Molecular and SEM studies on Thaparocleidus vistulensis (Siwak, 1932) (Monopisthocotyla, Ancylodiscoididae).

Presenting new molecular and scanning electron microscope (SEM) features, this study gives additional data to the better knowledge of Thaparocleidus vistulensis (Siwak, 1932) (Monopisthocotyla, Ancylodiscoididae), a parasite of the European catfish Silurus glanis Linnaeus, 1758 (Siluriformes, Siluridae) cultured in a commercial fish farm in Hungary. In addition, notes on the early development of sclerotized anchors are also provided. The main morphological difference of T. vistulensis compared to other congeneric species is associated with the male copulatory organ, which exhibits 5-7 loops in the middle of the penis length and a long open V-shaped sclerotized accessory piece, dividing terminally into two parts, securing the terminal part of the penis tube. The present study provides for the first time molecular characterization data based on the 2694 bp long nucleotide sequence of rDNA (ITS1, 5.8S, ITS2, and flanked with partial 18S and partial 28S) submitted in GenBank with the accession number OR916383. A phylogenetic tree based on ITS1 sequences supports a well-defined clade including T. vistulensis, forming a sister group with T. siluri, a species-specific monopisthocotylan parasite to S. glanis. The morphological characterization of T. vistulensis, especially for the male copulatory organ, together with the molecular data in the present study, extends knowledge about this monopisthocotylan species and provides new information for future phylogeny studies.

Two proteocephalid cestodes in the fish Malapterurus electricus and Heterobranchus bidorsalis from Lake Nasser, Egypt: a morphological, molecular, and histopathological study.

Despite the importance of the electric catfish (Malapterurus electricus) and the African giant catfish (Heterobranchus bidorsalis) in the foodweb of Lake Nasser, Egypt, little is known about their diseases and parasitic fauna. This work describes, for the first time, cestodiasis in M. electricus and H. bidorsalis. Corallobothrium solidum and Proteocephalus sp. were identified morphologically and molecularly from M. electricus and H. bidorsalis, respectively. Using PCR, sequencing, and phylogenetic analysis, the two cestodes shared rRNA gene sequence similarities yet were unique and the two new sequences for the proteocephalid genera were submitted to the GenBank database. The prevalence of infection was 75% and 40% for the two fish species, respectively. Infections significantly increased in the summer and spring and were higher in female fish than in male fish. The intestine was the preferred site of the two adult cestodes. However, in the case of C. solidum some larval cestodes were found outside the intestine in between the skin and abdominal musculature, attached to the mesentery, and within intestinal tunica muscularis. Desquamation of the intestinal epithelium and inflammation at the site of infection in addition to congestion of the intestinal wall of the tapeworm infected fish were evident, indicating that C. solidum and Proteocephalus sp. impacted the infected fish. The larval stages of C. solidum attempted to penetrate the intestine and sometimes they were encircled within fibrous layers infiltrated with inflammatory cells. The infected fish's musculature was free of cestode infections. Preventive measures should be implemented to prevent the spread of infections.

Two new Neotetraonchus species (Dactylogyridea, Dactylogyridae) parasitising the Peruvian sea catfish Galeichthys peruvianus (Siluriformes, Ariidae), including molecular data.

As part of a parasitological survey, several specimens of two new monopisthocotylean species, Neotetraonchus celsomanueli sp. nov. and N.peruvianus sp. nov. (Dactylogyridea, Dactylogyridae), were collected from the gill filaments of the Peruvian sea catfish Galeichthys peruvianus (Siluriformes, Ariidae) off Puerto Pizarro, Tumbes region, Peru. Neotetraonchus celsomanueli sp. nov. is characterised by an MCO with a T-shaped distal end and an accessory piece that is ribbed and expanded proximally with a worm-shaped termination. Neotetraonchus peruvianus sp. nov. is typified by its MCO, which has a sledgehammer-shaped distal end and an accessory piece with a claw-shaped distal end. Additionally, N.peruvianus sp. nov. is characterised by its jellyfish-shaped onchium. A partial 28S rDNA sequence was obtained from N.celsomanueli sp. nov., and a phylogenetic analysis was conducted. This analysis revealed the phylogenetic position of Neotetraonchus celsomanueli sp. nov. within a clade comprising monopisthocotylean parasites of diadromous and marine ariid catfishes, including Hamatopeduncularia spp., Chauhanellus spp., Thysanotohaptor Kritsky, Shameem, Kumari & Krishnaveni, , and Neocalceostomoides spinivaginalis Lim, 1995. This finding brings the number of known Neotetraonchus species to seven and represents the first described Neotetraonchus species infecting marine catfishes from Peru.

Immunological and molecular evaluation of zoonotic metacercarial infection in freshwater fish: A cross-sectional analysis.

Improperly cooked fish, carrying active metacercariae (MCs), can pose a significant risk for transmitting fish-borne zoonotic trematodes (FBZTs) to human consumers. This study aimed to enhance our understanding of FBZTs by conducting a comprehensive cross-sectional analysis involving various fish species, such as Nile tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus), and red-belly tilapia (Tilapia zillii). These fish specimens were collected from distinct Egyptian governorates, specifically Giza, Kafr al-Shaykh, and Fayoum. The recovered flukes from experimentally infected domestic pigeons were identified as Prohemistomum vivax, Haplorchis pumilio, and Pygidiopsis genata based on morphological features. Furthermore, the identity of the retrieved adult flukes was confirmed using three species-specific primers for PCR amplification and sequencing analysis of the ITS rDNA region and have been deposited in GenBank with the following accession numbers: P. vivax (OR291421.1 and OR291422.1), P. genata (OP099561.1), and H. pumilio (OM439581.1-OP090510.1). Quantitative real-time PCR targeting the immunological genes Tumor Necrosis Factor-alpha (TNF-alpha) and Interleukin-1 (IL-1Β) was employed to compare the cellular immune response between infected with EMCs and uninfected O. niloticus. The results indicated a significant increase in TNF- and IL-1Β levels in FBZTs-infected vs un-infected fishes. Importantly, the presence of adult flukes and EMCs led to substantial histological alterations in both experimentally infected pigeons and naturally infected fish tissues. These changes included the necrosis of fish muscle bundles and a pronounced inflammatory reaction with muscular necrosis in the digestive tracts of experimentally infected pigeons.

Evolutionary morphology of haptoral anchors in monogenoids (Dactylogyridae) of marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America.

Exploring the phylogenetic signal of morphological traits using geometric morphometry represents a powerful approach to assess the relative weights of convergence and shared evolutionary history in shaping species' forms. We evaluated the phylogenetic signal in shape and size of ventral and dorsal haptoral anchors of 10 species of monogenoids (Hamatopeduncularia, Chauhanellus and Susanlimocotyle) occurring in marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America. The phylogenetic relationships among these species were mapped onto the morphospaces of shape and size of dorsal and ventral anchors. Two different tests (squared change-parsimony and Kmult) were applied to establish whether the spatial positions in the phylomorphospace were influenced by phylogenetic relationships. A significant phylogenetic signal was found between anchor form and parasite phylogeny. Allometric effects on anchor shape were non-significant. Phylogenetically distant species on the same host differed markedly in anchor morphology, suggesting little influence of host species on anchor form. A significantly higher level of shape variation among ventral anchors was also found, suggesting that the evolutionary forces shaping ventral anchor morphology may operate with differing intensities or exhibit distinct mechanisms compared to their dorsal counterparts. Our results suggest that phylogenetic relationships were a key driver of changes in shape (but not size) of anchors of monogenoids of South American ariids. However, it seems that the emergence of the digitiform haptor in Hamatopenducularia and in some species of Chauhanellus played an important role in the reduction in anchor size and may cause secondary losses of anchors in other groups of monogenoids.

Cytotoxicity and immunological impact of Trypanosoma sp. infection on blood parameters of wild African catfish, Clarias gariepinus.

Fish trypanosomiasis is a common blood parasitic disease transmitted by aquatic invertebrates, such as leeches. This study aims to shed light on the cytotoxicity of Trypanosoma sp. on erythrocytes and its impacts on the innate immune response (serum lysozyme activity, nitric oxide production, phagocytic activity, serum total protein, and globulin) in wild African catfish, Clarias gariepinus. One hundred catfish were examined using blood smears stained with Giemsa and confirmed with PCR. The prevalence of infection was found to be 10% by microscope detection and 15% by PCR. The morphological identification of Trypanosoma as Trypanosoma mukasai was determined. Additionally, this study included previously undescribed features of Trypanosoma, such as the width of the anterior and posterior body, the length of the posterior pale region, and the number of folds. Various alterations in erythrocytes were observed, totaling 54.57%. Nuclear abnormalities, including fragmented nuclei, eccentric nuclei, and micronuclei, were also reported. Infected fish showed a reduction in serum total protein and globulin levels, while nitric oxide production, lysozyme activity, and phagocytic activity exhibited a significant increase compared to non-infected fish. We believe that our findings will contribute valuable data to the morphological and molecular identification of Trypanosoma sp. in African catfish, as well as their cytotoxic impact.

New species of Demidospermus (Monogenoidea: Dactylogyridae) from the gills of Pseudoplatystoma punctifer (Siluriformes: Pimelodidae) collected in the Peruvian Amazonia.

Pseudoplatystoma punctifer is a catfish species that occupies the first place in the statistics of fishing landings in the region of Loreto, being of economic importance in the Peruvian Amazonia. As an initiative to know the parasites present in the gills of P. punctifer from the Peruvian Amazonia, a study was carried out with fish collected in the Belén Market, in Loreto-Peru. Specimens were provided between June and October 2018 from local fishermen from the Belén Market, in Loreto-Peru and samples were processed and analyzed in the "Laboratorio de Parasitología y Sanidad Acuícola" from the "Instituto de Investigaciones de la Amazonía Peruana" (IIAP) in Iquitos, Loreto-Peru. The analyzes of the gills revealed the presence of two new species of Monogenoidea: Demidospermus aureagarciae n. sp. and D. doncellae n. sp. These species are unique among congeners by the morphology of the copulatory complex and vagina. Demidospermus aureagarciae n. sp presents a male copulatory organ as a coiled tube, with a complete counterclockwise ring, with dilated base with a developed sclerotized margin, from which a flap projects; a concave accessory piece, with a tapered and curved distal part and a saculiform vaginal vestibule, connected to the vaginal canal. Demidospermus doncellae n. sp. presents a copulatory complex that is an elongated coiled tube, with approximately three clockwise rings, with dilated base with a developed sclerotized margin, from which a flap projects; an accessory piece sheath like, and a sclerotized vagina with dextral position, with saclike vaginal vestibule, connected to an elongated canal.

Seasonal study of the relationship between the condition factor and the monogeneans parasite density of Heterobranchus isopterus Bleeker, 1863 and Clarias gariepinus (Burchell, 1822) fished in the Bagoué River (North-Western, Ivory Coast).

A comparative study on the relationship between condition factors and parasite density of Heterobranchus isopterus and Clarias gariepinus was conducted during the wet and dry seasons. Specimens were collected from the Bagoué River from August 2020 to July 2021. Two hundred eighty-four specimens of H. isopterus and 272 specimens of C. gariepinus were collected from all stations during both seasons. The standard length and weight of the fish were recorded and the condition factor was calculated for each individual. The gills were examined under a binocular loupe and the monogeneans were collected. Parasite counts showed that for both host species, the total number of parasites was higher in the dry season than in the wet season (p < 0.05). The correlation coefficient was determined to investigate the relationship between the condition factor and the total number of parasites. A significant positive correlation was observed between the condition factor and the number of parasites in both host species during the wet season. A negative correlation was observed in both hosts during the dry season. The information from this study could be taken into consideration in the sanitary management of the fish farming industry. The dry season could be considered as the season with favorable conditions for the development of most parasite species.

Identification of Myxobolus distalisensis n. sp. (Cnidaria: Myxozoa) infecting yellow catfish Tachysurus fulvidraco (Richardson), with a supplement description of M. voremkhai (Akhmerov, 1960) Landsberg and Lom, 1991.

With growing scale of intensive fish cultivation, the risk of parasite infection in commercial fish is increased. Precisely identifying and characterizing the parasites that infect the farmed fish is critical to understanding the dynamics of their communities. Here, two species of Myxobolus were identified in farmed yellow catfish Tachysurus fulvidraco (Richardson) in China. Myxobolus distalisensis n. sp. developed plasmodia in the gill filaments, with oval to elliptical myxospores measuring 11.3 ± 0.6 (10.4-12.6) × 8.1 ± 0.3 (7.5-8.6) × 5.5 ± 0.2 (5.2-5.8) µm. Two pyriform polar capsules of equal size were measured 5.3 ± 0.4 (4.5-6.3) × 2.7 ± 0.1 (2.3-3) µm. Myxobolus voremkhai (Akhmerov, 1960) Landsberg and Lom, 1991 developed plasmodia in the gill arch and had a myxospore morphology similar to the conspecific isolates described in previous studies. The consensus sequences of M. distalisensis was remarkably distinct from those deposited in the GenBank, with exception of whereas M. voremkhai showing 99.84% identity. The genetic data on both isolates differed considerably from each other, revealing only 86.96% molecular identity. Histologically, M. distalisensis resided in the filament cartilage, and the aggressive proliferation of the sporogenic stages led to lytic cartilage corrosion. In contrast, plasmodia of M. voremkhai grossly observed at the base of the gill filament were embedded by the connective tissue in the gills arch. Phylogenetically, both isolates were separately placed in different subclades, indicating difference in their evolutionary history. Besides, the taxon under the family Myxobolidae was demonstrated non-monophyletic origins, and parasite radiation largely followed their host affinity.

A New Species of Unibarra (Monogenoidea, Dactylogyridae) Parasite of Oxydoras niger From Juruá River, State of Acre, Brazil and New Data for U. paranoplatensis.

Monogenoids are ectoparasites that have a simple one-host lifecycle, high species diversity, and a relatively high host specificity. During studies on the helminth fauna of fishes from the Jurua River, in Acre State, Brazil, a new species of the monotypic genus Unibarra Suriano & Incorvaia, 1995 was found parasitizing Oxydoras niger Valenciennes, 1821. Unibarra juruaensis n. sp. is allocated in the genus based on the presence of a single haptoral bar, marginal hooks similar in shape and size, gonads partially overlapping, and a conspicuous filament which connects the base of the male copulatory organ with the accessory piece. The new species differs from the only species of the genus by the smaller size of the body and of the structures, by the morphology of copulatory complex, with an accessory piece thinner than that of U. paranoplatensis Suriano & Incorvaia, 1995 and by the presence of two eyespots. The type species, U. paranoplatensis, is referred in a new host, Pimelodus blochii Valenciennes, 1840, with new morphological data. A table of measurements of the new species and previous and the present reports of U. paranoplatensis is presented.

Parasitic fauna of farmed freshwater ornamental sutchi catfish (Pangasiandon hypophthalmus) and silver dollar (Metynnis hypsauchen) in Alborz province, Iran.

BACKGROUND: Parasitic infestations are one of the most significant problems in global aquaculture. In addition to direct economic losses due to significant mortalities, parasites may have a significant negative impact on the fish's behaviour, energetic demands, trophic position, interspecific competition, growth rate, and reproductive function. OBJECTIVES: We conducted the present study to evaluate the infection status of parasitic pathogens in freshwater sutchi catfish (Pangasianodon hypophthalmus) and silver dollar (Metynnis hypsauchen) farmed in Alborz province of Iran. METHODS: Between January and February 2021, 140 ornamental fish, including 70 sutchi catfish (P. hypophthalmus) and 70 silver dollar (M. hypsauchen), were delivered from various ornamental fish farms for parasitological analysis. Thorough macroscopic and microscopic examinations were performed to detect parasitic infections in delivered freshwater ornamental fish. RESULTS: A total of six parasite species, including five protozoan species (Nyctotherus piscicola, Trichodina heterodentata, Ichthyophthirius multifiliis, Protoopalina sp., and Hexamita sp.) and one monogenean species (Ancyrocephalus sp.), were identified in the examined fish. The overall prevalence of the recovered parasites was 46.43% (65/140) of the fish. CONCLUSIONS: In the current study, several parasites, including Hexamita sp., Ancyrocephalus sp., Protoopalina sp., and N. piscicola, were identified as the first records of the sutchi catfish (P. hypophthalmus) and/or silver dollar (M. hypsauchen), and these two fish species are known as new hosts for the isolated parasites in ornamental fish farms in Iran. Assessing the parasitic fauna of ornamental fish is therefore critical for preventing parasite introduction into adjacent provinces as well as neighbouring countries and promoting fish health.

An improved method for isolating camallanid (Nematoda) spicules for scanning electron microscopy.

In nematodes, the structure of male copulatory organs is a significant taxonomic distinguisher and includes the morphometry of the spicules. The description of these structures mainly relies on the study of whole mounts using light microscopy. In rare instances, protruding spicules have been described with scanning electron microscopy. Even fewer studies have described the ultrastructure of isolated spicules following their isolation. In the present study, two different methods of spicule isolation were performed on two parasitic camallanid nematodes, Procamallanus (Procamallanus) pseudolaeviconchus Moravec & van As, 2015 and Paracamallanus cyathopharynx (Baylis, 1923), from African sharptooth catfish to determine the practicality and efficiency of the methodologies. The first method involved using sharpened tungsten needles and microdissection of the spicule pouch to free the spicules, followed by soft tissue digestion if necessary. Alternatively, the spicules were isolated through mechanical release instead of dissection in a method developed in the current study. This involved freeing the spicules from surrounding soft tissue by placing live specimens between a coverslip and a glass slide in a drop of water and exerting pressure with small rotational movements. Both methods yielded favourable results, but Method 2 is recommended for future studies due to the many advantages.

Neotropical sisterhood: new species of Gyrodactylus von Nordmann, 1832 (Platyhelminthes: Monogenea) infecting Rhamdia guatemalensis and Rhamdia laticauda (Siluriformes: Heptapteridae) in Mexico.

We describe two new species of monogenean parasites of the genus Gyrodactylus von Nordmann, 1832 infecting Neotropical catfishes (Siluriformes) in southern Mexico: Gyrodactylus chulini n. sp. from 'chulín', Rhamdia laticauda collected in Oaxaca; and Gyrodactylus juili n. sp. from 'juil', Rhamdia guatemalensis from Veracruz. Morphologically, both new taxa are similar to Gyrodactylus spp. infecting catfishes (Siluriformes) in South America. Sequences of the internal transcribed spacers (ITS1-5.8S-ITS2 rDNA), the D2+D3 domains of the large ribosomal subunit (28S rDNA) and the cytochrome oxidase II (COII) gene were obtained from multiple parasite specimens and analysed using Bayesian inference. Phylogenetic hypotheses using ITS rDNA and COII genes, recovered two new Gyrodactylus species from Rhamdia spp.: G. chulini n. sp.; and Gyrodactylus juili n. sp., which are sister species to Gyrodactylus lilianae, a parasite of Rhamdia quelen in Brazil, and show strong affinity to other gyrodactytlids infecting Neotropical catfishes. This suggests that these new taxa, the first gyrodactylids described from Rhamdia spp. in Mexico, co-migrated to Tropical Middle America with their Neotropical catfish hosts, after the emergence of the Isthmus of Panama.

Spirocamallanus delirae n. sp. (Nematoda, Camallanidae), a parasite of Propimelodus eigenmanni (Siluriformes: Pimelodidae) from the Brazilian Amazon.

A new species of Spirocamallanus Olsen, 1952 (Camallanidae), is described based on specimens found parasitizing Propimelodus eigenmanni (Siluriformes), an Amazonian fish. The new species has buccal capsule with 15-19 spiral ridges, males with caudal alae supported by 3 pairs of precloacal and 6 pairs of postcloacal papillae, and two terminal spikes on tail end, and females with a digitiform projection ending in two small spikes on tail end. The new species shares characteristics with a group of Neotropical Spirocamallanus that are characterized by the presence of caudal alae, 3 pairs of precloacal papillae, unequal spicules and the presence of spines on the tail tip of males. Several species of this group have been reported from marine environments, in contrast with Spirocamallanus delirae n. sp., which occurs in Amazon freshwaters. Among the Brazilian congeners placed in the referred morphological group are S. rarus, S. freitasi, S. macaensis, and S. halithophus, the last two being parasites of marine fishes. The new species differs from S. rarus (3-4), S. macaensis (12-15), and S. halithophus (10-15) based on the number of spirals in the buccal capsule and from S. fretasi based on the morphology of the larger spicule that is bifid in the former and undivided in the new species. The present description of Spirocamallanus delirae n. sp. adds new data to the biodiversity of parasites from freshwater siluriform catfish in the Neotropical region.

Review of the metazoan parasites of the economically and ecologically important African sharptooth catfish Clarias gariepinus in Africa: Current status and novel records.

One of the most widely distributed African freshwater fish is the African sharptooth catfish Clarias gariepinus (Burchell) that is naturally distributed in 8 of the 10 ichthyofaunal regions of this continent. Clarias gariepinus is a highly valued and cheap staple to local communities and an ideal aquaculture species. Consequently, interest in the parasitic communities of C. gariepinus has increased as parasites may accidentally be ingested by humans when eating uncooked fish or can be introduced into culture systems through fish stocks supplied from local rivers which affect yield, growth, and marketability. This review provides an overview of the ∼107 metazoan parasite species known to parasitise C. gariepinus in Africa and their general life cycles, morphology, paratenic and post-cyclic infections, and the biogeography and validity of records are discussed. A brief overview is included on the application of some of these parasites in environmental studies and their link to human health.

Cucullanus pinnai pinnai and C. pinnai pterodorasi (Nematoda Cucullanidae): what does the integrative taxonomy tell us about these species and subspecies classification?

Cucullanus pinnai has been divided in two subspecies (C. pinnai pinnai and C. pinnai pterodorasi) based on the morphology of oesophastome. While C. pinnai pinnai apparently shows low host specificity and broad geographic occurrence, with certain morphological variations, C. pinnai pterodorasi was reported once, parasitizing Pterodoras granulosus. We used an integrative taxonomic approach to evaluate whether or not populations of C. pinnai pinnai from Trychomycterus spegazzinii (Escoipe River, Argentina) and Pimelodus fur (Miranda River, Brazil), and of C. pinnai pterodorasi from Pterodoras granulosus (Miranda River, Brazil) are conspecific. Parasites were observed using light microscopy and genetically characterized based on partial sequences of the 18S and 28S rDNA, ITS1-5.8S-ITS2, and COI mtDNA. Phylogenies were reconstructed and the Generalized Mixed Yule Coalescent (GMYC), Poisson Tree Process (bPTP), and Automatic Barcode Gap Discovery (ABGD) were used for species delimitation purposes. The present samples formed well-supported monophyletic assemblages, corroborating in part the results of morphological analyses; however, they grouped according to geographic origin. Species delimitation suggested conspecificity of C. pinnai pinnai with C. pinnai pterodorasi from Brazil; consequently, the morphology of oesophastome may be an intraspecific variation. Results also indicated that C. pinnai may represent a species complex as samples from Argentina were suggestive of an independent specific entity. However, definitive affirmations are premature, since there is no autapomorphy for separating C. pinnai from Brazil and Argentina and sampling was limited to three host species from two river basins. The phylogenetic reconstructions also confirmed the artificiality of some genera within Cucullanidae.

Diversification processes between monogenoids (Dactylogyridae) and their marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America.

Due to their high specificity, monogenoids from fish provide an interesting model to study historical associations of hosts and parasites. High agreement between host and parasite phylogeny is often interpreted as evidence of cospeciation. However, cophylogenetic signal may also arise from other, either adaptive or non-adaptive, processes. We applied the recently developed Cophylospace Framework to better understand the evolutionary relationship between monogenoids and marine catfish from the Atlantic coast of South America. The associations between 12 marine catfish and 10 monogenoid species were assessed. Molecular data of host and parasite species were used for phylogenetic reconstruction. We used anchor morphology based on Procrustes coordinates to evaluate whether closely related hosts are associated with morphologically similar parasites. To assess the association between parasite phylogeny and host morphology, we produced a distance matrix based on morphological characters of catfishes. Agreement between phylogenies and between phylogeny and morphology was measured using Procrustes R2 computed with PACo. The parasite phylogeny obtained in this study represents the first complete phylogenetic hypothesis of monogenoids parasitizing ariids from South America. The Cophylospace analysis suggested that phylogenetic and morphological distance of monogenoids contributes similarly to explain the pattern of host­parasite associations, whereas parasite phylogeny is more strongly associated with the morphological traits of the hosts than with host phylogeny. This evidence suggests that cospeciation is not a major force accounting for diversification in the monogenoids studied. Rather host morphological traits seem to be a more important driver, which conforms with evidence from other host‒monogenoid systems.

New species of Philocorydoras Suriano, 1986 (Monogenoidea: Dactylogyridae): Philocorydoras maltai n. sp., Philocorydoras beleniensis n. sp. and Philocorydoras alcantarai n. sp. from the gills of callichthyids (Siluriformes: Callichthyidae) from the Peruvian Amazonia.

During a research on gills ectoparasites of callichthyids fishes from the Peruvian Amazonia, the following new monogenoideans species were recovered: Philocorydoras maltai n. sp. from Corydoras splendens (Castelnau) and Brochis multiradiatus (Orcés, V.); Philocorydoras beleniensis n. sp. from C. ambiacus (Cope) and C. agassizii (Steindachner) and Philocorydoras alcantarai n. sp. from C. virginiae (Burgess). All new species described herein are mainly differentiated from their congeners based on the morphology of the copulatory complex. In P. maltai n. sp. the cirrus corresponds to a very thin curved and slightly sclerotized tube, with an inflated and distally narrow base; the accessory piece is sclerotized, curved in the anterior portion, sickle-shaped and with the terminal portion slightly bent. In P. beleniensis n. sp. the cirrus corresponds to a slightly curved sclerotized robust tube with its base folded back ending in three finger-like projections; the accessory piece is sclerotized, cobra-shaped, distal part with an inwardly-directed curvature. In P. alcantarai n. sp. the cirrus corresponds to a sclerotized arched long tube, with sclerotized accessory piece with a bifid termination, curved in its middle portion.

Temporal and seasonal variation of metazoan parasites in Pimelodus ornatus (Siluriformes: Pimelodidae) from the Amazon River, Brazil.

This study investigated the influence of temporal and seasonal (i.e., rainy and dry seasons) in communities and infracommunities of metazoan parasites in Pimelodus ornatus, a Siluriformes from the Amazon River in the state of Amapá, in northern Brazil. A total of 144 fish were collected during 2020 and 2021. In 2020, five species of parasites were found (1 Monogenea, 3 Nematoda, and 1 Cestoda), and in 2021, seven species of parasites were found (1 Monogenea, 3 Nematoda, 1 Cestoda, 1 Digenea, and 1 Crustacea). In 2020, Spirocamallanus inopinatus was dominant, while in 2021, Contracaecum sp. was dominant. Brillouin diversity, species richness, and evenness were higher in 2021. There were differences for some parasite infracommunities between years and between seasonal periods. Brillouin diversity and species richness were higher in the rainy season, but there were no differences in evenness and Berger-Parker dominance between the seasonal periods. Temporal and seasonal variations were mainly influenced by rainfall levels, oxygen levels, and environmental temperature and, later, by the availability of infective stages of parasites in the environment and the size of the hosts. Lastly, the influence of the temporal and seasonal variations on the structure of communities and infracommunities of parasites was weaker than expected due to the low infection rates of the majority of parasites found.

Cosmetocleithrum infinitum sp. n. (Monogenoidea: Dactylogyridae) parasite of the gills of Anadoras grypus (Siluriformes: Doradidae) from the Amazonas river, in Loreto, Peru.

Among Siluriformes, fishes of the family Doradidae harbor dactylogyrids from Cosmetocleithrum Kritsky, Thatcher and Boeger, 1986. Anadoras grypus (Cope) (Siluriformes, Doradidae) locally named in Peru as "rego-rego" hosts a new species of Cosmetocleithrum described herein as Cosmetocleithrum infinitum sp. n. The male copulatory organ (MCO) and vagina of the new species reveal its morphological uniqueness among members of Cosmetocleithrum. The MCO in the new species is an elongate, sclerotized sinuous tube, with 12 expanded coils, with counterclockwise orientation; the accessory piece is sclerotized, comprising a kind of cone, with a large opening at its base, with a branch in the posterior middle part and with pointed ends. The vagina is a sclerotized long, winding, coiled tube with a cone-shaped opening.