An integrated phylogenetic analysis on ascaridoid nematodes (Anisakidae, Raphidascarididae), including further description and intraspecific variations of Raphidascaris (Sprentascaris) lanfrediae in freshwater fishes from Brazil

Endoparasitic helminth fauna and diet of Geophagus sveni (Pisces) in Upper Paraná River basin

In freshwater ecosystems, parasite infection patterns are influenced by factors including spatial-temporal variations, host diet, and habitat. Fish often change diets, affecting their parasite communities. This study focused on non-native host fish Geophagus sveni, aiming to characterize diet and endoparasitic helminth fauna patterns in the invaded area, investigating spatial and seasonal possible differences of endoparasite infections and correlating with host diet, in São José dos Dourados River and Tietê River areas. The host fish were collected in these areas during the dry and rainy season using gillnets. The endoparasites were collected and preserved in alcohol and identified using taxonomic methods, and stomach contents were examined for diet analysis. Parasitism descriptors were calculated and evaluated spatially and seasonally by ANOVA and the Kruskal-Wallis tests. PERMANOVA assessed G. sveni diet differences, and RDA correlated the endohelminth abundance with the host diet. Two endoparasites were recorded: metacercariae of Austrodiplostomum compactum (Trematoda) and larvae and adults of Raphidascaris (Sprentascaris) lanfrediae (Nematoda). Spatial differences were observed for the mean abundance and prevalence of R. (S.) lanfrediae and A. compactum prevalence. Seasonal variations of parasitic descriptors occurred for the nematode in the Tietê River area. The detritus and aquatic insects were the most consumed items by G. sveni. Detritus consumption positively correlates with nematode abundance. The findings indicate that factors such as artificial channels and rainfall, which can influence resource availability, may affect the fish's diet and potentially influence the structure of its endoparasite community. The study emphasizes the importance of understanding trophic chain-transmitted parasites and calls for further research in Neotropical environments.

Review of the parasitic nematodes of marine fishes from off the American continent

The ichthyofauna of the Atlantic and Pacific coasts off the American continent is very rich. Consequently, a high biodiversity of nematodes parasitizing these vertebrates is also expected. Currently, data on nematode parasites of marine fish off the Americas are fragmented. A review of all adult nematode species reported parasitizing marine fish from off the American continent is herein presented, as well as comments on their patterns of diversity, life cycles and advances in the taxonomic and phylogenetic knowledge. A total of 209 valid species, 19 species inquirendae and 6 dubious records have been recorded, the majority from the fish taxa Eupercaria and Perciformes. The families Sciaenidae, Serranidae and Lutjanidae, as well as the tropical and temperate Atlantic waters, exhibited the highest records of parasitic nematodes. The Cucullanidae, Philometridae and Cystidicolidae were the most speciose families of nematodes, which may be related to technological advances and relatively recent efforts of taxonomists, resulting in description of new taxa and the resolution of taxonomic problems. Numerous taxonomic questions still need resolution and, even though genetic data have been important for this process, the database is very scarce. This is the first review on all currently known nematode species parasitizing marine fish off the Americas and may serve as an important basis of reference for future approaches on these organisms.

Parasite identification in mullet fish (Mugil curema) from Chautengo Lagoon, Guerrero, Mexico, based on morphology and molecular analysis

Parasite identification is crucial in areas where no sanitary inspection is conducted on fish, especially considering that parasitic zoonoses like anisakiasis and gnathostomiasis can pose a risk for human health. In this study, parasites in mullet fish (Mugil curema) from the Chautengo Lagoon, Guerrero, Mexico, were identified by morphological and molecular methods. A total of 122 specimens weighing 317 ± 51.25 g and 19.3 ± 1.14 cm in length were assessed. Their helminthofauna was classified by measuring internal structures, total length, and maximum width; a morphometric index was also calculated for larval stages. The prevalence of parasitosis in these mullets was 91.8%, with a mean infection intensity of 4.1. The acanthocephalan Floridosentis mugilis was identified by its external and internal structures. The nematodes found were of the Anisakidae family in stage 3 (L3), with a morphology consistent with Contracaecum sp. To determine the species, the ITS ribosomal gene and the mitochondrial genes COX2 and rrnS were molecularly characterized by PCR; then, they were aligned by CLUSTAL W, and a phylogenetic tree was obtained. In this analysis, the sequences were compared with those reported in GenBank. A total of 460 parasites were studied, 283 of which were nematodes (61.5%) and 177 were acanthocephalans (38.5%). The sequences of seven nematodes showed 99% homology with each other, and thus they formed an independent branch within the Contracaecum sp. group. This is the first report identifying Contracaecum multipapillatum in mullet fish in the Chautengo Lagoon, Guerrero.

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.

Deep in the systematics of Camallanidae (Nematoda): using integrative taxonomy to better understand the phylogeny and consistency of diagnostic traits

Due to conflicts between classic and molecular systematics of Camallanidae, different data types were used for the first time, to better understand the evolutionary history and taxa consistency within this family. Genetic [18S and 28S rDNA; cytochrome c oxidase subunit I (COI) mtDNA], morphological and life history traits were used to infer phylogenies using Bayesian inference, reconstructed from separated and concatenated datasets. The consistency of tree and morphological traits was evaluated using the consistency index. Characters were mapped on the trees and the phylogenetic informativeness of genetic markers was estimated. Phylogenetic informativeness of 18S provided better resolution for outer nodes, COI for inners and 28S had an intermediate profile. New sequences for two camallanid species were obtained. Phylogenies of genetic and concatenated data largely agreed, showing more divergence in the COI dataset, due to its higher mutation rate vs stable morphology for diagnosing higher taxa. No genus sustained monophyly. The lack of autapomorphy and phylogenetic proximity supported the partition of Batrachocamallanus as synonym of Procamallanus and Spirocamallanus, which should not be considered as subgenera. Although traits of buccal capsule, male tail, habitat, host and biogeographic were highly consistent, intrinsic patterns varied according to different taxa assemblages. Morphological systematics of Camallanidae, based on buccal capsule, is artificial for certain taxa.

Effectiveness of Gutting Blue Whiting (Micromesistius poutassou, Risso, 1827), in Spanish Supermarkets as an Anisakidosis Safety Measure

Anisakidosis is a parasitic zoonotic disease which can cause gastroallergic reactions in humans. In 2010, the European Food Safety Agency estimated that approximately 20,000 cases of anisakiasis had been reported across the world, with Spain having the highest number of infections in Europe. The blue whiting (Micromesistius poutassou, Risso, 1827) is one of the most widely fished species worldwide and represents around 25% of the white fish eaten in Spain. The Spanish Food Safety Authority requires obligatory evisceration of certain fish species before commercialization, but not for blue whiting. Nevertheless, some supermarkets carry this out themselves to prevent human infections and negative customer reactions deriving from the presence of ascaridoid larvae. To assess the effectiveness of eviscerations at supermarkets, a total of 320 blue whiting specimens were examined. The risk of larval migration from the visceral cavity to the musculature in gutted and ungutted fish was also assessed. Our results showed a total prevalence (25%) of ascaridoids in fish gutted at the supermarket, and a direct relationship was found between the presence of larvae in the muscle and time until evisceration. In ungutted fish, the standard length and weight were higher for infected than for non-infected fish. Also, massive infections had a higher prevalence in these larger specimens, in which the viability of larvae was also high. Larval viability was not found to be affected by a 24-h refrigeration period. Anisakis was the most prevalent genus identified in the fish examined. The results indicate that gutting at the supermarket is not an effective method for the total removal of ascaridoid larvae and that additional safety measures are advisable.

Genera and Species of the Anisakidae Family and Their Geographical Distribution

Simple Summary

The parasites of the Anisakidae family infest mainly marine mammals; however, they have the ability to infest paratenic hosts such as mollusks, small crustaceans and fish. The consumption of meat from animals of aquatic origin favors the acquisition of the disease known as Anisakiasis or Anisakidosis, depending on the species of the infecting parasite. Currently, the identification of the members of this family is carried out through the use of molecular tests, which brings about the generation of new information. The purpose of this review was to identify the genus and species of the Anisakidae family by reviewing scientific papers that used molecular tests to confirm the genus and species. The adaptability of the Anisakidae family to multiple hosts and environmental conditions allows it to have a worldwide distribution. As it is a zoonotic agent and causes non-specific clinical symptoms, it is important to know about the different members of the Anisakidae family, as well as the hosts where they have been collected.

Abstract

Nematodes of the Anisakidae family have the ability to infest a wide variety of aquatic hosts during the development of their larval stages, mainly marine mammals, aquatic birds, such as pelicans, and freshwater fish, such crucian carp, these being the hosts where the life cycle is completed. The participation of intermediate hosts such as cephalopods, shrimp, crustaceans and marine fish, is an important part of this cycle. Due to morphological changes and updates to the genetic information of the different members of the family, the purpose of this review was to carry out a bibliographic search of the genus and species of the Anisakidae family identified by molecular tests, as well as the geographical area in which they were collected. The Anisakidae family is made up of eight different parasitic genera and 46 different species. Those of clinical importance to human health are highlighted: Anisakis pegreffi, A. simplexsensu stricto, Contracaecumosculatum, Pseudoterranova azarazi, P. cattani, P. decipiens and P. krabbei. The geographical distribution of these genera and species is located mainly in the European continent, Asia and South America, as well as in North and Central America and Australia. Based on the information collected from the Anisakidae family, it was determined that the geographical distribution is affected by different environmental factors, the host and the ability of the parasite itself to adapt. Its ability to adapt to the human organism has led to it being considered as a zoonotic agent. The disease in humans manifests nonspecifically, however the consumption of raw or semi-raw seafood is crucial information to link the presentation of the parasite with the disease. The use of morphological and molecular tests is of utmost importance for the correct diagnosis of the genus and species of the Anisakidae family.

A new species of Raphidascaris (Nematoda: Raphidascarididae) infecting the fish Gymnogeophagus balzanii (Cichlidae) from the Pantanal wetlands, Brazil and a taxonomic update of the subgenera of Raphidascaris based on molecular phylogeny and morphology

Raphidascaris (Sprentascaris) andersoni n. sp. (Nematoda: Raphidascarididae) collected in the intestine of the humphead cichlid Gymnogeophagus balzanii (Perugia) from the Pantanal wetlands, State of Mato Grosso do Sul (Brazil) is described and genetically characterized. The new species differs from its congeners mainly by having a conspicuous papilla-like formation slightly anterior to the cloacal aperture. Furthermore, males of R. (S.) lanfrediae and R. (S.) mahnerti have caudal alae, and R. (S.) hypostomi and R. (S.) pimelodi lack lateral alae, whereas in the new species caudal alae are absent and lateral alae present. The remaining congeners, namely, R. (S.) marano and R. (S.) saltaensis differ from Raphidascaris (Sprentascaris) andersoni n. sp. mainly because males have three pairs of postcloacal papillae (vs five pairs). In the phylogenetic reconstructions, using three nuclear genetic markers (18S, ITS1-5.8S-ITS2 and 28S rDNA) and one mitochondrial (cox1 mtDNA), the new species was separated from other representatives of Raphidascarididae, and the absence of monophyly in Hysterothylacium and Raphidascaroides was confirmed. Moreover, the subgenera Sprentascaris and Ichthyascaris appeared to be monophyletic. Therefore, even though Raphidascaris (Raphidascaris) was apparently not monophyletic, the subgenera of Raphidascaris should be re-erected as valid genera. The updated diagnoses of Ichthyascaris, Raphidascaris and Sprentascaris are given. The present study represents the first parasitological survey in G. balzanii.

Integrative approach on Pharyngodonidae (Nematoda: Oxyuroidea) parasitic in reptiles: Relationship among its genera, importance of their diagnostic features, and new data on Parapharyngodon bainae

The first integrative approach using sequences of two genes (18S and 28S rRNA) plus morphological and life history traits, was explored in Pharyngodonidae nematodes parasitic in reptiles. Additionally, first genetic characterization of Parapharyngodon bainae and new data on its morphology are given. This approach evaluated the phylogenetic relationships among genera within Pharyngodonidae, as well as the importance of their diagnostic morphological features. Specimens of P. bainae were collected from faecal pellets of the lizard Tropidurus torquatus in the State of Minas Gerais, Brazil. Nematodes were fixed for scanning electron microscopy and molecular procedures. Morphological observations revealed the accurate structures of cephalic end, of cloacal region in males, of vulva and eggs. Phylogenetic reconstructions were based upon four datasets: aligned sequences of the 18S, of the 28S, of both concatenated genes and of combined morphological and molecular datasets. Bayesian inference and maximum likelihood were performed to infer the phylogenies of molecular datasets and maximum parsimony to infer that of all-combined data. Pharyngodonid parasites of reptiles seem to configure two general monophyletic lineages, as previously assertions. Results also showed the monophyly of Spauligodon, Skrjabinodon and Parapharyngodon, as well as the clear separation between the latter and Thelandros. Combination of datasets improved nodal supports. Analysis of the all-combined datasets revealed the importance of vulval position and egg morphology as phylogenetic informative traits. However, characters of male caudal morphology appear as are highly homoplastic, and seem to be product of convergent evolution or multiple losses of ancestral traits. The closely-related Thelandros and Parapharyngodon are kept valid and their diagnosis should be based upon the position of the operculum in eggs (terminal or subterminal, respectively). Some inconsistencies in the scarce molecular and morphological databases were noted. Thus, new genetic data is required for further conclusions and current database must be evaluated with attention.

Hysterothylacium fabri (Nematoda: Raphidascarididae) in Mullus surmuletus (Perciformes: Mullidae) and Uranoscopus scaber (Perciformes: Uranoscopidae) from the Mediterranean

Raphidascarididae are among the most abundant and widespread parasitic nematodes in the marine environment. The life-cycle of most raphidascaridid species is poorly known and information about their distribution and host range is lacking in many geographical areas, as is the taxonomy of several species. A study of larval and adult stages of Hysterothylacium fabri (Rudolphi, 1819) Deardorff and Overstreet, 1980 (Nematoda: Raphidascarididae) infecting the striped goatfish Mullus surmuletus Linnaeus, 1758 (Mullidae) and the Mediterranean stargazer Uranoscopus scaber Linnaeus, 1759 (Uranoscopidae) from the Ionian Sea (central Mediterranean) has been carried out by combining light and scanning electron microscopy observations and molecular analyses through polymerase chain reaction-restriction fragment length polymorphism and sequencing of the ITS rDNA gene. Results indicate that U. scaber and M. surmuletus represent suitable definitive and intermediate/paratenic hosts of H. fabri, respectively, in the Mediterranean and highlight the importance of combining genetic and morphological data to study the taxonomy and epidemiology of parasites widely distributed in different fish species and aquatic ecosystems.

Integrative taxonomy of Goezia spinulosa (Nematoda: Raphidascarididae) from arapaimas in the northwestern Brazil

Arapaima gigas, a fish with a high market value, has been farmed in different localities within Brazil. Among its parasites, adults of Goezia spinulosa are reported to cause ulcers in the stomach and to result in the death of farmed fingerlings. Due to the veterinary importance of this nematode in cultured arapaimas, an integrative taxonomic study is proposed, combining morphological, ultrastructural and genetic profiles of this parasite. The fish were obtained from semi-intensive fish farming in Acre State, Brazil. The fish measured 7-42cm in total length and the intensity of infection was 1-60 parasites per fish. The site of infection was mainly the stomach. Morphological and ultrastructural analyses of G. spinulosa showed the importance of its spiny body in firmly attaching the worm to the gastric mucosa, resulting in lesions, ulcers and deep gastric perforations of the stomach wall. New sequences for partial 18S rDNA, ITS1, 5.8S and ITS2 rDNA, partial 28S rDNA, cox1 mtDNA and for cox2 mtDNA are presented. Phylogenetic reconstructions based on the partial 18S and 28S rDNA shows species of Goezia occur in a clade well separated from other genera in both analyses. Both the partial 18S and 28S rDNA genes represented good genetic markers for distinguishing genera of the Raphidascarididae, with exception of Hysterothylacium. This integrated taxonomic study produced a robust profile for G. spinulosa that will aid the diagnosis of both adults and larval stages from arapaimas and possible intermediate hosts.