Checklist of nematodes parasitizing fish in the Brazilian Amazon.

This study presents a list of parasitic fish nematodes from the Brazilian Amazon based on the previous Brazilian list including scientific assessments carried out between 2010 and 2021. A total of 16 families, 48 species and 28 undetermined species of nematodes associated with fish are included in the checklist, in addition to 93 host species and 15 geographical records.

Morphological and molecular analyses of Pseudomazocraes sulamericana n. sp., Pseudomazocraes selene Hargis, 1957, Cemocotyle carangis (MacCallum, 1913) and Zeuxapta seriolae (Meserve, 1938) (Monogenea: Mazocraeidea) from carangid fishes in the south-western Atlantic Ocean.

An integrative taxonomy approach was followed to analyse morphological and molecular characters of the monogenean species Pseudomazocraes selene, Cemocotyle carangis and Zeuxapta seriolae; specimens were collected from the gills of the carangid fishes Selene vomer, Caranx latus and Seriola lalandi caught off the coasts of the states of Rio de Janeiro and Santa Catarina, Brazil. The research revealed the presence of Pseudomazocraes sulamericana n. sp., which can be differentiated from other congeners by the shape of clamps mid-sclerite possessing a ventral piece bifurcated at the end, with large and right-angled edges of almost the same length, and by the shape of larval hooks and rounded terminal lappet. New genetic sequences include partial 28S and 18S rDNA genes for all species, ITS1 and 5.8S rDNA for Zeuxapta seriolae and Cemocotyle carangis, and ITS2 and mtDNA cox1 for C. carangis. The phylogenetic concatenated analysis based on partial 28S rDNA and 18S rDNA sequences confirmed the position of C. carangis and Z. seriolae within the Heteraxinidae. The previous phylogenetic position of Chauhaneidae was discussed based on morphological studies and it is now confirmed by molecular data that Chauhaneidae is the sister group of Allodiscocotylidae and Protomicrocotylidae.

The philometrid nematode Philometroides acreanensis n. sp. from the stomach wall of the catfish Pimelodus blochii in north-western Brazil.

A new nematode species, Philometroides acreanensis n. sp. (Philometridae), is described from female specimens recovered from the stomach wall of the freshwater catfish Pimelodus blochii Valenciennes (Pimelodidae) collected in the Acre River (Amazon River basin), Acre State, Brazil. Based on examination by light and scanning electron microscopy, the new species differs from the two other South American congeneric species mainly in the body length of the gravid female (240-280 mm), the length of the oesophagus (1.25 mm in holotype) representing 0.5% of the entire body length, the range of cuticular embossment, as well as the location in the host (stomach), order of the fish host (Siluriformes) and the geographical distribution (Amazon River drainage system). This is the third known species of Philometroides Yamaguti, 1935 reported from South America. A key to species of Philometroides occurring in the fish of America is provided.

First report of neurotoxic effect of the cyanobacterium Cylindrospermopsis raciborskii on the motility of trematode metacercariae.

Cylindrospermopsis raciborskii (Woloszynska) is a photosynthetic cyanobacterium that can produce cytotoxic (cylindrospermopsin) and neurotoxic cyanotoxins (saxitoxins). In Brazil the strains of C. raciborskii are reported to produce only saxitoxins (STX) and their effect on fish parasites has not been tested to date. The fish Poecilia vivipara Bloch and Schneider is a common host for the trematode Pygidiopsis macrostomum Travassos off the coast of Rio de Janeiro, and this fish-parasite interaction is a model for behavioural and ecotoxicological studies. The aim of this work was to evaluate the motility of metacercariae of P. macrostomum from P. vivipara exposed to 40 mg l-1 and 400 mg l-1 of crude lyophilized extract of the cyanobacterium C. raciborskii (CYRF-01) for 48 h. The fish were separated into groups of ten individuals and, after exposure, five fish from each group were dissected for counting and checking the motility of metacercariae. The other five fish were dissected after 48 h in clean water. The detection and quantification of STX in the solutions of cyanobacteria, and the gills and guts of fish, were performed by an enzyme-linked immunosorbent assay. The crude extract of C. raciborskii caused temporary paralysis in metacercariae of P. macrostomum after exposure of fish to both concentrations, and the motility recovered after the fish were kept for 48 h in clean water. STX was detected in the guts and gills of all fish analysed, suggesting that this toxin is involved in the paralysis of metacercariae. This is the first report on the action of neurotoxins in metacercariae of fish.

Molecular characterization and confocal laser scanning microscopic study of Pygidiopsis macrostomum (Trematoda: Heterophyidae) parasites of guppies Poecilia vivipara.

Pygidiopsis macrostomum and Ascocotyle (Phagicola) pindoramensis (Digenea: Heterophyidae) parasitize guppies as intermediate hosts and, respectively, fish-eating mammals or birds as definitive hosts. Heterophyids have zoonotic potential, and molecular studies associated with morphological and ecological aspects have helped to clarify their taxonomy and phylogeny. Poecilia vivipara naturally parasitized by metacercariae of both species (100% prevalence) exhibit no external signs of parasitism. In this work, four new sequences of P. macrostomum (18S rDNA, 28S rDNA and ITS2 rDNA) and one new sequence of A. (P.) pindoramensis (mtDNA cox-1) are presented. Phylogeny reconstructions linked P. macrostomum to other heterophyids, but the separation of the Heterophyidae and Opisthorchiidae remains unclear. Additionally, we used indirect immunocytochemistry and the phalloidin-fluorescence techniques allied with confocal laser scanning microscopy to describe muscular and neuronal structures of P. macrostomum. A complex arrangement of muscular fibres is associated with the tegument, suckers, gut and reproductive system. Radial fibres around the ventral sucker are thick, branched and extend to the body wall. High-resolution confocal imaging revealed a typical digenean muscular arrangement and important heterophyid morphological traits. These data will support future control measures to reduce the parasitism in guppies reared in fish farming systems, especially for aquarium and experimental purposes.

Morphology and molecular analysis of Oncicola venezuelensis (Acanthocephala: Oligacanthorhynchidae) from the ocelot Leopardus pardalis in Brazil.

Oncicola venezuelensis Marteau, 1977 was found parasitizing adults of Leopardus pardalis (Linnaeus) found dead in Serra da Capivara National Park, Piauí state, Brazil, a new geographical locality reported for the species. The diversity of Oncicola Travassos, 1916 species is large, but genetic data are scarce. This article presents the results of genetic, morphological and ultrastructural studies carried out for taxonomic purposes. The first ultrastructural view showed a globular, short proboscis with 36 hooks, divided into six longitudinal rows of six hooks each. Hooks differ in size and shape: hooks I, II and III have a 'chisel-shaped' tip. The genetic profile included new sequences of ribosomal DNA ITS1, 5.8S and ITS2, and partial 28S rRNA regions. The results of maximum-likelihood tree analyses for each region showed Oligacanthorhynchidae Southwell et Macfie, 1925 close to Gigantorhynchidae Hamann, 1892 (supported >91%). Both use mammals and birds as definitive hosts. Morphological and ultrastructural studies combined with genetic analysis shed more light on the diversity of Oncicola species.

Genetic diversity of Lippia sidoides Cham. and L. gracilis Schauer germplasm.

The conservation of plants in germplasm banks ensures the characterization and availability of these resources for future generations. The present study used DNA markers to obtain genetic information about germplasm collections of Lippia sidoides and L. gracilis, which are maintained in an Active Germplasm Bank (AGB). Genetic variability of samples in the AGB was assessed using 12 combinations of amplified fragment length polymorphism (AFLP) primers (EcoRI/MseI). Twenty simple sequence repeat primers designed for L. alba were tested to determine their transferability in L. sidoides and L. gracilis. The AFLP markers generated 789 markers. The assessed loci exhibited a moderate Shannon diversity index (I = 0.42) in both species, suggesting that the conserved accessions possess an intermediate level of genetic diversity. Twelve microsatellite loci amplified satisfactorily, and nine loci were polymorphic in each species. A total of 23, 22, and 36 alleles, with an average of 2.5, 2.4, and 3.27 alleles per locus were identified for L. sidoides and L. gracilis accessions in the AGB, and Lippia sp sampled plants, respectively. Analyses of genetic structure permitted the identification of three different groups using both sets of markers, of which two were representative of L. sidoides. The information generated in this study may help to create, expand, and maintain collections of these species and may assist in genetic-breeding programs.

Development of a novel set of microsatellite markers for Lippia alba (Verbenaceae).

Microsatellite primers were developed and optimized for Lippia alba to characterize the L. alba germplasm bank of Universidade de São Paulo. A genomic library enabled the design of 9 microsatellite primers. Six of the 9 primers yielded polymorphic products, which defined 2 groups in the bank. The data provide support to characterize germplasm banks, genetic breeding programs for L. alba, and other genetic diversity studies and classifications of species in the genus Lippia.

A redescription of Lobatostoma kemostoma (MacCallum & MacCallum, 1913) (Trematoda: Aspidogastrea) from the florida pompano fish Trachinotus carolinus (Linnaeus, 1766) off the Brazilian coast.

A redescription of the aspidogastrean trematode Lobatostoma kemostoma (MacCallum & MacCallum, 1913) is provided based on examination of type material, voucher specimens available at institutional collections and newly collected specimens from the type host, Trachinotus carolinus (Linnaeus, 1766), off the Angra dos Reis, Brazil. Partial sequence of its 28S rDNA is given. Lobatostoma kemostoma can be distinguished from the other eight species of the genus by: (1) the hindbody being longer than the ventral disc; and (2) the cephalic lobes having the same shape and size. Features observed for the first time include the number and detailed arrangement of alveoli on the ventral disc, the terminal genitalia and the ovarian complex. New illustrations and morphometric data are given. In the present survey the host specificity in the genus, the validity of some morphological features and the occurrence of an Indian species of Lobatostoma from off the Brazilian coast are discussed. A lectotype of L. kemostoma from the type series deposited at United States National Parasite Collection is also designated.

Genetic diversity and population structure of Synthesium pontoporiae (Digenea, Brachycladiidae) linked to its definitive host stocks, the endangered Franciscana dolphin, Pontoporia blainvillei (Pontoporiidae) off the coast of Brazil and Argentina.

Pontoporia blainvillei (Gervais and d'Orbigny, 1844) is an endangered small cetacean endemic to South America with four Franciscana Management Areas (FMA) recognized as different population stocks. The role of the intestinal parasite Synthesium pontoporiae (Digenea: Brachycladiidae) as a possible biological marker to differentiate P. blainvillei stocks was evaluated using nuclear and mitochondrial DNA markers. Internal transcribed sequence 1 and 2 (ITS1 and ITS2) regions of S. pontoporiae did not show intraspecific variability. The mitochondrial NADH dehydrogenase subunit 3 (ND3) and cytochrome oxidase subunit I (COI) gene sequences suggested lack of population structure in S. pontoporiae and population expansion. The apparent panmixia of S. pontoporiae may be due to the high mobility of one or more of its intermediary hosts. Alternatively, it may be due to the small sample size. This result is incongruent with the previously proposed FMA.

Development and characterization of novel microsatellite markers in Hyptis pectinata (Lamiaceae).

A microsatellite-enriched library was constructed and a set of 19 SSR markers were developed to characterize a germplasm collection of Hyptis pectinata (L.) Poit., maintained at the Universidade Federal de Sergipe (UFS). Fifteen markers of 19 ranged from moderately to highly polymorphic. A total of 113 alleles were identified, with a mean of 7.52 alleles per locus. The mean HO and HE were 0.582 and 0.657, respectively. The primers developed were efficient tools for accessing the genetic diversity of the germplasm collection analyzed and may also be useful for other studies involving this species and other species in the genus Hyptis.

Cross-species transferability of microsatellite markers in the genus Lippia.

The cross-species transferability of 20 microsatellite markers was tested in the genus Lippia. Eleven markers were polymorphic after screening 19 accessions of Lippia sidoides and Lippia gracilis maintained in the Active Germplasm Bank (AGB) from Universidade Federal de Sergipe. Additionally, 40 accessions of Lippia spp were collected in Sergipe to increase the germplasm bank. A total of 23, 22, and 36 alleles were identified, with an average of 2.3, 2.2, and 3.27 alleles per locus, respectively, for each group. The markers that were used were efficient tools to access genetic diversity in the germplasm bank and will be useful for further research aiming at the conservation and management of these important aromatic species.

The influence of health education on the prevalence of intestinal parasites in a low-income community of Campos dos Goytacazes, Rio de Janeiro State, Brazil.

In a recent study by our group on the prevalence of intestinal parasitic infections and on the knowledge, attitudes and practices of local residents of Campos dos Goytacazes, Rio de Janeiro, Brazil, we observed that about 50% of the inhabitants were parasitized and had some knowledge of intestinal parasitic infections but did not apply this knowledge in daily practice. We were thus motivated to implement strategies in health education to promote preventive measures in the locality. The goal of the present work was to evaluate the influence of health education on the prevalence of intestinal parasitic infections in the region in an effort to strengthen public policies for controlling these diseases in Brazil. The methodology adopted was based on action-research and a theoretical framework of health promotion. Our results demonstrate that the study population exhibited an enhanced awareness of the importance of disease from intestinal parasitic infections. Attitudes and practices related to prevention were significantly improved after the shared health education. In conclusion, this study allowed the shared construction of knowledge that reflected the true needs of the residents.

A lepidopteran orthologue of reaper reveals functional conservation and evolution of IAP antagonists.

Genetic studies in Drosophila melanogaster have revealed that inhibitor of apoptosis (IAP) proteins and IAP antagonists such as reaper play a pivotal role in controlling cell death in insects. Interestingly, although the sequences and structures of IAPs are highly conserved, the sequence of IAP antagonists diverged very rapidly during evolution, making their identification difficult. Using a customized bioinformatics approach, we identified an IAP antagonist, IAP-binding motif 1 (Ibm1), from the genome of the silkworm Bombyx mori. This is the first reaper/grim orthologue identified in a nondipteran insect. Previous analysis indicated that both Reaper and Grim induce cell death through their N-terminal IBM as well as the Grim_helix3 (GH3) domain. Functional studies indicated that Ibm1 binds to an IAP protein from B. mori, BmIAP1, and induces apoptosis in insect cells via the IAP-binding motif, a seven amino acid sequence that is highly conserved in all IAP antagonists. Interestingly, Ibm1 also contains a region that is a statistically significant match to the GH3 domain. Mutational analysis indicated that the GH3-like motif in Ibm1 has an important supportive role in IAP-antagonist function and can trigger cell death under certain conditions.

Acid phosphatase activity during the interaction of the nematophagous fungus Duddingtonia flagrans with the nematode Panagrellus sp.

The use of Duddingtonia flagrans, a nematode-trapping fungus, has been investigated as a biological control method against free living larvae of gastrointestinal nematodes of livestock animals. This fungus captures and infects the nematode by cuticle penetration, immobilization and digestion of the internal contents. It has been suggested that this sequence of events occurs by a combination of physical and enzymatical activities. This report characterizes the acid phosphatase activity during the interaction of D. flagrans with the free-living nematode Panagrellus sp. The optimum pH for the hydrolysis of the acid phosphatase substrate p-nitrophenyl phosphate was 2.2, 2.8 and 5.4 from D. flagrans alone and 2.2 and 5.4 for Panagrellus sp alone, fungus-nematode interaction in liquid medium and fungus-nematode interaction in solid medium. Different acid phosphatase activity bands were detected by SDS-PAGE. Maximum acid phosphatase activity of the fungus or nematode alone and of the fungus-nematode interaction occurred within 70min of incubation in the presence of the substrate 4-methylumbelliferyl phosphate. The activity of this enzyme was significantly higher for the fungus-nematode interaction when compared to the organisms alone, indicating a synergistic response. Furthermore, structures appeared in the hyphae after 30min, nematodes were observed adhered after 40min and many were captured by the typical fungus traps after 70min of interaction. The participation of acid phosphatase activity and its importance during the interaction of the fungus with the nematode were discussed.

Redescription and surface ultrastructure of Pygidiopsis macrostomum (Digenea: Heterophyidae).

Pygidiopsis macrostomum Travassos, 1928, a poorly known species originally described from a single specimen from Rattus norvegicus (Erxleben, 1777) in Brazil, is redescribed on the basis of metacercariae from the mesenteries of naturally infected guppies Poecilia vivipara Bloch and Schneider, 1801 (Poeciliidae), and adults obtained from an experimental infection of hamsters. Pygidiopsis macrostomum is characterized by the absence of oral spines, vitellaria extending forward to ventral sucker, uterus reaching pharyngeal level, X-shaped excretory vesicle, and an oral sucker/acetabulum ratio of 1:0.8. The surface ultrastructure shows that the tegument of the metacercaria does not strongly differ from that of adults. The brush-shaped spines of P. macrostomum are similar to those reported for Pygidiopsis summa and Pygidiopsis ardeae, but no differences in spine shape were observed throughout the body.

Molecular and Morphological Characterization of Anisakid Nematode Larvae from the Sandperches Pseudopercis numida and Pinguipes brasilianus (Perciformes: Pinguipedidae) off Brazil.

Morphological and genetic data on the larvae of Anisakidae parasitizing the sandperches Pseudopercis numida and Pinguipes brasilianus were recorded from Cabo Frio, State of Rio de Janeiro, Brazil (23°S, 42°W). Twenty-five specimens of P. numida and 25 specimens of P. brasilianus were necropsied. The 352 larvae collected included 1 Anisakis sp., 344 Hysterothylacium sp., and 7 Raphidascaris sp. We present mtDNA sequence data for Anisakis sp. and Hysterothylacium sp., and we sequenced the ITS ribosomal DNA (rDNA) of Hysterothylacium sp. and Raphidascaris sp. The morphological and genetic profiles confirmed the identification of Anisakis typica (Diesing, 1860). Hysterothylacium sp. and Raphidascaris sp. were not identified to the species level due to the absence of similar sequences for adult parasites. The mtDNA sequence of Hysterothylacium sp. from P. numida showed a high similarity to the sequence of Hysterothylacium deardorffoverstreetorum. However, a phylogenetic analysis demonstrated the presence of different clades under the same name as the larval H. deardorffoverstreetorum. Pseudopercis numida is a new host record for A. typica.

Genetic markers in ribosomal DNA for the identification of members of the genus Anisakis (Nematoda: ascaridoidea) defined by polymerase-chain-reaction-based restriction fragment length polymorphism.

Polymerase-chain-reaction-based restriction fragment length polymorphism analysis was performed to establish genetic markers in rDNA, for the identification of the three sibling species of the Anisakis simplex complex and morphologically differentiated Anisakis species, i.e. Anisakis physeteris, Anisakis schupakovi, Anisakis typica and Anisakis ziphidarum. Different restriction patterns were found between A. simplex sensu stricto and Anisakis pegreffii with two of the restriction endonucleases used (HinfI and TaqI), between A. simplex sensu stricto and A. simplex C with one endonuclease (HhaI), and between A. simplex C and Aniskis pegreffii with three endonucleases (HhaI, HinfI and TaqI), while no variation in patterns was detected among individuals within each species. The species A. physeteris, A. schupakovi, A. typica and A. ziphidarum were found to be different from each other and different from the three sibling species of the A. simplex complex by distinct fragments using 10-12 of the endonucleases tested. The polymorphisms obtained by restriction fragment length polymorphisms have provided a new set of genetic markers for the accurate identification of sibling species and morphospecies.

Effect of the respiratory activity on photoinhibition of the cyanobacterium Synechocystis sp.

The influence of respiratory activity on photosynthesis in Synechocystis cells that had been exposed to high light intensity was studied using distinct conditions of nitrogen supply. The photoinhibitory rate of N-sufficient cells was not influenced by the presence of different nitrogen sources. In contrast, when N-starved cells were resupplied with ammonium, they were protected from photoinhibition. Although N-starved cells presented a higher rate of dark O(2) uptake than N-sufficient ones, the photoinhibitory rate increased in both cases after addition of sodium azide or sodium azide plus salicylhydroxamic acid in the photoinhibitory treatment. In the absence of the D(1) protein repair mechanism, photodamage to Photosystem II was faster in N-sufficient cells than in N-starved ones. Mitigation of photodamage disappeared when the respiratory activity of N-starved cells was partially suppressed by the addition of sodium azide or sodium azide and salicylhydroxamic acid. Our results suggest that electron flow through cyanobacterial terminal oxidases can assist Photosystem I in removing electrons from the reduced plastoquinone pool, thus contributing to both reopening of Photosystem II reaction centers and avoiding photogeneration of reactive oxygen species under photoinhibitory conditions.

Ultrastructure of spermatogenesis of Atriaster heterodus (Platyhelminthes, Monogenea, Polypisthocotylea).

The development of spermatozoa in the Polyopisthocotylea Atriaster heterodus was studied by transmission electron microscopy. Spermatogonia were undifferentiated, with irregular nuclei and little cytoplasm. Primary spermatocytes had sparse chromatin and typical synaptonemal complexes. The nuclear chromatin of secondary spermatocytes was in patches along the nuclear envelope and throughout the nucleoplasm. The complete process of fusion of the early spermatids to a common cytoplasmic mass forming a rosette was elucidated. Nuclei migrated to the center of the mass and changed from round to lamellar or tubular in shape. At the borders of the common cytoplasmic mass, the irregular zones of differentiation had microtubules, mitochondria, nuclei, centrioles, and intercentriolar bodies that give rise to 2 flagella. The spermatozoa presented a continuous row of cortical microtubules surrounding 2 parallels axonemes of the 9+1 type.