Glandular Esophagus Research Articles

Morphological and Molecular Evidence for a New Rhabdochonid Species (Nematoda: Rhabdochonidae) Parasitizing Profundulus oaxacae (Profundulidae) in the State of Oaxaca, Mexico.

The genus Rhabdochona Railliet, 1916 is one of the most speciose group of nematodes, parasites of freshwater fishes, with approximately 103 species described worldwide. Twenty-two species have been recorded in the Americas, 14 of them in Mexico. In this paper we describe a new species of Rhabdochona on the basis of light and scanning electron microscopy and molecular tools. Rhabdochona adentata n. sp. was recovered from the gallbladder of the freshwater Oaxaca killifish, Profundulus oaxacae (Meek, 1902) (Profundulidae) captured in the Río Grande, State of Oaxaca, Mexico. Rhabdochona adentata n. sp. differs markedly from its congeners by possessing an unusual prostom lacking anterior teeth, small simple deirids, and the location of the excretory pore at the level of the union of the muscular and glandular esophagus. Sequences of cytochrome c oxidase subunit I (COI) from mitochondrial deoxyribonucleic acid and the D2 + D3 domains of the large ribosomal subunit (28S) were obtained from 3 specimens and were analyzed using maximum likelihood and Bayesian inference analyses. Phylogenetic analyses using COI and 28S genes recovered 1 new lineage of Rhabdochona. The new species is described on the basis of a detailed morphological study. This parasite represents the first species of Rhabdochona without prostomal teeth and with a different site of infection, the gallbladder.

Further study on Procamallanus (Spirocamallanus) pintoi (Kohn et Fernandes, 1988) (Nematoda: Camallanidae) in Corydoras paleatus and Corydoras micracanthus (Siluriformes: Callichthyidae) from Salta, Argentina, with a key to congeneric species from Neotropical Realm.

This study describes the morphology of Procamallanus (Spirocamallanus) pintoi (Kohn et Fernandes, 1988), isolated from the intestine of Corydoras micracanthus Regan, 1912 and C. paleatus (Jenyns, 1842) (both Callichthyidae, Siluriformes) from Bermejo and Juramento River basins, respectively, province of Salta, Argentina. This is the first record of P. (S.) pintoi in C. micracanthus from Northwestern Argentina. The light and scanning electron microscopy observations of P. (S.) pintoi, revealed a few previously unreported morphological details of the cephalic region, vulva and caudal region of males. In addition, morphometric variability was observed in, mainly body size, glandular oesophagus length and position of the vulva between present specimens and those described in previous studies. A key to the species of Procamallanus (Spirocamallanus) from the Neotropical Realm is proposed.

Pseudodelphis eleginopsis n. sp. (Nematoda: Guyanemidae), a new tissue-dwelling parasite of the Patagonian blennie Eleginops maclovinus (Cuvier) (Perciformes: Eleginopsidae) in Argentina, with notes on related forms.

Based on light and scanning electron microscopical studies, a new nematode parasite, Pseudodelphis eleginopsis n. sp. (Dracunculoidea: Guyanemidae), is described from tissues behind the gills of the Patagonian blennie Eleginops maclovinus (Cuvier) (Perciformes: Eleginopsidae) off the Atlantic coast (San Matías and San José Gulfs) of Patagonia, Argentina. The new species is mainly characterised by the length of the body (males 10-13 mm, larvigerous females 31-59 mm), the number (14) and arrangement of cephalic papillae, the absence of a buccal capsule, the muscular to glandular oesophagus length ratio (1:3-4) of larvigerous females, the length of the spicules (48-63 µm) and the number (7 pairs) and arrangement of the caudal papillae in the male. Pseudodelphis eleginopsis n. sp. is the first species of this genus described from a marine fish in the Atlantic Ocean and the first known dracunculoid parasitising the fish host belonging to the family Eleginopsidae. As revealed by the examination of very young females of the new species, the female genital tract of Pseudodelphis spp. is monodelphic. The genus Syngnathinema Moravec, Spangenberg & Frasca, 2001 is considered a junior synonym of Pseudodelphis Adamson & Roth, 1990 and, consequently, S. californiense and S. chitwoodi are transferred to Pseudodelphis as P. californiensis (Moravec, Spangenberg & Frasca, 2001) n. comb. and P. chitwoodi (Moravec & Kuchta, 2013) n. comb., respectively. Two dracunculoid species, Pseudodelphis limnicola Brugni & Viozzi, 2006 and the previously established Philonema percichthydis Moravec, Urawa & Coria, 1997, both described from the same freshwater host species, Percichthys trucha (Valenciennes), in the same region (Patagonia), are considered to be identical; therefore, the valid name of this species is Pseudodelphis percichthydis n. comb. and P. limnicola becomes its junior synonym. A key to the species of Pseudodelphis is provided.

Neoascarophis sinensis n. sp. (Nematoda: Cystidicolidae), a parasite of Conger myriaster (Brevoort) (Anguilliformes: Congridae) in Chinese waters.

Neoascarophis sinensis n. sp. collected from the whitespotted conger Conger myriaster (Brevoort) (Anguilliformes: Congridae) in the Yellow and East China Seas, is described using both light and scanning electron microscopy. The new species is characterised mainly by the body size (8.5-10.5 mm in the males, 9.5-14.0 mm in the females), the location of the vulva (near equatorial region of the body), the non-bifurcate deirids, the lengths of the vestibule (40-50 µm in the males, 30-60 µm in the females) and glandular oesophagus (2.5-3.1 mm in the males, 3.1-3.5 mm in the females) and the morphology and length of the spicules (left spicule 400-410 µm, right spicule 130-150 µm). Neoascarophis sinensis n. sp. is the first species of Neoascarophis Machida, 1976 reported from the anguilliform fish and is also the only species of this genus found in the Chinese waters.

Description of Acuaria europaea n. sp. (Spirurida: Acuariidae) from Dendrocopos syriacus (Hemprich & Ehrenberg) and Oriolus oriolus (L.) (Aves) in Europe, with results of re-examination of related European species of Acuaria Bremser, 1811.

Acuaria europaea n. sp. is described from one Dendrocopos syriacus (Hemprich & Ehrenberg) (Piciformes: Picidae) (type-host) and three Oriolus oriolus (L.) (Passeriformes: Oriolidae) in Bulgaria (type-locality) and France. The new species is characterised by cordons extending slightly beyond the level of the anterior end of the glandular oesophagus, left spicule 297 µm long, right spicule 155 µm long, protruding vulvar region and strongly ventrally curved female tail. The male (holotype) and the female (allotype) of A. parorioli Chabaud & Petter, 1961 from O. oriolus are regarded as not being conspecific based on the differing morphology of their cordons; the female is identified as A. europaea n. sp. The type-material of Acuaria attenuata (Rudolphi, 1819) is redescribed. The species is characterised by a small and delicate body, cordons extending beyond the oesophago-intestinal junction and similar spicules in size and shape, 140 µm long. The only type-material of Acuaria anthuris (Rudolphi, 1819) available for examination consists of a male and a female (syntypes) from O. oriolus. The two specimens differ from one another by the relative lengths of their cordons and we consider them as belonging to two species. However, both type-specimens differ in their much shorter cordons from the species of Acuaria parasitising Corvidae. The present study reveals that the original description of A. anthuris has been based on heterogeneous material.

Prevalence and Morphological Characterization of Cheilospirura hamulosa, Diesing, 1861 (Nematoda: Acuarioidea), from Partridges in Iran.

This study reports data on the prevalence, morphology, and morphometry of the nematode Cheilospirura hamulosa on the basis of light and stereoscopic microscopy and also camera lucida. Specimens were recovered after necropsies of 100 partridges (Alectoris chukar) from Taleqan County in Alborz Province, Iran. The prevalence of C. hamulosa in partridges was of 30% with a mean intensity of 3.9 and range of infection of 1–12. The mean length and width of females were 17.5 ± 2.14 and 0.39 ± 0.04 mm, while those of males were 12.2 ± 0.67 and 0.3 ± 0.06 mm, respectively. The characteristic digitiform tail was observed in females, and the unequal spicules, caudal alae, and ten pairs of caudal papillae were seen in males. The taxonomic characteristic longitudinal cordons and muscular and glandular oesophagus were observed in both sexes. Ratio between cordons and body length in males and females was 1 : 1.33 and 1 : 1.68, respectively. Ratio between long and short spicules in males was 1 : 2.3. The average size of embryonated eggs was 51.25 × 29.5 μm. In the present study, C. hamulosa (Nematoda: Acuarioidea) is recorded for the first time from partridges in Iran. Therefore, the morphological characters described in this study will be useful in the future diagnostic and taxonomic studies of Acuarioidea family.

Terahertz spectroscopic imaging and properties of gastrointestinal tract in a rat model.

We have investigated basic properties of normal gastrointestinal (GI) tract tissues, including glandular stomach (GS), fore stomach (FS), large intestine (LI), small intestine (SI), and esophagus (ESO), from a rat model using terahertz (THz) reflection imaging and spectroscopy. The THz images collected from stratified squamous epithelia (SSE) of FS and ESO show a lower peak-to-peak value compared to those from columnar epithelia (CE) of GS, LI, or SI because the SSE contains less water than CE. The refractive index and absorption coefficient of FS were less than those of GS or LI, both having values similar to those of water. Additionally, we report internal reflection THz signals from ESO, although we were unable to determine the exact interface for this internal reflection.

Two new species of Cylicospirura Vevers, 1922 (Nematoda: Spirocercidae) from carnivores in southern Africa, with validation of the related genera Gastronodus Singh, 1934 and Skrjabinocercina Matschulsky, 1952

Two new species of Cylicospirura Vevers, 1922 are described from carnivores from southern Africa. Cylicospirura crocutae Junker et Mutafchiev sp. n. from Crocuta crocuta (Erxleben) in Zimbabwe is distinguished from its congeners by combinations of characters, including the presence of four cephalic and four external labial papillae, while internal labial papillae were not distinct, the presence of groups of small accessory teeth between the six large tricuspid teeth, the fifth and the sixth pairs of the caudal papillae being equidistant from the cloaca, and a large ratio of length of the muscular oesophagus to that of the glandular oesophagus. Cylicospirura pardalis Junker et Mutafchiev sp. n. from Panthera pardus (Linnaeus) in the Republic of South Africa is characterized by having tricuspid teeth with large, claw-like, abaxial cusps, four cephalic and six internal labial papillae. Based on the number of caudal papillae and the position of the vulva, the subgenera Gastronodus Singh, 1934 and Skrjabinocercina Matschulsky, 1952 are re-elevated to generic rank. Amended diagnoses are proposed for the genera Cylicospirura, Gastronodus and Skrjabinocercina. Petrowospirura lyncis Matschulsky, 1952 is recognized as valid and, together with P. petrowi Sadykhov, 1957 and P. barusi Arya, 1979, is transferred to Cylicospirura as C. lyncis (Matschulsky, 1952) Junker et Mutafchiev comb. n., C. petrowi (Sadykhov, 1957) Junker et Mutafchiev comb. n. and C. barusi (Arya, 1979) Junker et Mutafchiev comb. n., respectively.

Pseudascarophis brasiliensis sp. nov. (Nematoda: Cystidicolidae) parasitic in the Bermuda chub Kyphosus sectatrix (Perciformes: Kyphosidae) from southeastern Brazil

A new species of Pseudascarophis (Nematoda: Cystidicolidae) found in the stomach of Kyphosus sectatrix (Linnaeus) (Kyphosidae), off Rio de Janeiro, Brazil, is described. The new species can be differentiated from the other congeners by the presence of lateral alae, distinct but inconspicuous cephalic papillae at the anterior end, three pairs of precloacal and one pair of adcloacal papillae in males, egg morphology and morphometry of glandular oesophagus and spicules. Pseudascarophis tropica is transferred to Ascarophis as Ascarophis tropica (Solov'eva) comb. n. due to its ambiguous diagnosis.

Pseudascarophis brasiliensis sp. nov. (Nematoda: Cystidicolidae) parasitic in the Bermuda chub Kyphosus sectatrix (Perciformes: Kyphosidae) from southeastern Brazil

A new species of Pseudascarophis (Nematoda: Cystidicolidae) found in the stomach of Kyphosus sectatrix (Linnaeus) (Kyphosidae), off Rio de Janeiro, Brazil, is described. The new species can be differentiated from the other congeners by the presence of lateral alae, distinct but inconspicuous cephalic papillae at the anterior end, three pairs of precloacal and one pair of adcloacal papillae in males, egg morphology and morphometry of glandular oesophagus and spicules. Pseudascarophis tropica is transferred to Ascarophis as Ascarophis tropica (Solov'eva) comb. n. due to its ambiguous diagnosis.

Four Thai Patients With Chronic Diarrhea, Malabsorption, and Weight Loss

Diagnosis: Capillariasis associated with tubular narrowing of multiple small-bowel loops with fold effacement. The clinical and radiographic presentations of these cases are representative of Capillaria philippinensis infection. Infection with C. philippinensis is primarily acquired by ingestion of raw, undercooked, small, fresh- or brackish-water fish [1]. Capillaria philippinensis, first discovered in the Philippines, has subsequently been detected in Thailand, Japan, Iran, Egypt, and Taiwan, with major outbreaks reported in Thailand and the Philippines [2]. Typically, patients present with signs and symptoms of malabsorption inclusive of chronic diarrhea, edema, muscle wasting, and abdominal pain; laboratory data reveal low serum albumin and potassium [3–4]. The diagnosis of C. philippinensis is usually based on the detection of eggs (Figure 1), larva, and/or adult worms with or without egg in stool specimens (Figure 1), although excretion can be sporadic, necessitating multiple repeated stool examinations, with small intestinal aspiration or biopsy to confirm the diagnosis in some cases [1–2]. Notably, mortality has been reported in patients with C. philippinensis who did not have capillaria eggs or larva recovered from stool specimens [2–3]. The detection of the parasite’s stichosome (the posterior glandular esophagus) and stichocytes (large glandular cells) by hematoxylin and eosin stain are not diagnostic, as these can also be identified in biopsies of patients with Trichinella spiralis and Trichuris trichiura infection. The clinical presentations and locations of lesions can readily help in the differentiation and case detection of these 3 parasitic infections [5]. Whereas patients with C. philippinensis typically present with clinical manifestations of chronic watery diarrhea and malabsorption, those with T. trichiura usually present with prolonged diarrhea, blood-streaked stool, anemia, colitis, proctitis, and rectal prolapse (in patients with heavy infestation). Cases with T. spiralis usually have biphasic presentations that begin with clinical manifestations of nausea, vomiting, and diarrhea (intestinal phase) followed by intense myalgias and periorbital edema (muscular phase) [5]. Additionally, C. philippinensis typically involves the distal jejunum and proximal ileum, T. trichiura tends to cause lesions limited to the large bowel, and T. spiralis is typically associated with encysted larva that migrated to specific organ tissues (eg, muscle, myocardium, and brain). In each of our 4 reported cases, the initial stool specimen was negative for C. philippinensis. Subsequent stool specimens were positive for C. philippinensis in 2 patients, and all 4 had small-bowel biopsies remarkable for severe villous blunting, inflammatory cell infiltration, and visualization of nematodes in longitudinal sections with the identification of stichocytes

Description of Two New Nematode Species, Parasites of the Mississippi PaddlefishPolyodon spathula(Acipenseriformes: Polyodontidae)

Two new nematode species are described from the paddlefish Polyodon spathula (Walbaum) (Polyodontidae, Acipenseriformes) from the Mississippi River drainage, United States, based on specimens previously deposited in the U.S. National Parasite Collection. Those specimens were Camallanus polyodontis n. sp. (Camallanidae) from the host (site of infection not given) collected in the Yellowstone River, Montana in 1974 and Syngnathinema chitwoodi n. sp. (Daniconematidae) from the body cavity of fish collected in Mississippi in 1926. Camallanus polyodontis (male and female) is mainly characterized by the presence of a conspicuously large, oval, sclerotized formation at the base of tridents on the buccal capsule, by which it distinctly differs from all congeners. It also differs from other North American species of the genus by additional features such as the body size, the length of spicules, or the length of the female tail. Syngnathinema chitwoodi (a single subgravid female) differs from the only other congener, Syngnathinema californiense Moravec, Spangenberg and Frasca, 2001, a parasite of the circulatory system of the pipefish in California and British Columbia, mainly in that the posterior end of the muscular esophagus is not submerged into the anterior end of the glandular esophagus. Previous reports of Camallanus oxycephalus Ward and Magath, 1917 in P. spathula may be misidentifications of C. polyodontis.

Redescriptions and comments on the validity of Acuaria subula and A. skrjabini (Nematoda, Spirurida, Acuariidae), parasites of passerine birds

Acuaria subula (Dujardin, 1845) is redescribed by light microcopy (LM) and scanning electron microscopy (SEM) on the basis of specimens from its type host, Erithacus rubecula (Passeriformes, Muscicapidae), from Curonian Spit (Kaliningradskaya Oblast', Russia) and Bulgaria. Acuaria skrjabini (Ozerskaya, 1926) is redescribed by LM and SEM on the basis of specimens from Passer domesticus (type host) and P. hispaniolensis (Passeriformes, Passeridae) from Bulgaria. Contrary to previous opinions recognizing A. skrjabini as a junior synonym of A. subula, the present study confirms that they are distinct species. They can be distinguished on the basis of the ratio between the length of cordons and the body length, the ratio between the length of muscular oesophagus and glandular oesophagus, and the ratio between the total length of oesophagus and the body length. In addition, the plates forming the cordons in these two species exhibit different morphological characters. Another difference between these two species is associated with the particular irregular mosaic ornamentation of the cuticle on the ventral and lateral sides of body around the region of vulva of A. subula and its absence in A. skrjabini. Data on their host and geographical ranges are surveyed. The type series of Acuaria buttnerae Chabaud et Petter, 1961, described as a parasite of Calandrella brachydactyla (Passeriformes, Alaudidae) in France, is re-examined; the latter species is recognized as a junior synonym of A. skrjabini (new synonymy).

Ochoterenella esslingerin. sp. (Nematoda: Onchocercidae: Waltonellinae) fromBokermannohyla luctuosa(Anura: Hylidae) in Minas Gerais, Brazil, with notes onParaochoterenellaPurnomo & Bangs, 1999

The waltonelline Ochoterenella esslingeri n. sp., a filarial parasite of the anuran Bokermannohyla luctuosa in Minas Gerais, Brazil is described. Several characters distinguish this new species from the 15 species presently included in the genus: the cuticular ornamentation of the female that is restricted to the posterior region of the body, the irregular arrangement of the small, rounded bosses, the postoesophageal vulva, the short glandular oesophagus, the size and shape of the microfilariae, the long left spicule and high spicular ratio. Irregularly arranged, tiny, rounded bosses are common in the monotypic genus Paraochoterenella from an Indonesian ranid, which is not well defined but likely valid. In the Neotropical Realm, the type hosts of the species of Ochoterenella are Hylidae (O. esslingeri n. sp.), Leptodactylidae (two species) and the remaining 13 species were described from the giant toad Rhinella marina (Bufonidae).

Immunization with the recombinant antigen Ss-IR induces protective immunity to infection with Strongyloides stercoralis in mice

Human intestinal infections with the nematode Strongyloides stercoralis remain a significant problem worldwide and a vaccine would be a useful addition to the tools available to prevent and control this infection. The goal of this study was to test single antigens for their efficacy in a vaccine against S. stercoralis larvae in mice. Alum was used as the adjuvant in these studies and antigens selected for analysis were either recognized by protective human IgG (Ss-TMY-1, Ss-EAT-6, and Ss-LEC-5) or were known to be highly immunogenic in humans (Ss-NIE-1 and Ss-IR). Only mice immunized with the Ss-IR antigen demonstrated a significant decrease of approximately 80% in the survival of larval parasites in the challenge infection. Antibodies, recovered from mice with protective immunity to S. stercoralis after immunization with Ss-IR, were used to locate the antigen in the larvae. Confocal microscopy revealed that IgG from mice immunized with Ss-IR bound to the surface of the parasites and observations by electron microscopy indicated that IgG bound to granules in the glandular esophagus. Serum collected from mice immunized with Ss-IR passively transferred immunity to naïve mice. These studies demonstrate that Ss-IR, in combination with alum, induces high levels of protective immunity through an antibody dependent mechanism and may therefore be suitable for further development as a vaccine against human strongyloidiasis.

A New Species of Pseudodelphis (Dracunculoidea: Guyanemidae) in the Intertidal Fish Scartichthys viridis (Blenniidae) from Central Chile

A new species of nematode, Pseudodelphis chilensis n. sp., is described. This parasite was found in muscles of the pectoral fins of a blenniid fish, Scartichthys viridis , from central Chile. The new species differs from the other 2 described (P. oligocotti Adamson and Roth, 1990 and P. limnicola Brugni and Viozzi, 2006) for its longer glandular esophagus and a small caecum at the beginning of the glandular esophagus; both characteristics are in males and females. In addition, the male of P. chilensis n. sp. does not have an adanal caudal papillae, and it has longer spicules than the other 2 species. This is the first Pseudodelphis species described for Chile and the second for South America.

Mexiconema africanum sp. n. (Nematoda: Daniconematidae) from the catfish Auchenoglanis occidentalis from Lake Turkana, Kenya

A new species of dracunculoid nematode, Mexiconema africanum sp. n. (Daniconematidae), is described from the abdominal cavity and the intestine (rarely also the gall bladder) of the catfish Auchenoglanis occidentalis (Valenciennes) (Claroteidae, Siluriformes) from Lake Turkana, Kenya. The new species differs from two other congeners mainly in the absence of two large cell nuclei in the glandular oesophagus, presence of well-developed lateral cephalic elevations, more numerous (14) cephalic papillae and a much longer body of the gravid female (18-22 mm); from Mexiconema cichlasomae Moravec, Vidal and Salgado Maldonado, 1992 also in less numerous (two) caudal processes and a different arrangement of genital papillae in the male. M. africanum is the first representative of the dracunculoid family Daniconematidae described from Africa.

A New Species of Camallanidae from Ageneiosus ucayalensis (Pisces: Siluriformes) from Pará State, Brazil

Procamallanus (Spirocamallanus) belenensis n. sp. is described using light and scanning electron microcopy, based on specimens taken from Ageneiosus ucayalensis, Castelnau, 1855 (Pisces: Siluriforme), a freshwater fish commonly called mandubé, in Pard State, Brazil; Procamallanus (Spirocamallanus) rarus is recorded from the same host. To our knowledge there are no previous reports of nematodes from this fish species. Procamallanus (S.) belenensis is characterized by the presence of 8-13 cuticular spiral thickenings coating 2/3 of posterior region of the buccal capsule of males and females (the anterior third is smooth); small sub-equal spicules; 3 and 4-5 pairs of pre- and post-cloacal papillae, respectively; the proportion of muscular and glandular esophagus is 1:1.5-2; males present 2 spike-like projections at the tail tip, which are absent in females by light microscopy. The most closely related species are Procamallanus (Spirocamallanus) inopinatus and Procamallanus (Spirocamallanus) pintoi. The new species differs from the most closely related species by the presence of 8-10 cuticular spiral thickenings in the buccal capsule of males and 9-13 in the females, 8 pairs of male clocal papillae (3 pre- and 5 post-cloacal, respectively), and only males bearing 2 minute, spike-like projections at the posterior end.

TWO NEW SPECIES OF ASCAROPHIS (NEMATODA: CYSTIDICOLIDAE) IN MARINE FISHES FROM CHILE

In this study, we describe 2 new species of Ascarophis van Beneden, 1871 (Nematoda: Cystidicolidae), found in fishes from southern Chile. Ascarophis carvajali n. sp. was found in Austrolycus depressiceps and Patagonotothen cornucola, whereas Ascarophis draconi n. sp. was taken from Champsocephalus gunnari. These new Ascarophis species differ from other species in a combination of several morphometric and morphological characteristics. Although A. carvajali n. sp. was morphologically close to Ascarophis minuta, the new species has a larger ratio between glandular and muscular esophagus, filaments on both egg poles, and a shorter right spicule than A. minuta. Ascarophis draconi n. sp. was morphologically similar to Ascarophis adioryx and Ascarophisfiliformis. However, A. adioryx has eggs without filaments, a smaller ratio between glandular and muscular esophagus length, and a smaller ratio between left and right spicule lengths in contrast to A. draconi n. sp., whereas A. filiformis has a shorter glandular esophagus and left spicule length than A. draconi n. sp. Only 1 Ascarophis species has been recorded in a single fish from Chile (i.e., Ascarophis sebastodis in Sebastes capensis). Consequently, this study constitutes not only new species and records of Ascarophis in fishes from Chile, but also new records for the Pacific coast of South America.

Pseudodelphis limnicola sp. n. (Dracunculoidea: Guyanemidae) from the heart of Percichthys trucha (Perciformes: Percichthyidae) in Patagonian Andean lakes (Argentina)

During a survey of parasites of Percichthys trucha (Cuvier et Valenciennes) (Perciformes: Percichthyidae) in northwestern Patagonian lakes, a new dracunculoid of the family Guyanemidae was found parasitizing as adults the heart of the fish. This species belongs to the genus Pseudodelphis Adamson et Roth, 1990 by having deirids, glandular multinucleate oesophagus and anterior branch of the uterus, and by lacking caudal alae and a gubernaculum. Pseudodelphis limnicola sp. n. differs from Pseudodelphis oligocotti Adamson et Roth, 1990 by the number and distribution of the cephalic papillae, a muscular oesophagus submerged into the glandular portion and by lacking a peribuccal ring. This is the first record of a guyanemid inhabiting the heart of a Neotropical perciform fish.