MORPHOLOGICAL AND GENETIC CHARACTERIZATION OF DIDELPHONEMA LONGISPICULATA (NEMATODA: SPIRUROIDEA) IN THE BLACK-EARED OPOSSUM DIDELPHIS MARSUPIALIS.

Didelphonema longispiculata (Hill, 1939), a gastric nematode parasite of the black-eared opossum, Didelphis marsupialis Linnaeus, 1758, collected from 2 municipalities of Mato Grosso state, Brazil, in the ecotone region of the Amazon and Cerrado biomes was analyzed with integrative taxonomy using light and scanning electron microscopy (SEM) for morphological studies and sequencing of the 18S small subunit ribosomal RNA for phylogenetic inference through maximum likelihood and Bayesian phylogenetic inference. Here details of the helminth surface, oral aperture with octagonal border, pseudo- and inter-labia, amphids, external cephalic papillae, 2 dorsal and ventral internal plates distally indented, and stoma with strongly chitinized wall are presented. Caudal male papillae, spicules, female vulva, anus, and caudal tip were detailed using SEM. Morphological characteristics and phylogenetic data corroborated the taxonomic placement of the genus Didelphonema within the subfamily Ascaropsinae.

A new species of Pterygodermatites (Spirurida: Rictulariidae) in Marmosa constantiae Thomas, 1904 from an ecotone area of the biomes Cerrado/Amazon in the Mato Grosso State, Brazil.

A new species of nematode, Pterygodermatites (Paucipectines) sinopiensis n. sp. is described based on specimens recovered from the intestine of the white-bellied woolly mice opossum, Marmosa constantiae, trapped in the municipality of Sinop, Mato Grosso state, Brazil. The genus Pterygodermatites has 21 species described in mammals worldwide, and to date, only two species have been described for marsupials in Brazil. The new species is characterized by the presence of 23 small denticles and by the presence of 38-40 and 65 pairs of the cuticular processes in male and female species, respectively. Additionally, male species possess three ventral precloacal fans, and in female species, the cuticular processes are divided into 41 pairs of comb-like and 24 pairs of spine-like processes; the vulva opens approximately in pair 41. This study describes the parasite species fifth of marsupials in the Neotropical region.

New Pudicinae (Nematoda, Heligmonellidae) parasite of Trichomys fosteri (Rodentia: Echimyidae) from Pantanal, Brazil.

Pudica trichomysae n. sp. (Trichostrongylina, Heligmosomoidea, Helligmonellidae, Pudicinae) from the small intestine of Trichomys fosteri (Rodentia: Echimydae) from the Pantanal of Mato Grosso do Sul is described by light and scanning electron microscopy. Pudica trichomysae n. sp. is characterized by caudal bursa type 2-2-1, proportion of spicules length in relation to body length (SpL/BL) of 17 to 18% left and right, respectively. Dorsal ray divided at about the distal third into two branches, each branch divided into two long sub-branches, rays 9 and 10. Furthermore, this study shows for the first time details of the anterior region demonstrating papillae organization, amphids, derides, and opening of the excretory pore. The posterior end of the caudal bursa showed detail of the genital cone, papillae, and ray 1, and in the female, it showed interrupted ridges between the vulva and anus. In conclusion, the present species is the seventeenth described in the genus in South America and the first in Pantanal.

A longitudinal survey of gastrointestinal parasites of the black-eared opossum Didelphis aurita at an urban-sylvatic interface area in Southeast Brazil: a morphological and ecological characterization based on helminth eggs.

Parasites are important organisms in ecosystem dynamics and take part in the regulation and structure of host populations. The prevalence, abundance, and distribution of parasites in their host species may be affected by biotic and abiotic factors. Most studies of helminths of Brazilian marsupials are taxonomic descriptions or re-descriptions and records of occurrence. The use of noninvasive techniques for studying parasitic worms of vertebrate hosts is more common in large or threatened species. The aims of this study were to describe and identify the helminth morphotypes and to analyse the parasitological parameters of gastrointestinal helminth eggs obtained in faecal samples of marsupial Didelphis aurita at the Fiocruz Atlantic Forest Biological Station and surroundings, municipality of Rio de Janeiro, southeast Brazil. The common opossums were sampled during a capture-mark-recapture study. Faecal samples collected from each animal were analysed for helminth egg diagnosis using the methods of flotation in sugar solution and sedimentation. Eggs were compared with samples obtained from the uterus of adult worms obtained from a previous study carried out in the same area. Eleven helminth egg morphotypes were found. Among them, seven were identified at the species level. The highest values of parasitic load and prevalence were observed for the families Viannaiidae and Trichuridae. A significant relationship was found between the number of morphotypes and host body size in females. The influence of parasite load on host condition factor or body size was not observed.

Helminth communities of sigmonontine rodents in cocoa agroforestry systems in Brazil.

Agroforestry is an alternative kind of land use where the native vegetation is surrounded or intercalated by crops of economic interest. This system may maintain species richness by promoting the habitat heterogeneity or serving as ecological corridors. The aim of this study was to describe the gastrointestinal helminth fauna and to analyse the parasitological parameters of the helminth communities of six sigmodontine rodents in a cocoa agroforestry system in the municipality of Ilhéus, state of Bahia, Northeast Brazil. This is a novel study of helminth fauna in this kind of agroforestry. Rodents were captured in live-traps and euthanised for helminth recovery. Specimens were counted and identified to the species level whenever possible. Helminth abundance, intensity, and prevalence were calculated for each species and each host. The total abundance and prevalence of helminths were compared among localities and three attributes of the host: species, gender and age using generalised linear models. Considering all rodents, 52.14% of them were parasitised with at least one helminth species. Eight nematode species were identified and another seven morphospecies were identified to the genus level. The most abundant species were Hassalstrongylus epsilon, Stilestrongylus eta, Guerrerostrongylus zetta, and Syphacia alata. The opportunistic host species Oligoryzomys nigripes and Akodon cursor, besides the water rat Nectomys squamipes, were the most infected species for helminth parasites. Hylaeamys seuanezi was also an important host with the highest helminth species richness. This is the first report of the helminth fauna for this host. The locality most distant from the native vegetation and closest to the city had the highest helminth prevalence and mean species richness. The species richness in the helminth communities of Euryoryzomys russatus, N. squamipes and O. nigripes in these Cabruca agroforestries were within the range found in studies carried out in Atlantic Forest areas.

Evaluation of changes in the carbohydrate metabolism of Biomphalaria glabrata Say, 1818 exposed to experimental coinfection by Angiostrongylus cantonensis (Nematoda) and Echinostoma paraensei (Trematoda).

The interaction between intermediate snail hosts and helminths can cause metabolic changes in the former. The snails use their reserves for maintenance of their vital processes, by activating the internal defense system and repairing tissue damage, while also supplying necessary energy for the parasites' development. Our aims were to evaluate the lactate dehydrogenase activity and the glucose concentration in the hemolymph of Biomphalaria glabrata experimentally coinfected by Angiostrongylus cantonensis and Echinostoma paraensei. Besides these aspects, the glycogen content in the digestive gland complex and cephalopedal mass along with histochemical changes in parasitized snails were analyzed. The snails were divided in group A (infected by 1200 L1 of A. cantonensis), group E (infected by 20 E. paraensei miracidia), group A + E (co-infected with A. cantonensis first and after a week by E. paraensei), group E + A (co-infected with E. paraensei first and then by A. cantonensis) and control group (not infected). During four weeks after exposure, samples were collected for biochemical and histochemical analyses. In the infected snails, glucose levels and glycogen content in the digestive gland complex and cephalopedal mass were significantly lower, in contrast with an increase of lactate dehydrogenase activity. These results indicate that the intense energy demand resulting from the presence of parasites causes the host snail to accelerate the anaerobic degradation of carbohydrates to obtain energy, in an attempt to maintain homeostasis. Both parasites were observed in histochemical analysis to cause tissue damages in the snails. So, although the snails were able to sustain the coinfection, several metabolic and tissue changes occurred, mainly in those infected with E. paraensei and then with A. cantonensis.

New morphological and genetic data of Gigantorhynchus echinodiscus (Diesing, 1851) (Acanthocephala: Archiacanthocephala) in the giant anteater Myrmecophaga tridactyla Linnaeus, 1758 (Pilosa: Myrmecophagidae).

Gigantorhynchus echinodiscus (Diesing, 1851) is a parasite of anteaters in South America. Although described by Diesing in 1851, there is still a lack of taxonomic and phylogenetic information regarding this species. In the present study, we redescribe G. echinodiscus collected from a giant anteater, Myrmecophaga tridactyla Linnaeus, 1758, from the Brazilian Cerrado (Savannah) in the State of São Paulo by light and scanning electron microscopy. In addition, phylogenies were inferred from partial DNA gene sequence of the nuclear large subunit ribosomal RNA gene (28S rRNA). We provide for the first time details of the proboscis with a crown having 18 large hooks and numerous small hooks, a lateral papilla at the base of the proboscis, a ringed pseudo-segmented body, large testes, cemented glands in pairs, and a non-segmented region in the posterior end of the body, which contributed to the diagnosis of the species. Molecular phylogenetic analyses recovered G. echinodiscus forming a well-supported monophyletic group with Mediorhynchus sp., which was congruent with morphological studies that allocate both genera within the family Gigantorhynchidae. In conclusion, the present work adds new morphological and molecular information, emphasizing the importance of adopting integrative taxonomic approaches in studies of Acanthocephala.

A New Species of Bidigiticauda (Nematoda: Strongylida) from the Bat Artibeus Planirostris (Chiroptera: Phyllostomidae) in the Atlantic Forest and a Molecular Phylogeny of the Molineid Bat Parasites.

The nematode genus Bidigiticauda has 2 species (Bidigiticauda vivipara and Bidigiticauda embryophilum), which are parasites of bats from the Neotropical region. The present paper describes a new species of Bidigiticauda from a male Artibeus planirostris specimen collected in the Pratigi Environmental Protection Area in Bahia state, Brazil. The new species, Bidigiticauda serrafreirei n. sp., differs from B. embryophilum by having longer spicules, rays 5 and 6 arising from a common trunk and bifurcating in its first third, rays 3 and 4 emerging slightly separated from each other, and dorsal rays reaching the margin of the caudal bursa. The new species also differs from B. vivipara by the dorsal ray bifurcating at the extremity of the trunk. A molecular phylogenetic analysis was conducted to determine the evolutionary affinities of Bidigiticauda serrafreirei n. sp. within the Strongylida, which identified a clade that grouped Bidigiticauda with the other members of the Anoplostrongylinae. However, the molineid subfamilies did not group together, indicating that the family Molineidae is polyphyletic. Further analyses, which include additional taxa and genetic markers, should elucidate the complex relationships within the Molineidae, in particular its subfamilies and the evolution of the traits that define these groups.

A New Species of Pachysentis Meyer, 1931 (Acanthocephala: Oligacanthorhynchidae) in the Brown-Nosed Coati Nasua nasua (Carnivora: Procyonidae) from Brazil, with Notes on the Genus and a Key to Species.

INTRODUCTION: Pachysentis comprises 10 species, which have been reported parasitizing mammals in Africa and the American continent. However, species of Pachysentis have not been described in brow-nosed coatis. Pachysentis lauroi n. sp. (Oligacanthorhynchidae: Acanthocephala) is described from the brown-nosed coati Nasua nasua (Linnaeus, 1766) Storr, 1780 (Procyonidae: Carnivora) in the Brazilian Pantanal wetlands of the Mato Grosso do Sul State, Brazil. METHODS: Specimens were studied using light and scanning electron microscopy. RESULT: The new species is distinguished from other species of Pachysentis by the number of hooks in each longitudinal row (12 rows of 4 hooks, total of 48 hooks), presence of barbs on all hooks, and the organization of the cement glands. Notes on the genus Pachysentis [14] and a key to its species are provided. Critical comments on some species with a dubious diagnosis and questionable or missed key taxonomic characteristics are also reviewed. We also discuss the zoogeography of the members of the genus.

Metacommunity Structure of Helminths of Necromys lasiurus (Rodentia: Sigmodontinae) in Different Land Use Areas in the Brazilian Cerrado.

The ecology of host-parasite interactions can be studied in the infracommunity and component community scales, which may show different patterns in species distributions, interacting and affecting each other on a regional scale. Few studies have been carried out concerning the structure and variation of the helminth communities of wild rodents in Brazil. The rodent Necromys lasiurus is typical from the mammalian fauna of the Cerrado biome; however, the environmental disturbances are making this species occur in rural areas and in other biomes where it may act as host/reservoir of many diseases. This study aimed to describe the composition and structure of the helminth metacommunity in the rodent N. lasiurus in the Brazilian Cerrado, Uberlândia, State of Minas Gerais, using the analysis of metacommunity structure. Rodents were sampled in 3 habitat types: borders of soybean and corn plantations, pasturelands, and preserved areas of Cerrado borders. Adult helminths of 8 species were found in the gastrointestinal tract: Protospirura numidica criceticola, Physaloptera sp., Pterygodermatites ( Paucipectines) zygodontomis (Spirurida), Stilestrongylus freitasi (Rhabditida), Trichuris navonae (Trichurida) and Syphacia ( Syphacia) alata (Oxiurida) of the Phylum Nematoda; Rodentolepis akodontis (Cyclophyllidea) of the Phylum Platyhelminthes; and Moniliformis sp. (Moniliformida) of the Phylum Acanthocephala. Season and the kind of land use favored some helminths species in this rodent, especially in the plantation area, although diversity was not largely influenced by the land use. Plantation areas could provide an increase in the host abundance and the occurrence of other rodent species, favoring a higher rate of parasite exchange among different hosts. A checkerboard structure of metacommunity was found on the infracommunity scale, which suggests the existence of interspecific competition. A quasi-nested structure of metacommunity was observed on the component community scale showing that most species were influenced by the same environmental gradient and that the species-poor communities were subsets of species-rich communities. Syphacia alata, P. zygodontomis, S. freitasi, and R. akodontis were dominant species in all habitats and represented the core-species in the metacommunity.

Biological and histological changes in reproductive patterns of Biomphalaria glabrata experimentally co-infected by Echinostoma paraensei and Angiostrongylus cantonensis.

Investigation of co-infection by different helminths in snails can provide essential information about the biology of parasites co-existence under natural conditions. This study aimed to investigate the reproductive and histological changes of Biomphalaria glabrata experimentally co-infected with Echinostoma paraensei and Angiostrongylus cantonensis. Five groups of snails i.e. uninfected, with single and double infections, either E. paraensei first (E + A) or A. cantonensis first (A + E) were followed; three times a week during four weeks the numbers of egg masses, eggs and hatched snails were counted. Histological analysis of the ovotestis and albumen gland was performed after four weeks. The number of egg masses/snail, eggs/snail and hatched snails showed significative differences comparing the control group to all infected groups, especially in group E + A, with the majority of values of parameters analyzed lower than 50% of those observed for control snails. In addition, the mortality was higher in the group E + A than to control group. The histological analysis showed that presence of both parasites in the reproductive organs was associated with tissue damages.

Comparative pattern of growth and development of Echinostoma paraensei (Digenea: Echinostomatidae) in hamster and Wistar rat using light and confocal laser scanning microscopy.

Echinostoma paraensei (Digenea: Echinostomatidae) lives in the duodenum and bile duct of rodents and is reported as a useful model for studies on the biology of flatworms. Here, we compared the growth and development of pre and post ovigerous worms collected 3, 7, 14 and 21 days post infection from experimentally infected hamster (permissive host) and Wistar rat (less permissive hosts). Linear measurements and ratios were examined by light (morphology and morphometry) and confocal laser scanning microscopy. At day 3, either worm from hamsters or rats were small with poorly developed gonads. At seven day, worms increased in size and morphometric differences between hosts are statistically significant after this time. In addition, adult worms (14 and 21 days of age) harvested from hamster showed developed gonads and vitelline glands laterally distributed on the body, whereas worms from rat showed atrophied reproductive system characterized by underdeveloped vitelline glands and stunted ovary. The worm rate recovery in rat decreased from 29.3% (day 7) to 20.6% (day 14) and 8% (day 21), whilst it remained around 37% in hamster. In conclusion, this is the first appointment demonstrating that low permissiveness influences the reproductive system of echinostome since the immature stages of development. The phenotypic analysis evidenced that hamster provides a more favorable microenvironment for gonads development than rat, confirming golden hamster as a permissive host, whereas Wistar rat is less permissive host.

Effects of experimental Angiostrongylus cantonensis infection on the reproductive biology of Biomphalaria straminea and Biomphalaria tenagophila.

Eosinophilic meningoencephalitis is an endemic zoonosis in Southeast Asia and the Pacific Islands, but in recent years, new cases have been reported in various countries outside these regions, including Brazil, where it is considered an emerging disease. In this study, the effect of infection by the nematode Angiostrongylus cantonensis, one of the main etiologic agent of this disease, on the reproductive biology of the planorbid snails Biomphalaria straminea and B. tenagophila was investigated during the pre-patent period. Alterations in the reproductive biology of B. straminea and B. tenagophila were analyzed in laboratory-reared specimens infected by A. cantonensis during 21days; the number of eggs, number of egg masses, number of eggs/mass, number of eggs/snail, viable eggs/snail, survival and galactogen content in the albumen gland were measured. The results indicated the occurrence of initial compensation in reproductive effort in both snail species, but at different moments in the pre-patent period. More specifically, a reduction of 46.53% in the eggs/egg mass ratio in infected B. straminea was observed, a reflection of a 50% decline in the concentration of galactogen contained in the albumen gland. Changes in this parameter were also noted in B. tenagophila, but only at the end of the study period, with a reduction of 15.49%. Histological analyses indicate that changes observed can be explained by the tissue damages caused by the migration and development of the larvae. These results shed more light on the host-parasite relationship and indicate the importance of studying reproductive aspects for efforts to control infected snails. Considering that terrestrial snails can also transmit eosinophilic meningitis (in addition to aquatic mollusks), the data obtained expand knowledge of this host-parasite relationship and provide support for programs to control this zoonosis.

Light and scanning electron microscopy study of in vitro effects of artesunate in newly excysted metacercariae of Echinostoma paraensei (Trematoda: Digenea).

Chemotherapy of food-borne trematodes relies on two drugs, praziquantel and tricabendazole, and there is growing interest in finding alternative therapies. Plant oil extracts have long been used in traditional Chinese medicine as sources of bioactive compounds with antiparasitic activity. Species of the genus Echinostoma are used as good models to test effective compounds against food-borne trematodes. This study evaluated the anthelmintic activity of crude artesunate extracts in vitro on newly excysted metacercariae of Echinostoma paraensei by light and scanning electron microscopy (SEM). The flukes were incubated with 1 µg/mL, 10 µg/mL, 25 µg/mL, 50 µg/mL and 100 µg/mL of artesunate for 4, 12, 24, 48 and 72 h. When the exposure time and concentration of artesunate increased, there were changes in motor activity, tegument damage and death. Blebs and swelling were the most common damages quantified on the tegument. The in vitro study reproduced results described for other immature flukes incubated with artemisinin derivatives. Excysted metacercariae of E. paraensei constitute a good model to study in vitro drug effects.

The influence of Angiostrongylus cantonensis (Nematoda, Metastrongylidae) infection on the aerobic metabolism of Biomphalaria straminea and Biomphalaria tenagophila (Mollusca, Gastropoda).

Angiostrongylus cantonensis is considered the main agent responsible for human eosinophilic meningoencephalitis. This parasite has low specificity for mollusk hosts and it can also use aquatic snails as auxiliary hosts. Studies based on the metabolic profile of Biomphalaria spp. infected by A. cantonensis have been conducted to observe parasite-host interactions. In the present study, the glucose content in the hemolymph and glycogen content in the digestive gland and cephalopedal mass of Biomphalaria tenagophila and Biomphalaria straminea experimentally infected by A. cantonensis were evaluated, along with the activity of LDH. The snails were dissected from 6 to 21days after infection to collect the hemolymph and separate the tissues. Decreases of 96% and 6.4% in the glucose content triggered a transition from aerobic to anaerobic metabolism in the two infected snail species, B. straminea and B. tenagophila, respectively. That finding was confirmed by high-performance liquid chromatography. These results indicate that when infected, these snails are able to change their metabolic profile, suggesting a strategy to maintain their homeostatic balance.

In vivo and in vitro effects of the herbicide Roundup(®) on developmental stages of the trematode Echinostoma paraensei.

The exposure of wildlife and humans to toxic residues of Roundup(®) through agricultural practices or the food chain has been reported since the herbicide was found contaminating rivers. Glyphosate, N-(phosphonomethyl)glycine acid, is a nonselective post-emergent herbicide and is formulated as an isopropylamine salt with the surfactant taloamine polyethoxylate (POEA) representing the commercial formulation of Roundup(®). There is little knowledge about the effects of the herbicide on helminth parasites, particularly those whose life cycle is related to water bodies. Here we investigated the effects of the Roundup(®) on the food-borne trematode Echinostoma paraensei in experimental conditions using different developmental stages (eggs, miracidia, cercariae, metacercariae, newly excysted larvae (NEL), helminths at seven days and helminths at fourteen days). Three different herbicide concentrations were tested based on concentrations typically applied in the field: 225, 450 and 900 mg/L. Specimens were analyzed in vitro for hatching miracidia, mortality and excystment rate of metacercariae and in vivo for parasitic load and egg production. There was a significant difference in the hatching miracidia rate only for the newly embryonated eggs. The mortality of specimens and excystment rate of metacercariae were concentration-dependent. There was a significant difference in the miracidia mortality with respect to concentration until 56.3 mg/L. The same effect was observed for cercariae, and mortality was observed from 15 min onwards at concentrations of 225-900 mg/L. At low concentrations, mortality was detected after 30 min. The effects of the herbicide concentration on NEL and on helminths at seven and fourteen days showed a significant difference after 24 h. There was no significant difference in parasitic load and egg production after infection of rodents with exposed metacercariae. All developmental stages of the trematode E. paraensei were affected by Roundup(®) exposure under experimental conditions. These results suggest that dynamics of transmission of the trematode could be affected in the natural environments. The study also reinforces the usefulness of this trematode as a good model organism to test pesticides regarding human and environmental health.

Redescription of Oswaldocruzia chambrieri (Strongylida: Molineidae) from Rhinella margaritifera (Anura: Bufonidae) in Caxiuanã National Forest, Brazil.

Oswaldocruzia chambrieri Ben Slimane et Durette-Desset, 1993 is redescribed from specimens collected from the small intestine of the South American common toad, Rhinella margaritifera, from Caxiuanã National Forest in Pará, Brazil, using light and scanning microscopy and molecular analysis of Cytochrome Oxidase I (COI) - coding regions of DNA. The discovered nematodes are characterized by a type III caudal bursa with two papillae, rays 4 with a median groove, and spicules divided into a blade, a shoe and a fork. Cervical alae are absent, the cephalic vesicle is divided into two portions, and the synlophe has low ridges without chitinous supports. The present study establishes the Caxiuanã National Forest as a new location for O. chambrieri, which had previously been reported as a parasite of R. margaritifera in Ecuador, uses light microscopy and scanning electron microscopy (SEM) to identify new morphological characters of the species and represents the second molecular sequence deposited for the Oswaldocruzia genus.

WITHDRAWN: Alterations in the mitochondrial physiology of Biomphalaria glabrata (Mollusca: Gastropoda) after experimental infection by Angiostrongylus cantonensis (Nematoda: Metastongylidae).

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Evaluation of the mitochondrial system in the gonad-digestive gland complex of Biomphalaria glabrata (Mollusca, Gastropoda) after infection by Echinostoma paraensei (Trematoda, Echinostomatidae).

The effect of infection by Echinostoma paraensei on the mitochondrial physiology of Biomphalaria glabrata was investigated after exposure to 50 miracidia. The snails were dissected one, two, three and four weeks after infection for collection and mechanical permeabilization of the gonad-digestive gland (DGG) complex. The results obtained indicate that prepatent infection by this echinostomatid fluke significantly suppresses the phosphorylation state (respiratory state 3) and basal oxygen consumption of B. glabrata, demonstrating that the infection reduces the ability of the intermediate host to carry out aerobic oxidative reactions. Additionally, relevant variations related to the uncoupled mitochondrial (state 3u) of B. glabrata infected by E. paraensei were observed. Four weeks after exposure, a significant reduction in mitochondrial oxygen consumption after addition of ADP (3.68±0.26pmol O2/mg proteins) was observed in the infected snails in comparison with the respective control group (5.14±0.25). In the uncoupled state, the infected snails consumed about 62% less oxygen than the infected snails (7.87±0.84pmol O2/mg proteins) in the same period. These results demonstrate a reduction in oxidative decarboxylation rate of the tricarboxylic acid cycle and faster anaerobic degradation of carbohydrates in the infected snails. The possible mechanisms that explain this new metabolic condition in the infected organisms are discussed.

Squamasnema amazonica n. gen. n. sp. (Heligmonellinae): A new parasite of Proechimys roberti (Rodentia: Echimyidae) in the Brazilian Amazon.

A new species of nematode, Squamasnema amazonica n. gen. n. sp., is described based on specimens found parasitizing the small intestine of Proechimys roberti (Rodentia: Echimyidae) collected during a survey of the fauna of Tapirapé-Aquirí National Forest (Brazil, Eastern Brazilian Amazon). The nematodes were fixed and processed for light microscopy and scanning electron microscopy (SEM). These nematodes were classified under the family Heligmonellidae and the subfamily Heligmonellinae. Although several species in the family Heligmonellidae exhibit discontinuous ridges, Squamasnema n. gen. and Trichotravassosia are the only genera with columns of scales along their entire body, as an apomorphy of the synlophe. Squamasnema n. gen. has columns of cuticular cells along its body, except for on the left flank, and exhibits a synlophe with no size gradient or inclination and does not present chitinized structures supporting the synlophe. Therefore, due to these morphological differences of Squamasnema n. gen., the creation of a new genus was necessary.