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.

Two new species of dactylogyrids (Monogenea: Dactylogyridae) infecting the gill filaments of fishes in the southern Peruvian Amazon.

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.

A redescription of Hedruris moniezi Ibáñez & Córdova, 1976 (Nematoda: Hedruridae), an endoparasite of the Titicaca water frog Telmatobius culeus (Garman, 1876) (Anura: Telmatobiidae), with comments on all other known Hedruris species in Peru.

Hedruris moniezi Ibáñez & Córdova, 1976 (Nematoda: Hedruridae) was described using light and scanning electron microscopy (SEM) based on specimens collected from the stomach of Telmatobius culeus (Anura: Telmatobiidae) in Peru. We observed some characteristics not reported previously, including sessile and pedunculated papillae and amphid on the pseudolabia, bifid deirids, morphology of the retractable chitinous hook, morphology and arrangement of the plates on ventral surface of the posterior end of the males, and arrangement of caudal papillae. Telmatobius culeus represents a new host of H. moniezi. In addition, H. basilichtensis Mateo, 1971 is considered to be a junior synonym of H. oriestae Moniez, 1889. A key to valid species of Hedruris in Peru is provided.

Four new species of Anenterotrema Stunkard, 1938 (Digenea: Dicrocoellidae) infecting phyllostomid bats in the Peruvian Amazon.

During a research of digeneans (Platyhelminthes: Trematoda) infecting leaf-nosed bats (Chiroptera: Phyllostomidae) from the Kawsay Biological Station in Madre de Dios, southeastern Peru, four new species were described based on light and scanning electron microscopy (SEM): Anenterotrema paramegacetabulum n. sp. from the seba's short-tailed bat Carollia perspicillata Linnaeus, A. hastati n. sp., A. kawsayense n. sp., and A. peruense n. sp. from the greater spear-nosed bat Phyllostomus hastatus (Pallas). Anenterotrema paramegacetabulum n. sp. differs from all congeners by having a terminal oral sucker, a transversely elongated ventral sucker without clamp-shaped, and by having the testes located immediately posterior to ventral sucker. Anenterotrema hastati n. sp. is easily differentiated from the other congeneric species by having an almost clamp-shaped oral sucker, well-developed cirrus sac, a bilobulated seminal receptacle, and a group of well-developed unicellular glands located anterolateral to cirrus sac. Anenterotrema kawsayense n. sp. is characterized by possessing protuberances on the anterior margin of the oral sucker. Anenterotrema peruense n. sp. is mainly characterized by having the testes located principally anterior to ventral sucker and the cirrus sac located perpendicular to midline of the body. The present finding brings to 12, the number of known species of Anenterotrema. A key to the species of Anenterotrema Stunkard, 1938 is provided.

Proposal of Cynoscionella n. g. (Monogenea: Diplectanidae), with description of a new species from the gills of Cynoscion phoxocephalus (Actinopterygii: Sciaenidae) in Peru and reassignment of two species of Diplectanum Monticelli, 1903.

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.

Six new species of Rhamnocercus Monaco, Wood & Mizelle, 1954 (Monogenea: Diplectanidae) infecting the gills from South American sciaenid fishes.

A parasitological survey searching diplectanids (Monogenea: Diplecatnidae) infesting the gills of marine fishes from South America was carried out during the 2019-2020 period. The gills of four sciaenid species, 2 Cheilotrema fasciatum Tschudi, 1 smalleye croaker Nebris microps Cuvier, 2 royal highhat Pareques lanfeari (Barton), and 1 minor stardrum Stellifer minor (Tschudi), were sampled. Six new species of Rhamnocercus Monaco, Wood & Mizelle, 1954 were described: Rhamnocercus chacllae n. sp. and Rhamnocercus chaskae n. sp. from P. lanfeari, Rhamnocercus fasciatus n. sp. from C. fasciatum, Rhamnocercus microps n. sp. from N. microps, and Rhamnocercus rimaci n. sp. and Rhamnocercus tantaleani n. sp. from S. minor. Rhamnocercus chacllae n. sp. can be differentiated from its congeners by its L-shaped male copulatory organ (MCO) and by having an anteromedial slight notch at ventral bar. Rhamnocercus chaskae n. sp. differs from the other species of the genus by its long and straight MCO with bifid distal end and by having haptoral accessory spines at level of ventral bar with quadrifid distal portion. Rhamnocercus fasciatus n. sp. is characterized by possessing a straight and long MCO with truncated distal end, haptoral accessory spines at level of ventral bar with bifid distal portion, dorsal bars with a knob at lateral extremity, and a large vagina with bell-shaped. Rhamnocercus microps n. sp. differs from all congeners mainly by having a short and straight MCO with the distal end of internal tube spatulate and uncovered by external tube. Rhamnocercus rimaci n. sp. is can be distinguished from all other species of Rhamnocercus by having an almost J-shaped MCO with the distal end of external tube slight expanded and the distal end of internal tube narrow and uncovered by external tube. Rhamnocercus tantaleani n. sp. is mainly characterized by its MCO, which is tubular and straight, having the distal end of external tube bifurcated (right branch well-expanded and left branch narrow) and the distal end of internal tube enveloped by left branch of the external tube. This is the first data on the parasites of P. lanfeari, a little known, but popular fish in local markets from Peru. Rhamnocercus microps n. sp. is the first described species of Rhamnocercus in Brazil. The present finding brings to 12, the number of known species of Rhamnocercus. A key to Rhamnocercus species is provided.

New record of monogeneans (Platyhelminthes: Monogenea) infecting some marine fishes from the Peruvian coastal zone

A parasitological survey searching monogeneans infesting marine fish was carried out during June 2018 and January 2020 from the coastal zone of Puerto Pizarro, Tumbes (northern Peru) and from the coastal zone of Chorrillos, Lima (central Peru). The gills, skin, nasal cavities, or branchial gill-cover of seven species were sampled. Ten monogenean species assigned to six families and nine genera were identified. The monogeneans Callorhynchocotyle callorhynchi (Manter, 1955); Capsala biparasiticum (Goto, 1894) Price, 1938; Euryhaliotrema sagmatum Kritsky & Boeger, 2002; Listrocephalos kearni Bullard, Payne &Braswell, 2004; Magniexcipula lamothei Bravo-Hollis, 1981; Nasicola klawei (Stunkard, 1962) Yamaguti, 1968; and Pseudorhabdosynochus anulus Violante-Gonzalez & Rojas-Herrera, 2011 are registered for the first time in Peru. While Capsala gregalis (Wagner & Carter, 1967) Chisholm & Whittington, 2007; Heterocotyle margaritae Chero, Cruces, Sáez, Santos & Luque, 2020; and Monocotyle luquei Chero, Cruces, Iannacone, Sanchez, Minaya, Sáez & Alvariño, 2016 have been previously registered in Peruvian waters, however, the region of Tumbes (northern Peru) represent a new locality record for these species.

Durante junio de 2018 y enero de 2020 se realizó un levamiento parasitológico para buscar monogeneos que infectan peces marinos en la zona costera de Puerto Pizarro, departamento de Tumbes (norte de Perú) y en la zona costera de Chorrillos, departamento de Lima (centro de Perú). Se analizaron las branquias, la piel, las cavidades nasales o el opérculo de siete especies. Se identificaron diez especies de monogeneos, asignadas a seis familias y nueve géneros. Los monogeneos Callorhynchocotyle callorhynchi (Manter, 1955); Capsala biparasitica (Goto, 1894) Price, 1938; Euryhaliotrema sagmatum Kritsky y Boeger, 2002; Listrocephalos kearni Bullard, Payne y Braswell, 2004; Magniexcipula lamothei Bravo-Hollis, 1981; Nasicola klawei (Stunkard, 1962) Yamaguti, 1968; y Pseudorhabdosynochus anulus Violante-Gonzalez & Rojas-Herrera, 2011 son registrados por primera vez en Perú. Mientras que, Capsala gregalis (Wagner y Carter, 1967) Chisholm y Whittington, 2007; Heterocotyle margaritae Chero, Cruces, Sáez, Santos & Luque, 2020; y Monocotyle luquei Chero, Cruces, Iannacone, Sanchez, Minaya, Sáez & Alvariño, 2016 han sido previamente registrados en aguas peruanas, sin embargo, la región de Tumbes (norte de Perú) representa un nuevo registro de localidad para estas especies.

Bicentenariella n. g. (Monogenea: Dactylogyridae) including descriptions of three new species and two new combinations from serranid fishes (Actinopterygii: Serranidae: Anthiinae) in the South American Pacific Ocean.

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.

First Data on the Parasites of the Pacific Kingcroaker Menticirrhus elongatus (Perciformes: Sciaenidae): Description of a New Species of Rhamnocercoides (Dactylogyridea: Diplectanidae).

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.

A new species of Heterocotyle (Monogenea: Monocotylidae), a gill parasite of the diamond stingray Hypanus dipterurus (Myliobatiformes: Dasyatidae) from the Peruvian coastal zone.

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.

A new genus and three new species of dactylogyrids (Monogenea), gill parasites of the threadfin bass, Pronotogrammus multifasciatus Gill (Perciformes: Serranidae) in the Southeastern Pacific Ocean off Peru.

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.

Redescription and First Nucleotide Sequences of Rhinobatonchocotyle pacifica Oliva & Luque, 1995 (Monogenea: Hexabothriidae), a Parasite of Pseudobatos planiceps (Garman, 1880) (Rhinopristiformes: Rhinobatidae) from Peru.

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.

Four new species of dactylogyrids (Monogenea: Dactylogyridae) parasitic on gills of labrid and sparid fishes from Southeastern Pacific Ocean off Peru.

During a research on gill ectoparasites of Peruvian marine fishes, four dactylogyrid (Monogenea) species, parasitising two teleost species, Bodianus diplotaenia (Gill) (Labridae) and Calamus brachysomus (Lockington) (Sparidae), were found. Euryhaliotrema luisae n. sp. ex C. brachysomus is differentiated from other congeneric species by the morphology of the male copulatory organ, which comprises a coil of nine counterclockwise rings, and by the morphology of the anchors and bars. Euryhaliotrema magnopharyngis n. sp. ex C. brachysomus can be distinguished from all other congeners by having a well-developed pharynx occupying much of the anterior region and by the ventral bar, which is V-shaped, with well-elongated, thin arms. In addition, E. luisae n. sp. and E. magnopharyngis n. sp. can be differentiated from all other members of Euryhaliotrema Kritsky & Boeger, 2002 by the presence of a glandular oval plate lying on peduncle. Haliotrema diplotaenia n. sp. ex B. diplotaenia is characterised by the structure of the male copulatory organ, comprising a tapered-shaped cirrus tube with twisted acute tip and a filament-shaped accessory piece with medial and distal expansions, and by the morphology of the ventral bar (inverted W-shaped, with short lateral ends and two anterior conical protuberances). Haliotrema saezae n. sp. ex B. diplotaenia differs from all other members of Haliotrema Johnston & Tiegs, 1922 by having a tubular copulatory organ with curved distal tip and a filament-shaped accessory piece without lateral expansions, and by the morphology of anchors and bars. The present findings are added to the other six marine dactylogyrids previously reported from Peru.

Hypanocotyle bullardi n. gen. n. sp. (Monogenea: Hexabothriidae) from gill of the diamond stingray Hypanus dipterurus (Jordan et Gilbert) (Myliobatiformes: Dasyatidae) in the Southeastern Pacific Ocean off Peru.

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.

A new genus and species of the Dasybatotreminae Bychowsky, 1957 (Monogenea: Monocotylidae), parasitic on Hypanus dipterurus (Jordan Gilbert) (Myliobatiformes: Dasyatidae) in the Southeastern Pacific Ocean off Peru.

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.

Diplectanids (Monogenea) parasitic on sciaenid fish from Peru with the proposal of Pseudorhamnocercoides n. gen., the description of Rhamnocercus dominguesi n. sp. and the redescription of Rhamnocercoides menticirrhi Luque and Iannacone, 1991.

Rhamnocercoides menticirrhi Luque and Iannacone, 1991 is redescribed from newly collected material of snakehead kingcroaker Menticirrhus ophicephalus (Jenyns, 1840) from Peru, and as a result of this redescription, the diagnosis of Rhamnocercoides is emended. Rhamnocercus dominguesi n. sp. is described from the Peruvian banded croaker Paralonchurus peruanus (Steindachner, 1875). It differs from congeneric species mainly in the morphology of the male copulatory organ (with distal and proximal portion of the external tube expanded and distal portion of the internal tube uncovered by external tube) and the number of peduncular spines (18-22, arranged in 2 longitudinal rows). Pseudorhamnocercoides n. gen. is proposed for species with two longitudinal rows of peduncular spines with anterior and posterior roots, two longitudinal rows of acicular spines associated with peduncular spines, a medial constriction in the ventral bar and more than six haptoral accessory spines at level of the ventral bar with fan-like distal extremity. Rhamnocercoides stichospinus (Seamster and Monaco, 1956) is transferred to Pseudorhamnocercoides n. gen as Pseudorhamnocercoides stichospinus (Seamster and Monaco, 1956) n. comb (assigned as type species).

Three monogeneans parasitic on marine sciaenid fish from Peru including description of Cynoscionicola veranoi n. sp. (Microcotylidae), and redescription of C. americanus Tantaleán, Martínez and Escalante, 1987 and Hargicotyle sciaenae Oliva and Luque, 1989 (Diclidophoridae).

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.

Monocotyle luquei n. sp. (Monogenea: Monocotylidae), from the gills of diamond stingray Dasyatis dipterura (Jordan and Gilbert, 1880) (Myliobatiformes: Dasyatidae), in the South Pacific.

Monocotyle luquei n. sp. (Monogenea: Monocotylidae) was described from gills of diamond stingray Dasyatis dipterura (Jordan and Gilbert, 1880) (Dasyatidae) off Peru. The new species can be differentiated from the other species of the genus by the combination of the following characteristics: (1) accessory sclerites on the dorsal posterior surface of the body absent, (2) only one testis is present, (3) 1-2 loops in the copulatory organ, (4) the male copulatory organ with a sclerotized accessory piece, (5) shape of five sclerites in marginal papillae, (6) size of anchor and (7) posterolateral septa bifurcated. This is the first record of species of Monocotyle Taschenberg, 1878 from the southern Pacific.