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We characterize lesion-associated capsaline infections on yellowfin tuna, Thunnus albacares, in the Gulf of Mexico by comparing our specimens with published descriptions and museum specimens ascribed to Capsala biparasiticum and its synonyms: vouchers of C. biparasiticum from parasitic copepods; the holotype of Capsala neothunni; and vouchers of Capsala abidjani. Those from parasitic copepods differed by having a small, rounded body, large anterior attachment organs, closely spaced dorsomarginal body sclerites, small testes, and a short and wide testicular field. No morphometric feature in the holotype of C. neothunni ranged outside of that reported for the newly-collected specimens, indicating conspecificity of our specimens. The specimens of C. abidjani differed by having a large anterior attachment organ, few and dendritic testes, and a short, wide testicular field. Large subunit ribosomal DNA (28S) sequences grouped our specimens and Capsala sp. as sister taxa and indicated a phylogenetic affinity of Nasicola klawei. The haptoral attachment site comprised a crater-like depression surrounded by a blackish-colored halo of extensively rugose skin, with abundant pockmarked-like, irregularly-shaped oblong or semi-circular epidermal pits surrounding these attachment sites. Histology confirmed extensive folding of epidermis and underlying stratum laxum, likely epidermal hyperplasia, foci of weak cell-to-cell adhesions among apical malpighian cells as well as that between stratum germinativum and stratum laxum, myriad goblet cells in epidermis, rodlet cells in apical layer of epidermis, and lymphocytic infiltrates and melanin in dermis. The present study comprises (i) the first published report of this parasite from yellowfin tuna captured in the Gulf of Mexico-NW Atlantic Ocean Basin, (ii) confirmation of its infection on the skin (rather than on a parasitic copepod), (iii) the first molecular data for this capsaline, and (iv) the first observations of histopathological changes associated with a capsalid infection on a wild-caught epipelagic fish.

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Several fish species are known as host for Digenea trematods. Here, we describe three trematod species as parasites of the Bigeye tuna (Thunnus obesus), which  is an important fishing resource for Brazil. We examined 35 specimens of T. obesus obtained from fishermen in Cabo Frio, Rio de Janeiro, southeastern Brazil. We found Brachyphallus parvus and Tetrochetus coryphaenaein the stomach and Lecithochirium microstomumin the intestine of fish. (AU)

Diversas espécies de peixes são conhecidas como hospedeiros detrematódes. Aqui nós registramos três espécies Digenea parasitando Thunnus obesus (Albacora-bandolim), que é um importante recurso pesqueiro para o Brasil. Examinamos 35 espécimes de T. obesus obtidos de pescadores em Cabo Frio, Rio de Janeiro, Brasil. Encontramos Brachyphallus parvus e Tetrochetus coryphaenae parasitando o estômago e Lecithochirium microstomum parasitando o intestino deste hospedeiro. (AU)

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RESUMO

Several fish species are known as host for Digenea trematods. Here, we describe three trematod species as parasites of the Bigeye tuna (Thunnus obesus), which  is an important fishing resource for Brazil. We examined 35 specimens of T. obesus obtained from fishermen in Cabo Frio, Rio de Janeiro, southeastern Brazil. We found Brachyphallus parvus and Tetrochetus coryphaenaein the stomach and Lecithochirium microstomumin the intestine of fish.

Diversas espécies de peixes são conhecidas como hospedeiros detrematódes. Aqui nós registramos três espécies Digenea parasitando Thunnus obesus (Albacora-bandolim), que é um importante recurso pesqueiro para o Brasil. Examinamos 35 espécimes de T. obesus obtidos de pescadores em Cabo Frio, Rio de Janeiro, Brasil. Encontramos Brachyphallus parvus e Tetrochetus coryphaenae parasitando o estômago e Lecithochirium microstomum parasitando o intestino deste hospedeiro.

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Numerous myxozoan cysts (∼ 1 mm) were found in the musculature of blackfin tuna (Thunnus atlanticus) harvested off the Caribbean island of St. Kitts. Myxospores were consistent with quadrate members of the Kudoidae, measuring 8.8 (8.2-9.4) µm wide, 7.3 (6.6-8.3) µm thick, and 6.2 (5.8-6.9) µm long with 4 uniform drop-like polar capsules measuring 2.7 (2.2-3.2) µm long and 2.0 (1.7-2.2) µm wide. The 18S small-subunit (SSU) and 28S large-subunit (LSU) ribosomal DNA sequences did not result in direct matches to any published sequences. However, the SSU sequences (1,786 base pairs [bp]) obtained from 6 individual cysts were identical and demonstrated high homology to Kudoa thunni (99.0%) from albacore (Thunnus alalunga). Alternatively, 33 unique sequences were obtained for the LSU (∼ 800 bp), demonstrating 0.1 to 5.0% variability between them, although a majority of these sequences (60%) demonstrated high homology (>99%) to K. thunni. Morphologically, the case isolate was smaller than published descriptions of K. thunni; however, rDNA sequence homology, and phylogenetic placement based on concatenated SSU and LSU rDNA sequences suggests this case isolate and K. thunni are conspecific. To our knowledge this is the first report of K. thunni infection in blackfin tuna from the Caribbean.

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A new genus and species of didymozoid digenean is described from the skipjack tuna Katsuwonus pelamis (Linnaeus) in the Southwest Atlantic Ocean off Brazil. Pozdnyakovia gibsoni n. g., n. sp. is placed in the Gonapodasmiinae Ishii, 1935. The new genus differs from other genera in the morphology of the posterior regions of the fused pair; this consists of an unlobed, rounded mass fused only dorsally and with a large, elliptical ventral aperture opening into a longitudinal deep cavity from which emerge the two elongate anterior regions. It also differs in the form of the testes, which form two sets of three to four branches in each partner.

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Infrapopulation genetic variation of the oioxenous, hermaphroditic flatworm Nasicola klawei (Monogenea: Capsalidae) infecting the nasal cavities of nine yellowfin tuna, Thunnus albacares, from the Gulf of Mexico was analyzed using the first internal transcribed spacer (ITS1) single strand conformation polymorphism (SSCP), ITS1 sequencing, and amplified fragment length polymorphism (AFLP). Of a total of 32 worms, six had unique ITS1-SSCP types and the rest was grouped by three types. Two worms of the same infrapopulation shared an ITS1-SSCP type in nine instances but no infrapopulation was monophyletic by ITS1-SSCP analysis. ITS1 sequences (420 bp) varied by 1-11 (0.2-2.6%) nucleotides. Twenty-three AFLP profiles of 80-110 bands failed to support genomic monophyly of any N. klawei infrapopulation. 28S rDNA (990 bp) sequences from four worms representing four infrapopulations were identical and matched conspecific GenBank sequences. Concordant ITS1-SSCP and AFLP analyses indicated that these N. klawei infrapopulations principally resulted from tuna being repeatedly colonized by planktonic, infective larvae (oncomiracidia) rather than by a single host colonization followed by parasite maturation, self-fertilization, and production of auto-infecting progeny.

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Adults of Rhadinorhynchus ornatus Van Cleave, 1918 were collected from the small intestine of skipjack tuna, Katsuwonus pelamis (Linnaeus), in the high seas of the Pacific Ocean off the west coast of South America (new parasite locality record) and described using optical microscopy and a scanning electron microscope (SEM). Our specimens were somewhat comparable to those described from North America and Japan, but had more trunk spines. Definitive differences between the length and thickness of each of the dorsal and ventral proboscis hooks are noted for the first time, with most ventral middle hooks being relatively shorter and more robust than dorsal middle hooks. The SEM documented, for the first time, the different surface topography of the tegument in the proboscis, the neck, and in 3 trunk regions; the presence of microtrichs in the mid- and posterior trunk regions; the elevated base of trunk spines; the circular arrangement of basal proboscis hooks; the different morphology of all dorsal and ventral proboscis hooks and the striations of their surface; the ribbed surface topography of eggs; the elevated slit-like female gonopore; and the rimmed edge of the bursa. The presence of microtrichs on the tegumental surface is further supported by transmission electron microscopy studies. This is the first report of microtrichs in any species of Acanthocephala and the second report of striations in proboscis hooks. The geographical distribution of R. ornatus appears to correspond, at least in part, to that of its epipelagic primary host, K. pelamis, throughout the world in waters ranging in temperature from 14.7 to 30 C.

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Until now, Anisakis typica has been the sole anisakid identified by means of genetic markers from the Atlantic Ocean off Brazil. In this study we developed, and applied to larvae and adults, an A. typica-specific molecular identification protocol based on the complete intergenic transcribed spacer (ITS) region. Anisakids from the dolphin Sotalia guianensis and from the frigate tuna, Auxis thazard, caught off the coast of Brazil, were processed using two DNA extraction methods. Molecular diagnosis identified A. typica in 13 of 15 samples. Complete ITS analysis showed that the remaining two isolates were in fact A. physeteris. Maximum parsimony analysis of complete ITS region (915 bp) confirmed these results. Our study verified the dominance of A. typica infecting hosts from the Brazilian coast and showed, for the first time, the presence of A. physeteris in the intermediate/paratenic host A. thazard in this region.

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The study of different species of tunas has revealed high numbers of cysts of Koellikerioides internogastricus Yamaguti, 1970, parasitizing Thunnus atlanticus (Lesson), Thunnus albacares (Bonnaterre) and Thunnus obesus (Lowe), caught along the Rio de Janeiro coastline, Atlantic Ocean, Brazil. This parasite was isolated from mucosa and submucosa of the stomach of the three tuna species studied. We report K. internogastricus for the first time on the Brazilian coast, representing the first record of this species in South America and in T. atlanticus, a new host. The pathological alterations induced by K. internogastricus in the stomach of T. albacares, T. atlanticus and T. obesus are also described for the first time. Original measurements and figures are presented.

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Two species of Didymozoidae, Didymosulcus palati (Yamaguti 1970) and Didymosulcus philobranchiarca (Yamaguti 1970) were reported for the first time in South America, Atlantic Ocean, parasitizing three different tuna species from the coast of Rio de Janeiro, Brazil: Thunnus atlanticus (Lesson), Thunnus albacares (Bonnaterre) and Thunnus obesus (Lowe). Pairs of D. philobranchiarca were found on gill arches of T. albacares and T. obesus, in longitudinal rows of yellow cysts located inside grooves in the hard denticle palate (new site) of the three hosts species studied, and as disperse groups of cysts in the operculum (new site) and gill arches of T. atlanticus (new host record). D. palati occurred as disperse groups of encysted worm pairs in the gill arches of T. albacares and T. obesus and in gill arches and operculum of T. atlanticus (new host record). The pathological alterations induced by D. philobranchiarca in the palate of T. atlanticus are described for the first time. Original measurements and figures are presented.

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Two species of Didymozoidae, Didymosulcus palati (Yamaguti 1970) and Didymosulcus philobranchiarca (Yamaguti 1970) were reported for the first time in South America, Atlantic Ocean, parasitizing three different tuna species from the coast of Rio de Janeiro, Brazil: Thunnus atlanticus (Lesson), Thunnus albacares (Bonnaterre) and Thunnus obesus (Lowe). Pairs of D. philobranchiarca were found on gill arches of T. albacares and T. obesus, in longitudinal rows of yellow cysts located inside grooves in the hard denticle palate (new site) of the three hosts species studied, and as disperse groups of cysts in the operculum (new site) and gill arches of T. atlanticus (new host record). D. palati occurred as disperse groups of encysted worm pairs in the gill arches of T. albacares and T. obesus and in gill arches and operculum of T. atlanticus (new host record). The pathological alterations induced by D. philobranchiarca in the palate of T. atlanticus are described for the first time. Original measurements and figures are presented.

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Two species of Nasicola Yamaguti, 1968 are described from the nasal cavities of tunas ( Thunnus spp.) from off the coast of Brazil: N. brasiliensis n. sp. from T. obesus (Lowe) and the type-species, N. klawei (Stunkard, 1962), from T. albacares (Bonn.). The new species is differentiated from N. klawei on the basis of the large number of testes and from N. hogansi Wheeler & Beverley-Burton, 1986 by its greater body-size, proportionately smaller haptor and smaller number of marginal spines. The host-specificity of Nasicola spp. is commented upon.

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Rhipidocotyle pentagonum (Ozaki, 1924) is reported for the first time in South America parasitizing Auxis thazard and in a new host Katsuwonus pelamis. Tergestia laticollis (Rudolphi, 1819) is reported for the first time in South America and in Thunnus albacares, representing a new host record. Copiatestes filiferus (Leuckart, in Sars, 1885) is recorded for the first time in Brazil and in Thunnus albacares, another new host record. Tetrochetus coryphaenae (Yamaguti, 1934) is presented for the first time in Brazil parasitizing Thunnus albacares.

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Didymocystis wedli a parasite from the gills of Thunnus albacares from the coast of the State of Rio de Janeiro, is described by use of light and scanning electron microscopy. This is the first report of this species in Brazil and South America. New data are presented on the surface topography as demonstrated by scanning electron microscopy.

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Didymocystis wedli a parasite from the gills of Thunnus albacares from the coast of the State of Rio de Janeiro, is described by use of light and scanning electron microscopy. This is the first report of this species in Brazil and South America. New data are presented on the surface topography as demonstrated by scanning electron microscopy

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The camallanid nematode Oncophora melanocephala (Rudolphi, 1819) is redescribed from specimens collected in tunas, Thunnus thynnus (L.), T. albacares (Bonnaterre), T. atlanticus (Lesson) and Auxis thazard (Lacépède) from the Atlantic littoral of Rio de Janeiro, Brazil. In addition to a specific structure of the buccal capsule, the species is characterized by the presence of seven pairs of preanal and five pairs of postanal subventral papillae in the male and by an unusual shape of body in the adult female; deirids are described for the first time in O. melanocephala. The structure of the buccal capsule of O. melanocephala, particularly the presence of a large posterior portion of capsule and a colourless connecting ring between buccal capsule and oesophagus, shows close affinities of Oncophora Diesing, 1851 with Paracamallanus Yorke et Maplestone, 1928. The findings of O. melanocephala in T. atlanticus and A thazard represent new host records.

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