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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. [ABSTRACT FROM AUTHOR]

This study aimed to comprehensively update and expand the knowledge on the diversity and richness of helminth parasites found in Peruvian amphibians. A systematic search was conducted across primary databases, encompassing both indexed and non-indexed articles, to compile the most recent data. As of the present study, a total of 83 distinct helminth taxa have been documented in association with 78 anuran species of the order Anura, marking a 176.7% increase from previously recorded figures. Nematodes exhibited the highest species richness, totalling 52 taxa (62.65%), followed by trematodes (21 taxa, 25.3%), acanthocephalans and cestodes (4 taxa each, 4.8%), and monogeneans (2 taxa, 2.4%). The overwhelming majority (85.5%) of the collected parasites (71 taxa) were identified as mature helminths, with the remaining 14.5% (12 taxa) in their larval stages. Notably, Cosmocerca brasiliense Travassos, 1925 (Cosmocercidae), and Physaloptera sp. (Physalopteridae) were the most prevalent nematodes, having infected the broadest range of host species. Rhinella marina Linnaeus, 1758 (Bufonidae), emerged as the anuran host with the highest diversity, harboring 17 distinct helminth species. These findings underscore the crucial role of helminth parasites in shaping amphibian ecosystems and their significance as bioindicators of environmental health. Protecting both amphibian hosts and their associated helminth parasites is paramount, as it is intrinsically linked to the preservation of ecological equilibrium within these ecosystems. [ABSTRACT FROM AUTHOR]

Introduction: A new monogenean, Rhamnocercoides lambayequensis n. sp. (Dactylogyridea: Diplectanidae), is described based on the specimens collected from the gills of the Pacific kingcroaker Menticirrhus elongatus (Günther 1864) (Perciformes: Sciaenidae), a demersal fish endemic to Eastern Pacific, captured off the South American Pacific coast, Lambayeque Region, Peru. Materials and Methods: Monogeneans were fixed in hot 4% formalin. Some monogeneans were transferred directly onto a slide in a drop of glycerin–ammonium picrate mixture (GAP). Others were mounted stained with Gomori's trichrome in Canada balsam. Drawings were made using of a drawing tube. Results: The new species is mainly characterized by its MCO, which is tubular and straight, with external (distally expanded and bifurcated) and internal tubes (distally uncovered by external tube). Rhamnocercoides lambayequensis n. sp. is also characterized by having the following features: a weakly sclerotized almost pyriform vagina; haptoral acicular spines with expanded distal portion and by having a small group of haptoral accessory spines associated with haptoral lobes arranged as spikes. Conclusions: This is the first data on the parasites of M. elongatus, a little known, but popular fish in local markets. The present finding brings to two, the number of known species of Rhamnocercoides Luque and Iannacone 1991, and represents the sixth described marine diplectanid species infecting sciaenid fishes from Peru. [ABSTRACT FROM AUTHOR]

Introduction: A new monogenean, Heterocotyle margaritae n. sp. (Monocotylidae: Heterocotylinae), is described based on specimens collected from the gills of the diamond stingray, Hypanus dipterurus (Jordan & Gilbert, 1880) (Myliobatiformes: Dasyatidae) captured off the South Pacific coast, Lima Region, Peru. Materials and methods: Monogeneans were fixed in hot 4% formalin, observed and measured as permanent mounts stained with Gomori's trichrome, and mounted in Canada balsam. Drawings were made with the aid of a drawing tube. Results: The new species is distinguished from all congeners mainly by having a funnel-shaped male copulatory organ, spatulate distally with lateral folds and by its club-shaped accessory piece. The most similar congener, H. americana Hargis, 1955, resemble H. margaritae n. sp. regarding the general structure of the male copulatory organ (funnel-shaped with an accessory piece). However, besides other features, the new species differ from H. americana by having an accessory piece without a dorsal button (vs an accessory piece with a dorsal button in H. americana). Conclusions: This is the first report of a member of Heterocotyle Scott, 1904 in the Southeastern Pacific Ocean. The present finding brings to 20 the number of known species of Heterocotyle, and represents the fifth described monogenean species from Hypanus dipterurus. [ABSTRACT FROM AUTHOR]

Introduction: Specimens of Rhinobatonchocotyle pacifica Oliva & Luque, 1995 (Hexabothriidae) were collected from the gill filaments of Pacific guitarfish, Pseudobatos planiceps (Garman, 1880) (Rhinopristiformes: Rhinobatidae), from off the coast of Chorrillos, Lima, Peru. Since the original description of R. pacifica was incomplete, we herein redescribe R. pacifica based on re-examination of the holotype, paratypes, and newly collected voucher specimens. Nucleotide sequences (18S, 28S) for R. pacifica are presented for the first time, and a phylogenetic analysis conducted. Materials and Methods: Monogeneans were examined with light microscopy and partial sequences of 18S and 28S rDNA genes were obtained. Results: The following taxonomically important morphological features are described: presence of seminal receptacle, spiniform papillae within oral cavity, haptoral sucker sclerites and anchors, hook surface striations, muscular pad associated with each haptoral sucker sclerite (except sclerite 1), muscular bulbs in appendix suckers, and oötype lacking longitudinal rows of large cells (oötype not côtelé). The genital complex is detailed. The diagnosis of Rhinobatonchocotyle is emended to include species with or without seminal receptacle. Representative nucleotide sequences of partial 18S and 28S rDNA genes of R. pacifica were obtained for the first time and used for reconstructing the phylogeny of Hexabothriidae. Conclusion: The phylogenetic reconstruction confirmed the species within the Hexabothriidae. [ABSTRACT FROM AUTHOR]

Cynoscionicola veranoi n. sp. (Monogenea: Microcotylidae) is described based on specimens collected from the gills of lorna drum Sciaena deliciosa (Tschudi, 1846) (Sciaenidae) from Peru. The new species can be differentiated from the other congeneric species by the combination of the following characteristics: (1) haptor with two types of clamps, (2) number and shape of the spines in anterolateral pouches of genital atrium (10-11 curved spines and 3-4 short and bifid spines with a knob in each lateral margin), (3) number and shape of the spines in posterolateral pouches of genital atrium (13-18 bifid spines), (4) 4-6 small spherical unarmed pouches in the genital atrium, and (5) 10-15 testes. In addition, a redescription of Cynoscionicola americanus Tantaleán, Martínez and Escalante, 1987 and Hargicotyle sciaenae Oliva and Luque, 1989 (Diclidophoridae) based on examination of type material and newly collected specimens from snakehead kingcroaker Menticirrhus ophicephalus (Jenyns, 1840) and S. deliciosa (type hosts), respectively, are provided herein. [ABSTRACT FROM AUTHOR]

Introduction: The present study describes three new dactylogyrid species infecting the gill filaments of cichlid fishes (Cichliformes: Cichlidae) from the Amazon basin, Peru: Sciadicleithrum amazoniensis n. sp. on Biotodoma cupido (Heckel, 1840), and Sciadicleithrum feliciajaramae n. sp. and Sciadicleithrum souzatecci n. sp. on Bujurquina peregrinabunda Kullander, 1986., 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: Sciadicleithrum amazoniensis n. sp. is characterized by the presence of a male copulatory organ (MCO) with a coil of approximately 2 counterclockwise rings, an accessory piece articulated to base of the MCO with an expanded proximal end and a bifurcated distal end, and a sinistral vaginal aperture. Sciadicleithrum feliciajaramae n. sp. can be differentiated from all its congeners by its J-shaped MCO with about half a counterclockwise loop and a rod-shaped accessory piece articulated to the base of the MCO, with the distal end bent. Sciadicleithrum souzatecci n. sp. differs from all other members of Sciadicleithrum by having an elongated MCO with about a clockwise loop and a funnel-shaped base. Additionally, Sciadicleithrum souzatecci n. sp. is characterized by its weakly sclerotized, C-shaped accessory piece with a robust middle process., Conclusions: Present findings are added to the other 26 species previously known in Sciadicleithrum.This is the first data on the parasites of B. peregrinabunda., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Two new dactylogyrid species were found infecting the gill filaments of two freshwater fishes collected in the Amazon River basin around Madre de Dios, Peru, namely, Demidospermus wilveri n. sp. from Loricaria sp. (Siluriformes: Loricariidae), and Notozothecium agusti n. sp. from Brycon amazonicus (Spix & Agassiz) (Characiformes: Bryconidae). Demidospermus wilveri n. sp. is characterized by having the following combination of characteristics: (1) a male copulatory organ (MCO) with 1½ rings and a spoon-shaped distal end, (2) an accessory piece with expanded distal end, (3) dorsal and ventral bars with broadly V-shaped and expanded ends, and (4) hooks similar in size. Notozothecium agusti n. sp. differs from its ten congeners by the following combination of characteristics: (1) a coiled MCO with 1½ rings and a sinuous accessory piece with kidney-shaped distal end, (2) an rod-shaped and straight dorsal bar, (3) and anchors with robust superficial roots. Demidospermus wilveri n. sp. represents the thirty-second species in the genus, the eighth from Peru and the fifth parasitising a loricariid catfish from the Peruvian Amazon. Notozothecium agusti n. sp. is the second species of the genus described in Peru and the first species infecting a bryconid host., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Cynoscionella n. g. is proposed for Cynoscionella sanmarci n. sp. and two previously described species of Diplectanum Diesing, 1858 were reassigned into the new genus. The three species are gill parasites of sciaenid fishes (Perciformes: Sciaenidae). The new genus is closely related with Diplectanum (sensu stricto), but is mainly distinguished by its male copulatory organ (MCO) having a slightly sclerotized sleeve-shaped base, lacking accessory piece and accessory copulatory organ. In addition, Cynoscionella n. g. differs from Diplectanum species by having the ventral anchors with well-developed roots, and a prostatic reservoir simple. Cynoscionella sanmarci n. sp. is a parasite of the cachema weakfish Cynoscion phoxocephalus Jordan & Gilbert, a demersal teleost collected from off the coastal zone of Puerto Pizarro, Tumbes region, northern Peru. Diplectanum bilobatum Hargis, 1955 from the spotted weakfish Cynoscion nebulosus (Cuvier) and D. monticellii Domingues & Boeger, 2003 from the smooth weakfish Cynoscion leiarchus (Cuvier), are transferred to Cynoscionella n. g. as Cy. bilobatum (Hargis, 1955) n. comb. and Cy. monticelli (Domingues & Boeger, 2003) n. comb. The present finding represents the first data on the monogenean parasites of C. phoxocephalus. This is the thirteenth marine diplectanid species recorded from Peru., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Bicentenariella n. g. is proposed to accommodate three new species of dactylogyrid monogeneans found on the gills of the threadfin bass Pronotogrammus multifasciatus Gill (Perciformes: Serranidae) from the Southeastern Pacific Ocean off Peru: Bicentenariella claudiae n. sp. (type-species), B. sinuosa n. sp. and B. puertopizarroensis n. sp. Bicentenariella n. g. is mainly characterised by possessing a broadly X-shaped dorsal bar, which has the anterior arms longer than posterior ones and by having a ventral bar with two medial projections. Bicentenariella n. g. is also characterised by having: (i) anchors equal, each with elongate superficial root and short deep root; (ii) an haptor with bilaterally paired lobes, lacking haptoral reservoirs; (iii) hooks with protruded obtuse thumb and undilated shank; (iv) a tubular tapered-shaped male copulatory organ with basal flap bifurcated or not (MCO), lacking accessory piece; (v) a delicate membrane associated with the shaft of the MCO present or absent; (vi) a muscular trumpet-shaped vagina, vaginal aperture dextrolateral; (vii) eyespots absent, accessory chromatic granules present; and (viii) a not lobulated testis. Bicentenariella claudiae n. sp. is characterised by having a MCO with whip-shaped distal end and a rod-shaped ventral bar with hatchet-shaped lateral ends. Bicentenariella sinuosa n. sp. is typified by possessing a MCO with an irregular filamentous membrane surrounding its shaft and a dumbbell-shaped ventral bar. Bicentenariella puertopizarroensis n. sp. can be differentiated from its congeners by having a tubular-shaped MCO with twisted distal end and a narrow W-shaped ventral bar. Parancylodiscoides peruensis Cruces, Chero, Sáez & Luque, 2017 from Hemanthias peruanus (Steindachner) and P. signiferi Cruces, Chero, Sáez & Luque, 2017 from H. signifer (Garman), are transferred to Bicentenariella n. g. as B. peruensis n. comb and B. signiferi n. comb., respectively., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Pronotogrammella n. g. is erected to accommodate Pronotogrammella boegeri n. sp. (type-species), Pr. scholzi n. sp. and Pr. multifasciatus n. sp. (Monogenea: Dactylogyridae). The new species are gill parasites of the threadfin bass Pronotogrammus multifasciatus Gill (Perciformes: Serranidae), a demersal teleost collected from off the coastal zone of Puerto Pizarro, Tumbes, Peru. Pronotogrammella n. g. is mainly characterised by having broadly fork-shaped dorsal anchors, which have an accessory anchor sclerite articulated to the tip of the superficial roots. Pronotogrammella n. g. is also characterised by having: (i) a tubular tapered-shaped male copulatory organ (MCO), filamentous distally, with a clockwise coil at distal end or not, lacking accessory piece; (ii) a dorsal bar with an anteromedial delicate umbelliform membrane supported by two processes; (iii) hooks with upright blunt thumb and uniform shank; (iv) a vaginal aperture dextrolateral; (v) a subquadrangular haptor, with inconspicuous lateral flaps and lacking haptoral reservoirs; and (vi) eye-spot or chromatic granules absent. Pronotogrammella boegeri n. sp. is characterised by its crosier-shaped MCO having a clockwise coil at distal end and by its dorsal bar with a straight anteromedial processes. Pronotogrammella scholzi n. sp. is typified by possessing of a dorsal bar with the anteromedial processes like cow horns, hoof-shaped deep roots of the dorsal anchors and a broader shaft of the MCO. Pronotogrammella multifasciatus n. sp. differs from all congeners by having a tubular MCO with twisted shaft and a base with a short and broad arm and by having an almost dumbbell-shaped ventral bar.

Peruanocotyle n. gen. is proposed to accommodate Peruanocotyle chisholmae n. sp. (Monogenea: Monocotylidae). The new species is a gill parasite of the diamond stingray, Hypanus dipterurus (Jordan Gilbert) (Myliobatiformes: Dasyatidae), a demersal chondrichthyan collected off the coast of Callao, Peru. Peruanocotyle n. gen. is placed in the Dasybatotreminae Bychowsky, 1957 because its anterior attachment organ has multiple glandular openings. Peruanocotyle chisholmae n. gen., n. sp. is unique among the Dasybatotreminae, by having: a well-developed, broadly ovoid anterior attachment organ with numerous grooves and an anteromedial notch; three prominent anterior glands that are connected to numerous peripheral glands; an unusual whip-shaped male copulatory organ composed of four connate tubes; an ejaculatory duct with slightly sclerotized walls where the proximal end has criss-crossed creases and the distal portion is highly convoluted; an ejaculatory bulb with one bipartite internal seminal vesicle; a wheel-shaped haptor with one central loculus and eight peripheral loculi; anchors that are much shorter than the width of marginal membrane and have an accessory sclerotized piece present; four oval testes, arranged in two groups; an ovary that has six clavate, proximal lobules and a distal portion that is strongly coiled; intestinal ceca with large lateral and medial diverticula; an oral opening surrounded by numerous small dome-like papillae; and a single vagina with sclerotized walls. Dasybatotreminae is amended to accommodate the new genus, and the new species is fully described and illustrated herein. The present finding adds to the other three marine monocotylids previously reported from Peru, namely Anoplocotyloides chorrillensis Luque Iannacone, 1991; Anoplocotyloides papillatus (Doran, 1953) Young, 1967 and Monocotyle luquei Chero, Cruces, Iannacone, Sanchez, Minaya, Sáez Alvariño, 2016.

A new genus and species of monogenean belonging to Hexabothriidae, Hypanocotyle bullardi n. gen. n. sp., is described based on specimens collected from the gill filaments of the diamond stingray, Hypanus dipterurus (Jordan et Gilbert) (Myliobatiformes: Dasyatidae), a demersal chondrichthyan collected off the coast of Callao, Peru. Hypanocotyle n. gen. has the following combination of diagnostic features that differentiate it from other hexabothriid genera: haptor symmetrical; vasa efferentia having proximal (narrow, with thin glandular wall) and distal (expanded, interlaced, with thick glandular wall) portions, joining medially to form vas deferens; vas deferens having proximal (expanded, sinuous, with thick glandular wall) and distal (narrow, strongly sinuous, with thin glandular wall) portions; male copulatory organ unarmed, proximal portion slightly sinuous and tube-like, distal portion funnel-shaped; prostatic glands present, distributed around of the MCO; seminal receptacle present; ootype lacking longitudinal rows of large cells (no oötype côtelé); vaginae parallel, with well-differentiated proximal (glandular, narrow, tube-like, slightly sinuous) and distal (musculoglandular, convoluted) portions; gland cells surrounding the vaginal duct along the entire length of distal portion, densely clustered in middle portion; uterine eggs with 2 elongate filaments. Phylogenetic reconstructions by maximum-likelihood method, based on newly obtained partial 18S and 28S sequences, shows that H. bullardi n. gen. is included within the family Hexabothriidae, order Diclybothriidea. This is the second hexabothriid genus recorded from a diamond stingray (Dasyatidae), and the fourth hexabothriid species recorded from Peru. A key to hexabothriid genera is provided., (Copyright © 2018. Published by Elsevier B.V.)