Henneguya (Cnidaria: Myxobolidae) species infecting Oligosarcus jenynsii (Characiformes: Characidae) in a Neotropical shallow lake from Argentina: morphological and molecular characterisation.

Two previously undescribed myxozoan species, Henneguya sardellae sp. n. and H. margaritae sp. n., found infecting connective tissues of the Neotropical characid fish Oligosarcus jenynsii (Günther) from Argentina are morphologically and molecularly characterised. Mature spores of H. sardellae sp. n. are ellipsoid, with two, straight and visibly fused caudal appendages cleaved at its blunt terminal end; measuring 33.5 ± 1.2 (30.9-35.5) µm in total length, spore body 17.5 ± 0.6 (16.3-18.6) µm, 7.8 ± 0.4 (7.0-8.8) µm wide and 6.9 ± 0.2 (6.6-7.2) µm thick, with two elongated, unequally-sized polar capsules situated at anterior end, and 11-13 turns of polar tubules. Mature spores of H. margaritae sp. n. are pyriform, with two caudal appendages visible fused together and much longer than spore body, with unequal endings; measuring 35.9 ± 2.8 (29.2-40.7) µm in total length, spore body 11.5 ± 0.9 (9.2-13.0) µm long, 5.8 ± 0.4 (5.1-6.7) µm wide and 5.5 ± 0.2 (5.1-5.8) µm thick, with two polar capsules similar in size, pyriform polar capsules containing polar tubules with 4-5 coils. Both species showed a membraneous sheath surrounding the spore body and caudal appendages; in H. sardellae sp. n. this feature can deploy laterally. Phylogenetic analyses based on SSU rDNA sequences showed that H. sardellae sp. n. and H. margaritae sp. n. clustered with other myxobolids parasitising Characiformes in Brazil, Cichliformes in Mexico and Cyprinodontiformes in Mexico and the United States. The description of these two new species of Henneguya as the first described species of the genus that parasitise freshwater fish in Argentina highlights the importance of further research on the diversity and distribution of myxozoans in this region.

The description of two new species of Chloromyxum from skates in the Argentine Sea reveals that a limited geographic host distribution causes phylogenetic lineage separation of myxozoans in Chondrichthyes.

During a survey on the myxosporean fauna of Rajiformes from the Atlantic coast of Argentina, in waters off Buenos Aires Province (34°-42°S; 53°-62°W), the gall bladders of 217 specimens belonging to seven species of skates, representatives of two families, were examined. As a result, three species of Chloromyxum Mingazzini, 1890, namely C. atlantoraji n. sp., C. zearaji n. sp. and C. riorajum Azevedo, Casal, Garcia, Matos, Teles-Grilo and Matos, 2009 were found infecting three endemic host species, the spotback skate Atlantoraja castelnaui (Arhynchobatidae), the yellownose skate Zearaja chilensis (Rajidae) and the Rio skate Rioraja agassizii (Arhynchobatidae), respectively. These species were described based on myxospore morphology and morphometry characterization, as well as by providing their small subunit ribosomal DNA (SSU rDNA) sequences. The SSU rDNA-based phylogenetic analyses showed that these three species constituted a well-established monophyletic subclade within the marine Chloromyxum clade, while branches subtending the other Chloromyxum species were poorly resolved or unresolved, independently of the host taxonomic identities (Carchariniformes, Myliobatiformes, Orectolobiformes, Pristiophoriformes, Rajiformes, Squaliformes and Torpediniformes) and/or host geographic distribution (Atlantic coast of Portugal, Atlantic coast of the USA, Australian waters or Mediterranean Sea). The possible causes of these discrepancies are discussed, providing new insights into the phylogeny of the marine Chloromyxum clade.

A new species of Caudotestis (Digenea: Opecoelidae) parasitizing the horsefish, Congiopodus peruvianus (Scorpaeniformes: Congiopodidae) from the Patagonian Shelf, Argentina.

A new species of digenean, Caudotestis patagonensis n. sp. (Digenea: Opecoelidae), is described and illustrated based on specimens collected from the intestine of the horsefish, Congiopodus peruvianus (Cuvier, 1829) (Scorpaeniformes: Congiopodidae) from the Patagonian Shelf, Argentina (45-48 ° S, 60-64°W). This opecelid differs from the 4 previously known species of Caudotestis mainly in the extent of its seminal vesicle within the hindbody and the distribution of vitelline follicles. Moreover, the new species can also be distinguished by possessing the following combination of features: oral and ventral suckers nearly equal in size, ventral sucker at boundary of anterior third of body, intestinal bifurcation in posterior third of forebody and anterior to genital pore, genital pore submedial sinistral, anteriormost extent of the excretory vesicle reaching ovarian region, ovary nearly equidistant from both ventral sucker and anterior testis, posteriormost extent of the uterine loops just reaching ovarian region, testes oval and in tandem, ceca ending in front of the anterior testis, and size and number of eggs. This is the fifth recognized species of Caudotestis, the first report of a species of this genus in the southern Atlantic Ocean, and the second from a congiopodid fish.

New species of Acanthochondria (Copepoda: Chondracanthidae) infecting the longtail southern cod, Patagonotothen ramsayi (Perciformes: Nototheniidae), from Patagonian waters, Argentina.

Acanthochondria lilianae n. sp. (Copepoda: Chondracanthidae) is described and illustrated based on specimens of both sexes collected from inner surface of the operculum of the longtail southern cod, Patagonotothen ramsayi (Regan) (Perciformes: Nototheniidae), from the Patagonian Shelf, Argentina (42-48°S, 60-63°W). Acanthochondria lilianae n. sp. is characterized by the combination of a Type B-III antennule and Type A leg 2, in addition to both the cephalosome and the trunk being wider than long. The new species most closely resembles Acanthochondria incisa Shiino, 1955, Acanthochondria ophidii (Krøyer, 1863), Acanthochondria priacanthi Shiino, 1964, and Acanthochondria tasmaniae Heegaard, 1962, but differs from these species in the general measurements and proportions of the body, shape and size of head, shape and size of genitoabdomen, and fine details of appendages such as the armature of antennule, ornamentation of both pairs of legs, number of teeth on mandible and maxilla, and ornamentation on maxilliped. This is the first Acanthochondria species recorded from a nototheniid and the second southernmost record of a species of this genus in the southwestern Atlantic Ocean.