Parasites (Monogenea) of tilapias Oreochromis niloticus and Coptodon rendalli (Cichlidae) in a river spring in Brazil.

In the present study, we examined 30 individuals of introduced African cichlids, Oreochromis niloticus and Coptodon rendalli, collected in a river spring of the Pardo River, Paranapanema River basin, southeastern Brazil. Based on morphological and molecular analyses of the partial LSU rDNA gene, we identified four species of monogeneans, Cichlidogyrus tilapiae, C. thurstonae, C. mbirizei, and Scutogyrus longicornis on the gills of O. niloticus, whereas individuals of C. rendalli were infested only with C. papernastrema. This is the first record of C. mbirizei and C. papernastrema in tilapias from Brazil. The ecological consequences of the introduction of exotic species of tilapia such as O. niloticus and C. rendalli along with their monogenean parasites in a wild environment represented by a river spring are discussed. Our new molecular data on Cichlidogyrus and Scutogyrus contribute to the investigation of the phylogenetic interrelationships of these widely distributed genera of monogeneans since their species composition is still unsettled.

Title: Parasites (Monogenea) des tilapias Oreochromis niloticus et Coptodon rendalli (Cichlidae) dans une source au Brésil. Abstract: Dans la présente étude, nous avons examiné 30 individus de cichlidés africains introduits, Oreochromis niloticus et Coptodon rendalli, collectés dans une source fluviale du fleuve Pardo, bassin du fleuve Paranapanema, dans le sud-est du Brésil. Sur la base d'analyses morphologiques et moléculaires du gène partiel de l'ADNr LSU, nous avons identifié quatre espèces de monogènes, Cichlidogyrus tilapiae, C. thurstonae, C. mbirizei et Scutogyrus longicornis sur les branchies d'O. niloticus, alors que les individus de C. rendalli étaient infestés uniquement par C. papernastrema. Il s'agit du premier signalement de C. mbirizei et C. papernastrema chez des tilapias du Brésil. Les conséquences écologiques de l'introduction d'espèces exotiques de tilapia telles que O. niloticus et C. rendalli ainsi que leurs monogènes parasites dans un environnement sauvage représenté par une source fluviale sont discutées. Nos nouvelles données moléculaires sur Cichlidogyrus et Scutogyrus contribuent à l'étude des interrelations phylogénétiques de ces genres de monogènes largement distribués puisque leur composition spécifique est encore incertaine.

Molecular phylogeny of two Rhinoxenus species (Monogenea: Dactylogyridae) from the nasal cavities of serrasalmids (Characiformes: Serrasalmidae) from Brazil.

The dactylogyrid genus Rhinoxenus (Monogenea: Dactylogyridae) is composed of specialized monogeneans infecting the nasal cavities of freshwater fishes from the Neotropical region. This taxon currently comprises 11 species and is easily distinguished from other monogeneans by the absence of the dorsal bar, ventral anchor with inconspicuous roots covered by a sclerotized cap, dorsal anchor greatly modified into a needle-like shape, and hook pair 2 located into bilateral lobes of the trunk. Specimens of Rhinoxenus euryxenus and Rhinoxenus paranaensis were found infecting the nasal cavities of Serrasalmus marginatus and Serrasalmus maculatus, respectively, from the Paraná River basin in Brazil. For the first time, molecular data of Rhinoxenus spp. were obtained and used as a basis for phylogenetic analyses of the genus. Furthermore, our findings represent the first record of R. paranaensis in Brazil.

A new species of Tiddergasilus Marques & Boeger, 2018 (Copepoda: Ergasilidae) from the gills of Astyanax lacustris (Lütken) (Osteichthyes: Characidae) in Brazil.

A new parasitic copepod, Tiddergasilus bipartitus n. sp. (Copepoda, Ergasilidae), is described herein based on three adult females found attached to the gills of the yellow-tail lambari Astyanax lacustris (Lütken), sampled in Pardo River, municipality of Botucatu, São Paulo State, Brazil. Tiddergasilus bipartitus n. sp. was recognized as a new member of the monotypic genus Tiddergasilus Marques & Boeger, 2018 by having: antennule 6-segmented; maxillary basis armed with 2 terminal teeth and ornamented with multiple spinules; second and third leg both with endopod 3-segmented. The new copepod can be distinguished from its congener, Tiddergasilus iheringi (Tidd, 1942), by the morphology of the antennal claw, number of somites/segments in abdomen and fourth leg, and by the ornamentation of the first leg. This report expands the geographic distribution and diversity of fish species parasitized with Tiddergasilus spp. in Brazil. Moreover, it also represents the first report of an ergasilid species in the Pardo River. A list of diagnostic features for the Brazilian species of Ergasilus von Nordmann, 1832 is provided herein, in order to aid comparisons with the species of this complex genus.

Morphological and molecular characterization of the cryptic species Myxobolus cataractae n. sp. (Cnidaria: Myxozoa: Myxobolidae) parasitizing Imparfinis mirini (Siluriformes: Heptapteridae).

We describe Myxobolus cataractae n. sp., found parasitizing Imparfinis mirini from Cachoeirinha stream, a tributary of Pardo River, Paraná River basin, municipality of Botucatu, São Paulo State, Brazil. We based the description on myxospore morphology, histology, and small subunit ribosomal DNA partial sequences. Whitish and elongated mass of myxospores were found in gill filaments, occupying an intrafilamental position. The myxospores were slightly ellipsoidal and the morphometric measurements revealed a myxospore body length of 7.8 ± 0.4 µm; myxospore width of 5.9 ± 0.4 µm; and thickness of 3.9 ± 0.3 µm. The polar capsules are equal in size and measured 3.5 ± 0.2 µm in length and 1.7 ± 0.2 µm in width. The polar tubules had 6-7 coils. Myxobolus cataractae n. sp. is classified as the intrafilamental type and chondreal subtype by the histological analysis of gills. Phylogenetic analysis showed a well-supported subclade formed by species that parasitize gills of Siluriformes, with M. imparfinis as a sister species of Myxobolus cataractae n. sp. Using molecular and morphological characterization, this cryptic species was identified as a new species of the genus Myxobolus.

Description of Two Novel Henneguya (Cnidaria: Myxosporea) Infecting Curimatid Fish, Using Morphological, Histological, and Molecular Analyses.

PURPOSE: We describe two new Henneguya spp. (Myxobolidae) found parasitizing Cyphocharax modestus from Pardo river, Paraná river basin, municipality of Botucatu, São Paulo State, Brazil: Henneguya fastigata n. sp. from gill lamellae and Henneguya pardensis n. sp. from gill arches. We based the descriptions on myxospore morphology, histology, and small subunit ribosomal DNA sequences. METHODS: In this investigation, 50 specimens of Cyphocharax modestus were examined between July and December 2020 for myxozoan infections. Morphological characterization was based on the mature myxospores. The small subunit ribosomal DNA sequences were used for molecular and phylogenetic study. RESULTS: Phylogenetic analysis provided the evolutionary position of these new species with other myxobolids species. Myxospores of the two species had similar morphology and morphometrics, but differed in spore body width and length, and ssrDNA sequences differed by 7.2%. These data supported the diagnosis of the parasites as distinct and novel species. The phylogenetic analysis showed a well-supported subclade formed by species that parasitize curimatid fishes, with Henneguya gilbert as a sister species of Henneguya fastigata n. sp., and Henneguya pardensis n. sp. as a sister species of both species. CONCLUSION: Our analysis was consistent with previous studies suggesting that orders and families of the hosts are strongly correlated with phylogenetic signals in the Myxobolidae. These are the first species of myxozoans described in the Pardo river.

Rhinergasilus unguilongus n. sp. (Copepoda: Ergasilidae): A Gill Parasite of the Freshwater Fish Prochilodus lineatus (Valenciennes, 1837) (Actinopterygii: Prochilodontidae) from the Neotropical Region, Brazil.

PURPOSE: To describe, based on morphological features, a new copepod species of Rhinergasilus, Rhinergasilus unguilongus n. sp., collected from gills of the Streaked prochilod, Prochilodus lineatus (Valenciennes, 1837), sampled in the Veados and Paranapanema Rivers, two tributaries of the Jurumirim Reservoir (Upper Paranapanema River, Paraná River Basin), São Paulo State, Brazil. METHODS: Fish were collected using multi-panel gill nets. The gills of each fish were washed and examined for copepods using a stereo microscope. The copepods found were stored in 70% ethanol, cleared in lactic acid, and mounted in Hoyer's medium. Drawings were made with the aid of a microscope equipped with a drawing tube. RESULTS: The new copepod species can be distinguished from its two congeners, Rhinergasilus piranhus (type-species) Boeger et Thatcher, 1988 and Rhinergasilus digitus Narciso, Brandão, Perbiche-Neves et Silva, 2020, due to its extremely long antennary claw (etymology of the species), being longer than the other antennary segments; third leg lacking any interpodal plate; and third endopodal segment of third leg lacking a distal spine. CONCLUSIONS: Based on the morphological differences, we erected a new species of Rhinergasilus. The new copepod represents the second report of a Rhinergasilus species parasitizing a fish from the Jurumirim Reservoir. It also represents the first report of this genus in P. lineatus.

A New Species of Rhinergasilus Boeger et Thatcher, 1988 (Copepoda: Ergasilidae) from Gills of Astyanax fasciatus (Cuvier, 1819) (Actinopterygii: Characidae).

PURPOSE: To describe a new species of a parasitic copepod, Rhinergasilus digitus n. sp. (Cyclopoida, Ergasilidae), collected from the gills of the red-tailed lambari Astyanax fasciatus (Characiformes, Characidae) in two tributaries of the Jurumirim Reservoir (Upper Paranapanema River), São Paulo State, Brazil: Ribeirão dos Veados and Paranapanema River. METHODS: Fish were collected using multi-panel gills nets. The gill of each fish was washed and examined in a stereo microscope for copepods. The copepods found were stored in 70% ethanol, cleared in lactic acid, and mounted in Hoyer's medium. Drawings were made with the aid of a Leica microscope DMLS equipped with a drawing tube. RESULTS: The new species differs from its congeneric species, Rhinergasilus piranhus (type-species), in having comparatively biggest body size (body length: 535-598 µm in the new species vs. 237-282 µm in R. piranhus); second antennary segment armed with a minute sensillum near middle of inner margin and a row of spinules on outer margin; third exopodal segment of leg 1 with digitiform process; interpodal plates two and three both ornamented with spinules along posterior margin; leg 5 reduced and represented by two unequal setae. CONCLUSIONS: Based on the morphological differences described above, we erected a new species of Rhinergasilus. Rhinergasilus digitus n. sp. is the second ergasilid described from A. fasciatus, as well as it represents the first report of this genus in a characid fish.

A New Genus of Ergasilidae (Copepoda: Cyclopoida) from the Gills of Astyanax fasciatus (Cuvier, 1819) (Actinopterygii: Characidae).

PURPOSE: To describe a new genus and a new species of an ectoparasitic ergasilid (Copepoda, Ergasilidae) parasite of the red-tailed lambari, Astyanax fasciatus, from Jurumirim Reservoir (Upper Paranapanema River), São Paulo State, Brazil. METHODS: The host fish were collected using multi-panel gill nets. The gill of each fish was washed and examined in a stereo microscope for copepods. The copepods found were stored in 70% ethanol, cleared in lactic acid, and mounted in Hoyer's medium. Some specimens were dissected in glycerol medium and then each dissected part was mounted on individual slides. RESULTS: A new genus and a new species of Ergasilidae were described herein. Duoergasilus basilongus n. gen., n. sp. differs from all other ergasilids in having the second and third pair of biramous swimming legs (P2 and P3) each with a 2-segmented endopod, and by its unique maxillary basis, resembling a whip. CONCLUSIONS: The new copepod is the first 'four-legged' ergasilid with all swimming legs having a 2-segmented endopod. Duoergasilus basilongus n. sp. represents the first record of a parasitic copepod on A. fasciatus in Jurumirim Reservoir, as well as its represents the first description to species level of an ergasilid infecting an Astyanax species in Brazil. A key to the 28 accepted genera of Ergasilidae is provided.