A new species of Parspina Pearse, 1920 (Digenea: Cryptogonimidae) from Pimelodella gracilis (Valenciennes) (Siluriformes: Heptapteridae) in the Paraná River basin, Argentina, and a key to the genus

A new species of cryptogonimid belonging to the genus Parspina Pearse, 1920 is described from the intestine of Pimelodella gracilis (Valenciennes) in the Paraná River basin, Argentina. Parspina pimelodellae n. sp. is characterised by having: (i) a body length/width ratio of 1:3.6–5.3 at the level of the ventral sucker; (ii) 21 oral spines; (iii) an oral sucker larger than the ventral sucker, with a sucker width ratio of 1:0.6–0.7; (iv) a postcaecal region of 16–19% of the body-length; (v) a compact, transversely elongate ovary, anterior to and well separated from the testes; (vi) small, branched vitelline follicles, extending from the level of the ventral sucker to the anterior margin of the ovary; and (vii) a large seminal vesicle situated posterodorsal to the ventral sucker. A key to the species of Parspina is presented.     

Zoogonidae (Digenea) from southern Great Barrier Reef fishes with a description of Steganoderma (Lecithostaphylus) gibsoni n. sp.

Two species of the Zoogonidae are recorded from Heron Island on the southern Great Barrier Reef. Steganoderma (Lecithostaphylus) gibsoni n. sp. is described from the intestine of Abudefduf whitleyi (Pomacentridae). The new species is distinguished by the combination of the following: pedunculate ventral sucker, caeca extending well past testes, presence of two-chambered internal seminal vesicle, vitelline follicles extending only to anterior margin of testes, and testes close to ventral sucker. Zoogonus pagrosomi Yamaguti, 1939 is recorded from Lethrinus atkinsoni (Lethrinidae). This species has been recorded previously only from a sparid from Japan. A new combination, Steganoderma (Lecithostaphylus) fugus (Zhang, Qiu & Li, 1986), is made.     

Steganoderma szidati n. sp. (Trematoda: Zoogonidae) from Galaxias maculatus (Jenyns) and G. platei Steindachner in Patagonia,Argentina

Steganoderma szidati n. sp. is described from the intestine of two freshwater fishes, Galaxias maculatus and G. platei (Galaxiidae), from Andean lakes in Patagonia, Argentina. This freshwater zoogonid species fits in the genus Steganoderma (sensu Bray, 1987) because of the length of the caeca and the position of the vitelline follicles. The new species is characterised by possesing 6-13 vitelline follicles situated between the anterior margin of the ventral sucker and the poterior margin of the testis. The gonads are in the anterior hindbody and the ovary is anterior to the right testis. The cirrus has two conspicuous spines at its distal end, and the seminal vesicle always exhibits a constriction. The excretory vesicle never reaches the level of the posterior margin of the testes.     

A new species of Saturnius Manter, 1969 (Digenea: Hemiuridae) from Mediterranean mullet (Teleostei: Mugilidae)

A new hemiurid digenean, Saturnius gibsoni n. sp., is described from the stomach lining of Mugil cephalus L. off Oran, Mediterranean coast of Algeria. Characteristic morphological features of the new species include small size of the body which is comprised of six pseudosegments, small ventral sucker, weakly developed mound-shaped flange at the level of the ventral sucker, and eggs being large in relation to the size of the body. Saturnius gibsoni n. sp. resembles S. minutus Blasco-Costa, Pankov, Gibson, Balbuena, Raga, Sarabeev & Kostadinova, 2006 and two unidentified Saturnius spp. in the small size of the body and most metrical features. However, in spite of the presence of five transverse septa resulting in six pseudosegments and the range overlap of some metrical features, the ventral sucker in S. minutus is much larger, the ventral sucker muscular flange is more prominent, the last pseudosegment is narrower in relation to body width and more rounded, and the eggs are smaller (mean 21 × 10 vs 25 × 12 μm). Furthermore, the partial sequences of the 28S rRNA gene region (domains D1–D3; 1,195 nt) obtained from two isolates of S. gibsoni n. sp. differed by 11 nt (0.9%) from that of S. minutus. Both unidentified forms of Saturnius are clearly distinguishable from S. gibsoni n. sp. by the presence of six stout, transverse muscular septa, forming seven pseudosegments (vs five septa forming six pseudosegments). Bayesian inference analysis of partial 28S rDNA sequences based on a total of 15 species from the families Hemiuridae and Lecithasteridae depicted the Bunocotylinae Dollfus, 1950 as a strongly supported basal clade, with Bunocotyle progenetica (Markowski, 1936) as the closest sister taxon to Saturnius spp.     

Two new species of flukes (Digenea: Bucephalidae: Prosorhynchinae) from the Western Moray Gymnothorax woodwardi (Anguilliformes: Muraenidae) from off Western Australia, with replacement of the pre-occupied generic name Folliculovarium Gu & Shen, 1983

Two new species of bucephalid trematodes are described from the rectum and intestine of the western moray eel Gymnothorax woodwardi McCulloch (Anguilliformes: Muraenidae: Muraeninae) off Point Peron in Western Australia. Dollfustrema gibsoni n. sp. is distinguished by body size, a pharynx that is intertesticular and level (latero-dextrally) with the anterior portion of the cirrus-sac, an ovary positioned dextrally to the testes and slightly anterior to (in part) the anterior testis, a uterus that extends anteriorly to the vitelline follicles but not to the level of the rhynchus, and vitelline follicles that form a confluent arc anterior to the gonads. Muraenicola nom. nov. is proposed as a replacement generic name for the pre-occupied Folliculovarium Gu & Shen 1983 nec Singh & Sinha 1981. Muraenicola botti n. sp. is distinguished from its congeners by body size, the size of the cirrus-sac (relative to body size), and in possessing tegumental spines, testes that are oblique (rather than in tandem) and eight ovarian lobes. It differs further in having an intestinal caecum that extends anteriorly to the level of the vitelline follicles and in the position of the pharynx and cirrus-sac relative to each other (lateral in part) as well as to the gonads. M. botti n. sp. also lacks a metraterm. These are the first reports of these genera from fishes off Australia and from the southern hemisphere.     

A new species of Petasiger (Digenea: Echinostomiformes: Echinostomatidae) in the brown pelican, Pelecanus occidentalis, (Aves: Pelecaniformes: Pelecanidae), from the Area de Conservación Guanacaste, Costa Rica

A new species of Petasiger inhabits Pelecanus occidentalis, from the Area de Conservación Guanacaste, Costa Rica. The new species most closely resembles Petasiger novemdecim Lutz 1929 and Petasiger caribbensis Nassi, 1980 by having 19 circumoral spines and vitelline follicles confluent between the ventral sucker and gonads. The new species differs from both of these species by having a cirrus sac that is anteroposteriorly elongate and that reaches posteriorly to the midventral sucker, an ovary and Mehlis' gland that overlap the anterior testis dorsally, a uterus that lies dorsal to the ventral sucker, and a dextromedial genital pore. In P. novemdecim and P. caribbensis the cirrus sac is round and does not extend posteriorly to the anterior margin of the ventral sucker, both the ovary and Mehlis' gland are anterior to the anterior testis, the uterus runs lateral to and not dorsal to the ventral sucker, and the genital pore opens medially and sinistromedially, respectively.     

<Emphasis Type="Italic">Allassogonoporus dromiciops</Emphasis> n. sp. (Digenea: Allassogonoporidae) from <Emphasis Type="Italic">Dromiciops gliroides</Emphasis> (Marsupialia: Microbiotheriidae) in Patagonia,Argentina

A new species of Allassogonoporus Olivier, 1938, from a naturally infected specimen of Dromiciops gliroides, is described. Adults of A. dromiciops n. sp. were recovered from the small intestine. This new species can be distinguished from all other species of the genus by having: the largest body and eggs, a lobed testes and ovary, a Y-shaped excretory vesicle and vitelline follicles beginning at the level of the posterior margin of the oral sucker. This is the first record of a species of Allassogonoporus in South America and the first record of a digenean parasitising D. gliroides.     

Galaxitaenia toloi n. gen., n. sp. (Eucestoda: Pseudophyllidea) from Galaxias platei (Pisces: Osmeriformes, Galaxiidae), in the Patagonian region of Argentina

Galaxitaenia n. gen. (Eucestoda: Pseudophyllidea) is proposed to accommodate Galaxitaenia toloi n. gen., n. sp. from Galaxias platei, a freshwater fish inhabiting Andean lakes in Argentine Patagonia. Galaxitaenia belongs to the Triaenophoridae because it possesses a marginal genital pore, a ventral uterine pore, and a follicular vitelline gland. The new genus can be distinguished from other triaenophorids by the following combination of characters: a scolex with a prominent rectangular apical disc without hooks, grooves, or indentations; neck present; segments wider than long to quadrangular; testes in 2 lateral fields, often connected anteriorly; cirrus unarmed; an ovary situated posteriorly; a vagina posterior to the cirrus sac; vitelline follicles medullary, in 2 ventral fields forming 2 wings interrupted medially; a uterus saccate to branched; and eggs without operculum. The types, distribution, and density of microtriches were analyzed on the surface of the tegument of scolex, neck, and immature segments. The presence of tumuli were observed on the apical disc of the scolex. Galaxitaenia toloi n. sp. is the first triaenophorid species recorded in a South American freshwater fish and the fourth helminth parasitizing the intestine of G. platei.     

Siphoderina hustoni n. sp. (Platyhelminthes: Trematoda: Cryptogonimidae) from the Maori snapper Lutjanus rivulatus (Cuvier) on the Great Barrier Reef

A new cryptogonimid trematode, Siphoderina hustoni n. sp., is reported, collected off Lizard Island, Queensland, Australia, from the Maori snapper Lutjanus rivulatus (Cuvier). The new species is moderately distinctive within the genus. It is larger and more elongate than most other species of Siphoderina Manter, 1934, has the shortest forebody of any, a relatively large ventral sucker, a long post-testicular zone, and is perhaps most recognisable for the substantial space in the midbody between the ventral sucker and ovary devoid of uterine coils and vitelline follicles, the former being restricted to largely posterior to the ovary and the latter distributed from the level of the anterior testis to the level of the ovary. In phylogenetic analyses of 28S ribosomal DNA, the new species resolved with the other nine species of Siphoderina for which sequence data are available, all of which are from Queensland waters and from lutjanid and haemulid fishes. Molecular barcode data were also generated, for the ITS2 ribosomal DNA and cox1 mitochondrial DNA markers. The new species is the first cryptogonimid known from L. rivulatus and the first metazoan parasite reported from that fish in Australian waters.

     

Trematodes of Red Sea fishes: <Emphasis Type="Italic">Hexangium brayi</Emphasis> n. sp. (Angiodictyidae Looss, 1902) and <Emphasis Type="Italic">Siphodera aegyptensis </Emphasis>n. sp. (Cryptogonimidae Ward, 1917), with a review of their genera

Specimens of the marine fishes Siganus luridus (Siganidae) and Caesio suevica (Lutjanidae) were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt. Twelve (30%) and eight (17%) fish, respectively, were found to harbour intestinal trematodes. S. luridus was parasitised by Hexangium brayi n.␣sp. (Angiodictyidae) and C. suevica by Siphodera aegyptensis n. sp. (Cryptogonimidae). H. brayi n. sp. is differentiated from the other two species of the genus by the vitelline follicles which are confined to the inter-caecal field, its body shape which is distinctly pyriform, the terminations of the intestinal caeca which are distinctly saccular, the eggs which are few in number, and by the excretory vesicle which gives off a lateral arm on each side that divides into two long collecting ducts. S. aegyptensis n. sp. is most similar to S.␣cirrhiti Yamaguti, 1970, but differs in having a definite number of testes (nine), seven arranged in a ring and the other two situated symmetrically or diagonally within this ring, and vitelline follicles extending posteriorly to the level of the anterior lobes of the ovary. Both genera Hexangium Goto & Ozaki, 1929 and Siphodera Linton, 1910 are reviewed in detail and redefined.     

Paraoistosomum novaeguineae n. gen., n. sp. (Digenea) from a New Guinea crocodile: a surprising relative of the enigmatic Oistosomum caduceus Odhner, 1902

Paraoistosomum novaeguineae n. gen., n. sp. is described based on specimens from the kidneys of a New Guinea crocodile Crocodylus novaeguineae collected in Papua New Guinea. The body shape and the topology of most internal organs of the new species are strongly reminiscent of Oistosomum caduceus Odhner 1902, the sole member of Oistosomum, a genus of unclear phylogenetic relationships and systematic position described from the Nile crocodile in Sudan in 1902 and never reported since then. At the same time, the new species has a number of significant differences from Oistosomum caduceus. Among them are much shorter intestinal ceca, a relatively larger ventral sucker, ovary anterolateral to ventral sucker (posterolateral in O. caduceus ), vitellaria arranged in 2 clusters of loosely organized follicles at the level of ventral sucker (2 narrow long lateral fields in O. caduceus ), much longer esophagus, and other characters. Most importantly, the new species has the genital pore situated at the anterior body end adjacent to the oral sucker, whereas O. caduceus has the genital pore in front of the ventral sucker. These dramatic differences suggest establishment of a new genus for the species from Papua New Guinea. The anatomy of P. novaeguineae n. gen., n. sp. suggests that these genera may not belong to the Plagiorchiidae, the current familial allocation of Oistosomum. Scarcity of material and lack of molecular data do not permit clarification of this problem at the present time.     

The Psilostomidae Looss, 1900 (<Emphasis Type="Italic">sensu stricto</Emphasis>) (Digenea: Echinostomatoidea): description of three new genera and a key to the genera of the family

Three new psilostomid genera, Byrdtrema n. g., Longisaccus n. g. and Macracetabulum n. g., each with a single species, are described from ducks, Aix sponsa (L.) and Bucephala albeola (L.) in North America. Byrdtrema n. g. and Macracetabulum n. g. possess a bipartite seminal vesicle and share this character with four psilostomid genera, Grysoma Byrd, Bogitsh & Maples, 1961, Neopsilotrema Kudlai, Pulis, Kostadinova & Tkach, 2016, Psilostomum Looss, 1899 and Psilotornus Byrd & Prestwood, 1969. Byrdtrema n. g. differs from Macracetabulum n. g. in the shape of the body (elongate vs elongate-oval); the position of the ventral sucker (in first third of body vs just pre-equatorial); the shorter forebody; as well as in the smaller size of the eggs in relation to body length. Both new genera differ from (i) Grysoma by the nature of the vitellarium (large, compact follicles with small vitelline cells vs weakly defined follicles with large vitelline cells, respectively) and the smaller size of the eggs in relation to body length; (ii) Psilostomum in the posterior extend of the cirrus-sac in relation to ventral sucker (slightly posterior vs more posterior), the location of the genital pore (at the level of oesophagus vs just postbifurcal), the shorter length of uterine and longer post-testicular fields in relation to body length, and the anterior limits of vitellarium (at the level of ventral sucker vs posterior to ventral sucker); (iii) Psilotornus by the presence of a muscular pharynx (vs absent or rudimentary) and the location of the cirrus-sac (antero-dorsal to ventral sucker or more posterior vs entirely anterior to ventral sucker) and ovary (in hindbody vs in forebody). Byrdtrema n. g. differs from Neopsilotrema in the shape of the body (elongate vs subspherical to elongate-oval) and ventral sucker (elongate-oval vs subspherical to transversely oval), the shorter forebody and smaller eggs in relation to body length. Macracetabulum n. g. differs from Neopsilotrema by the shape of the ventral sucker (elongate-oval vs subspherical to transversely oval), the anterior limits of vitellarium (level of middle of ventral sucker vs level of intestinal bifurcation or anterior testis); and the slightly smaller size of eggs in relation to body length. Among the psilostomid genera, Longisaccus n. g. shows close affinities to Psilochasmus Lühe, 1909 in the presence of the long cirrus-sac and tubular internal seminal vesicle but can be clearly distinguished from the latter by the absence of the retractile tail-like process. In combination with molecular data, the above differences justify the recognition of three new genera. A key to the genera of the Psilostomidae is provided.     

Description of the life-cycle stages of Brachylaima cribbi n. sp. (Digenea: Brachylaimidae) derived from eggs recovered from human faeces in Australia

The life-cycle of Brachylaima cribbi n. sp. was established in the laboratory. Asymmetrical brachylaimid eggs, measuring 26-32 microm (29.1 microm) long and 16 -17.5 microm (16.6 microm) wide, were recovered from human faeces and fed to the helicid land snail Theba pisana as the first intermediate host. Sporocysts and cercariae were recovered from the T. pisana eight weeks after infection. The cercariae were used to infect the helicid land snails Cernuella virgata and Helix aspersa as second intermediate hosts. Metacercariae were recovered from the kidneys of these snails and used to infect mice. Adults of Brachylaima cribbi n. sp. were recovered from the small intestine of the mice. The differential features of B. cribbi n. sp. are the specificity for helicid snails as first and second intermediate hosts; characteristic ventral sucker and body cercarial chaetotaxy; and a long slender adult worm with equal size suckers in the first quarter of the worm, the ventral sucker occupying 41% of the body width, the uterus extending anterior to the ventral sucker and the vitelline follicles falling short of the posterior margin of the ventral sucker. No other known Brachylaima species exhibits all of these features. B. cribbi n. sp. is the first brachylaimid known to have infected humans and is probably of European origin, as the intermediate host snails were all introduced into Australia from Europe.     

Six new species of Lepidapedon Stafford, 1904 (Digenea: Lepocreadiidae) from deep-sea macrourid fishes from the Gulf of Mexico and Caribbean Sea, with revised keys to the species of the genus

Species of the genus Lepidapedon are divided into various groups and subgroups based on vitelline distribution relative to the acetabulum and anterior extent of the excretory vesicle. Members of this genus predominantly parasitise gadiform fishes and are commonly collected from relatively deep waters. A recent study of deep-sea helminths from macrourids of the Gulf of Mexico and Caribbean Sea revealed six new species of this genus. L. mexicanensis n. sp., of the elongatum group, elongatum subgroup, differs from other species in this subgroup in proportions (as % of body length), lacking confluent vitelline fields between both the ovary and anterior testis and the testes, and in having a smaller egg and body size. L. nezumiatis n. sp., of the elongatum group, desclersae subgroup, differs from both L. filiformis and L. desclersae in having intermediate egg and body sizes, and a longer oesophagus than prepharynx. L. caribbaei n. sp. and L. longivesicula n. sp., of the garrardi group, congeri subgroup, differ from L. congeri in having a sucker-ratio of 1:<1. L. caribbaei n. sp. and L. longivesicula n. sp. differ from each other in that L. caribbaei n. sp. has numerous long, barb-like, deeply imbedded spines, a less elongate body, an infundibuliform oral sucker, a similar-sized oesophagus and prepharynx, and a caecal bifurcation which is closer to the acetabulum than oral sucker, while L. longivesicula n. sp. has shorter, serrate or plate-like, lightly imbedded, widely to sporadically spaced spines, a more elongate body, a spherical to subspherical oral sucker, a longer oesophagus than prepharynx, and a caecal bifurcation which is closer to the oral sucker than acetabulum. L. desotoensis n. sp., of the rachion group, rachion subgroup, is distinct from both L. luteum and L. abyssensis in having a smaller size, lacking cervical glands or pharyngeal gland cells, and possessing dark-staining particles in the mesenchyme, while it differs from L. abyssensis specifically in having a much longer oesophagus than prepharynx, lateral vitelline fields that are not confluent intertesticularly, and wider eggs. L. zaniophori n. sp., also of the rachion subgroup, differs from both L. cascadensis and L. genge in having a smaller egg size, a shorter prepharynx and oesophagus than pharynx, and vitelline fields that are intertesticular but only slightly encroach between the ovary and anterior testis. L. sammari and L. spiniferi are designated as incertae sedis, and L. quiloni and L. stromateusi are designated as species inquirendae. New parasite keys and host records for Coelorinchus coelorhincus, C. caribbaeus and Nezumia cyrano are offered. Support is given to Lepidapedon probably being the dominant digenean genus in deep water.     

Two new species of <Emphasis Type="Italic">Bacciger</Emphasis> Nicoll, 1914 (Trematoda: Faustulidae) in species of <Emphasis Type="Italic">Herklotsichthys</Emphasis> Whitley (Clupeidae) from Queensland waters

Two new species of Bacciger Nicoll, 1914 (Faustulidae) are described infecting clupeids collected from the waters off Queensland, Australia; Bacciger minor n. sp. is described from Herklotsichthys castelnaui (Ogilby) in Moreton Bay, southern Queensland and Bacciger major n. sp. is described from Herklotsichthys quadrimaculatus (Rüppell) collected off Lizard Island, on the northern Great Barrier Reef. The two species both differ from previously described species of Bacciger in the combination of their generally elongate bodies, an entire rather than deeply lobed ovary, vitelline follicles that reach to at least the intestinal bifurcation, instead of restricted to further posteriorly but principally distributed in the hindbody, and intestinal caeca extending posteriorly well past the ventral sucker. The two new species have non-overlapping size ranges and differ in their sucker ratios, the distribution of the vitelline follicles and in the shape of the cirrus-sac. ITS2 and 28S rDNA sequence data distinguish the two new species unambiguously. Phylogenetic analysis of available 28S data show they are most closely related to Pseudobacciger cheneyae Sun, Bray, Yong, Cutmore & Cribb, 2014, also recorded off Lizard Island. These are the first faustulids reported from species of Herklotsichthys Whitley, but overall members of the Clupeidae undoubtedly harbours the richest faustulid fauna of any fish family. Baccigeroides ovatus (Price, 1934) n. comb. is proposed for Bacciger ovatus (Price, 1934) Bray & Gibson, 1980 (syn. B. opisthonema Nahhas & Cable, 1964) based on the position of the genital pore being far anteriorly removed from the ventral sucker.     

Trematodes from Red Sea fishes: Neohypocreadium aegyptense n. sp. (Lepocreadiidae), Fairfaxia cribbi n. sp. and Macvicaria chrysophrys (Nagaty & Abdel-Aal, 1969) (Opecoelidae)

Specimens of the marine fishes Chaetodon lineolatus (Chaetodontidae), Lethrinus nebulosus (Lethrinidae) and Acanthopagrus bifasciatus (Sparidae) were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt. Fifteen (75%), four (16%) and fourteen (35%) fish, respectively, were found to harbour intestinal trematodes. C. lineolatus was parasitised by Neohypocreadium aegyptense n. sp. (Lepocreadiidae), L. nebulosus by Fairfaxia cribbi n. sp. (Opecoelidae) and A. bifasciatus by Macvicaria chrysophrys (Nagaty & Abdel-Aal, 1969) Bray, 1985 (Opecoelidae). N. aegyptense n. sp. is most similar to N. chaetodoni (Mahavi, 1972), but is smaller and differs in having acinous rather than digitate ovarian lobes, vitelline follicles extending anteriorly to midway between the ventral sucker and the intestinal bifurcation and an external seminal vesicle extending posteriorly to reach the anterior margin of the ovary. The generic diagnosis of Neohypocreadium is amended. F. cribbi n. sp. resembles F. lethini Cribb, 1990, but differs in having relatively smaller gonads, cirrus-sac and eggs, and larger suckers and pharynx. M. chrysophrys, collected from its type-host and locality, is redescribed. Plagioporus saoudi Ramadan, 1985 is considered its synonym.     

A new genus and species of proteocephalidean tapeworm (Cestoda) from Pangasius larnaudii (Siluriformes: Pangasiidae) in Southeast Asia

A new proteocephalidean cestode is described from spot pangasius, Pangasius larnaudii (Siluriformes: Pangasiidae), from Tonle Sap Lake in Cambodia and a new genus, Pangasiocestus , is proposed to accommodate it. The genus is placed in the Gangesiinae because its scolex possesses a large rostellum-like apical organ and its genital organs (testes, ovary, vitellarium, and uterus) are situated in the medulla, with some vitelline follicles paramuscular. Pangasiocestus romani n. gen. and n. sp., the type and only species of the new genus, is characterized mainly by its rosette-like scolex composed of 4 lobes bearing a small sucker in their center, and the apical part with a large, discoidal, rostellum-like apical organ devoid of hooks, by weakly developed inner longitudinal musculature formed by very few isolated muscle fibers, uneven size of testes in immature and mature proglottids, with lateral testes smaller and more dense than median ones, by very narrow lateral bands of vitelline follicles, formed usually by single follicles, and by the vagina anterior to the cirrus sac. This is the first proteocephalidean cestode from a pangasiid catfish identified to the species level (proteocephalidean cestodes from 3 Pangasius spp. reported in an unpublished account from Vietnam, misidentified as Proteocephalus osculatus (Goeze, 1782) [?= Glanitaenia osculata ], are not considered).     

Two new species and a new phyllobothriid cestode genus from sharks of the genus Negaprion Whitley (Carcharhiniformes)

Alexandercestus n. g. (Cestoda: Tetraphyllidea) is erected for two cestode species found parasitising the two known species of lemon sharks (Carcharhiniformes: Negaprion spp.). This new genus differs from all other phyllobothriid genera except for Hemipristicola Cutmore, Theiss, Bennett & Cribb, 2011, Marsupiobothrium Yamaguti, 1952, Nandocestus Reyda, 2008, Orectolobicestus Ruhnke, Caira & Carpenter 2006, Orygmatobothrium Diesing, 1863, Paraorygmatobothrium Ruhnke, 1994 and Phyllobothrium van Beneden, 1849 in possessing uniloculate bothridia with an apical sucker and neck scutes. Alexandercestus differs from Orectolobicestus and Nandocestus in lacking marginal loculi on the bothridia, from Paraorygmatobothrium in possessing uninterrupted vitelline follicles at the level of the ovary and from Phyllobothrium in being euapolytic as opposed to anapolytic and in lacking posteriorly bifid bothridia. The new genus lacks the central accessory bothridial organ seen in specimens of Orygmatobothrium, and lacks the central bothridial accessory sucker of specimens of Marsupiobothrium. Alexandercestus spp. compare most favourably with specimens of Hemipristicola, especially with respect to aspects of proglottid morphology, but differ in possessing aristate gladiate spinitriches rather than serrate gladiate spinitriches on the proximal bothridial surface. In addition, the bothridia of Alexandercestus spp. are comparatively more fleshy and foliose than those in specimens of Hemipristicola. Two new species of Alexandercestus n. g. are described, Alexandercestus gibsoni n. sp. from Negaprion acutidens, collected from off northern Australia and the Marshall Islands, and Alexandercestus manteri n. sp. from N. brevirostris, collected off the islands of Bimini and the Florida Keys. The two new species differ in total length and vitelline follicle distribution. Bayesian inference and parsimony analysis of the D1–D3 region of the large nuclear ribosomal DNA of 17 published and seven novel sequences placed A. gibsoni as the sister taxon to a clade containing Hemipristicola gunterae Cutmore, Theiss, Bennett & Cribb, 2011 and species of Paraorygmatobothrium. This result supports the erection of Alexandercestus as a genus separate from Hemipristicola and Paraorygmatobothrium. At the present time, species of Alexandercestus are known only from hosts of the carcharhinid genus Negaprion Whitley; examination of extensive survey data suggests this may be the extent of the host distribution of this genus.