Towards resolving the problematic status of the digenean genus Astiotrema Looss, 1900: Taxa excluded from Astiotrema (sensu stricto) with special reference to plagiorchioid genera closely related to the restricted concept of Astiotrema.

The restricted concept of Astiotrema Looss, 1900 has been revised to include only eight species and various representative synonyms. However, several remaining taxa of Astiotrema (sensu lato) still need more inspection and scrutiny to determine their correct taxonomic position. Following a comprehensive review, four new genera are erected to accommodate some taxa excluded from Astiotrema (sensu stricto), three of which are closely related to this restricted concept of Astiotrema. Plesioastiotrema n. gen. is erected to accommodate Plesioastiotrema monticellii (Stossich, 1904) n. comb. (syn. Astiotrema monticellii Stossich, 1904) as the type-species and Plesioastiotrema magniovum (Fischthal & Kuntz, 1965) n. comb. (syn. Astiotrema magniovum Fischthal & Kuntz, 1965). Homeoastiotrema n. gen. is established for its type-species, Homeoastiotrema turneri (Bray, Van Oosterhout, Blais & Cable, 2006) n. comb., to accommodate Astiotrema turneri Bray, Van Oosterhout, Blais & Cable, 2006. Ichthyastiotrema n. gen. is erected with its type-species, Ichthyastiotrema fotedari (Dhar, 1977) n. comb. (syn. Astiotrema fotedari Dhar, 1977). A distinct morphologically and taxonomically distant taxon from Astiotrema (sensu stricto) is proposed in its own genus, Alloastiotrema n. gen. with its type-species, Alloastiotrema birmanii (Khan, Gul-E-Lala, Ghazi, Khatoon, Waheed & Khan, 2021) n. comb., to accommodate Astiotrema birmanii Khan, Gul-E-Lala, Ghazi, Khatoon, Waheed & Khan, 2021 and positioned distant from Astiotrema (sensu stricto). Astiotrema erinaceum (Poirier, 1886) Stossich, 1904, Astiotrema trituri Grabda, 1959 and Astiotrema (Biguetrema) tananarivense Deblock & Capron, 1962 are adopted synonyms of Galactosomum erinaceum (Poirier, 1886) Bittner & Sprehn, 1928, Neoastiotrema trituri (Grabda, 1959) Tkach, 2008 and Laiogonimus tananarivensis (Deblock & Capron, 1962) Fischthal & Thomas, 1968, respectively. Astiotrema lazeri El-Naffar, Saoud & Hassan, 1984 and Astiotrema gangeticus Gupta & Singh, 1985 nec Harshey, 1932 are synonymized with Glossidium pedatum Looss, 1899 and Orientocreadium batrachoides Tubangui, 1931, respectively. Based on its contradiction to the diagnosis of members of the Orientocreadiidae Yamaguti, 1958, we declare Orientocreadium lucknowensis Nigam, Chandra, Johri & Saxena, 2015 as incertae sedis. Longigula Qiu, Zhang & Li, 1983 and Kalipharynx Boeger & Thatcher, 1983 are morphologically closest to Astiotrema (sensu stricto) compared to members of the Plagiorchiidae Lühe, 1901 based on both genera possessing a cirrus-pouch with a unipartite, saccular seminal vesicle. The problematic status of Pseudoparamacroderoides Gupta & Agrawal, 1968 (sensu lato), the closest related genus to Astiotrema (sensu stricto), is discussed through evaluating the differential characteristics among listed species to indicate the extent of their validity and identifying the genuine species within this genus to re-evaluate the confusing and overlapping species to help understand their relationships with closely related plagiorchioids. Accordingly, only three species are recognized within Pseudoparamacroderoides Gupta & Agrawal, 1968 (sensu stricto): Pseudoparamacroderoides dongthapensis Truong, Curran & Bullard in Truong, Curran, Dutton & Bullard, 2021; Pseudoparamacroderoides pseudobagri (Wang in Wang, Zhao, Chen & Tao, 1983) n. comb. (syns. Astiotrema pseudobagri [Wang in Wang, Zhao, Chen & Tao, 1983] Karar, Blend, Dronen & Adel, 2021; Gauhatiana pseudobagri Wang in Wang, Zhao, Chen & Tao, 1983); and Pseudoparamacroderoides seenghali Gupta & Agrawal, 1968 (Syn. Pseudoparamacroderoides vittati Kakaji, 1969 n. syn.). Pseudoparamacroderoides raychaudhurii Agarwal & Kumar, 1983 is re-evaluated as Alloglossidium raychaudhurii (Agarwal & Kumar, 1983) n. comb. Anomalomacroderoiditrema n. gen. is erected for the type-species, Anomalomacroderoiditrema keni (Agarwal & Agarwal, 1984) n. comb., to accommodate specimens of Pseudoparamacroderoides keni Agarwal & Agarwal, 1984. Although the morphological convergence of Gauhatiana Gupta, 1953 within the Plagiorchioidea Lühe, 1901 has been suggested, it is neither a plagiorchiid nor a macroderoidid and does not appear closely related to Astiotrema (sensu stricto); it evidently is a member of the Monorchiidae Odhner, 1911. Alloglyptus Byrd, 1950 is taxonomically positioned as a gorgoderoid in the Allocreadiidae Looss, 1902, neither a plagiorchioid taxon nor closely related to Astiotrema (sensu stricto). The ambiguity of the seminal receptacle in some taxa of Astiotrema is discussed.

AIR SAC TREMATODES (CYCLOCOELIDAE STOSSICH, 1902) INFECTING BIRDS IN ZOOLOGICAL INSTITUTIONS IN THE UNITED STATES.

Air sac trematodes (Digenea: Cyclocoelidae) were detected in 23 avian species from eight aviaries in the United States. Most of the infected host species were passeriform birds, but a few species in other orders also were infected. Four species of adult flukes were encountered: Circumvitellatrema momota, Morishitium sp., Psophiatrema greineri, and Szidatitrema yamagutii. Findings from retrospective review of medical records, necropsy records, and author observations are presented. Potential terrestrial snail intermediate hosts were collected from three indoor aviaries. A high prevalence (47%) of larval trematode infections was demonstrated in one species of nonnative snail (Prosopeas achatinacea); one larva was isolated and matched to the adult species (C. momota) from birds using PCR. Problems with introducing potentially infected wild-caught birds into aviaries, and exchanging captive individuals between aviaries where they potentially may carry infections, are discussed.

A NEW SPECIES OF PROSOGONOTREMA (SCLERODISTOMIDAE: PROSOGONOTREMATINAE) FROM THE FLATHEAD GREY MULLET, MUGIL CEPHALUS LINNAEUS (MUGILIFORMES: MUGILIDAE), FROM THE ARABIAN GULF OFF IRAQ.

Prosogonotrema iraqiense n. sp. (Sclerodistomidae: Prosogonotrematinae) is described in the flathead grey mullet, Mugil cephalus Linnaeus (Mugiliformes: Mugilidae), collected from the Arabian Gulf off Iraq during June and October 2019. Currently there are 11 species of ProsogonotremaVigueras, 1940 commonly accepted: Prosogonotrema arabicaYadav, 1980; Prosogonotrema bilabiatumVigueras, 1940 (type species); Prosogonotrema caesionisGu and Shen, 1979; Prosogonotrema diacanthiBilqees and Durrani, 1980; Prosogonotrema karachienseBilqees and Durrani, 1980; Prosogonotrema pavasiLokhande, 1990; Prosogonotrema piscicola (Srivastava, 1949) Gibson, 2002 (Syn. Bhaleraoia piscicolaSrivastava, 1949); Prosogonotrema plataxumGu and Shen, 1979; Prosogonotrema posterouterinaYadav, 1980; and Prosogonotrema symmetricumOshmarin, 1965 originally described from marine fishes, and Prosogonotrema nickoliBilqees and Khan, 1992 described from a freshwater cyprinid. Six additional species that have been considered synonyms of P. bilabiatum are also considered. Prosogonotrema diacanthi is considered a junior synonym of P. piscicola and Prosogonotrema carangiHussain and Rao, 1980nec Velasquez, 1961 is determined to be a species distinct from P. bilabiatum and is reassigned herein as Prosogonotrema aluteri nomen novum per the ICZN. Prosogonotrema iraqiense differs from all currently recognized species in the genus by having the width of the ventral sucker approach or exceed the width of the body and from all except P. pavasi (body length/width ratio 1:1.4-1:1.5) by having a distinctive narrower, more elongate body profile with a larger body length/width ratio (1:5.8-1:6.1 vs. 1: 2.0-1:4.1). A key to the 18 species we recognize in Prosogonotrema is included.

Reconsideration of the species assigned to Faustula Poche, 1926 (Digenea: Microphalloidea) with the proposal of five new genera in the Faustulidae Poche, 1926.

The assignment of species to Faustula Poche, 1926 (Faustulidae Poche, 1926) is reconsidered with the proposal of Gangafaustula n. gen. to accommodate Gangafaustula makundai (Agarwal Verma, 1981) n. comb.; Gobifaustula n. gen. to accommodate Gobifaustula qikouensis (Qui Li, 1995) n. comb.; Lingulitrema n. gen. to accommodate Lingulitrema hilsai (Kumar Agarwal, 1984) n. comb.; Schellitrema n. gen. to accommodate Schellitrema gasterostei (Schell, 1973) n. comb. and Varanasifaustula n. gen. to accommodate Varanasifaustula indica (Agarwal Verma, 1981) n. comb. Faustula hilsai Kumar Agarwal, 1984 is determined to be a species distinct from Faustula hilsai Rizvi, 1971 and F. hilsai Rizvi, 1971 is synonymized with Faustula basiri Hafeezullah Siddiqi, 1970. Faustula rahemii Al-Daraji, 2004 also is synonymized with F. basiri. Faustula pyriformis Kumar Agarwal, 1984 is transferred to Pronoprymna Poche, 1926 as Pronoprymna pyriformis (Kumar Agarwal, 1984) n. comb. Faustula sayori (Yamaguti, 1942) Yamaguti, 1958, now synonymized with Pronoprymna petrowi (Layman, 1930) Bray Gibson, 1980, is renamed Pronoprymna sayori (Yamaguti, 1942) n. comb. based on the presence of an entire (smooth) ovary in P. petrowi (Syn. Monorcheides petrowi Layman, 1930) as originally described, and Faustula varanasiensis (Agarwal Kumar, 1977) is transferred to Bacciger Nicoll, 1914 as Bacciger varanasiensis (Agarwal Kumar, 1977) n. comb. We currently propose the following 5 species be retained in Faustula: F. basiri; Faustula brevichrus (Srivastava, 1935) Yamaguti, 1958; Faustula clupeae (Srivastava, 1935) Yamaguti, 1958; Faustula gangetica (Srivastava, 1935) Yamaguti, 1958 and Faustula keksooni (MacCallum, 1918) Poche, 1926. A revised key to the species of Faustula and a key to the genera within the Faustulidae are provided.

Towards resolving the problematic status of the digenean genus Astiotrema Looss, 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto).

Species of Astiotrema Looss, 1900 (sensu lato) infect a wide range of fishes, amphibians and reptilians. They also possess a considerably wide spectrum of morphological features. Several species were recognized for variable, confusing, overlapping and unspecialized morphological characters rather than for unique distinguishing features, causing continuing dispute around the validity of several species. Following comprehensive review, a revised restricted concept of Astiotrema is proposed including a morphologically strict definition. Both Tremiorchis Mehra Negi, 1926 and Astioglossimetra Bilqees, Khatoon Khan, 2002 are synonymized with Astiotrema (sensu stricto). Several nominal species are synonymized, others are excluded and characters for each recognized species are presented and explained. Only eight species are recognized: Astiotrema cyclemysi Siddiqi, 1965, Astiotrema emydis Ejsmont, 1930, Astiotrema fotedari Dhar, 1977, Astiotrema impletum (Looss, 1899) Looss, 1900, Astiotrema karachiensis (Bilqees, Khatoon Khan, 2002) n. comb., Astiotrema odhneri Bhalerao, 1936, Astiotrema ranarum (Mehra Negi, 1926) Fotedar, 1971 and Astiotrema reniferum (Looss, 1898) Looss, 1900. A key to the species of Astiotrema (sensu stricto) is presented, a comprehensive list of all host-locality records is included and host-parasite specificity is elucidated.

Two New Species of Telorchis (Digenea: Telorchiidae) from a Green Turtle, Chelonia Mydas (Cheloniidae), from the Upper Texas Coast with a Key to North American Species of Telorchis.

Sea turtles are difficult to sample because of their protected status; however, museum collections and sea turtle stranding networks provide unique opportunities for parasitological research. Four gastrointestinal tracts from stranded, endangered green turtles, Chelonia mydas, were collected between 1993 and 1995 from the upper Texas coast and opportunistically sampled for parasite fauna. Two new species of Telorchis, a common freshwater amphibian and reptilian intestinal parasite genus, were found and described. Telorchis marinus n. sp. differs from Telorchis mydas n. sp. by its short body length, lack of pharyngeal glands, long esophagus relative to total body length, short and straight cirrus sac, short ventral sucker to ovary length relative to total body length, and an ovary located in the anterior one-third of body; it differs from its congeners in the number of ovary lengths between the ventral sucker and ovary, the number of ventral sucker lengths the cirrus sac extends beyond the posterior margin of the ventral sucker, and the vitelline field extent. Telorchis mydas differs from its congeners in the number of ovary lengths between the ventral sucker and ovary, the number of ventral sucker lengths the cirrus sac extends beyond the posterior margin of the ventral sucker, and the combination of having its ovary position near the midbody and a long, sinuous cirrus sac that is 35-44% of the total body length. Given the taxonomic complexities within Telorchis, a revised key to North American species is provided using morphological characteristics to assist future researchers in delineating true species and appropriate synonymies with molecular explorations. We reject the majority of synonymies in the genus until molecular data are available; we accept the synonymies of Telorchis necturi as Telorchis stunkardi and Telorchis gutturosi as Telorchis chelopi. Both Telorchis linstowi and Telorchis stossichi should be considered as species inquirenda. This is the first confirmed report of Telorchis from a marine host and the first report on parasites of cheloniid sea turtles in Texas, and this study adds to the ever-growing evidence that collections are essential to understanding biodiversity.

A new genus and species of Anchitrematidae Mehra, 1935 (Digenea: Gorgoderoidea) in a freshwater fish from the River Nile at Qena, Egypt with amendation of the family.

Museum specimens of a previously unknown species of the Anchitrematidae from a freshwater fish collected from the River Nile at Qena, Egypt were examined. This species is somewhat similar to species of Anchitrema, but was found to have a thick, continuous, shelf-like rim around the periphery of the ventral aspect of the distome, the lateral aspect of the forebody was composed of large internal patches of lightly vacuolated, somewhat glandular cells that formed pad-like structures (pelops-like structures), and it possessed a uterine seminal receptacle; characteristics that previously have not been found in any species in the family. Species currently assigned to Anchitrema or Mujibia (the only two genera in the family) are known only from reptiles and mammals and no species has previously been reported from a freshwater fish. We feel that these differences are sufficient enough to warrant the erection of Piscianchitrema n. gen. and amendation of the family. We support the synonymies of Anchitrema congolense with Anchitrema latum, and Anchitrema lucknowensis with Anchitrema indicum. The current status of species previously described in the family is discussed, and keys to the genera and species of Anchitrema are provided.

Unusual opecoelids from Red Sea triggerfishes with special reference to characteristic concepts of the Opistholebetinae Fukui, 1929 (Digenea: Opecoelidae).

Three digeneans belonging to the Opecoelidae are reported and described from triggerfishes (Tetraodontiformes: Balistidae) collected in the northern Red Sea off Egypt. Both Macvicaria longicirrata (Manter, 1963) Aken-Ova, Cribb Bray, 2008 and Neopycnadena tendu (Bray Justine, 2007) n. comb. were recovered from the intestine of the titan triggerfish, Balistoides viridescens (Bloch Schneider)-each represents a new host record-and Gaevskajatrema balistes n. sp. was found parasitizing the lower intestine of the Picasso triggerfish, Rhinecanthus assasi (Forsskål). We continue to support synonymy of Gaevskajatrema ponticum (Koval, 1966) Machkevsky, 1990 with Gaevskajatrema perezi (Mathias, 1926) Gibson Bray, 1982, not as a differentiated species. We adopt the restricted posterior extension of the ceca and vitellarium to the testicular zone, without extension of either into the post-testicular space, as diagnostic in distinguishing Gaevskajatrema. Gaevskajatrema balistes n. sp. differs from G. perezi based on its substantially smaller body size with fewer eggs, a longer cirrus-pouch reaching ovarian level and it parasitizes a distinct host group from a structurally and ecologically different ecosystem. Neopycnadena n. gen. is erected for Pseudopycnadena tendu Bray Justine 2007 based on its possessing a large broadly oval cirrus-pouch with a massive field of prostatic cells occupying the entire volume of the cirrus-pouch, a wide, cup-shaped and thick-walled ejaculatory duct, distinct dorsal position of the excretory pore, the bifurcal dextral position of the genital pore, its report from a distinct host group and distant locality and its phylogenetic uniqueness compared with Pseudopycnadena fischthali Saad-Fares Maillard 1986. Neopycnadena n. gen. is ecologically similar to opistholebetines in their life-cycles and morphology; however, phylogenetically separate from opistholebetines as well as from the Polypipapiliotrematinae Martin, Cutmore Cribb in Martin, Sasal, Cutmore, Ward, Aeby Cribb, 2018 and members of Clade [C] of Martin and colleagues, thus we conclude that Neopycnadena n. gen. is unique. Neopycnadeninae n. subfam. is proposed to accommodate Neopycnadena n. gen. We consider that the probable characterization of tetraodontiform specialist taxa (as indicated by the presence of a muscular post-oral ring) and the specificity of the Opistholebetinae Fukui, 1929 sensu stricto with a tetraodontiform host are no longer reliable characters differentiating Gaevskajatrema and Macvicaria Gibson Bray, 1982. The nature of the post-oral structure is discussed and it is adopted to be a diagnostic feature at the generic level among taxa of the Opistholebetinae sensu latu. It is concluded that the expanded concept of the Opistholebetinae is more supported than the restricted one, Birendralebes Srivastava Ghosh, 1972 remains incertae sedis within the Opecoelidae Ozaki, 1925 rather than in the Opistholebetinae, and we provide a generic key to the Opistholebetinae.

Occurrence of Podocotyle Dujardin, 1845 (Opecoelidae, Podocotylinae) in three species of deep-sea macrourids from the Gulf of Mexico and Caribbean Sea with an updated key to species and host-parasite checklist.

Podocotyle pearsei Manter, 1934 is documented from the intestine of Vaillant's grenadier, Bathygadus melanobranchus Vaillant (Macrouridae: Bathygadinae), collected from the northeastern and western Gulf of Mexico from 783-841 m depth. The finding of P. pearsei in B. melanobranchus represents the first originally published report of this genus from this host and the fifth documented host species for P. pearsei. We report three unidentified species of Podocotyle, represented by one individual each, from the intestine of the western Atlantic grenadier, Nezumia atlantica (Parr) (Macrouridae: Macrourinae), and from Bathygadus favosus Goode Bean (Macrouridae: Bathygadinae) found at 637 m, 710 m and 1,143 m depths in the northeastern Gulf of Mexico off Florida and from the Caribbean Sea off Colombia. We provide a checklist of the parasites known from the three macrourid species relevant to this study, comment on the biogeography of the five species of Podocotyle now known from the deep sea and discuss the low host specificity observed across this genus. The high number of fish hosts for Podocotyle (i.e. type hosts include at least 22 piscine families) encompassing a wide phylogenetic diversity and diet makes it unlikely that members of a single genus could evolve such a broad array of life histories (i.e. utilize dissimilar intermediate hosts), and we predict in the future that Podocotyle will be taxonomically divided up. Morphological and especially molecular work is needed for Podocotyle as well as for other digenean genera known to inhabit the deep sea. Podocotyle sp. 1 2 represent the first originally published reports of this genus from N. atlantica while Podocotyle sp. 3 represents the first report of this genus from B. favosus. Podocotyle koshari Nagaty, 1973 is declared a species inquirenda, and a dichotomous key to the 27 species of Podocotyle we recognize is provided.

Re-examination of the phylogenetic relationships within the Gyliauchenidae Fukui, 1929 (Digenea) based on morphological and molecular evidence with a proposal for Paragyliaucheninae n. subfam. and a description of Flagellotrema convolutum Ozaki, 1936.

Flagellotrema convolutum Ozaki, 1936 was found parasitising the intestine of two new host fish species, the Indian sail-fin surgeonfish, Zebrasoma desjardinii (Bennett) (Acanthuridae), and the Picasso triggerfish, Rhinecanthus assasi (Forsskål) (Balistidae), from the northern Red Sea off Egypt. Another description of this species is provided with detailed morphological observations made of the genital systems. Using newly acquired molecular data from the D1-D3 regions of 28S rDNA, the phylogenetic relationships of subfamilies and genera within the Gyliauchenidae Fukui, 1929 are elucidated with morphological support. The Petalocotylinae Ozaki, 1934 and the Robphildollfusiinae Paggi & Orecchia, 1963 are recognized as valid subfamilies within the Gyliauchenidae. The Apharyngogyliaucheninae Yamaguti, 1942 and the Ichthyotreminae Caballero & Bravo-Hollis, 1952 remain junior synonyms of the Gyliaucheninae Fukui, 1929. Based on its unique position relative to all gyliauchenid subfamilies and its distinct separation from all other gyliauchenine genera, the Paragyliaucheninae n. subfam. is erected to contain Paragyliauchen Yamaguti, 1934. Paragyliauchen differs from all other gyliauchenine genera by having a pharynx differentiated into two, well-developed muscular regions: an anterior region composed of a ring with indented projections anteriorly and a posterior region that is ellipsoidal or barrel-shaped. Modified and/or new keys to the four subfamilies we recognize within the Gyliauchenidae as well as the genera within each subfamily are presented, and we discuss the evolutionary development and etymology of the unique anatomy of the anterior of gyliauchenids.

Diphyllobothrium stemmacephalum Cobbold, 1858 (Diphyllobothriidea) from common bottlenose dolphin, Tursiops truncatus (Montagu) from the Texas Gulf coast, USA.

Cobbold (1858) established Diphyllobothrium Cobbold, 1858 with the description of Diphyllobothrium stemmacephalum Cobbold, 1858 from the common harbor porpoise, Phocoena phocoena (Linnaeus) (Phocoenidae), from the North Sea off Scotland. Diphyllobothrium stemmacephalum typically has been reported from a number of Phocoenidae and Delphinidae hosts from a variety of localities: common harbor porpoise from the northern Atlantic Ocean, Baltic Sea and Black sea (e.g. Cobbold, 1858; Delyamure 1955; Delyamure 1968; Delyamure 1971; Delyamure et al. 1985; Anderson, 1987); bottlenose dolphin, Tursiops truncatus (Montagu), from the Gulf of Mexico (Ward Collins 1959), the Black sea (Delyamure et al. 1985); common harbor porpoise off Newfoundland (Brattey Stenson 1995), the Black Sea (Krivokhizin Birkun 1994 [see Yera et al. 2008]), off Denmark (Herreras et al. 1997); long-finned pilot whale, Globicephala melas [Traill], North Atlantic off Faroe Island (Balbuena Raga 1993); Atlantic white-sided dolphin, Lagenorhynchus acutus [Gray], off Massachusetts (Olson Caira 1999).

Revision of the Megaperidae Manter, 1934 n. comb. (Syn. Apocreadiidae Skrjabin, 1942) including a reorganization of the Schistorchiinae Yamaguti, 1942.

Modified and/or new keys to the four subfamilies now recognized within the Megaperidae Manter, 1934 n. comb. (Syn. Apocreadiidae Skrjabin, 1942) as well as the genera within each subfamily are presented. Two new genera, Paraschistorchis n. gen. and Plesioschistorchis n. gen., both within the Schistorchiinae Yamaguti, 1942, are erected and keys are provided to the species considered in both new genera-distinguished by possessing caeca that end either in separate ani or blindly. Plesioschistorchis callyodontis (Yamaguti, 1942) n. comb. and Plesioschistorchis haridis (Nagaty, 1957) n. comb. are re-described from new material collected from the common parrotfish, Scarus psittacus Forsskål (Perciformes: Scaridae), inhabiting the Red Sea off Egypt; S. psittacus represents a new host record for both species. The taxonomic status of Schistorchis sensu stricto Lühe, 1906 is examined and revised, a key to the four species we consider in this genus offered, and the monotypic genus Megacreadium Nagaty, 1956 declared a junior synonym of Schistorchis. Members of Schistorchis sensu stricto possess a unique "complex" (i.e. highly cellular/glandular) instead of "simple" (i.e. entirely muscular) type of oral sucker that is quite large in relation to body size; an elongate, somewhat sub-rectangular-shaped body; 5+ testes arranged in at least two rows; caeca that open via separate ani; a long post-testicular region; a median genital pore either at the anterior margin of or just anterior to the ventral sucker; and species of Schistorchis sensu stricto parasitize the intestine of marine fish within the Order Tetraodontiformes Berg. With the revision of this genus, we re-describe Schistorchis carneus Lühe, 1906 from the lower and mid-intestine of the white-spotted puffer, Arothron hispidus (Linnaeus) (Tetraodontiformes: Tetraodontidae), collected in the Red Sea off Egypt. Finally, a plea is made for further study of the Megaperidae n. comb. focusing, in particular, on the following: (1) obtaining new type/voucher materials of Plesioschistorchis manteri (Gupta & Tandon, 1984) n. comb. and Schistorchis paruchini Kurochkin, 1974; (2) elucidating the life histories (i.e. intermediate hosts) of members of the Postporinae Yamaguti, 1958 and Schistorchiinae; and (3) generating DNA sequence data for more species of megaperids to help future workers produce increasingly accurate taxonomic classifications that better reflect phylogenetic relationships within this ecologically diverse group of digeneans.

Intraspecific variation in adult Uvitellina iraquensis Dronen, Ali & Al-Amura, 2013 (Cyclocoelidae: Haematotrephinae) from two collection sites of white-tailed lapwing, Vanellus leucurus (Lichtenstein) (Charadriiformes: Charadriidae), in Iraq.

A total of 19 white-tailed lapwing, Vanellus leucurus, were collected from Huwazah Marsh, north-eastern Basrah Province, Iraq from February to March and in October, 2011 (collection site #1) and 60 V. leucurus were collected from Al-Hammar Marshes, Thi-Qar Province, southern Iraq from July to November, 2012 (collection site #2), and examined for cyclocoelids. Nineteen Uvitellina iraquensis Dronen, Ali & Al-Amura, 2013 from site #1 and 17 specimens from site #2 were fixed with minimal compression for comparisons of morphological characteristics, measurements, morphometric percentages and morphometric ratios commonly used to distinguish species of cyclocoelids. An additional five adult specimens from site #1 were fixed without compression for comparisons. Specimens from site # 1 (n=24) represented only fully-developed, non-senescing adults, while those from site #2 (n=17) could be divided into fully-developed (non-senescing) adults (n=8); younger (smaller, less developed) adults (n=5) and senescing adults (n=4). The following characteristics were relatively consistent, and appeared to be valuable in identifying groups of similar species and distinguishing species in Uvitellina: the presence or absence of the oral sucker; the oral sucker/pharynx width ratio; the posterior extent of the cirrus sac relative to the intestinal bifurcation; the position of the genital pore relative to the pharynx; the position of the testes in the body; the length of the intertesticular space; the length of the posttesticular space; the lateral disposition of the uterine loops; the presence of a posteriorly-directed, tail-like extension off the posterior confluence of the vitelline fields; the posterior extent of the uterine loops relative to the gonads; and the size of fully-developed eggs. It may be beneficial to calculate the percentage that measurements represent relative to the body length to provide insight into the relationship of the size of a structure to increased size of the specimens (growth). Specimens fixed without compression appeared to be less uniform, less symmetrical, shorter, more distorted and the internal details were more difficult to see.

Pseudopecoelus mccauleyi n. sp. and Podocotyle sp. (Digenea: Opecoelidae) from the deep waters off Oregon and British Columbia with an updated key to the species of Pseudopecoelus von Wicklen, 1946 and checklist of parasites from Lycodes cortezianus (Perciformes: Zoarcidae).

Pseudopecoelus mccauleyi n. sp. (Opecoelidae: Opecoelinae) is described from the intestine of the bigfin eelpout, Lycodes cortezianus (Gilbert, 1890) (Perciformes: Zoarcidae), collected at 200-800 m depths in the Northeastern Pacific Ocean off Oregon and Vancouver Island, British Columbia. The new species is distinguished by possessing a unique combination of the following diagnostic characters: vitelline fields that extend to the posterior margin of the ventral sucker; a slender, tubular and sinuous seminal vesicle that extends some distance into the hindbody; an unspecialized, protuberant ventral sucker; a genital pore at pharynx level; lobed to deeply multilobed testes; a lobed ovary; and an egg size of 68-80 µm × 30-46 µm. A single specimen of Podocotyle Dujardin, 1845 (Digenea: Plagioporinae) is also described from the intestine of an individual Coryphaenoides sp. (Gadiformes: Macrouridae) collected at 2,800 m depth off Oregon. A listing of parasites from the bigfin eelpout as well as observations of parasite diversity within relevant hosts are offered, new host and locality records are noted, and a brief discussion of Pseudopecoelus von Wicklen, 1946 in the deep sea is presented taking note of the low level of host specificity recorded (i.e. spp. of Pseudopecoelus are now known to parasitize deep-water fish from at least 20 piscine families). A new dichotomous key to the 39 recognized species of Pseudopecoelus is introduced.

Podocotyle nimoyi n. sp. (Digenea: Opecoelidae: Plagioporinae) and a re-description of Podocotyle pearsei Manter, 1934 from five species of deep-sea macrourids from the Gulf of Mexico and Caribbean Sea.

Two rare species of Podocotyle Dujardin, 1845 (Digenea: Opecoelidae) parasitizing five macrourid species inhabiting the deep waters of the northeastern Gulf of Mexico and Caribbean Sea off Panama are described. Podocotyle nimoyi n. sp. was found in the intestine of the pugnose grenadier, Sphagemacrurus grenadae (Parr), and the common Atlantic grenadier, Nezumia aequalis (Günther) (Gadiformes: Macrouridae), at depths of 534-995 m in the Northeast Gulf of Mexico off Florida and represents the fifth species of Podocotyle endemic to the deep sea. Podocotyle pearsei Manter, 1934, was re-described from the intestine of the bullseye grenadier, Bathygadus macrops Goode & Bean, the doublethread grenadier, Gadomus arcuatus (Goode & Bean), and the western softhead grenadier, Malacocephalus occidentalis Goode & Bean (Gadiformes: Macrouridae), collected from 591-728 m depths in the Northeast Gulf of Mexico off Florida and the Caribbean Sea off Panama. The following new host records are established: P. nimoyi n. sp. is the third parasite species known from S. grenadae and the first digenean species reported from this host; P. nimoyi n. sp. is the first reported species of Podocotyle parasitizing N. aequalis; and this is the first report of P. pearsei or any representative of the genus Podocotyle infecting B. macrops, G. arcuatus and M. occidentalis. A listing of all digenean parasites previously reported from the five macrourid species examined herein is given and some observations are made about Podocotyle in the deep sea.

Pelopscreadium aegyptense n. gen., n. sp. and Pelopscreadium spongiosum (Bray & Cribb, 1998) n. comb., (Digenea: Lepocreadiidae), each from disjunct populations of the Yellow boxfish, Ostracion cubicus Linnaeus (Ostraciidae).

Bianium spongiosum Bray & Cribb, 1998 (Lepocreadiidae), described from the yellow boxfish, Ostracion cubicus Linnaeus (Ostraciidae), off Lizard Island, Queensland, Australia, possesses a combination of the following three morphological features which distinguishes it from all the other species currently assigned to the genus: (1) large internal patches of large cells forming sponge-like pads we have termed "pelops"("pelop" sing.) laterally in the forebody extending from near the anterior extremity to about the level of the intestinal bifurcation rather than possessing a scoop; (2) ceca that reach to near the posterior extremity where they end blindly without ani; and (3) a vitellarium which is present laterally but not dorsal to the ceca. Based on this we propose the erection of Pelopscreadium n. gen. (Lepocreadiidae) with the assignment of B. spongiosum to this new genus as the type-species, Pelopscreadium spongiosum (Bray & Cribb, 1998) n. comb. Pelopscreadium aegyptense n. sp., also from the yellow boxfish but from the Red Sea off Sharm El-Naga, Egypt, is described as the second member of the new genus because it shares these three characteristics with P. spongiosum.

Updated keys to the genera in the subfamilies of Cyclocoelidae Stossich, 1902, including a reconsideration of species assignments, species keys and the proposal of a new genus in Szidatitreminae Dronen, 2007.

Keys to the six subfamilies, 22 genera within subfamilies and 128 species recognized within the Cyclocoelidae are provided. Lists of species in each genus are provided, along with taxonomic summaries that include type host, type locality, additional hosts, additional localities, previously proposed synonyms, and remarks for each species. The following synonymies are proposed: Cyclocoelum mutabile (Zeder, 1800)-Syn. C. microstomum (Creplin, 1929); Cyclocoelum leidyi Harrah, 1922-Syn. C. cuneatum Harrah, 1922; Cyclocoelum mehrotrai Sinha & Sahay, 1975-Syn. C. mathuri Jain, 1984; Selfcoelum allahabadi (Khan, 1935) n. comb.-Syns. Cyclocoelum agamprasadi Jain, 1983, Cyclocoelum erythropis Khan, 1935 and Cyclocoelum indicum Khan, 1935; Selfcoelum obliquum (Harrah, 1921) n. comb.-Syn. Cyclocoelum mehrii Khan, 1935; Uvitellina adelphus (Johnston, 1917)-Syn. Cyclocoelum (Uvitellina) dollfusi Tseng, 1930; Uvitellina kaniharensis (Gupta, 1958)-Syn. U. indica Siddiqi & Jairajpuri, 1962; Uvitellina simile (Stossich, 1902) n. comb.-Syn. U. magniembria Witenberg, 1923; Uvitellina vanelli (Rudolphi, 1819)-Syns. U. keri Yamaguti, 1933 and U. tageri Yamaguti, 1933; Wardianum triangulare (Harrah, 1922)-Syn. Wardianum catoptrophori Dronen, 2007; Haematotrephus limnodromi Dronen, Gardner & Jiménez, 2006-Syn. H. selfi Dronen, Gardner & Jiménez, 2008; and Hyptiasmus arcuatus (Brandes, 1892 of Stossich, 1902)-Syn. H. coelonodus Witenberg, 1923. Based on the lack of adequate descriptive information, Cyclocoelum cornu (Zeder, 1800); Cyclocoelum crenulatum (Rudolphi, 1809); Haematotrephus nigropunctatum (von Linstow, 1883) n. comb.; Haematotrephus robustus Ukoli, 1968; Hyptiasmus californicus (Wootton, 1966); and Hyptiasmus vigisi Savinov, 1960 are considered to be species inquirendae. Hyptiasmus witenbergi Tret'iakova, 1940 (described in a dissertation) is considered to be a nomen nudum. Comparative tables containing measurements, morphometric percentages and morphometric ratios for species in the family are provided and the comparative characteristics used to distinguish species in the Cyclocoelidae are discussed.

Re-evaluation of Tellervotrema katadara (Kuramochi, 2001) Kuramochi, 2009 (Opecoelidae: Plagioporinae) and supplementary morphological data for T. beringi (Mamaev, 1965) Gibson & Bray, 1982 with new host and locality.

The trematode genus Tellervotrema Gibson & Bray, 1982 was erected for Podocotyle-like species that parasitize archybenthal macrourid fishes (also known as grenadiers or rattails) and that possess no vitelline follicles dorsal to the ceca but do have a symmetrical pair of isolated groups of vitelline follicles in the posterior forebody. Tellervotrema katadara (Kuramochi, 2001) Kuramochi, 2009 is resurrected as a valid species based on an examination and re-description of holotype and paratype specimens collected from the intestine of the bathygadine macrourid Gadomus colletti Jordan & Gilbert from 518-582 m depth in Tosa Bay, off the Pacific coast of southern Japan. Tellervotrema beringi (Mamaev, 1965) Gibson & Bray, 1982 is re-described from specimens originally identified as T. katadara, collected from the intestine of the longfin grenadier, Coryphaenoides longifilis Günther, and found at 1,196 m depth off the Pacific coast of the Tohoku region, northern Honshu, Japan. New host and locality records for T. beringi are presented along with a brief listing of museums housing type and voucher specimens of the three species now recognized in Tellervotrema. A comprehensive listing is given of all parasites reported from the two macrourid species relevant to this study and a key is presented for members of Tellervotrema. Finally, we hypothesize that the life cycles for T. beringi and T. katadara in the deep waters of the North Pacific Ocean off Japan most likely include a gastropod as a first intermediate host, one or more of a variety of invertebrates (amphipods, decapods, mysids) and/or finfish as second intermediate hosts, and the grenadiers, C. longifilis and G. colletti, as definitive hosts, respectively.

Description of a new species of Podocotyle Dujardin, 1845 (Digenea: Opecoelidae: Plagioporinae) from the cusk-eel, Luciobrotula corethromycter Cohen, 1964 (Ophidiiformes: Ophidiidae), from the Gulf of Mexico and Caribbean Sea.

Podocotyle bathyhelminthos n. sp. (Opecoelidae: Plagioporinae) is described from the cusk-eel, Luciobrotula corethromycter Cohen, 1964 (Ophidiiformes: Ophidiidae), collected at depths of 622-1,280 m in the northern Gulf of Mexico and Caribbean Sea off Colombia. The new species is distinguished by possessing a combination of the following features: an elongate oval body shape, a sucker width ratio of 1:1.4-1.9, deeply lobed and irregularly-shaped testes, a cirrus-sac that extends just in to the hindbody, a trilobed ovary and vitellarium that extend to the ventral sucker level. Several unique features in P. bathyhelminthos n. sp. were not present in all, or almost all, recognized species of Podocotyle including a conspicuous deep cleft at the posterior end of the worm, a small transverse ridge on the ventral surface immediately anterior to the ventral sucker, uterine loops extending ventral to the caeca and, at times, lateral to the caeca, a thick-walled metraterm extending 1/3 to 1/2 the length of the cirrus-sac and P. bathyhelminthos n. sp. parasitizes a deep water piscine host. Podocotyle etheostomae Aliff, 1973 is declared a nomen nudum. A brief discussion of Podocotyle Dujardin, 1845 in deep waters is presented, and a gastropod, caridean shrimp and cusk-eel are hypothesized as hosts in the life cycle of P. bathyhelminthos n. sp. in the deep sea.