The TMEM43 S358L mutation affects cardiac, small intestine, and metabolic homeostasis in a knock-in mouse model.

The transmembrane protein 43 (TMEM43/LUMA) p.S358L mutation causes arrhythmogenic cardiomyopathy named as ARVC5, a fully penetrant disease with high risk of ventricular arrhythmias, sudden death, and heart failure. Male gender and vigorous exercise independently predicted deleterious outcome. Our systems genetics analysis revealed the importance of Tmem43 for cardiac and metabolic pathways associated with elevated lipid absorption from small intestine. This study sought to delineate gender-specific cardiac, intestinal, and metabolic phenotypes in vivo and investigate underlying pathophysiological mechanisms of S358L mutation. Serial echocardiography, surface electrocardiography (ECG), treadmill running, and body EchoMRI have been used in knock-in heterozygous (Tmem43WT/S358L), homozygous (Tmem43S358L), and wildtype (Tmem43WT) littermate mice. Electron microscopy, histology, immunohistochemistry, transcriptome, and protein analysis have been performed in cardiac and intestinal tissues. Systolic dysfunction was apparent in 3-mo-old Tmem43S358L and 6-mo-old Tmem43WT/S358L mutants. Both mutant lines displayed intolerance to acute stress at 6 mo of age, arrhythmias, fibro-fatty infiltration, and subcellular abnormalities in the myocardium. Microarray analysis found significantly differentially expressed genes between left ventricular (LV) and right ventricular (RV) myocardium. Mutants displayed diminished PPARG activities and significantly reduced TMEM43 and ß-catenin expression in the heart, whereas junctional plakoglobin (JUP) translocated into nuclei of mutant cardiomyocytes. Conversely, elongated villi, fatty infiltration, and overexpression of gut epithelial proliferation markers, ß-catenin and Ki-67, were evident in small intestine of mutants. We defined Tmem43 S358L-induced pathological effects on cardiac and intestinal homeostasis via distinctly disturbed WNT-ß-catenin and PPARG signaling thereby contributing to ARVC5 pathophysiology. Results suggest that cardiometabolic assessment in mutation carriers may be important for predictive and personalized care.NEW & NOTEWORTHY This manuscript describes the findings of our investigation of cardiac, small intestine, and metabolic features of Tmem43-S358L mouse model. By investigating interorgan pathologies, we uncovered multiple mechanisms of the S358L-induced disease, and these unique mechanisms likely appear to contribute to the disease pathogenesis. We hope our findings are important and novel and open new avenues in the hunting for additional diagnostic and therapeutic targets in subjects carrying TMEM43 mutation.

Echocardiography phenotyping in murine genetic reference population of BXD strains reveals significant QTLs associated with cardiac function and morphology.

The genetic reference population of recombinant inbred BXD mice has been derived from crosses between C57BL/6J and DBA/2J strains. The DBA/2J parent exhibits cardiomyopathy phenotypes, whereas C57BL/6J has normal heart. BXD mice are sequenced for studying genetic interactions in cardiomyopathies. The study aimed to assess cardiomyopathy traits in BXDs and investigate the quantitative genetic architecture of those traits. Echocardiography, blood pressure, and cardiomyocyte size parameters obtained from 44 strains of BXD family (n > 5/sex) at 4-5 mo of age were associated with heart transcriptomes and expression quantitative trait loci (eQTL) mapping was performed. More than twofold variance in ejection fraction (EF%), fractional shortening (FS%), left ventricular volumes (LVVols), internal dimensions (LVIDs), mass (LVM), and posterior wall (LVPW) thickness was found among BXDs. In male BXDs, eQTL mapping identified Ndrg4 on chromosome 8 QTL to be positively correlated with LVVol and LVID and negatively associated with cardiomyocyte diameter. In female BXDs, significant QTLs were found on chromosomes 7 and 3 to be associated with LVPW and EF% and FS%, respectively, and Josd2, Dap3, and Tpm3 were predicted as strong candidate genes. Our study found variable cardiovascular traits among BXD strains and identified multiple associated QTLs, suggesting an influence of genetic background on expression of echocardiographic and cardiomyocyte diameter traits. Increased LVVol and reduced EF% and FS% represented dilated cardiomyopathy, whereas increased LV mass and wall thickness indicated hypertrophic cardiomyopathy traits. The BXD family is ideal for identifying candidate genes, causal and modifier, that influence cardiovascular phenotypes.NEW & NOTEWORTHY This study aimed to establish a cardiac phenotype-genotype correlation in murine genetic reference population of BXD RI strains by phenotyping the echocardiography, blood pressure, and cardiomyocyte diameter traits and associating each collected phenotype with genetic background. Our study identified several QTLs and candidate genes that have significant association with cardiac hypertrophy, ventricular dilation, and function including systolic hyperfunction and dysfunction.

Exploring the Regulation and Function of Rpl3l in the Development of Early-Onset Dilated Cardiomyopathy and Congestive Heart Failure Using Systems Genetics Approach.

BACKGROUND: Cardiomyopathies, diseases affecting the myocardium, are common causes of congestive heart failure (CHF) and sudden cardiac death. Recently, biallelic variants in ribosomal protein L3-like (RPL3L) have been reported to be associated with severe neonatal dilated cardiomyopathy (DCM) and CHF. This study employs a systems genetics approach to gain understanding of the regulatory mechanisms underlying the role of RPL3L in DCM. METHODS: Genetic correlation, expression quantitative trait loci (eQTL) mapping, differential expression analysis and comparative functional analysis were performed using cardiac gene expression data from the patients and murine genetic reference populations (GRPs) of BXD mice (recombinant inbred strains from a cross of C57BL/6J and DBA/2J mice). Additionally, immune infiltration analysis was performed to understand the relationship between DCM, immune cells and RPL3L expression. RESULTS: Systems genetics analysis identified high expression of Rpl3l mRNA, which ranged from 11.31 to 12.16 across murine GRPs of BXD mice, with an ~1.8-fold difference. Pathways such as "diabetic cardiomyopathy", "focal adhesion", "oxidative phosphorylation" and "DCM" were significantly associated with Rpl3l. eQTL mapping suggested Myl4 (Chr 11) and Sdha (Chr 13) as the upstream regulators of Rpl3l. The mRNA expression of Rpl3l, Myl4 and Sdha was significantly correlated with multiple echocardiography traits in BXD mice. Immune infiltration analysis revealed a significant association of RPL3L and SDHA with seven immune cells (CD4, CD8-naive T cell, CD8 T cell, macrophages, cytotoxic T cell, gamma delta T cell and exhausted T cell) that were also differentially infiltrated between heart samples obtained from DCM patients and normal individuals. CONCLUSIONS: RPL3L is highly expressed in the heart tissue of humans and mice. Expression of Rpl3l and its upstream regulators, Myl4 and Sdha, correlate with multiple cardiac function traits in murine GRPs of BXD mice, while RPL3L and SDHA correlate with immune cell infiltration in DCM patient hearts, suggesting important roles for RPL3L in DCM and CHF pathogenesis via immune inflammation, necessitating experimental validations of Myl4 and Sdha in Rpl3l regulation.

Restrictive cardiomyopathy: from genetics and clinical overview to animal modeling.

Restrictive cardiomyopathy (RCM), a potentially devastating heart muscle disorder, is characterized by diastolic dysfunction due to abnormal muscle relaxation and myocardial stiffness resulting in restrictive filling of the ventricles. Diastolic dysfunction is often accompanied by left atrial or bi-atrial enlargement and normal ventricular size and systolic function. RCM is the rarest form of cardiomyopathy, accounting for 2-5% of pediatric cardiomyopathy cases, however, survival rates have been reported to be 82%, 80%, and 68% at 1-, 2-, and 5-years after diagnosis, respectively. RCM can be idiopathic, familial, or secondary to a systemic disorder, such as amyloidosis, sarcoidosis, and hereditary hemochromatosis. Approximately 30% of cases are familial RCM, and the genes that have been linked to RCM are cTnT, cTnI, MyBP-C, MYH7, MYL2, MYL3, DES, MYPN, TTN, BAG3, DCBLD2, LNMA, and FLNC. Increased Ca2+ sensitivity, sarcomere disruption, and protein aggregates are some of the few mechanisms of pathogenesis that have been revealed by studies utilizing cell lines and animal models. Additional exploration into the pathogenesis of RCM is necessary to create novel therapeutic strategies to reverse restrictive cardiomyopathic phenotypes.

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.

Systems genetics analysis defines importance of TMEM43/LUMA for cardiac- and metabolic-related pathways.

Broad cellular functions and diseases including muscular dystrophy, arrhythmogenic right ventricular cardiomyopathy (ARVC5) and cancer are associated with transmembrane protein43 (TMEM43/LUMA). The study aimed to investigate biological roles of TMEM43 through genetic regulation, gene pathways and gene networks, candidate interacting genes, and up- or downstream regulators. Cardiac transcriptomes from 40 strains of recombinant inbred BXD mice and two parental strains representing murine genetic reference population (GRP) were applied for genetic correlation, functional enrichment, and coexpression network analysis using systems genetics approach. The results were validated in a newly created knock-in Tmem43-S358L mutation mouse model (Tmem43S358L) that displayed signs of cardiac dysfunction, resembling ARVC5 phenotype seen in humans. We found high Tmem43 levels among BXDs with broad variability in expression. Expression of Tmem43 highly negatively correlated with heart mass and heart rate among BXDs, whereas levels of Tmem43 highly positively correlated with plasma high-density lipoproteins (HDL). Through finding differentially expressed genes (DEGs) between Tmem43S358L mutant and wild-type (Tmem43WT) lines, 18 pathways (out of 42 found in BXDs GRP) that are involved in ARVC, hypertrophic cardiomyopathy, dilated cardiomyopathy, nonalcoholic fatty liver disease, Alzheimer's disease, Parkinson's disease, and Huntington's disease were verified. We further constructed Tmem43-mediated gene network, in which Ctnna1, Adcy6, Gnas, Ndufs6, and Uqcrc2 were significantly altered in Tmem43S358L mice versus Tmem43WT controls. Our study defined the importance of Tmem43 for cardiac- and metabolism-related pathways, suggesting that cardiovascular disease-relevant risk factors may also increase risk of metabolic and neurodegenerative diseases via TMEM43-mediated pathways.

Deficiency in nebulin repeats of sarcomeric nebulette is detrimental for cardiomyocyte tolerance to exercise and biomechanical stress.

The actin-binding sarcomeric nebulette (NEBL) protein provides efficient contractile flexibility via interaction with desmin intermediate filaments. NEBL gene mutations affecting the nebulin repeat (NR) domain are known to induce cardiomyopathy. The study aimed to explore the roles of NEBL in exercise and biomechanical stress response. We ablated exon3 encoding the first NR of Nebl and created global Neblex3-/ex3- knockout mice. Cardiac function, structure, and transcriptome were assessed before and after a 4-wk treadmill regimen. A Nebl-based exercise signaling network was constructed using systems genetics methods. H9C2 and neonatal rat cardiomyocytes (NRCs) expressing wild-type or mutant NEBL underwent cyclic mechanical strain. Neblex3-/ex3- mice demonstrated diastolic dysfunction with preserved systolic function at 6 mo of age. After treadmill running, 4-mo-old Neblex3-/ex3- mice developed concentric cardiac hypertrophy and left ventricular dilation compared with running Nebl+/+ and sedentary Neblex3-/ex3- mice. Disturbance of sarcomeric Z-disks and thin filaments architecture and disruption of intercalated disks and mitochondria were found in exercised Neblex3-/ex3- mice. A Nebl-based exercise signaling network included Csrp3, Des, Fbox32, Jup, Myh6, and Myh7. Disturbed expression of TM1, DES, JUP, ß-catenin, MLP, α-actinin2, and vinculin proteins was demonstrated. In H9C2 cells, NEBL was recruited into focal adhesions at 24-h poststrain and redistributed along with F-actin at 72-h poststrain, suggesting time-dependent redistribution of NEBL in response to strain. NEBL mutations cause desmin disorganization in NRCs upon stretch. We conclude that Nebl's NR ablation causes disturbed sarcomere, Z-disks, and desmin organization, and prevents NEBL redistribution to focal adhesions in cardiomyocytes, weakening cardiac tolerance to biomechanical stress.NEW & NOTEWORTHY We demonstrate that ablation of first nebulin-repeats of sarcomeric nebulette (Nebl) causes diastolic dysfunction in Neblex3-/ex3- mice. Exercise-induced development of diastolic dysfunction, cardiac hypertrophy and ventricular dilation in knockouts. This was associated with sarcomere disturbance, intercalated disks disruption, and mitochondrial distortion upon stress and altered expression of genes involved in Nebl-based stress network. We demonstrate that G202R and A592 mutations alter actin and desmin expression causing disorganization of desmin filaments upon cyclic strain.

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.

Clinostomum poteae n. sp. (Digenea: Clinostomidae), in the trachea of a double-crested cormorant Phalacrocorax auritus Lesson, 1831 and molecular data linking the life-cycle stages of Clinostomum album Rosser, Alberson, Woodyard, Cunningham, Pote & Griffin, 2017 in Mississippi, USA.

Clinostomum spp. (Digenea: Clinostomidae) are a group of trematodes commonly found in the buccal cavity and oesophagus of a variety of piscivorous birds. The metacercariae, colloquially known as "yellow grubs," have been reported from a diverse group of freshwater fishes worldwide. In the catfish farming region of the southeastern USA, piscivorous birds present a continuous challenge for aquaculturists in the form of fish depredation and the introduction of trematodes into these static, earthen pond systems. Clinostomum spp. are commonly encountered in farm-raised catfish. While generally considered pests of minimal importance, heavy infections can result in unmarketable fillets. Of the piscivorous birds that frequent catfish aquaculture operations in the southeastern US, the double-crested cormorant (Phalacrocorax auritus Lesson) is one of the most damaging, although reports of Clinostomum spp. from P. auritus are limited. In this study, adult trematodes morphologically consistent with Clinostomum sp. were found in the trachea of a double-crested cormorant captured in Lowndes Co., Mississippi, USA. These specimens differed from other recognised Clinostomum spp. in several key morphological characters. Moreover, sequence data of mitochondrial cytochrome c oxidase subunit 1 gene (cox1), nicotinamide adenine dinucleotide dehydrogenase subunit 1 gene (nad1) and ribosomal internal transcribed spacer (ITS) regions did not match any known Clinostomum sp. for which sequence data are available. While genetically similar to C. marginatum and C. album Rosser, Alberson, Woodyard, Cunningham, Pote & Griffin, 2017 reported from the great egret Ardea alba L. in Mississippi, these adult clinostomids were larger in size and limited to the trachea, whereas both C. marginatum Rudolphi, 1819 and C. album are found in the oral cavity and esophagus. Given these distinct morphological and molecular characters we propose a new member of the genus, known hereafter as Clinostomum poteae n. sp. Additionally, larval stages in the life-cycle of C. album are morphologically and molecularly identified for the first time from ramshorn snails Planorbella trivolvis Say and fathead minnows Pimephales promelas Rafinesque.

Clinostomum album n. sp. and Clinostomum marginatum (Rudolphi, 1819), parasites of the great egret Ardea alba L. from Mississippi, USA.

Members of the genus Clinostomum Leidy, 1856, colloquially known as yellow grubs, are cosmopolitan parasites of piscivorous birds, freshwater snails, fish and amphibians. In the southeastern United States, piscivorous birds present a continuous challenge for producers of farm-raised catfish. Ciconiiform birds are common hosts of Clinostomum spp. in North America and are endemic on most commercial catfish operations. The great egret Ardea alba L. is an avian predator often found foraging on commercial catfish operations, but to date the trematode fauna of great egrets preying on catfish ponds remains mostly understudied. Thirteen great egrets were captured from commercial catfish ponds in northeast Mississippi, and examined for trematode infections. Two morphologically distinct Clinostomum spp. were observed in the great egrets sampled, one morphologically consistent with Clinostomum marginatum (Rudolphi, 1819) and one morphologically unique species. These morphological descriptions were supplemented with molecular sequence data (c.4,800 bp of ribosomal DNA and c.600 bp of mitochondrial DNA). Gene sequences confirmed the identification of C. marginatum. However, the second species differed significantly from its congeners in both morphology and DNA sequence. Given these distinct morphological and molecular characters we propose this second species as Clinostomum album n. sp.

Austrodiplostomum sp., Bolbophorus sp. (Digenea: Diplostomidae), and Clinostomum marginatum (Digenea: Clinostomidae) metacercariae in inland silverside Menidia beryllina from catfish aquaculture ponds, with notes on the infectivity of Austrodiplostomum sp. cercariae in channel catfish Ictalurus punctatus.

In the southeastern USA, catfish aquaculture is burdened by predation from piscivorous birds and the digenetic trematodes they carry. In addition to cultured ictalurid fish, other forage or incidental fish species inhabit catfish production ponds. Of these, the inland silverside Menidia beryllina was recently found to harbor larval metacercariae of several trematode species. Three species of metacercariae were reported, two of which represent the first morphological descriptions of an Austrodiplostomum sp. and Bolbophorus sp. metacercaria, respectively. A total of 15 silversides were collected from a commercial catfish pond and examined for trematode infection. These fish were parasitized by metacercariae of an Austrodiplostomum sp. (100 % prevalence) in the eyes and brain, a Bolbophorus sp. (86.7 % prevalence) in the musculature, and Clinostomum marginatum (33.3 % prevalence) in the musculature and fins. All three trematode species were characterized morphologically and molecularly by sequencing of the cytochrome c oxidase subunit 1 gene (CO1). In addition, the internal transcribed spacer 1 region (ITS1), 5.8S rRNA gene, and ITS2 region were determined for the Bolbophorus sp., which linked this metacercaria to a Bolbophorus sp. cercaria from a planorbid snail Planorbella trivolvis and an unnamed Bolbophorus sp. adult from the American white pelican Pelecanus erythrorhynchos. Furthermore, Biomphalaria havanensis snails were collected from the same pond and found actively shedding cercariae morphologically and molecularly consistent with a diplostomid cercaria reported from Bi . havanensis in catfish ponds in Mississippi, USA. Sequence comparisons deemed these cercariae conspecific to the Austrodiplostomum sp. from inland silverside described here. Channel catfish fingerlings were exposed to these cercariae at doses of 50 and 100 cercariae per fish. The infectivity of this Austrodiplostomum sp. in channel catfish was assessed at 10 and 20 days post exposure (dpe). Metacercariae were observed in both the eyes and brain of infected channel catfish, supporting molecular data that suggests the cercaria and metacercaria are both stages of a previously unidentified Austrodiplostomum sp. life cycle.

Myxobolus ictiobus n. sp. and Myxobolus minutus n. sp. (Cnidaria: Myxobolidae) from the gills of the smallmouth buffalo Ictiobus bubalus Rafinesque (Cypriniformes: Catostomidae).

The smallmouth buffalo Ictiobus bubalus Rafinesque (Catostomidae) is native to North American waterways and occasionally grown in pond aquaculture. Species of Myxobolus Bütschli, 1882 have been reported from the gills, integument, and intestinal tract of buffalo fish, although there is ambiguity in some host records. In the summer of 2013, thirteen adult smallmouth buffalo were seined from a 0.1-acre (0.04-hectare) experimental research pond at the Thad Cochran National Warmwater Aquaculture Center in Stoneville, Mississippi, USA, and examined for the presence of parasitic infection. Two previously unknown species of Myxobolus were observed parasitising the gills. Plasmodia of the two species differed from each other in both size and shape. Morphologically the two species were distinct from one another and from other Myxobolus spp. previously reported from buffalo fish. Myxospores of Myxobolus ictiobus n. sp. were spherical and measured 12.7-14.5 (13.9 ± 0.4) µm in length and 10.7-13.6 (12.5 ± 0.7) µm in width with a thickness of 10.3-14.8 (12.6 ± 2.3) µm. Polar capsules measured 5.6-7.4 (6.6 ± 0.4) µm in length and 3.7-4.9 (4.5 ± 0.8) µm in width and each contained a coiled polar filament with 5-6 turns. Myxospores of Myxobolus minutus n. sp. were circular in shape and measured 7.4-9.6 (8.6 ± 0.7) µm in length and 7.5-9.9 (8.8 ± 0.7) µm in width with a thickness of 6.5-7.3 (6.7 ± 0.3) µm. Polar capsules measured 3.6-4.9 (4.3 ± 0.3) µm in length and 2.8-3.8 (3.3 ± 0.3) µm and each contained a coiled polar filament with 5-6 turns. Supplemental 18S rRNA gene sequencing identified unique sequences for each isolate. Phylogenetic analysis of 18S rRNA sequences demonstrated a strong clustering of both isolates with other species of Myxobolus from cypriniform fish.

Characterization of the Life Cycle of a Fish Eye Fluke, Austrodiplostomum ostrowskiae (Digenea: Diplostomidae), with Notes on Two Other Diplostomids Infecting Biomphalaria havanensis (Mollusca: Planorbidae) from Catfish Aquaculture Ponds in Mississippi, USA.

Ocular diplostomiasis is caused by trematode species in the family Diplostomidae, specifically those in the genera Austrodiplostomum, Diplostomum, and Tylodelphys. Diplostomid trematodes are globally distributed parasites of fish. Heavy infections of diplostomids that parasitize the eyes of fish can result in acute mortality while chronic infections are often characterized by impaired vision or blindness. In the southeastern United States, commercial catfish production is threatened by piscivorous birds and the many trematode species that parasitize them. The life cycles typically involve a piscivorous avian definitive host, a mollusk first intermediate host, and a fish second intermediate host. A survey of parasites infecting the snail host Biomphalaria havanensis (= B. obstructa ) in catfish production ponds was undertaken. Snails were collected from 2 separate ponds during the summer of 2014 and observed for the release of trematode cercariae. A total of 1,740 snails were collected. Three distinct longifurcate pharyngeate cercariae were observed and these cercariae were characterized morphologically and molecularly. Sequencing of ∼4,200 base pairs (bp) of the nuclear ribosomal genes and ∼450 bp of the mitochondrial cytochrome c oxidase gene revealed 3 genetically distinct species. One morphotype shared 99-100% sequence identity with metacercariae from the aqueous and vitreous humors of gizzard shad Dorosoma cepedianum and channel catfish Ictalurus punctatus as well as an adult trematode, Austrodiplostomum ostrowskiae, a parasite of the double-crested cormorant Nannopterum auritus. The remaining 2 cercariae morphotypes shared 99-100% sequence identity with an unidentified Tylodelphys sp. and Austrodiplostomum sp. metacercaria from the brain and eyes of several freshwater fish. Herein we molecularly link the cercaria, metacercaria, and adult stage of the life cycle of A. ostrowskiae, identifying the snail host for this parasite, in addition to providing notes on 2 cercariae representing 2 other diplostomids.

Morphological, Histological, and Molecular Description of Unicauda fimbrethilae n. sp. (Cnidaria: Myxosporea: Myxobolidae) from the Intestinal Tract of Channel Catfish Ictalurus punctatus.

The channel catfish Ictalurus punctatus is a known host for 10 species of Henneguya, but few other myxozoan genera are described from this species. Unicauda is a genus of myxozoan parasites within the family Myxobolidae that consists of 10 valid species from freshwater fish. Herein, we describe a novel species of Unicauda from the intestinal tract of farm-raised channel catfish in Mississippi. Myxospores were consistent with the genus Unicauda but exhibited a unique branching at the terminal end of the caudal process that has not previously been reported. Myxospores measured 90.39 ± 14.97 µm (mean ± SD; range = 70.88-126.02 µm) in total length. The spherical spore body measured 7.31 ± 0.26 µm (6.75-7.84 µm) in length and 7.01 ± 0.63 µm (6.1-8.01 µm) in width. The 2 polar capsules measured 3.45 ± 0.33 µm (3.02-4.03 µm) in length and 2.65 ± 0.32 µm (2.18-3.11 µm) in width. The single caudal process measured 82.98 ± 14.97 µm (63.39-118.63 µm) in length from the base of the spore body to the end of the most terminal projection. Terminal projections measured 26.83 ± 8.8 µm (12.34-42.29 µm) in length and 0.95 ± 0.23 µm (0.52-1.6 µm) in width. The 18S rRNA gene sequence obtained did not match any published sequences. Given the uniqueness of the myxospore morphology, histological presentation, and gene sequence data, we describe this as an unreported species, Unicauda fimbrethilae n. sp.