Priscilla de Oliveira Fadel Yamada

Using an integrative taxonomic approach, we describe two new species of Monopisthocotyla, Mymarothecioides leporini n. sp. and Mymarothecioides paranaensis n. sp., parasitising the gills of anostomid fishes from the Jaguaribe River and Paraná River basins, Brazil. These descriptions represent the first record of species of Mymarothecioides in hosts of the family Anostomidae. Mymarothecioides leporini n. sp. is distinguished by a male copulatory organ (MCO) with a spoon-shaped distal portion and a ventral bar with an ornamented anteromedial process. Mymarothecioides paranaensis n. sp. differs from its congeners by possessing a sclerotised, arcuate MCO with a rounded tip and a rectangular-shaped basal flap. Molecular analyses of Large Subunit ribosomal DNA (LSU rDNA) and Mitochondrial Region of Cytochrome C Oxidase subunit 1 (COI mtDNA) markers support the validity of both taxa, placing them as distinct molecular operational taxonomic units (MOTUs). High genetic distances (17.8%–18.7% for COI) confirmed the separation between the two new species. Additionally, this study provides the first molecular characterisation for the genus. These findings expand the known geographical distribution and host range of Mymarothecioides , contributing to the knowledge of dactylogyrid diversity in Neotropical freshwater systems.

The dactylogyrid fauna recorded in Trachelyopterus galeatus (Actinopterygii: Auchenipteridae) is composed of species belonging to three genera, namely Cosmetocleithrum Kritsky, Thatcher, and Boeger, 1986, Vancleaveus Kritsky, Thatcher, and Boeger, 1986, and Demidospermus Suriano, 1983. During a helminthological survey of T. galeatus from the Ubaldinho weir, Ceará state, Brazil, two new dactylogyrid species were found on the gills of this host. Philocorydoras lophus n. sp. can be distinguished from all congeners by the morphology of the copulatory complex, accessory piece with a crest-shaped flap in the medial portion, and a robust funnel-shaped male copulatory organ (MCO) with a round distal end, whereas all the other congeners possess thin funnel-shaped MCO with tapering distal end. Ameloblastella conus n. sp. differs from all congeners by having a ventral bar with a robust median projection; an MCO with 3½-4½ rings, and mainly by having a sclerotized vaginal duct with a cone-shaped distal portion. This is the first record of species of these two genera (Philocorydoras and Ameloblastella) in a host of the Auchenipteridae.

Purpose: A new species of Gussevia Kohn et Paperna, 1964 (Monopisthocotyla, Dactylogyridae) is described based on specimens recovered from the gills of Astronotus ocellatus (Agassiz, 1831) (Cichliformes, Cichlidae) collected in the Ubaldinho weir, state of Ceará, Brazil. Materials and methods: Some obtained monopisthocotylans were mounted on slides using Gray and Wess medium and studied using an optical microscope with a phase-contrast. Illustrations were made using a drawing tube attached to a Leica DM750 microscope and vectorized using Inkscape 1.4 software. Results: Gussevia lamarckii n. sp. is characterized by having an accessory piece nonarticulated with the MCO base, comprising two dorsal subunits, one Y-shaped and the other one rod-shaped; and an elongated peduncle. Furthermore, the new species can be easily distinguished from the other congeners by possessing (1) a ventral anchor with an external protuberance at the junction between the root and the shaft, and (2) a superficial groove at the base of the dorsal anchor. Conclusions: This study presents a new species of the genus Gussevia , the fourth described from Astronotus fish and the first from A. ocellatus and the aquatic ecosystems of the Caatinga domain.

This study aimed to investigate the parasitic fauna of Prochilodus brevis in two reservoirs in southern state of Ceará, Brazil. Twenty-five individuals were collected from the Lima Campos reservoir, in the municipality of Icó, and 14 from the Ubaldinho reservoir, in the municipality of Cedro. All the analyzed specimens were parasitized by at least one species of metazoan. The parasitic fauna comprised four taxonomic groups: Myxozoa (Henneguya sp. and Myxobolus sp.), Monopisthocotyla (Apedunculata discoidea, Tereancistrum curimba, Tereancistrum pirassununguensis, Tereancistrum takemotoi, Tereancistrum ancistrum, Tereancistrum kritskyi, Tereancistrum scleritelongatum, Tereancistrum spiralocirrum and Gyrodactylidae gen. sp.), Digenea (Austrodiplostomum compactum and Diplostomum lunaschiae), and Acanthocephala (Neoechinorhynchus curemai). In the present study, the parasite community richness of P. brevis, including 14 parasite associations in total, with a maximum of 12 species at each locality, represents an important contribution to the knowledge of fish parasite fauna in the Brazilian semiarid region, which remains poorly studied. These findings not only enhance our understanding of the parasitic biodiversity of fish in the Brazilian semiarid region but also underscore the importance of ongoing studies for the understanding and conservation of aquatic ecosystems.

Based on morphological and molecular data, we describe a new species of Diaphorocleidus parasitizing the nasal cavities of Tetragonopterus argenteus from the Lima Campos weir, municipality of Icó, state of Ceará, Brazil. Diaphorocleidus radius n. sp. resembles other congeners in the morphology of the accessory piece, all by having a bifurcated accessory piece (pincer-shaped), composed of two subunits articulated. However, the new species can be easily distinguished from all congeners by the morphology of the sclerotized structures of the haptor (ventral anchor with well-developed superficial root, ornamented deep root, recurved blade, elongated and lightning-shaped tip; and ventral bar robust, plate-shaped, truncated in lateral ends). Phylogenetic analyses of LSU rDNA and COI mtDNA sequences, conducted using Bayesian Inference and Maximum Likelihood, placed Diaphorocleidus radius n. sp. within Diaphorocleidus , grouping it with species parasitizing acestrorhamphid hosts. Genetic distances between Diaphorocleidus radius n. sp. and other congeneric species such as D. armillatus and D. forficata showed clear differentiation. Both molecular markers support the distinctiveness of Diaphorocleidus radius n. sp., consistent with its recognition as a new taxon.

The integration of molecular data with morphological analysis has greatly advanced the understanding of parasitic diversity, particularly within groups like Dactylogyridae. While morphological features have long been used to classify genera and species, molecular studies have often revealed discrepancies that challenge traditional taxonomies. Urocleidoides (Mizelle & Price, 1964) is one such example, with previous research suggesting it may not be monophyletic. Meanwhile, Annulotrematoides (Kritsky & Boeger, 1995) has lacked any molecular data until now, limiting our understanding of its evolutionary relationships. In this study, we provide the first molecular sequences for Annulotrematoides, which were grouped with Urocleidoides spp. Our analysis of Annulotrematoides bonaerensis Rossin & Timi, 2016 and Urocleidoides surianoae Rossin & Timi, 2016 found parasitizing the gills of Cyphocharax modestus (Fernández–Yépez) revealed a strong phylogenetic relationship between these two species, despite their classification in different genera. This discovery challenges the current morphological–based taxonomy of Urocleidoides and suggests that U. surianoae may not be accurately placed within its genus. The clustering of Urocleidoides with Annulotrematoides for the first time highlights the need for a taxonomic re–evaluation of these groups. Additionally, this work underscores the importance of molecular data in resolving evolutionary relationships and advancing our understanding of parasitic diversity.

Asymmetrione clibanarii Markham, 1975 is a bopyrid ectoparasite of the branchial chamber of hermit crab species from the genus Clibanarius Dana, 1852. This parasite was previously recorded in isolated sites along the western Atlantic: USA, Colombia, and Ascension Island. In this study, we expand the geographical distribution of Asymmetrione clibanarii southward to Brazil. Specimens were collected during low tide from intertidal zones at Paraíso Beach, municipality of Cabo de Santo Agostinho, Pernambuco, Brazil. Three pairs (one female and one male) of Asymmetrione clibanarii were exclusively found in the right branchial chambers of the three specimens of the host Clibanarius antillensis Stimpson, 1859. All females of A. clibanarii were ovigerous and accompanied by males. This record expands the known geographic distribution of A. clibanarii, suggesting its potential presence throughout the range of its host species, which are widely distributed in the Atlantic.

Tereancistrum is a common genus of Neotropical monopisthocotylans; however, information on its diversity and phylogeny remains limited. In this study, we describe four new species of Tereancistrum parasitizing the gills of Prochilodus brevis (Characiformes: Prochilodontidae) from a weir in the state of Ceará, Brazil. Tereancistrum spiralocirrum n. sp. and Tereancistrum scleritelongatum n. sp. are characterized by a dextro-ventral vaginal pore and a Y-shaped dorsal bar. Notably, Tereancistrum spiralocirrum n. sp. is the first species in the genus to possess a male copulatory organ (MCO) with multiple rings (16 to 18). In contrast, Tereancistrum ancistrum n. sp. and Tereancistrum kritskyi n. sp. are distinguished by a sinistral vaginal pore, a sclerotized MCO in the form of a coiled tube with slightly more than one clockwise ring, and an accessory piece that is non-articulated with the base of the MCO. However, Tereancistrum ancistrum n. sp. is unique in lacking a dorsal bar. Sequences of the LSU rDNA obtained from seven species of Tereancistrum parasitizing P. brevis and Leporinus piau, along with published sequences of other Dactylogyridae members, were included in the molecular analyses. Phylogenetic reconstructions supported the monophyly of Tereancistrum.

Parasite biodiversity is underestimated or unknown in many regions, yet information on parasites is critical to understanding ecosystem structure and how this will change into the future. Understanding the diversity and role of parasites is especially important in regions exposed to anthropogenic pressures, such as aquatic ecosystems, as their interactions with other stressors can either exacerbate or mediate negative impacts. Water scarcity in the Brazilian semi-arid has led to a proliferation of reservoirs for human use. These artificial waterbodies host a diversity of taxa, including a large number of fish species; however, fish parasite diversity remains undocumented. This study investigated the parasitological diversity of fishes from reservoirs in the Paraíba and Mamanguape River basins in the Caatinga domain, Brazil – one of the most populated semi-arid regions worldwide. Eight reservoirs were studied, with fish sampled across the two phases of the hydrological cycle (dry and rainy seasons) using gillnets, cast nets, and trawl nets. Endo- and ecto-parasites were identified and enumerated, and parasitological indices (prevalence, intensity, and abundance) were calculated. In total, 1,170 individuals of 21 fish species were examined. Of these individuals, 42% were parasitized with at least one of 54 parasite taxa. We recorded 32 new geographical occurrences of parasites and 23 new fish-parasite interactions, expanding our understanding of ichthyoparasite diversity in the Brazilian semi-arid. Moving forward, it is important to develop knowledge around how anthropogenic changes (e.g., biological invasions, climate, and land use change) influence host-parasite structure and dynamics and ecosystem functioning in these ecosystems.