A new species of the genus Paradistomum (Platyhelminthes: Trematoda) from Iwasaki's snail-eating snake Pareas iwasakii, with a note on morphological variations of Paradistomum megareceptaculum (Tamura, 1941).

Dicrocoeliid trematodes were detected from Iwasaki's snail-eating snake Pareas iwasakii in Iriomote Island, Okinawa Prefecture, Japan, and described as a new species Paradistomum dextra n. sp. in the present study. This new species can be distinguished from the type series of the other members of the genus based on size of eggs and morphological characteristics of body, oral and ventral suckers, and reproductive organs. However, the new species was hard to distinguish from Paradistomum megareceptaculum infecting snakes in Japan, including Iriomote Island where is the type locality of the new species, because it is closely similar to some part of the broad range of morphological variations in P. megareceptaculum. On the other hand, a partial sequence of 28S ribosomal DNA clearly distinguished these two species. Moreover, the new species' host snake Pareas iwasakii is reported to exclusively feed on land snails while host snakes of P. megareceptaculum feed on small vertebrates, indicating that the new species is also ecologically different from P. megareceptaculum. We also redescribed P. megareceptaculum based on adults sampled in this study and past studies to record the morphological variations of this species.

Integrative Taxonomy of Urocleidoides spp. (Monogenoidea, Dactylogyridae) Parasites of Pseudanos trimaculatus (Characiformes: Anostomidae) from Eastern Amazon, Brazil.

Two new species of Urocleidoides are described from the gills of Pseudanos trimaculatus (Characiformes: Anostomidae) from the coastal drainages of the Eastern Amazon, Brazil. Urocleidoides itabocaensis n. sp. is characterized by having a sclerotized, tubular, sigmoid male copulatory organ (MCO), a circular sclerotized tandem brim associated with the base of the MCO; an accessory piece articulated with the MCO, a V-shaped, divided into two subunits, distal subunit spoon-shaped; and a vaginal pore dextroventral with opening marginal. Urocleidoides omphalocleithrum n. sp. is characterized by presenting a C-shaped or sigmoid MCO; an accessory piece articulated with the MCO, L-shaped, divided into two subunits, distal subunit gutter-shaped; a vaginal pore dextroventral with opening marginal; and a ventral bar broadly V-shaped, with anteromedial projection. Molecular phylogenetic analysis based on partial 28S rDNA and COI mtDNA genes indicate that U. itabocaensis n. sp. and U. omphalocleithrum n. sp. are closely related and appear as a sister group to other Urocleidoides species (U. paradoxus, U. digitabulum and U. sinus) parasitizing anostomid fishes. This study represents the first record of monogenoids from the gills of P. trimaculatus for the Eastern Amazon.

Pathological, morphological, and molecular characterization of the infection by Brachycladium goliath in humpback whale Megaptera novaeangliae.

The humpback whale (Megaptera novaeangliae) is a cosmopolitan migratory, seasonal mysticete that frequents the Brazilian coast. Strands of specimens may occur during the migratory stay in the country. In 2021 and 2022, three live humpback whales stranded on the coast of Rio Grande do Sul and Santa Catarina states in southern Brazil. After euthanasia, specimens were necropsied, and organs were thoroughly examined for lesions. Grossly, in all three cases, the liver exhibited multifocal, irregular, firm, white areas on the hepatic capsule, which extended into the parenchyma. On the cut surface, the livers were yellow to pale brown with orangish to greenish areas, the bile ducts were prominent, thickened, and severely dilated, and leaf-shaped flukes were found inside of them. Additionally, one case showed moderate atrophy of the right hepatic lobe. The histological findings included dilation of bile ducts, hyperplasia of the bile duct epithelium, marked inflammatory infiltration of lymphocytes, plasma cells, and eosinophils, and portal fibrosis. The parasite Brachycladium goliath was both morphologically and molecularly identified based on diagnostic key for trematodes and the original description of the species, and the amplification and sequencing of the ITS-2 region, respectively. Even though hepatic injury was not the primary cause of stranding, it may have contributed to the debilitation of the whales. To the authors' knowledge, this is the first study that reports M. novaeangliae as a definitive host of B. goliath and that describes the lesions caused by the parasite in cetaceans.

Untangling the Derogenes varicus species complex in Scandinavian waters and the Arctic: description of Derogenes abba n. sp. (Trematoda, Derogenidae) from Hippoglossoides platessoides and new host records for D. varicus (Müller, 1784) sensu stricto.

Several studies have shown that the euryxenic trematode Derogenes varicus (Müller, 1784) represents a species complex. Four lineages have been designated (DV1-4) with the DV1 clade corresponding to D. varicus sensu stricto. Herein, we investigate newly collected specimens of D. varicus sensu lato from Scandinavian and Arctic waters using integrative taxonomy. The trematodes were collected from Melanogrammus aeglefinus, Eutrigla gurnardus, Trachinus draco, and Merluccius merluccius off the Atlantic coast of Sweden and from Hippoglossoides platessoides from Arctic Svalbard. 28S sequences of derogenids from Sweden were identical to D. varicus sensu stricto, confirming its euryxeny. The 28S sequences of Derogenes sp. from H. platessoides were identical to Derogenes DV2 and differed from D. varicus sensu stricto by 3% and from Derogenes DV3 by 2%. The 28S sequence divergences of Derogenes sp. from H. platessoides with D. ruber and D. lacustris were 3 and 10%, respectively. ITS2 and cox1 divergences between Derogenes sp. from H. platessoides and other Derogenes species/lineages were at levels of interspecific differences. The species from H. platessoides is described here as D. abba n. sp. We also examined the type material of Progonus muelleri (Levinsen, 1881), the type and only species of the genus Progonus, with redescription and designations of paralectotypes. Based on specimens from Theodor Odhner's collections at the Swedish Museum of Natural History, SMNH, Stockholm, we provide novel morphological and anatomical data for D. varicus sensu lato species complex. Lastly, we investigated Arthur Looss's "lost collection" of Trematodes at the SMNH and characterised a putative species Derogenes sp. "limula".

Title: Démêler le complexe d'espèces Derogenes varicus dans les eaux scandinaves et arctiques : description de Derogenes abba n. sp. (Trematoda, Derogenidae) parasite d'Hippoglossoides platessoides et nouveaux signalements d'hôtes pour D. varicus (Müller, 1784) sensu stricto. Abstract: Plusieurs études ont montré que le trématode euryxene Derogenes varicus (Müller, 1784) représente un complexe d'espèces. Quatre lignées ont été désignées (DV1­4), le clade DV1 correspondant à D. varicus sensu stricto. Ici, nous étudions des spécimens nouvellement collectés de D. varicus sensu lato dans les eaux scandinaves et arctiques en utilisant la taxonomie intégrative. Les trématodes ont été collectés de Melanogrammus aeglefinus, Eutrigla gurnardus, Trachinus draco et Merluccius merluccius au large de la côte atlantique de la Suède et d'Hippoglossoides platessoides du Svalbard arctique. Les séquences 28S des Derogenidae de Suède étaient identiques à D. varicus sensu stricto, confirmant son euryxénie. Les séquences 28S de Derogenes sp. de H. platessoides étaient identiques à Derogenes DV2 et différaient de D. varicus sensu stricto par 3% et de Derogenes DV3 par 2%. Les divergences des séquence 28S de Derogenes sp. de H. platessoides avec D. ruber et D. lacustris étaient respectivement de 3 et 10%. Les divergences ITS2 et cox1 entre Derogenes sp. de H. platessoides et d'autres espèces/lignées de Derogenes se situaient à des niveaux de différences interspécifiques. L'espèce de H. platessoides est décrite ici comme Derogenes abba n. sp. Nous avons également examiné le matériel type de Progonus muelleri (Levinsen, 1881), type et seule espèce du genre Progonus, avec une redescription et des désignations de paralectotypes. Sur la base de spécimens des collections de Theodor Odhner au Musée suédois d'histoire naturelle (SMNH), Stockholm, nous fournissons de nouvelles données morphologiques et anatomiques sur le complexe d'espèces de D. varicus sensu lato. Enfin, nous avons étudié la « collection perdue ¼ de Trématodes d'Arthur Looss au SMNH et caractérisé une espèce putative, Derogenes sp. « limula ¼.

Morphological and molecular characterization of brown-banded broodsacs and metacercariae of Leucochloridium (Trematoda: Leucochloridiidae) parasitizing the semi-slug Omalonyx unguis (Succineidae) in Argentina.

Trematodes of the genus Leucochloridium exhibit an unusual transmission strategy among mollusks (intermediate host). The fully developed sporocyst, housing encysted metacercariae, displays vivid coloration and rhythmic activity in the snail's tentacle, mimicking insect larvae. These strategies attract insectivorous birds, their final hosts, thereby increasing the chances of completing their life cycle. In South America, the reports of adults and larval stages of Leucochloridium are scarce. Brown-banded broodsac of Leucochloridium sp. were obtained from Omalonyx unguis collected in a shallow lake from Corrientes Province, Argentina. Here, we morphologically characterized the larval stages (broodsac and metacercaria), identified the parasite through DNA sequences from nuclear 28S-rRNA (28S) and the mitochondrial cytochrome c oxidase I (COI) genes, and explored its evolutionary affinities with the Leucochloridium species available in GenBank. The present broodsac displays brown bands, with a yellowish background in the first two-thirds and yellowish-white in the last third. Based on morphological comparisons, the broodsac and metacercaria described in this study could not be conclusively categorized under any known South American species of Leucochloridium. In relation to the phylogenetic reconstructions, Leucochloridium sp. consistently clustered with L. perturbatum, and species delimitation analyses resulted in recognized Leucochloridium sp. from Argentina as a distinct species. The DNA sequences obtained in this study constitute the first genetic data generated for sporocyst broodsacs in South America. Future studies, incorporating morphology, genetic, and biological data, will be essential for both species identification and the elucidation of leucochloridiid diversity in the region.

Morphological and molecular data on Pseudozoogonoides ugui Shimazu, 1974 (Digenea: Microphalloidea: Zoogonidae) ex Pseudaspius hakonensis (Günther, 1877) and taxonomic problems in Zoogoninae genera.

New morphological and molecular data were generated for trematodes recovered from the intestines of the fish Pseudaspius hakonensis from two locations in the south of the Russian Far East. Morphologically, these trematodes are identical to Pseudozoogonoides ugui (Microphalloidea: Zoogonidae) from Japan. According to results of phylogenetic analysis based on 28S rDNA sequence data, P. ugui was closely related to Zoogonoides viviparus, and P. subaequiporus appears as a sister taxon to these two species. Genetic distance values, calculated based on both 28S rDNA and ITS2 rDNA, between P. ugui and Z. viviparus represents an interspecific differentiation level. Our results have an ambiguous explanation, indicating that the implication of the presence of one or two compact vitellarial aggregations for the differentiation of Zoogonoides and Pseudozoogonoides should be reconsidered or that our results open up the question of the taxonomical status of trematodes previously denoted as Z. viviparus and P. subaequiporus.

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.

Integrative Taxonomy of Prosogonotrema bilabiatum Vigueras, 1940 (Digenea: Sclerodistomidae): A Parasite in Atlantic Spadefish Chaetodipterus faber (Broussonet, 1782) (Acanthuriformes: Ephippidae) from Brazil.

OBJECTIVES: The present work aims to expand the knowledge of the digenean species Prosogonotrema bilabiatum (Sclerodistomidae), a parasite of Chaetodipterus faber (Acanthuriformes) from Brazil, with an integrative taxonomic approach, using light microscopy, scanning electron microscopy, histology, and molecular biology. METHODS: Forty-one digenean specimens were stained with hydrochloric carmine for morphological studies. Eleven parasites were dehydrated through a graded ethanol series, critical point dried with carbon dioxide, and coated with gold for scanning electron microscopy analysis. Four specimens were processed following histological routine and stained with hematoxylin and eosin and Gomori trichrome. DNA extracted was amplified using 28S partial primer D1-D3. Maximum likelihood and Bayesian inference were performed for phylogenetic analysis. RESULTS: Morphometric and morphological data of the specimens studied ranged in accordance as observed in previous descriptions of the species. Observations from scanning electron microscopy and histology corroborated with those observed in stained whole mounts. Molecular analysis showed that specimens of P. bilabiatum from Brazil clustered with another two sequences of this species from different hosts and localities, with a high node support value. CONCLUSIONS: The integrative taxonomic approach allowed to record and describe new characteristics of P. bilabiatum related to the tegument, the structure and the arrangement of its tissues. The use of molecular markers confirmed that specimens identified as P. bilabiatum from different hosts and localities are all conspecific. Further studies, mainly molecular with less conserved genetic markers, should be carried out to better understand the phylogenetic relationships of Prosogonotrema with Hemiuroidea.

Two new species of Monopisthocotyla (Dactylogyridea: Dactylogyridae) parasitizing the nasal cavities of Bryconops melanurus (Characiformes: Iguanodectidae) from coastal drainages of the Eastern Amazon, Brazil.

The present study integrates molecular and morphological data to support the proposal of new species of Telethecium Kritsky, Van Every & Boeger, 1996 and Diaphorocleidus Jogunoori, Kritsky & Venkatanarasaiah, 2004 from the nasal cavities of Bryconops melanurus (Bloch) of the coastal drainages of the Eastern Amazon. Telethecium tiquira sp. n. is characterized by possessing a male copulatory organ (MCO) with two circular sclerotized brims on the base, a coiled tubular shaft having 1 counterclockwise rings, an accessory piece with enlarged base, pincer-shaped at the distal portion; a sclerotized calyx-shaped vaginal vestibule, and hooks with proximal shank dilatation comprising 3/4 of the shank length. Also, Telethecium tiquira sp. n. can be easily distinguished from other species of the genus by the absence of a protruding bag located at the level of the copulatory complex. Diaphorocleidus forficata sp. n. is characterized by having a MCO with two counterclockwise rings, circular sclerotized tandem brim associated with the base of the MCO; accessory piece non-articulated with the MCO, bifurcate, pincer-shaped; vaginal pore sinistral-ventral with opening marginal, vaginal canal sclerotized, elongated, comprising one loop in the proximal portion before entering to the seminal receptacle; ventral anchor with shaft elongated and evenly curved on the axis; point short and slightly curved, and hooks similar in shape and size, hooks with proximal dilatation comprising approximately of the shank length. Furthermore, D. forficata sp. n. is supported by phylogenetic analysis based on sequences of the partial 28S rDNA gene, which placed D. forficata sp. n. in a well-supported clade of Diaphorocleidus spp. of characiform fishes. Thus, the two new species described here expand our knowledge about the diversity of monopisthocotylan parasites from the nasal cavities of Neotropical fishes. The findings of this study provide valuable insights into the biodiversity of the region and highlight the importance of further research in this area.

Two new species of Diaphorocleidus and new data on D. affinis (Monogenoidea: Dactylogyridae) parasitizing Bryconops cf. affinis (Characiformes: Iguanodectidae) from the Munim River basin, State of Maranho, northeastern Brazil.

During a study conducted on the helminth fauna of fishes in the middle Munim River basin, State of Maranho, northeastern Brazil, three species (two new) of Diaphorocleidus Jogunoori, Kritsky & Venkatanarasaiah, 2004 are reported from the gills of the piaba Bryconops cf. affinis (Iguanodectidae): Diaphorocleidus affinis (Mizelle, Kritsky & Crane, 1968), D. forcipiformis n. sp. and D. munimensis n. sp. New morphological data, drawings, and geographic distribution were provided for D. affinis. Diaphorocleidus forcipiformis n. sp. is characterized by a male copulatory organ with 2 rings counterclockwise and base forming a small tube with two circular flanges and accessory piece bifurcated, claw-shaped, with parts similar in shape and size, one of them distally bifid. Diaphorocleidus munimensis n. sp. is differentiated by the accessory piece, which is composed of two large pieces, united in their proximal part, claw-shaped, and distally hooked. The findings of this initial survey on the helminth parasites of fishes in this area emphasize the importance of carrying out comparable surveys on other fish species. Such surveys may lead to the identification of unknown species or new occurrences.

Microanatomy and ultrastructure of the nervous system of adult Renicola parvicaudatus (Digenea: Renicolidae).

The digenean complex life cycle includes various morphological forms with different locomotory and behavioral activities, and the functional specialization of their nervous system is of importance for the transmission of these parasites. Adult digeneans acquire many adaptive features associated with the final settlement in a vertebrate host. Our study describes the general morphology and ultrastructure of the nervous system of the adult renicolid digenean Renicola parvicaudatus parasitizing the renal tubules of herring gulls. Using immunocytochemical and electron microscopic methods, we identified the distinctive characteristics of ganglia and synapses in the studied species. A comparative analysis of the organization of the nervous system of adult individuals and their continuously-swimming stylet cercariae revealed a number of stage-related differences in the composition of ganglia, the distribution of serotonin- and FMRFamide-immunoreactive neurons, the cytomorphology of neuron somata and free sensory endings. Thus, in adults, the presence of FMRFamide-positive neuron somata, accessory muscle bundles in the ganglionic cortex, and eight types of neuronal vesicles was detected, but no glia-like elements were identified. Their neurons are characterized by a larger volume of cytoplasm and also show greater ultrastructural diversity. Although the sensory papillae of adults do not vary in their external morphology as much as those of larvae, their sensory bulbs are more diverse in cytomorphology. Following our previous data on the "support" cell processes related to various tissues of the larvae and considered as glia-like structures, we also briefly present the identified features of the parenchyma, attachment organs and excretory system of adult individuals. The excretory system of adult R. parvicaudatus is characterized by the presence of unique terminal cells with several flame tufts, which are not typical either for the larvae of this species or for other digeneans studied so far. We also used molecular phylogenetic analysis to clarify species identification.

Description of two new species of dactylogirids (Monogenoidea: Dactylogyridae) from Mylossoma albiscopum (Cope, 1872) (Characiformes: Serrasalmidae) from the Peruvian Amazonia.

INTRODUCTION: Two new dactylogyrid monogeneans, Anacanthorus cultro n. sp. and Notozothecium palometae n. sp., are described based on specimens collected from the gill filaments of Mylossoma albiscopum (Cope, 1872) (Characiformes: Serrasalmidae), a pelagic and herbivore teleost collected in the Tigre river, Loreto, Peru. MATERIALS AND METHODS: Some monogeneans were stained with Gomori's trichrome and mounted in Canada Balsam to determine internal soft structures. Others were cleared in Hoyer's medium for the study of sclerotized structures. Drawings were made using a drawing tube and a microprojector. RESULTS: Anacanthorus cultro n. sp. is characterized by the presence of a rod-shaped male copulatory organ (MCO) lacking featherlike structures, and a knife-shaped accessory piece with a submedial knob. Notozothecium palometae n. sp. can be distinguished from all congeners by its MCO with a subbasal spur and an accessory piece with inverted hammer shaped. CONCLUSIONS: This is the first data on the parasites of M. albiscopum, a popular fish in local markets. Anacanthorus cultro n. sp. is the twenty-fifth documented species of the genus in Peru, while N. palometae n. sp. represents the seventh species of the genus known to infect freshwater fish species in Peru.

Assessment of the genetic diversity of lymnaeid (Gastropoda: Pulmonata) snails and their infection status with trematode cercariae in different regions of Thailand.

Lymnaeid snails are some of the most widespread snails and are the first intermediate host of trematode parasites that affect human and livestock health. A full understanding of the genetic relationship of hosts and parasites is of paramount importance for effective parasite management. The present study assessed the prevalence of trematode larvae in lymnaeid snails and examined the genetic diversity of these snails collected across Thailand. We collected 672 lymnaeid snails from 39 locations in 22 provinces of six regions in Thailand. Subsequently, cercarial infection in the snails was observed by using the shedding method. Lymnaeid snails released 5 types of trematode cercariae, namely, xiphidiocercariae, echinostome cercariae I, echinostome cercariae II, furcocercous cercariae, and strigea cercariae. The phylogenetic analysis based on ITS2 and 28S rDNA sequences revealed 5 cercaria types assigned to four trematode families, of which two belong to the group of human intestinal flukes. Combination of shell morphology and sequence analysis of the mitochondrial COI and 16S rDNA genes, the lymnaeid snails were classified into two species, Radix rubiginosa and Orientogalba viridis. Moreover, the combined dataset of mtDNA genes (COI + 16S rDNA) from R. rubiginosa and O. viridis revealed 32 and 15 different haplotypes, respectively, of which only a few haplotypes were infected with cercariae. The genetic diversity and genetic structure revealed that R. rubiginosa and O. viridis experienced a bottleneck phenomenon, and showed limited gene flow between populations. Population demographic history analyses revealed that R. rubiginosa and O. viridis experienced population reductions followed by recent population expansion. These findings may improve our understanding of parasite-lymnaeid evolutionary relationships, as well as the underlying molecular genetic basis, which is information that can be used for further effective control of the spread of trematode disease.

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.

The first record of Brachylaima ezohelicis (Trematoda: Brachylaimidae) in the red fox (Vulpes vulpes schrencki).

Brachylaima spp. are trematodes that have a unique life cycle as they exclusively use land snails as the intermediate host. Although their intermediate host has been well studied, very little information is available about their definitive host, partly as isolation of its adult stage from wild animals is rare. We found three trematodes in the small intestine of a red fox (Vulpes vulpes schrencki) in Hokkaido, the northernmost island of Japan. The trematodes were identified as Brachylaima ezohelicis based on morphological features and genetic analysis, which is believed to have a definitive avian host. The morphological features of the isolated trematodes were consistent with B. ezohelicis samples grown in the definitive host except for body length. Our study suggests that B. ezohelicis uses mammals as definitive hosts as well as birds.

Dactylogyrids (Platyhelminthes, Monogenea) from the gill lamellae of doradids (Siluriformes) with description of five new species of Cosmetocleithrum and new geographical distribution for known species from the Neotropical Region, Brazil.

Five new species of Cosmetocleithrum were described parasitizing the gill filaments of neotropical doradid fishes. Cosmetocleithrum undulatum n. sp., Cosmetocleithrum brachylecis n. sp. and Cosmetocleithrum ludovicense n. sp. are described from Platydoras brachylecis from a market-place of São Luís, State of Maranhão, Brazil. Cosmetocleithrum sacciforme n. sp. and Cosmetocleithrum basicomplexum n. sp. are described from Oxydoras niger from Juruá River, State of Acre, Brazil. Cosmetocleithrum undulatum and Cosmetocleithrum brachylecis resemble Cosmetocleithrum falsunilatum Feronato, Razzolini, Morey & Boeger, 2022 mainly by the unique male copulatory organ (MCO) morphology but differ from these and all congeneric species mainly by the morphology of the MCO, accessory piece and hooks pairs. Cosmetocleithrum ludovicense is closer to Cosmetocleithrum confusus Kritsky, Thatcher & Boeger, 1986 and to Cosmetocleithrum akuanduba Soares, Santos Neto & Domingues, 2018 but differs from those mainly by the morphology of the accessory piece. Cosmetocleithrum sacciforme differs from all congeneric species mainly by the morphology of the accessory piece formed by a single plate of saccular appearance. Cosmetocleithrum basicomplexum also shares morphological characters with Cosmetocleithrum gigas Morey, Cachique & Babilonia, 2019 considering the size of the body and shape of the anchors, but differs mainly in the morphology of the bars and hooks. Besides the new species, new data are presented for Cosmetocleithrum leandroi Soares, Neto & Domingues, 2018, C. akuanduba and C. confusus regarding morphological characteristics and biogeography.

Title: Dactylogyridae (Platyhelminthes, Monogenea) des lamelles branchiales de Doradidae (Siluriformes) avec description de cinq nouvelles espèces de Cosmetocleithrum et nouvelle répartition géographique d'espèces connues de la région néotropicale au Brésil. Abstract: Cinq nouvelles espèces de Cosmetocleithrum sont décrites, parasitant les filaments branchiaux de poissons Doradidae néotropicaux. Cosmetocleithrum undulatum n. sp., Cosmetocleithrum brachylecis n. sp. et Cosmetocleithrum ludovicense n. sp. sont décrits de Platydoras brachylecis provenant d'un marché de São Luís, État du Maranhão, Brésil. Cosmetocleithrum sacciforme n. sp. et Cosmetocleithrum basicomplexum n. sp. sont décrits d'Oxydoras niger de la rivière Juruá, État d'Acre, Brésil. Cosmetocleithrum undulatum et Cosmetocleithrum brachylecis ressemblent à Cosmetocleithrum falsunilatum Feronato, Razzolini, Morey & Boeger, 2022 principalement par la morphologie unique de l'organe copulateur mâle (OCM), mais diffèrent de ces espèces et de toutes les espèces congénères principalement par la morphologie de l'OCM, de la pièce accessoire et des paires de crochets. Cosmetocleithrum ludovicense est proche de Cosmetocleithrum confusus Kritsky, Thatcher & Boeger, 1986 et de Cosmetocleithrum akuanduba Soares, Santos Neto & Domingues, 2018 mais en diffère principalement par la morphologie de la pièce accessoire. Cosmetocleithrum sacciforme se distingue de toutes les espèces congénères principalement par la morphologie de la pièce accessoire formée d'une seule plaque d'aspect sacculaire. Cosmetocleithrum basicomplexum partage également des caractères morphologiques avec Cosmetocleithrum gigas Morey, Cachique & Babilonia, 2019 compte tenu de la taille du corps et de la forme des anchors, mais en diffère principalement par la morphologie des barres et des crochets. Outre les nouvelles espèces, de nouvelles données sont présentées pour Cosmetocleithrum leandroi Soares, Neto & Domingues, 2018, C. akuanduba et C. confusus concernant les caractéristiques morphologiques et la biogéographie.

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.

The elucidation of the life cycle of Saccocoelioides nanii Szidat, 1954 (Digenea: Haploporidae) using molecular techniques.

In South America, the knowledge of trematode diversity parasitizing freshwater fishes is still scarce, as less than 5% of the freshwater fish fauna has been examined for parasites. A similar situation applies to studies on digenean life cycles, which have become increasingly rare. Among the digenean families parasitizing freshwater fishes in the region, Haploporidae is considered the richest in species diversity. However, information about the developmental stages of haploporid life cycles remains fragmentary. Particularly, in Argentina, nine cercariae attributed to the family Haploporidae have been described using morphological analysis, and only two life cycles of this family have been completely elucidated. In this study a new type of cercaria, morphologically assigned to the family Haploporidae and collected from the snail Heleobia parchappii (Cochliopidae) in Los Padres shallow lake, Buenos Aires province, was identified using morphological and molecular techniques. The molecular analysis, based on 28S and ITS2 sequences, revealed that the cercariae were 100% identical to adult specimens of Saccocoelioides nanii (Haploporidae) parasitizing the fish Prochilodus lineatus (Prochilodontidae) from Los Talas, Buenos Aires province. Our results not only provide information about the life cycle of S.nanii but also show that a molecular and morphological approach can be extremely useful in identifying the developmental stages of digeneans and elucidating their life cycles.

Polymorphic parasitic larvae cooperate to build swimming colonies luring hosts.

Parasites have evolved a variety of astonishing strategies to survive within their hosts, yet the most challenging event in their personal chronicles is the passage from one host to another. It becomes even more complex when a parasite needs to pass through the external environment. Therefore, the free-living stages of parasites present a wide range of adaptations for transmission. Parasitic flatworms from the group Digenea (flukes) have free-living larvae, cercariae, which are remarkably diverse in structure and behavior.1,2 One of the cercariae transmission strategies is to attain a prey-like appearance for the host.3 This can be done through the formation of a swimming aggregate of several cercariae adjoined together by their tails.4 Through the use of live observations and light, electron, and confocal microscopy, we described such a supposedly prey-mimetic colony comprising cercariae of two distinct morphotypes. They are functionally specialized: larger morphotype (sailors) enable motility, and smaller morphotype (passengers) presumably facilitate infection. The analysis of local read alignments between the two samples reveals that both cercaria types have identical 18S, 28S, and 5.8S rRNA genes. Further phylogenetic analysis of these ribosomal sequences indicates that our specimen belongs to the digenean family Acanthocolpidae, likely genus Pleorchis. This discovery provides a unique example and a novel insight into how morphologically and functionally heterogeneous individuals of the same species cooperate to build colonial organisms for the purpose of infection. This strategy bears resemblance to the cooperating castes of the same species found among insects.5.