Species-specific in situ hybridization confirms arrested development of Henneguya ictaluri in hybrid catfish (Channel Catfish × Blue Catfish) under experimental conditions, with notes on mixed-species infections in clinical cases of proliferative gill disease from Mississippi catfish aquaculture.

OBJECTIVE: Proliferative gill disease (PGD) in Channel Catfish Ictalurus punctatus and hybrid catfish (Channel Catfish × Blue Catfish I. furcatus) is attributed to the myxozoan Henneguya ictaluri. Despite evidence of decreased H. ictaluri transmission and impaired parasite development in hybrid catfish, PGD still occurs in hybrid production systems. Previous metagenomic assessments of clinical PGD cases revealed numerous myxozoans within affected gill tissues in addition to H. ictaluri. The objective of this study was to investigate the development and pathologic contributions of H. ictaluri and other myxozoans in naturally and experimentally induced PGD. METHODS: Henneguya species-specific in situ hybridization (ISH) assays were developed using RNAscope technology. Natural infections were sourced from diagnostic case submissions in 2019. Experimental challenges involved Channel Catfish and hybrid catfish exposed to pond water from an active PGD outbreak, and the fish were sampled at 1, 7, 10, 12, 14, 16, 18, and 20 weeks postchallenge. RESULT: Nine unique ISH probes were designed, targeting a diagnostic variable region of the 18S ribosomal RNA gene of select myxozoan taxa identified in clinical PGD cases. Partial validation from pure H. ictaluri, H. adiposa, H. postexilis, and H. exilis infections illustrated species-specific labeling and no cross-reactivity between different myxozoan species or the catfish hosts. After experimental challenge, mature plasmodia of H. ictaluri and H. postexilis formed in Channel Catfish but were not observed in hybrids, suggesting impaired or delayed sporogenesis in the hybridized host. These investigations also confirmed the presence of mixed infections in clinical PGD cases. CONCLUSION: Although H. ictaluri appears to be the primary cause of PGD, presporogonic stages of other myxozoans were also present, which may contribute to disease pathology and exacerbate respiratory compromise by further altering normal gill morphology. This work provides molecular confirmation and more resolute developmental timelines of H. ictaluri and H. postexilis in Channel Catfish and supports previous research indicating impaired or precluded H. ictaluri sporogony in hybrid catfish.

Pseudomurraytrema fergusoni n. sp. (Monogenea: Dactylogyridae) from gills of Pealip Redhorse, Moxostoma pisolabrum (Catostomidae) from Arkansas, USA, with a description of gill pathology.

Pseudomurraytrema fergusoni n. sp. is described from the Pealip Redhorse, Moxostoma pisolabrum from the Black River (White River drainage), Lawrence County, Arkansas, USA. This represents the second monogenean described from M. pisolabrum as well as the second species of Pseudomurraytrema reported from an Arkansas catostomid. The description includes partial 18S rRNA and 28S rRNA gene sequences (732 bp and 851 bp, respectively), helping fill a void in sequence data from North American monogeneans, particularly those in the genus Pseudomurraytrema. In addition, histopathologic changes associated with the infection resulted in severe localized pathologic lesions in gills of the host, suggesting compromise of respiratory surfaces within affected areas adjacent to the worms.

A NEW SPECIES OF MYXOBOLUS (CNIDARIA: MYXOSPOREA: MYXOBOLIDAE) FROM THE GILLS OF CREEK CHUB, SEMOTILUS ATROMACULATUS (CYPRINIFORMES: LEUCISCIDAE: PLAGIOPTERINAE), FROM THE OUACHITA DRAINAGE OF ARKANSAS.

During October and November 2021, 33 creek chubs, Semotilus atromaculatus, were collected from 3 sites in Polk County, Arkansas (Ouachita River drainage), and their gills, gallbladder, fins, integument, musculature, and other major organs were examined for myxozoans. The gills of 9 (27%) were infected with a new myxozoan, Myxobolus fountainae n. sp. Qualitative and quantitative morphological data were from fresh and formalin-fixed preserved spores, while molecular data consisted of a 1918 base pair sequence of the partial small subunit ribosomal RNA gene. Phylogenetic analysis grouped M. fountainae n. sp. with the other leuciscid-infecting myxobolids from North America and within a larger clade of European myxozoans. In addition, histological information is provided on the infection. A previous record of Myxobolus muelleriBütschli, 1882, from the gills and ureters of S. atromaculatus is considered invalid and represents an unknown species. Myxobolus fountainae n. sp. is the only named myxozoan known to infect the gill filaments of S. atromaculatus, whereas Myxobolus pendula (Guilford, 1967) infects the gill arches.

Molecular phylogeny supports invalidation of Didelphodiplostomum and Pharyngostomoides (Digenea: Diplostomidae) and reveals a Tylodelphys from mammals.

Alaria, Didelphodiplostomum and Pharyngostomoides are among genera of diplostomid digeneans known to parasitize mammalian definitive hosts. Despite numerous recent molecular phylogenetic studies of diplostomids, limited DNA sequence data is available from diplostomids parasitic in mammals. Herein, we provide the first 28S rDNA and cox1 mtDNA sequences from morphologically identified, adult specimens of Didelphodiplostomum and Pharyngostomoides. Newly generated 28S sequences were used to infer the phylogenetic interrelationships of these two genera among other major lineages of diplostomoideans. The phylogeny based on 28S and a review of morphology clearly suggests that Pharyngostomoides should be considered a junior synonym of Alaria, while Didelphodiplostomum should be considered a junior synonym of Tylodelphys. Pharyngostomoides procyonis (type species), Pharyngostomoides adenocephala and Pharyngostomoides dasyuri were transferred into Alaria as Alaria procyonis comb. nov., Alaria adenocephala comb. nov. and Alaria dasyuri comb. nov.; Didelphodiplostomum variabile (type species) and Didelphodiplostomum nunezae were transferred into Tylodelphys as Tylodelphys variabilis comb. nov. and Tylodelphys nunezae comb. nov. In addition, Alaria ovalis comb. nov. (formerly included in Pharyngostomoides) was restored and transferred into Alaria based on a morphological study of well-fixed, adult specimens and the comparison of cox1 DNA sequences among Alaria spp. The diplostomid genus Parallelorchis was restored based on review of morphology.

Kudoa hypoepicardialis and associated cardiac lesions in invasive red lionfish Pterois volitans in Grenada, West Indies.

Invasive red lionfish Pterois volitans (Linnaeus, 1758) represent an ongoing ecological threat within temperate and tropical waters. Relatively little is known regarding the overall health of P. volitans and their potential for spreading pathogens in non-native regions. Lionfish collected from inshore reefs of Grenada, West Indies, in 2019 and 2021 were identified as P. volitans based on cytochrome c oxidase subunit 1 barcoding. Gross and microscopic examination of tissues revealed myxozoan plasmodia in the hearts of 24/76 (31.6%) lionfish by histopathology or wet mount cytology. Further histopathologic examination revealed severe granulomatous inflammation and myofiber necrosis associated with developing plasmodia and presporogonic life stages. Fresh myxospores were morphologically and molecularly consistent with Kudoa hypoepicardialis, being quadrate in apical view with 4 valves and 4 equal polar capsules. The spore body was 5.1-7.9 (mean: 6.0) µm long, 8.1-9.8 (8.7) µm wide, and 6.9-8.5 (7.7) µm thick. Polar capsules were 2.3-2.7 (2.5) µm long and 0.9-1.6 (1.3) µm wide. 18S small subunit rDNA sequences were 99.81-99.87% similar to sequence data from the original description of the species. Novel 28S large subunit rDNA and elongation factor 2 data, which did not match any previously reported species, were provided. This is the first account of a myxozoan parasite of P. volitans, a new host record and locality for K. hypoepicardialis, and one of few reports describing pathogen-associated lesions in invasive lionfish.

EXPERIMENTAL ELUCIDATION OF THE LIFE CYCLE OF DREPANOCEPHALUS SPATHANS (DIGENEA: ECHINOSTOMATIDAE) WITH NOTES ON THE MORPHOLOGICAL PLASTICITY OF D. SPATHANS IN THE UNITED STATES.

The echinostomatid Drepanocephalus spathans (syn. Drepanocephalus auritus) parasitizes the double-crested cormorant Phalacrocorax auritus. In North America, the marsh rams-horn snail Planorbella trivolvis and ghost rams-horn snail Biomphalaria havanensis serve as snail intermediate hosts, both of which inhabit catfish aquaculture ponds in the southeastern United States. Studies have demonstrated D. spathans exposure can be lethal to juvenile channel catfish Ictalurus punctatus. Two studies were undertaken to elucidate the life cycle of D. spathans to establish a developmental time line. In both studies, D. spathans cercariae collected from naturally infected P. trivolvis individuals were used to infect channel catfish fingerlings, which were then fed to double-crested cormorants (DCCOs) that had been pharmaceutically dewormed. In study 1, laboratory-reared P. trivolvis and B. havanensis individuals were placed in aviary ponds with experimentally infected DCCO and examined bi-weekly for release of cercariae. Trematode eggs were observed in the feces of exposed birds 3 days post-infection. Birds were sacrificed 18 days post-exposure (dpe), and gravid adults morphologically and molecularly consistent with D. spathans were recovered. Snails from the aviary pond were observed shedding D. spathans cercariae 18-54 dpe. In study 2, trematode eggs were observed in the feces of exposed DCCOs beginning 8 dpe. Once eggs were observed, birds were allowed to defecate into clean tanks containing naïve laboratory-reared P. trivolvis individuals. Additionally, eggs from experimental DCCO feces were recovered by sedimentation and placed in an aquarium housing laboratory-reared P. trivolvis individuals. Birds in study 2 were sacrificed after 60 days, and gravid D. spathans specimens were recovered. Snails from the experimental DCCO tanks shed D. spathans cercariae 89-97 dpe. Lastly, trematode eggs were isolated and observed for the hatching of miracidia, which emerged on average after 16 days at ambient temperatures. No D. spathans adults were observed in control birds fed non-parasitized fish. This is the first experimental confirmation of the D. spathans life cycle, resolving previously unknown developmental time lines. In addition, the effects of fixation on adult trematode morphology were assessed, clarifying reports of pronounced morphological plasticity for D. spathans.

New data on Henneguya postexilis Minchew, 1977, a parasite of channel catfish Ictalurus punctatus, with notes on resolution of molecular markers for myxozoan phylogeny.

Previous morphological and histological data are supplemented with molecular and ultrastructural data for a Henneguya sp. isolated from farm-raised channel catfish Ictalurus punctatus in Mississippi, USA. Myxospores were cryptic, encapsulated within a thin layer of epithelium in the gill lamellae with spore measurements consistent with the original description of Henneguya postexilis Minchew, 1977. Myxospores were 42.7-49.1 µm in total length with spore bodies 12.1-17.2 × 3.6-4.8 × 2.9-3 µm. Polar capsules were of unequal length, with the longer capsule being 4.4-6.7 × 1.1-1.6 µm and the shorter capsule being 4.4-6.4 × 1.1-1.6 µm. Polar tubules had 6-8 turns. Caudal processes were 25.7-38.1 µm in length. Spores were encapsulated in a thin layer of epithelium in the gill lamellae. Molecular data from the most commonly used markers for myxozoan identification and phylogeny, partial 18S small subunit ribosomal gene (SSU), partial 28S large subunit ribosomal gene (LSU), and elongation factor 2 (EF2) were generated for H. postexilis. Additionally, novel data for LSU and EF2 were generated for archived myxozoan specimens from farm-raised catfish (H. mississippiensis, H. ictaluri, H. exilis, H. adiposa, H. sutherlandi, H. bulbosus, Unicauda fimbrethilae), as well as archived specimens from wild fish (H. laseeae [from Pylodictis olivaris], Hennegoides flockae [from Aphredoderus sayanus], Myxobolus cloutmani [from Cycleptus elongatus]. These include the first EF2 sequence data for the genera Hennegoides and Unicauda. Phylogenetic analyses using these data placed H. postexilis in well supported clades with other ictalurid-infecting Henneguya species. Phylogenetic signal assessments on these analyses suggest that while SSU provided the greatest phylogenetic signal, LSU yielded comparable signal, supporting previous work implying this region may be underutilised in reconstructing myxobolid phylogenies.

Molecular phylogenetic analysis of Neodiplostomum and Fibricola (Digenea, Diplostomidae) does not support host-based systematics.

Fibricola and Neodiplostomum are diplostomid genera with very similar morphology that are currently separated based on their definitive hosts. Fibricola spp. are normally found in mammals, while Neodiplostomum spp. typically parasitize birds. Previously, no DNA sequence data was available for any member of Fibricola. We generated nuclear ribosomal and mtDNA sequences of Fibricola cratera (type-species), Fibricola lucidum and 6 species of Neodiplostomum. DNA sequences were used to examine phylogenetic interrelationships among Fibricola and Neodiplostomum and re-evaluate their systematics. Molecular phylogenies and morphological study suggest that Fibricola should be considered a junior synonym of Neodiplostomum. Therefore, we synonymize the two genera and transfer all members of Fibricola into Neodiplostomum. Specimens morphologically identified as Neodiplostomum cratera belonged to 3 distinct phylogenetic clades based on mitochondrial data. One of those clades also included sequences of specimens identified morphologically as Neodiplostomum lucidum. Further study is necessary to resolve the situation regarding the morphology of N. cratera. Our results demonstrated that some DNA sequences of N. americanum available in GenBank originate from misidentified Neodiplostomum banghami. Molecular phylogentic data revealed at least 2 independent host-switching events between avian and mammalian hosts in the evolutionary history of Neodiplostomum; however, the directionality of these host-switching events remains unclear.

A NEW SPECIES OF MYXOBOLUS (CNIDARIA: MYXOSPOREA: MYXOBOLIDAE) FROM THE BLUE SUCKER, CYCLEPTUS ELONGATUS (LESUEUR) (CYPRINIFORMES: CATOSTOMIDAE: CYCLEPTINAE), FROM ARKANSAS.

During 9-10 February 2018 and 21-22 February 2020, 7 adult Blue Suckers, Cycleptus elongatus, were collected by hoop nets from the Red River, Little River County (n = 3), and the Black River, Lawrence County (n = 4), Arkansas, and their gills, gallbladders, fins, integument, other major organs, and musculature were examined for myxozoans. All 7 (100%) were infected with an unknown species of gill-infecting Myxobolus sp. Twenty formalin-fixed plasmodia (cysts) of Myxobolus cloutmani n. sp. were elliptoidal, 407 µm long × 270 µm wide. Formalin-fixed myxospores were orbicular to broadly elliptoidal, 8.7 µm long × 7.8 µm wide. Two polar capsules were pyriform and subequal in size, extending over halfway in the myxospore. The larger polar capsule was 5.5 µm long × 3.1 µm wide, while the shorter was 5.1 × 2.9 µm. A coiled polar filament possessed 5 or 6 coils. The myxospore was 3.7 µm thick in sutural view, with a distinct sutural ridge. Qualitative and quantitative morphological data were from formalin-fixed as well as ethanol-preserved spores, while molecular data consisted of a 2,010 base pair sequence of the partial 18S ribosomal RNA gene and a 2,502 base pair sequence of the partial 28S ribosomal RNA gene. Phylogenetic analysis grouped M. cloutmani n. sp. with the other catostomid-infecting myxobolids. This is the first myxozoan reported from C. elongatus.

Characterisation of myxozoan fauna of western mosquitofish, Gambusia affinis (Baird and Gerard) (Cyprinodontiformes: Poeciliidae), inhabiting experimental catfish ponds in Mississippi, USA.

Characterising myxozoan taxa parasitising fish hosts in catfish aquaculture ponds is crucial to understanding myxozoan community dynamics in these diverse and complex ecological systems. This work investigated the myxozoan fauna of the western mosquitofish, Gambusia affinis, a common, incidental species found in catfish aquaculture ponds in the southeastern United States. 598 fish were sampled in May of 2018 and 2019 from the pond facility of the Thad Cochran National Warmwater Aquaculture Center in Stoneville, Mississippi, USA. Fish were examined microscopically using wet mount preparations of fresh tissue and histology for myxozoans. 18S rRNA gene sequences were amplified from myxospores obtained at necropsy. Updated morphologic, histologic, and 18S rRNA gene sequence features are provided for Henneguya gambusi, Myxobolus pharyngeus, and Myxidium phyllium. Two potentially novel myxozoans were observed during this survey, an undocumented Myxobolus sp. associated with chondrolysis of bones throughout the body and a putative Myxobilatus sp. observed histologically in the renal tubules, ureters, and urinary bladder. However, inadequate samples were obtained for proper species descriptions. Lastly, the life cycle of M. pharyngeus, which is thought to utilize the oligochaete worm Dero digitata as their definitive host, was putatively confirmed by 18S rRNA sequence matching to actinospore stages from oligochaetes in catfish ponds in Mississippi. This work provides novel and expanded morphologic, histologic, molecular and biologic data of five myxozoan parasites of G. affinis, expanding our knowledge of myxozoan diversity in catfish aquaculture ponds.

Eimeria varia Upton, Campbell, Weigel & McKown, 1990 is a Junior Synonym of Eimeria megabubonis Upton, Campbell, Weigel & McKown, 1990.

AIM: The present work aims to morphologically and molecularly characterize an Eimeria sp. recovered from an adult, captive barred owl Strix varia in Mississippi, USA. While the owl was shedding oocysts, no clinical signs of coccidiosis were observed. MATERIALS AND METHODS: Oocysts collected from a barred owl, S. varia were isolated from feces by fecal flotation and characterized by light microscopy. The oocysts were allowed to sporulate in K2Cr2O7 for 7 days and measured for comparison with previously described Eimeria species. Genomic DNA was extracted from measured oocysts and the cytochrome c oxidase subunit 1 mitochondrial gene was amplified and sequenced for comparison and phylogenetic analyses with publicly available sequence data. RESULTS: Oocysts collected from S. varia were morphologically and molecularly consistent with all previous accounts of Eimeria megabubonis from the great horned owl Bubo virginianus and morphologically consistent with the only account of Eimeria varia from S. varia. Phylogenetic analyses grouped the E. megabubonis sequence from the present study with previously reported sequences from E. megabubonis. CONCLUSION: Morphological and molecular data from oocysts collected in this study reveal S. varia is a host for E. megabubonis. Agreement between current data, morphological and molecular data of E. megabubonis, and morphological data from the original description of E. varia indicates E. varia is a junior synonym of E. megabubonis.

Characterisation of Myxobolus stellatus n. sp. (Cnidaria: Myxobolidae) infecting the cranial nerves and ganglia of the spotfin hatchetfish Thoracocharax stellatus (Kner) (Characiformes: Gasteropelecidae) from Colombia.

A previously undescribed Myxobolus sp. was isolated from the cranial nerves and ganglia of the spotfin hatchetfish Thoracocharax stellatus (Kner) that exhibited neurologic signs following importation from Colombia. Associated plasmodia formed space-occupying masses within nerves, compressing neuronal cell bodies and causing axonal degeneration. Myxospores from these fish were morphologically and molecularly distinct from other myxobolids infecting the central nervous system of characins. In valvular view, spores are pyriform with a rounded posterior and tapering anterior aspect. Myxospore bodies are 17.0-19.4 (mean 18.4) µm long and 8.2-9.3 (mean 8.8) µm wide. Polar capsules are asymmetrical and pyriform with a neck-like projection at the apical end. The small polar capsule measures 4.3-5.9 × 2.2-3.1 (mean 5.0 × 2.6) µm, while the large polar capsule measures 9.1-10.7 × 4.9-6.3 (mean 9.9 × 5.4) µm wide. The sequence generated for the small subunit rRNA (18S) gene did not directly match any sequences available on GenBank, but demonstrated 92% nucleotide similarity to Myxobolus axelrodi Camus, Dill, Rosser, Pote & Griffin, 2017 infecting Paracheirodon axelrodi (Schultz). This study provides the first morphological, histological and molecular characterisation of Myxobolus stellatus n. sp. from the spotfin hatchetfish.

Morphological and Molecular Characterisation of Myxidium kudoi Meglitsch, 1937 from the Blue Catfish Ictalurus furcatus, Valenciennes in Oklahoma, USA.

BACKGROUND: Myxidium kudoi Meglitsch, 1937 has been described from the type host, blue catfish Ictalurus furcatus, with no additional host records or molecular data available for this species. PURPOSE: To provide molecular data and a novel host locality for this species and carry out phylogenetic analyses to infer the evolutionary relationship of the species to other members of the family Myxidiidae for which DNA sequence data is available. METHODS: These data were collected using myxospores from the gallbladder of a blue catfish, Ictalurus furcatus collected from Lake Texoma, Oklahoma, USA. Myxospores were morphologically consistent with the only other account of this species and not any other Myxidium species described from siluriform fishes. RESULTS: Myxospores were oblong with rounded ends and were 10.8-12.6 (11.6 ± 0.5) µm in length and 4.7-6.6 (5.7 ± 0.5) µm in width. Polar capsules were subspherical and 2.7-3.9 (3.4 ± 0.3) µm in length and 2.4-3.5 (3.1 ± 0.3) µm in diameter, with each capsule containing a polar filament with 3-4 coils. Molecular data consisted of a 2918-bp sequence of the partial 18S, complete ITS1, 5.8S, ITS2, and partial 28S ribosomal rRNA regions as well as a 2455-bp sequence of partial 28S ribosomal RNA. The partial 18S and 28S data was used in a concatenated Bayesian phylogenetic analysis to further infer the evolutionary relationships of the Myxidiidae. Additionally, the partial 18S data was used in a separate phylogenetic analysis. CONCLUSIONS: The present work reports novel morphological and molecular data for Myxidium kudoi as well as a novel locality of occurrence for this species. In concatenated phylogenetic analysis using 18S and 28S data and other molecular data from Myxozoa, M. kudoi grouped with other freshwater Myxidiidae. In the single-locus, 18S analysis, M. kudoi grouped with Myxidium rhodei from Rutilus rutilus and Myxidium amazonense from Corydoras melini, the only other Myxidium species of catfish for which molecular data are available.

Ithyoclinostomum yamagutii n. sp. (Digenea: Clinostomidae) in the great blue heron Ardea herodias L. (Aves: Ardeidae) from Mississippi, USA.

With only six recognised genera, the family Clinostomidae Lühe, 1901 remains a global research interest of parasitologists and ecologists. Recent efforts have focused on providing molecular data to investigate species diversity, elucidate life-cycles, and make inferences on the group's evolutionary history. Of the clinostomid genera, the monotypic Ithyoclinostomum Witenberg, 1926 has remained more enigmatic compared to the commonly encountered Clinostomum Leidy, 1856. Recent morphological and molecular evidence from metacercariae suggests a second Ithyoclinostomum species may exist in freshwater cichlids in Central America and Mexico. In a recent survey of great blue herons Ardea herodias L. from commercial catfish production farms in Mississippi, USA, two specimens of an abnormally large (> 20 mm) clinostomid were encountered in the oesophagus of a single bird. These specimens were identified as an Ithyoclinostomum sp. morphologically distinct from the only nominal species Ithyoclinostomum dimorphum (Diesing, 1850). Using morphological and molecular data these adult specimens were confirmed as conspecific with the larval metacercariae previously described from Central America and Mexico and represent the novel species, Ithyoclinostomum yamagutii n. sp.

Pathology associated with Odhneriotrema incommodum infection in wild-caught American alligators Alligator mississippiensis and assessment of potential first intermediate snail hosts.

AIMS: To assess pathological changes associated with natural infections of the trematode Odhneriotrema incommodum in wild-caught American alligators Alligator mississippiensis and assess potential first intermediate hosts. MATERIALS AND METHODS: Tongues from two wild-caught alligators were obtained from a commercial alligator processor in Port Gibson, Mississippi, USA. Tongues were subjected to gross parasitological examination and routine histological assessment. Eggs were expressed from adult trematodes collected from these tongues into distilled water, where they hatched into infectious miracidia. The snails Planorbella trivolvis, Physa gyrina, and Biomphalaria havanensis were exposed to these miracidia and observed for cercarial emergence for 200 days post-exposure. RESULTS: Histological assessment of alligator tongues revealed marked hemorrhage, necrosis, presence of bacteria, and inflammation at sites of Odhneriotrema incommodum attachment, differing from previous histological reports from controlled experimental studies. Cercarial emergence was not observed in snails exposed to infectious miracidia. CONCLUSIONS: Wild-caught alligators infected with Odhneriotrema incommodum exhibit more severe pathology than was previously noted from experimentally infected alligators. This adverse pathology may be associated with microbes present in eutrophic natural habitats that are absent from controlled environments used in experimental exposures. Impacts of this parasite in wild alligator populations are likely underestimated and damage associated with parasite attachment could increase host susceptibility to secondary infections. Given the importance of alligators as game animals and sustained demand for alligator products, further study into the role of O. incommodum on alligator health is warranted. Results of snail exposures to miracidia suggest these snail species are not suitable first intermediate hosts for this trematode and the true first intermediate host of O. incommodum remains unknown.

Molecular and Histopathological Data on Levisunguis subaequalis Curran, Overstreet, Collins & Benz, 2014 (Pentastomida: Eupentastomida: Porocephalida: Porocephaloidea: Sebekidae: Sebekinae) from Gambusia affinis in Alabama, USA.

Levisunguis subaequalis Curran, Overstreet, Collins & Benz, 2014 , was recently described from the lungs of the definitive hosts, softshell turtles, Apalone ferox (Schneider, 1783), and Apalone spinifera aspera (Agassiz, 1857) as well as the viscera of an intermediate host, the western mosquitofish, Gambusia affinis (Baird and Girard, 1853). However, the original account lacked molecular data. Furthermore, histological examination of infected host tissues in the original account of L. subaequalis did not reveal any pathological changes in the intermediate host. The present work provides a robust morphological description of the nymph and novel molecular data from the 18S and 28S ribosomal gene regions and the cytochrome c oxidase subunit 1 (COI) mitochondrial gene. Phylogenetic analyses using Bayesian inference and maximum likelihood analysis with concatenated sequence data from these 3 regions, as well as each region individually, placed the turtle pentastomid L. subaequalis as a sister clade to the crocodilian pentastomids of the genus Sebekia Sambon, 1922. While only concatenated phylogenetic analyses agreed with the currently accepted classification of the Eupentastomida and phylogenetic signal assessment indicated that the concatenated data set yielded the most phylogenetic signal, data from more taxa are still needed for robust phylogenetic inferences to be made. The intensity of infection ranged from 2 to 171 nymphs per fish, compared with the highest previously reported intensity of 6. These high-intensity infections with L. subaequalis were characterized by the nymphs occupying 5-50% of the coelomic cavity of G. affinis. However, despite this heavy parasite infection, fish exhibited minimal pathology. Observed pathology was characterized by compression or effacement of organs adjacent to the nymphs, particularly liver, swim bladder, and intestines, as well as the formation of granulomas around shed pentastomid cuticles. Nonetheless, the morphological and molecular data provided in the present work will bolster future efforts to identify this pentastomid in other hosts where pathology may be present in addition to aiding in the advancement of the field of molecular pentastomid systematics.

Eimeria spp. (Apicomplexa: Eimeriidae) from great horned owls, Bubo virginianus (Gmelin) (Aves: Strigiformes) from Arkansas and Oklahoma, USA, with novel molecular information on Eimeria bubonis Cawthorn & Stockdale, 1981.

Although nine nominal species of Eimeria Schneider, 1875 have been reported from owls (Strigiformes Wagler), molecular data are available for only one, Eimeria megabubonis Upton, Campbell, Weigel & McKown, 1990. This species has been reported from the great horned owl, Bubo virginianus (Gmelin) at the type-locality of Kansas, USA, and the additional localities of Oklahoma and Mississippi, USA. Eimeria bubonis Cawthorn & Stockdale, 1981, also from B. virginianus, is represented in the literature only by its original description from Saskatchewan, Canada. The present work reports a novel host locality of E. bubonis from B. virginianus in Arkansas, USA. Additionally, novel molecular data from the 18S ribosomal RNA gene and the cytochrome c oxidase subunit 1 mitochondrial gene is provided for E. bubonis. Phylogenetic analysis using the newly generated and previously published sequence data for Eimeria spp. is also presented.

Redescription of Eimeria megabubonis Upton, Campbell, Weigel & McKown, 1990 (Apicomplexa: Emeriidae) from the great horned owl Bubo virginianus (Gmelin).

While nine nominal species of Eimeria Schneider, 1875 have been described from strigiform birds, molecular sequence data are not available for any of these species. In the present study, oöcysts of a coccidian were isolated by faecal flotation from the lower intestinal contents of an opportunistically collected, recently deceased great horned owl Bubo virginianus (Gmelin), sporulated in potassium dichromate, and subjected to morphological and molecular characterisation. Comparisons of morphological data with previous accounts of Eimeria spp. from owls were consistent with Eimeria megabubonis Upton, Campbell, Weigel & McKown, 1990. Novel molecular data for the 18S ribosomal RNA gene region and the mitochondrial cytochrome c oxidase subunit 1 gene are provided. The results of phylogenetic analysis based on concatenated sequence data from these regions are presented and implications for the evolutionary history of Eimeria are discussed.

Arrested Development of Henneguya ictaluri (Cnidaria: Myxobolidae) in ♀ Channel Catfish × â™‚ Blue Catfish Hybrids.

Henneguya ictaluri is the etiologic agent of proliferative gill disease (PGD) in farm-raised Channel Catfish Ictalurus punctatus and hybrid catfish in the southeastern United States, and significant annual losses are attributed to this disease. Research suggests that H. ictaluri infection dynamics in Blue Catfish I. furcatus and hybrid catfish (Channel Catfish × Blue Catfish) differ from those in Channel Catfish. Two separate infectivity trials were conducted to investigate H. ictaluri development in Channel Catfish, Blue Catfish, and their hybrids. On two separate occasions with two different year-classes, fish were exposed to pond water containing H. ictaluri actinospores and sampled weekly for 12 weeks (trial 1) or 14 weeks (trial 2). In trial 1, the presence of H. ictaluri was evaluated histologically and by quantitative PCR of fish tissues, including gills, blood, anterior kidney, brain, heart, liver, posterior kidney, spleen, and stomach. Henneguya ictaluri DNA was detected in significantly higher concentrations throughout multiple organ systems in the Channel Catfish compared to the hybrid catfish and Blue Catfish, with the gills having higher quantities. Myxospores were observed in Channel Catfish gill tissue at 8 weeks postexposure. No myxospores were observed in Blue Catfish or hybrid catfish. The second trial focused on gills only and yielded similar results, with Channel Catfish having significantly greater H. ictaluri DNA quantities than hybrids or Blue Catfish across all time points. Myxospores were observed in Channel Catfish beginning at 6 weeks postexposure and were found in 36% (58/162) of Channel Catfish sampled for molecular and histological analysis during weeks 6-14. Myxospores in hybrid catfish were sparse, with single pseudocysts observed in two hybrid catfish (1.2%) at 14 weeks postexposure. These results imply arrested development of H. ictaluri in hybrid catfish. As such, culture of hybrid catfish may be an effective management strategy to minimize the burden of PGD.

Morphological, Molecular, and Histopathological Data for Sebekia mississippiensis Overstreet, Self, and Vliet, 1985 (Pentastomida: Sebekidae) in the American Alligator, Alligator mississippiensis Daudin, and the Spotted Gar, Lepisosteus oculatus Winchell.

Novel molecular data from both mitochondrial ( cytochrome c oxidase subunit 1) and ribosomal regions ( 18S, ITS1-5.8S, ITS2, and 28S) are provided for Sebekia mississippiensis Overstreet, Self, & Vliet, 1985 , a pentastome infecting the American alligator, Alligator mississippiensis Daudin, 1801, and the spotted gar, Lepisosteus oculatus Winchell, 1864. Adult and nymphal pentastomes are described from the lungs and liver of the type host, A. mississippiensis, collected from Mississippi, while additional nymphs are described from the esophageal lining of L. oculatus specimens collected from Louisiana. This sequencing data will facilitate more accurate identification of various life cycle stages of S. mississippiensis, enabling future work to resolve many ambiguities in the literature regarding this species. Additionally, histopathological data are provided from both the definitive and intermediate hosts.