Verónica A. Ivanov

A NEW SPECIES OF ACANTHOBOTHRIUM (CESTODA: TETRAPHYLLIDEA: ONCHOBOTHRIIDAE) FROM THE OCELLATE RIVER STINGRAY, POTAMOTRYGON MOTORO (CHONDRICHTHYES: POTAMOTRYGONIDAE), IN ARGENTINA

Examination of the spiral intestines of 44 freshwater stingrays, Potamotrygon motoro, from tributary rivers of the Paraná River in Argentina, allowed for the collection of specimens of an undescribed species of Acanthobothrium. Acanthobothrium ramiroi n. sp. can be distinguished from all other congeners by the combination of the following characters: asymmetrical hooks (medial and lateral hooks conspicuously different in size and form, with axial prong of medial hooks stouter than abaxial prong), hook size (total length of medial hooks up to 242 μm, total length of lateral hooks up to 239 μm), bothridia not fused to the scolex proper at posterior ends, worm size (51–84 mm long), and the presence of a conspicuous vaginal sphincter. The new species is different from all other species of Acanthobothrium in freshwater potamotrygonids, except Acanthobothrium terezae, in having conspicuous asymmetrical hooks. The main differences that allow for the distinction between A. ramiroi and A. terezae include hook size, the way the bothridia are attached to the scolex proper, and the shape of the older gravid segments. The discovery of a new species of Acanthobothrium from a potamotrygonid extends our understanding of the diversity of the genus in freshwater stingrays in South America.

NOTOMEGARHYNCHUS NAVONAE N. GEN. AND N. SP. (EUCESTODA: TETRAPHYLLIDEA), FROM SKATES (RAJIDAE: ARHYNCHOBATINAE) IN THE SOUTHERN HEMISPHERE

Notomegarhynchus n. gen. (Eucestoda: Tetraphyllidea) is proposed to accommodate Notomegarhynchus navonae n. gen., n. sp. from Atlantoraja castelnaui in Mar del Plata, Argentina. Notomegarhynchus shetlandicum n. comb. from Bathyraja eatonii and B. maccaini in South Shetlands region, Antarctica, is a second species in the genus. Notomegarhynchus belongs to the Echeneibothriinae within the Phyllobothriidae. It can be distinguished from all other tetraphyllidean genera by the structure of the scolex in form of a massive myzorhynchus consisting of a proscolex and an apical organ, both of which are nonretractable and noninvaginable; in addition, there are 4 pedunculated and nonloculate acetabula. Notomegarhynchus shetlandicum is differentiated from N. navonae particularly in details of acetabular and myzorhynchus morphology, arrangement of testes, and shape of eggs. The inclusion of Notomegarhynchus in the Echeneibothriinae requires emendation of the diagnosis of the subfamily to include taxa possessing postvaginal testes. In addition, new terminology is proposed for distinct regions of the scolex.

Phylogenetic analysis and reconfiguration of genera in the cestode order Diphyllidea

The generic boundaries of the Diphyllidea are reassessed based on parsimony and likelihood phylogenetic analyses of 28S rDNA (ribonucleic acid large subunit), 18S rDNA (ribonucleic acid small subunit), and COI (cytochrome oxidase subunit I) sequence data for 31 species representing morphological variation across the order. Trees resulting from these analyses yielded a number of well-supported clades that are congruent with unique morphological features mandating generic revision of the order and erection of at least two new genera. Species originally assigned to Echinobothriumvan Beneden, 1849 but bearing a corona of spines on the region of the scolex anterior to the bothria and posterior to the apical organ armature are transferred to Coronocestus n. gen.; members of this genus typically parasitize triakid sharks, although one report from a hemiscylliid shark exists. Species with lateral hooklets arranged in continuous bands, rather than in two distinct clusters, are transferred to Halysioncum n. gen.; all species parasitize batoids, mostly myliobatids and rhinopterids, but a few records also exist from arhynchobatids, rhinobatids, platyrhinids and urotrygonids. Our analyses support transfer of the five species originally assigned to MacrobothridiumKhalil and Abdul-Salam, 1989 owing to their lack of cephalic peduncle spines to Echinobothrium. As a consequence, Echinobothrium sensu stricto includes species both with and without spines on the cephalic peduncle, but all members of the genus possess lateral hooklets arranged in clusters on either side of the dorsal and ventral apical hooks. With respect to diphyllideans parasitizing catsharks, AhamulinaMarques, Jensen and Caira, 2012 is unique in possessing apical hooks but lacking lateral hooklets and DitrachybothridiumRees, 1959 is unique in entirely lacking scolex armature. By far the majority of species of Echinobothrium sensu stricto parasitize skates of the family Rajidae, guitarfish of the family Rhinobatidae, and stingrays of the dasyatid genera Taeniura Müller and Henle, Dasyatis Rafinesque, and Himantura Müller and Henle, although a single species each has been reported from Anacanthobatidae, Rhynchobatidae, Platyrhinidae and Myliobatidae. It now seems clear that while by far the majority of diphyllideans parasitize batoids, the diphyllideans parasitizing sharks, and catsharks in particular, remain problematic. Additional collections from these carcharhiniform hosts are likely to be particularly illuminating.

Calliobothrium spp. (Eucestoda: Tetraphyllidea: Onchobothriidae) in Mustelus schmitti (Chondrichthyes: Carcharhiniformes) from Argentina and Uruguay

Three species of Calliobothrium inhabit the spiral intestine of Mustelus schmitti in Argentina and Uruguay. Calliobothrium verticillatum australis is redescribed and its taxonomic status modified to species as C. australis. Calliobothrium barbarae n. sp. can be distinguished from all other species of Calliobothrium, which are small bodied, nonlaciniate, and without accessory piece between the bases of axial hook, by worm length, number of segments, cocoon morphology, and hooks shape. Calliobothrium lunae n. sp. is different from other Calliobothrium spp., which are small bodied, nonlaciniate, and have an accessory piece, by the number of segments and testes, hook shape, cocoon morphology, and the presence of ciliumlike projections on the distal surface of muscular pads. Calliobothrium australis is clearly distinguished from other large-bodied, laciniate species of the genus by worm length, number of testes, ovary shape, cocoon morphology, hook shape, and in being hyperapolytic. The oioxenous specificity involving Calliobothrium spp. and Mustelus spp. described by previous authors is confirmed in this study.

PROPOSED LIFE CYCLE OF ASCAROPHIS MARINA (NEMATODA: CYSTIDICOLIDAE) IN ARGENTINE WATERS

The life history of Ascarophis marina in Argentina is proposed on the basis of morphometric features of larval and adult specimens, as well as of trophic relationships among invertebrate and vertebrate hosts in the same geographic area. Adult and larval specimens of A. marina were found in the alimentary tract of the teleost fishes Parona signata (Carangidae) and Urophycis brasiliensis (Gadidae). Third-stage larvae ocurred in the shrimps Peisos petrunkevitchi (Sergestidae) and Artemesia longinaris (Penaeidae).

Ascarophis marina n. comb. (Nematoda: cystidicolidae) from the fishes Parona signata (Carangidae) and Urophycis brasiliensis (Gadidae) in the southwestern Atlantic.

The taxonomic position of Cystidicola marina Szidat, 1961 is revised, based on the re-examination of type and new specimens collected from the type host, Urophycis brasiliensis (Gadidae), and a new host, Parona signata (Carangidae), in the southwestern Atlantic. The species is redescribed and transferred to Ascarophis as A. marina n. comb. It is distinguished from other species of Ascarophis by the following combination of characters: body length (male: 10.2-22.5 mm, female: 32.8-44.2 mm), number of egg filaments (2 on each pole), egg size (0.030-0.039 mm x 0.015-0.021 mm), and left spicule length (0.4-0.6 mm).

Echinobothrium notoguidoi n. sp. (Cestoda: Diphyllidea) from Mustelus schmitti (Chondrichthyes: Carcharhiniformes) in the Argentine Sea.

A new cestode, Echinobothrium notoguidoi n. sp., is described from the spiral intestine of the shark Mustelus schmitti, from coastal waters off Mar del Plata, Argentina. This species is distinguished from all others in the genus by a rostellar armature consisting of 2 apical groups of 31 large hooks each, arranged in 2 rows (16 anterior, 15 posterior) with 13 hooklets per side, a wide corona of 8-11 rows of spines posterior to the rostellum, 8 rows of 24-26 spines on the cephalic peduncle, and 11-15 testes per proglottid. The new species most closely resembles 2 congeners that also parasitize sharks, Echinobothrium musteli and Echinobothrium scoliodoni, on the basis of the armature of the rostellum and cephalic peduncle and the presence of a corona of small spines. Echinobothrium notoguidoi can be differentiated from E. musteli by the number of hooklets (3) and testes (22), and from E. scoliodoni by the number of large hooks (10-13), spines on the cephalic peduncle (> 100), and segments (40-50). Echinobothrium notoguidoi is clearly distinguished from Echinobothrium pigmentatum described previously from Zapteryx brevirostris in Argentine waters by the following combination of characters: corona of hooks lacking, possession of fewer apical hooks (20), hooklets in a continuous row instead of separate groups, fewer spines in the cephalic peduncle (9-13 per row), and fewer testes (5-7) per proglottid.

A New Species of Tetraphyllidean (Cestoda) from the Largespot River Stingray, Potamotrygon falkneri (Potamotrygonidae: Chondrichthyes), from the Paraná Basin

Abstract Rhinebothrium paranaensis n. sp. (Tetraphyllidea: Cestoda) is described from the freshwater stingray Potamotrygon falkneri collected in the Colastiné River, a tributary to the Lower Paraná River in Argentina. The specimens were studied in detail using light and scanning electron microscopy and histology. Rhinebothrium paranaensis can be distinguished from all valid species in the genus using the following combination of characters: worm length, number of proglottids, diamond-shaped bothridia lacking constriction, number of loculi on the distal surface of bothridium, and the lack of vaginal sphincter and external seminal vesicle.

Description of Three New Species of Echinobothrium (Cestoda: Diphyllidea) from Indo-Pacific Elasmobranchs of the Genus Glaucostegus (Rajiformes: Rhinobatidae)

Abstract: Three new species of diphyllidean cestodes are described from rhinobatid elasmobranchs of the genus Glaucostegus from the Indian and Pacific Oceans. All 3 new species have 11 apical hooks (6 type-A and 5 type-B hooks) and, therefore, differ in this feature from all but 5 of the 39 valid species of Echinobothrium. In addition, Echinobothrium tetabuanense n. sp. from Glaucostegus cf. typus in the Sulu Sea, Borneo differs from all of its congeners in the number and arrangement of hooklets, number of spines on the cephalic peduncle, and the number and distribution of testes. Echinobothrium sematanense n. sp. from Glaucostegus thouin in the South China Sea, Borneo, can be distinguished from its congeners based on the following combination of characters, i.e., small size (worms less than 1 mm long), number of hooklets, spines per column on the cephalic peduncle, and number of testes. Echinobothrium weipaense n. sp. from northern Australia is unique in the position of the cirrus sac and genital pore, both structures being well posterior and not overlapping the ovary. An emended description of the microthrix pattern on the scolex of Echinobothrium chisholmae from G. typus in Australia is also presented.

ORYGMATOBOTHRIUM SPP. (CESTODA: TETRAPHYLLIDEA) FROM TRIAKID SHARKS IN ARGENTINA : REDESCRIPTION OF ORYGMATOBOTHRIUM SCHMITTII AND DESCRIPTION OF A NEW SPECIES

Two species of Orygmatobothrium were found inhabiting triakid sharks collected from the coast of Buenos Aires Province, Argentina. Orygmatobothrium schmittii from Mustelus schmitti is redescribed, including new information on the microtrich pattern. Orygmatobothrium juani n. sp. from Mustelus fasciatus can be distinguished from all other species in the genus using the following combination of characters: worm length, number of proglottids, number of testes, testes distribution, size of eggs, ornamented egg shell, shape of bothridial cleft at level of the marginal accessory sucker, and the extension of vitelline follicles. Species in Orygmatobothrium share a common microtrich pattern with the distal bothridial surface covered with maisiform microtriches interspersed with filiform microtriches, a proximal bothridial surface covered with trifid microtriches, with a medial projection conspicuously larger than the lateral basal projections interspersed with filiform microtriches, an inner and outer surface of the accessory sucker and glandulomuscular organ covered with short filiform microtriches, the scolex proper and cephalic peduncle surface covered with bladelike microtriches, and the germinative zone and entire strobila covered with scutes formed by densely packed filiform microtriches. This general configuration is basically similar to the microtrich pattern described in species of Orectolobicestus and Paraorygmatobothrium.