotide information for a parasite from silver carp in North America.

A NEW SPECIES OF HENNEGUYA THÉLOHAN, 1892 (CNIDARIA: BIVALVULIDA: MYXOBOLIDAE) INFECTING THE SUBMUCOSA OF THE INTESTINE AND PYLORIC CECA OF RED DRUM, SCIAENOPS OCELLATUS (LINNAEUS) (PERCIFORMES: SCIAENIDAE) FROM COASTAL ALABAMA.

A new species of Henneguya Thélohan, 1892 (Bivalvulida: Myxobolidae) is described from the submucosa of the intestine and pyloric ceca of red drum (Sciaenops ocellatus [Linnaeus, 1766] [Perciformes: Sciaenidae]) from the Gulf of Mexico off Gulf Shores, Alabama. Henneguya albomaculata n. sp. differs from all congeners by the combination of myxospore dimensions, polar tubule coil count, the presence of an iodinophilic vacuole in the sporoplasm, and small-subunit ribosomal deoxyribonucleic acid (SSU rDNA) sequence. A phylogenetic analysis of the SSU rDNA recovered H. albomaculata sister to Henneguya cynosioniDykova, de Buron, Roumillat, and Fiala, 2011 in a clade composed of 11 species of Henneguya and 1 species of Myxobolus Bütschli, 1882 (Bivalvulida: Myxobolidae) that collectively infect fishes in marine or estuarine systems. Histologic sections of infected intestine and pyloric ceca revealed plasmodia of H. albomaculata n. sp. developing in the loose connective tissue of the submucosa. The new species comprises the second species of Henneguya reported from red drum.

MOLECULAR CHARACTERIZATION OF SPOROCYSTS AND CERCARIAE (DIGENEA: BUCEPHALIDAE) INFECTING THE EASTERN OYSTER CRASSOSTREA VIRGINICA FROM VIRGINIA.

The identity of a larval bucephalid infecting the eastern oyster, Crassostrea virginica (Gmelin, 1791), from a tidal river in Virginia is investigated using ribosomal deoxyribonucleic acid (rDNA). The internal transcribed spacer (ITS1, 5.8S, ITS2) region and a portion of the 28S rDNA were isolated from genomic DNA from sporocysts containing cercariae and compared with sequences from GenBank and from our previous collections of possibly related bucephalids. The studied larval bucephalid was 100% identical at the ITS1, 5.8S, and partial 28S rDNA sequences with Prosorhynchoides paralichthydis (Corkum, 1961) Curran and Overstreet, 2009; however, it differed from P. paralichthydis by 6 bases plus 3 deletions in the ITS2 region. This level of variation at the ITS2 region has been demonstrated among some Indo-Pacific species of Prosorhynchoides Dollfus, 1929, suggesting that the larval bucephalid represents an unidentified or innominate species of Prosorhynchoides that is closely related to P. paralichthydis.

Species of Hexabothriidae (Monogenea) may have extensive distribution ranges reflecting multiple host species: evidence from three new South African records.

Many hexabothriid genera require renewed taxonomic attention to provide additional detailed comparative data from new material to resolve existing species quandaries. Our current study describes and provides additional museum material for three hexabothriid species from three genera from South Africa: Erpocotyle catenulata (Guberlet), which is confirmed as a valid species, Heteronchocotyle gymnurae Neifar, Euzet and Ben Hassine, and Hypanocotyle bullardi Chero, Cruces, Sáez, Carolina, Camargo, Portes Santos and Luque. Evidence of these three hexabothriid species from South Africa suggests that hexabothriids have more globally widespread distributions, and that they are less host-specific than previously considered. A detailed summary of hexabothriids reported from the triakid hosts, Galeorhinus galeus and Mustelus mustelus is provided, and the host-specificity of hexabothriids is discussed.

RESURRECTION OF PLESIOCREADIUM WINFIELD, 1929 (DIGENEA: MACRODEROIDIDAE) WITH PHYLOGENETIC ANALYSES AND SUPPLEMENTAL OBSERVATIONS OF ITS TYPE SPECIES FROM RIVERS IN ARKANSAS, MISSISSIPPI, NEW YORK, AND TENNESSEE.

We herein resurrect and emend PlesiocreadiumWinfield, 1929 (Digenea: Macroderoididae) and provide a supplemental description of its type species, Plesiocreadium typicumWinfield, 1929, based on adult specimens collected from the intestine of bowfins, Amia calva Linnaeus, 1766 (Amiiformes: Amiidae), captured in the L'Anguille River (Mississippi River Basin, Arkansas), Big Lake (Pascagoula River Basin, Mississippi), Chittenango Creek (Oneida Lake, New York), and Reelfoot Lake (Tennessee River Basin, Tennessee). Plesiocreadium spp. (Pl. typicum and Plesiocreadium flavum [Van Cleave and Mueller, 1932] n. comb.) differ from other macroderoidids by having a dorsoventrally flat forebody, ceca that extend posteriad beyond the testes and that do not form a cyclocoel, testes that are greater than one-half of maximum body width, a cirrus sac that is dorsal to the ventral sucker and arches dextrad or sinistrad, a uterine seminal receptacle, asymmetrical vitelline fields that remain separated anteriorly and posteriorly and that extend anteriad to the level of the ventral sucker, and an I-shaped excretory vesicle. Bayesian phylogenetic analyses (ITS2 and 28S) recovered monophyletic Plesiocreadium sensu stricto (as defined herein) sister to Macroderoides trilobatusTaylor, 1978 and that clade sister to the remaining macroderoidids, with sequences ascribed to species of Macroderoides Pearse, 1924 recovered as paraphyletic. We regard Macroderoides parvus (Hunter, 1932) Van Cleave and Mueller, 1934, M. trilobatus, and RauschiellaBabero, 1951 as incertae sedis. Arkansas, New York, and Tennessee comprise new locality records for Pl. typicum.

ENCYCLOBREPHUS BREVIVITELLUS N. SP. (DIGENEA: PLAGIORCHIOIDEA, INCERTAE SEDIS) INFECTING THE MEKONG SNAIL-EATING TURTLE, MALAYEMYS SUBTRIJUGA, IN THE MEKONG RIVER, VIETNAM, WITH PHYLOGENETIC ANALYSES BASED ON RDNA.

A new digenean species belonging in EncyclobrephusSinha, 1949 is described, and the generic diagnosis is amended to accommodate variation in several features of the new species. Worms were collected from the intestines of 2 specimens of the Mekong snail-eating turtle, Malayemys subtrijuga (Schlegel and Müller, 1845). Permanent whole-mounted worms were studied using light microscopy, and ribosomal DNA (rDNA) sequences were generated from 3 worms. We investigated the phylogenetic relationship of the new species among some digenea using separate Bayesian inference analyses, 1 based on the 28S rDNA gene and rooted using a species from the Monorchioidea Odhner, 1911, and a second based on the internal transcribed spacer 1 region rooted by a species in the Microphalloidea Ward, 1901. Prior to the analyses, Encyclobrephus was classified in the Encyclometridae Mehra, 1931. Previous studies using rDNA from the type species for the family, Encyclometra colubrimurorum (Rudolphi, 1819) Baylis and Cannon, 1924, have demonstrated that En. colubrimurorum is closely related to species of Polylekithum Arnold, 1934 in the Gorgoderoidea Looss, 1901. Nevertheless, phylograms from both analyses indicated that the new species of Encyclobrephus belongs in the Plagiorchioidea Lühe, 1901, related to species in the families Cephalogonimidae Looss, 1899, Plagiorchiidae Lühe, 1901, Reniferidae Pratt, 1902, and Telorchiidae Looss, 1899. The present results suggest that Encyclobrephus is not closely related to En. colubrimurorum. Familial classification of Encyclobrephus is contingent on molecular data availability for the type species but it should be removed from the Encyclometridae and classified as incertae sedis within the Plagiorchioidea. Encyclometridae belongs in the Gorgoderoidea, not the Plagiorchioidea.

FOREGUT ULTRASTRUCTURE OF ADULT SANGUINICOLA VOLGENSIS (RASÍN, 1929) MCINTOSH, 1934 (DIGENEA: APOROCOTYLIDAE).

Herein, we use scanning and transmission electron microscopy to describe the foregut (mouth, pharyngeal canal, and associated epithelia and musculature) of an adult freshwater fish blood fluke, Sanguinicola volgensis (Rasín, 1929) McIntosh, 1934, infecting the blood of sabre, Pelecus cultratus Linnaeus, 1758 (Cypriniformes: Leuciscidae) from the Volga River, Russia. Our results indicate that S. volgensis has a pharynx and lacks an oral sucker and that its pharyngeal canal acts as a peristaltic pump that sucks blood into the esophagus, whereupon digestion commences with granules secreted from the esophageal epithelium. We saw no evidence of longitudinal muscle fibers beneath the pharyngeal canal epithelium, pharyngeal glands, or pharyngeal epithelial cells or muscle cells within the pharyngeal muscular complex; collectively indicating the presence of a pharynx rather than an oral sucker. The specialized epithelial lining associated with the mouth and pharyngeal canal evidently is unique among neodermatans; it is smooth, ∼40 nm thick anteriorly, and thickens (∼250-700 nm) posteriorly as the mouth cavity transitions into the pharyngeal canal. The pharyngeal canal epithelium has lumps of dense material resembling those of the basal lamina and fibrous coat of the tegument. The actin-like material within the pharyngeal cavity epithelium could provide structural support to the pharynx.

RESOLVING THE PARAPHYLETIC TURTLE BLOOD FLUKES: REVISION OF SPIRORCHIIDAE STUNKARD, 1921 AND PROPOSAL OF CARETTACOLIDAE YAMAGUTI, 1958, HAPALOTREMATIDAE (STUNKARD, 1921) POCHE, 1926, BARACKTREMATIDAE N. FAM., PLATTIDAE N. FAM., AND ATAMATAMIDAE N. FAM.

Turtle blood flukes ("spirorchiids") comprise a paraphyletic assemblage including the monophyletic Schistosomatidae Stiles and Hassall, 1898 as a crown group. We herein morphologically diagnose the natural groups of turtle blood flukes and propose family names for them. Spirorchiidae Stunkard, 1921 (Spirorchis MacCallum, 1919 [type]; Spirhapalum Ejsmont, 1927; Plasmiorchis Mehra, 1934; MonticelliusMehra, 1939; VasotremaStunkard, 1928; provisionally UterotremaPlatt and Pichelin, 1994) has a ventral sucker (lost in Spirorchis), an esophageal gland surrounding the entire esophagus, lateral esophageal diverticula (plicate organ and medial esophageal diverticulum present or absent), a glandular mass at the esophagus base, paired ceca surrounded by vitelline follicles for their entire length, a non-filamented, ovoid egg, and typically a Manter's organ. Baracktrematidae n. fam. (Baracktrema Roberts, Platt, and Bullard, 2016 [type]; Unicaecum Stunkard, 1925; NeospirorchisPrice, 1934) has no ventral sucker, a single cecum or cyclocoel, a coiled or looped testis extending into the anterior body half, a convoluted post-cecal and post-gonadal uterus, a uterine pouch, no metraterm, no Manter's organ, and non-filamented eggs. Plattidae n. fam. (Platt Roberts and Bullard, 2018 [type]; Hapalorhynchus Stunkard, 1922; Coeuritrema Mehra, 1933; Enterohaematotrema Mehra, 1940; CardiotremaDwivedi, 1967; Ruavermis Dutton and Bullard, 2020) has the anatomical sequence of a ventral sucker, external seminal vesicle, cirrus sac, anterior testis, ovary, transverse vitelline duct, and posterior testis (except Enterohaematotrema) plus a pars prostatica, dorsal genital pore, globular excretory vesicle, and no Manter's organ. Carettacolidae Yamaguti, 1958 (CarettacolaManter and Larson, 1950 [type]) has a spinose oral sucker, a spinose and contractile ventral sucker (transverse cavity present), numerous testes distributing in a post-ovarian, inter-cecal column, and an ovary and transverse vitelline duct that are pre-testicular. Hapalotrematidae (Stunkard, 1921) Poche, 1926 (Hapalotrema Loos, 1899 [type]; AmphiorchisPrice, 1934; LearediusPrice, 1934; Cheloneotrema Simha and Chattopadhyaya, 1980; NeocaballerotremaSimha, 1977; Satyanarayanotrema Simha and Chattopadhyaya, 1980; Shobanotrema Simha and Chattopadhyaya, 1980) has the anatomical sequence of a ventral sucker, anterior testis(es), external seminal vesicle and cirrus sac, ovary, and posterior testis(es). Atamatamidae n. fam. (Atamatam Bullard and Roberts, 2019 [type]; Paratamatam Bullard and Roberts, 2019; Pitiutrema Dutton and Bullard, 2019) has an oral sucker with anteroventral spines, vasa efferentia connecting to a pre-ovarian external seminal vesicle, a cirrus sac directed postero-laterad and having an internal seminal vesicle and glandular luminal wall, and a dendritic ovary flanked by the external seminal vesicle and oviducal seminal receptacle. A 28S phylogenetic analysis failed to reject the monophyly of these families.

AZYGIID PARASITES OF NORTH AMERICAN ENDEMIC PLEUROCERIDS AND CENTRARCHIDS: REVISION OF LEUCERUTHRUS MARSHALL AND GILBERT, 1905 (DIGENEA: AZYGIIDAE), DESCRIPTION OF TWO NEW SPECIES, AND PHYLOGENETIC ANALYSIS.

We revise monotypic LeuceruthrusMarshall and Gilbert, 1905 (Azygiidae Lühe, 1909) by emending its generic diagnosis, redescribing its type species (Leuceruthrus micropteriMarshall and Gilbert, 1905), reassigning 2 species (Leuceruthrus stephanocauda [Faust, 1921] n. comb., Leuceruthrus ocalana [Smith, 1935] n. comb.), describing 2 new congeners (Leuceruthrus ksepkai n. sp. and Leuceruthrus blaisei n. sp.), and providing a phylogenetic analysis based on the internal transcribed spacer 2 (ITS2). Leuceruthrus is unique by having oblique preovarian testes, a vitellarium that does not extend anteriad into the forebody, and a uterus that is intercecal and between the ovary and ventral sucker. We describe the cercaria of Leuceruthrus cf. stephanocauda from cercariae shed from Elimia cf. carinifera and Elimia cf. modesta from Big Canoe Creek, Alabama. Leuceruthrus ksepkai n. sp. is described from cercariae shed from rasp elimia, Elimia floridensis (Reeve, 1860) from Holmes Creek, Florida, and Elimia sp. 1 from the Chocktawhatchee River, Florida. It differs from its congeners by the combination of having broadly rounded furcae with slight marginal pigmentation in live cercariae, no spines on the tail stem, distinct anterior and posterior ridges that flank the tail stem portion accommodating the withdrawn distome, minute protuberances occupying the lateral margin of the tail stem for its entire length, and protuberances that encircle the anterior third of the posterior tail stem (immediately posterior to the tail stem portion containing the withdrawn distome). Leuceruthrus blaisei n. sp. infects Elimia sp. and is the only known congener having proportionally small furcae (>tail stem maximum width) with a nipple-like distal projection and numerous minute projections on the tail stem surface. Our phylogenetic analysis included all of our new sequences plus all publicly available ITS2 sequences for Leuceruthrus spp. and Proteromera spp., and supported the monophyly of Leuceruthrus. It recovered L. ksepkai and L. cf. ksepkai in a polytomy, and Leuceruthrus blaisei as monophyletic (identical sequences), with L. micropteri and L. cf. stephanocauda recovered as sister taxa. The present study comprises the first systematic treatment of Leuceruthrus in over a century, the first description of a new species of Leuceruthrus in 117 yr, and the first taxonomic characterization of a species of Leuceruthrus from the Mobile River Basin. It also increases the number of accepted congeners from 1 to 5 and provides new host records (E. cf. carinifera and E. floridensis) for Leuceruthrus spp.

Two new species of Myxobolus (Myxozoa: Myxobolidae) infecting the gill and scales of the smallmouth bass, Micropterus dolomieu (Centrarchiformes: Centrarchidae) in the French Broad River Basin, North Carolina.

Two new species of Myxobolus Bütschli, 1882 (Bivalvulida: Myxobolidae) are described from the gill and scales of smallmouth bass (Micropterus dolomieu Lacepède, 1802 [Centrarchiformes: Centrarchidae]) from the Watauga River, French Broad River Basin, North Carolina, United States. Myxobolus intralamina n. sp. infects the lumen of the lamellar arterioles and Myxobolus infrabractea n. sp. infects the inner surface of the scale. They differ from all congeners by a combination of myxospore dimensions, polar tubule coil count, and the presence or absence of an iodinophilic vacuole in the sporoplasm and an intercapsular process. A phylogenetic analysis of the small subunit ribosomal DNA (SSU rDNA) recovered M. intralamina n. sp. sister to Myxobolus lepomis and Myxobolus branchiarum and M. infrabractea n. sp. sister to Myxobolus micropterii in a clade composed of five Myxobolus spp. infecting centrarchids and Henneguya spp. (Myxobolidae) infecting percids. Histological sections of infected gill revealed intra-lamellar plasmodia of M. intralamina n. sp. within the lumen of the lamellar arterioles and plasmodia of M. infrabractea n. sp. developing beneath the scales. These new species comprise the first species of Myxobolus reported from a black bass (Micropterus Lacepède, 1802) in the Southeast United States.

Huffmanela cf. huffmani (Nematoda: Trichosomoididae) infecting swim bladder, peritoneum, and gonad of variable platyfish, Xiphophorus variatus (Cyprinodontiformes: Poeciliidae) and eastern mosquitofish, Gambusia holbrooki (Poeciliidae) in Florida; taxonomy, phylogenetic analysis, and pathological changes.

Variable platyfish, Xiphophorus variatus (Meek, 1904) (Cyprinodontiformes: Poeciliidae) and eastern mosquitofish, Gambusia holbrooki Girard, 1859 (Poeciliidae) from earthen ponds in west central Florida were examined for parasitic infections. At necropsy, we observed myriad nematodes (adults and eggs), which we identified as Huffmanela cf. huffmani, infecting the swim bladder, gonad, and visceral peritoneum. Nucleotide sequences (small subunit ribosomal DNA, 18S) of H. cf. huffmani from variable platyfish and eastern mosquitofish were identical; likewise for newly obtained 18S sequences of Huffmanela huffmani Moravec, 1987 from the swim bladder of red breast sunfish, Lepomis auritus (Linnaeus, 1758) (Centrarchiformes: Centrarchidae) and warmouth, Lepomis gulosus (Cuvier, 1829) from the San Marcos River (type locality for Huffmanela huffmani Moravec, 1987), Texas. The sequences of H. huffmani and H. cf. huffmani differed by 7 (1%) nucleotides. Pathological changes comprised proliferation of the tunica externa of the swim bladder in low-intensity infections in addition to inflammation, proliferation, and tissue necrosis of swim bladder, peritoneum, and gonad in high-intensity infections. The lesion was severe, affecting the cellular constituents of the swim bladder wall and reducing the size of the swim bladder lumen; potentially reducing swim bladder physiological efficiency. The present study is the first record of a freshwater species of Huffmanela Moravec, 1987 from beyond the San Marcos River, first record of a species of Huffmanela from a livebearer, first nucleotide sequences and phylogenetic analysis for Huffmanela, and first evidence that an infection by a species of Huffmanela causes pathological changes that could impact organ function.