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.

Deep in the systematics of Camallanidae (Nematoda): using integrative taxonomy to better understand the phylogeny and consistency of diagnostic traits.

Due to conflicts between classic and molecular systematics of Camallanidae, different data types were used for the first time, to better understand the evolutionary history and taxa consistency within this family. Genetic [18S and 28S rDNA; cytochrome c oxidase subunit I (COI) mtDNA], morphological and life history traits were used to infer phylogenies using Bayesian inference, reconstructed from separated and concatenated datasets. The consistency of tree and morphological traits was evaluated using the consistency index. Characters were mapped on the trees and the phylogenetic informativeness of genetic markers was estimated. Phylogenetic informativeness of 18S provided better resolution for outer nodes, COI for inners and 28S had an intermediate profile. New sequences for two camallanid species were obtained. Phylogenies of genetic and concatenated data largely agreed, showing more divergence in the COI dataset, due to its higher mutation rate vs stable morphology for diagnosing higher taxa. No genus sustained monophyly. The lack of autapomorphy and phylogenetic proximity supported the partition of Batrachocamallanus as synonym of Procamallanus and Spirocamallanus, which should not be considered as subgenera. Although traits of buccal capsule, male tail, habitat, host and biogeographic were highly consistent, intrinsic patterns varied according to different taxa assemblages. Morphological systematics of Camallanidae, based on buccal capsule, is artificial for certain taxa.

An integrative approach assesses the intraspecific variations of Procamallanus (Spirocamallanus) inopinatus, a common parasite in Neotropical freshwater fishes, and the phylogenetic patterns of Camallanidae.

Integrative taxonomy was used to evaluate two component populations of Procamallanus (Spirocamallanus) inopinatus in Brazil and the phylogeny Camallanidae. Parasite populations were collected in the characiform Anostomoides passionis from River Xingu (Amazon basin) and Megaleporinus elongatus from River Miranda (Paraguay basin). Morphology was analysed using light and scanning electron microscopy (SEM). Genetic characterization was based on partial sequences of the 18S and 28S rDNA, and COI mtDNA. Phylogenies were based on 18S and COI due to data availability. Generalized Mixed Yule Coalescent (GMYC), Poisson Tree Process (PTP) and *BEAST were used for species delimitation and validation. SEM revealed for the first time the presence of minute denticles and pore-like structures surrounding the oral opening, phasmids in females and confirmed other important morphological aspects. Statistical comparison between the two-component populations indicated morphometric variations, especially among males. The different component population of P. (S.) inopinatus showed variable morphometry, but uniform morphology and were validated as conspecific by the GMYC, PTP and *BEAST. Some camallanid sequences in GenBank have incorrect taxonomic labelling. Host, environment and geographic aspects seem to be related to some lineages within Camallanidae; however, their real phylogenetic meanings are still unclear.

An integrative taxonomic assessment of Procamallanus (Spirocamallanus) huacraensis (Nematoda: Camallanidae), infecting the freshwater catfish Trichomycterus spegazzinii (Siluriformes: Trichomycteridae) in Argentina.

Procamallanus (Spirocamallanus) huacraensis infecting the catfish Trichomycterus spegazzinii from Escoipe River, Salta province (Argentina), is redescribed and genetically characterised for the first time, based on three genetic markers (nuclear 18S and 28S rRNA; cytochrome c oxidase subunit I [cox1] mtDNA). The phylogeny of Camallanidae was also discussed. Morphological evaluation of P. (S.) huacraensis using light and scanning electron microscopy revealed the previously undescribed features: location of deirids, accurate morphology of larvae (L1) and ovijector in females, as well as phasmids in males. Differences were found comparing the newly collected material and the type specimens, probably because the original description lacked detailing. Unfortunately, type specimens of P. (S.) huacraensis were no available for loan. The results of morphological and genetic analyses supported the validity of P. (S.) huacraensis. Inconsistencies regarding the taxonomic identification of species of Camallanidae in GenBank database were noted. Based on the current genetic database of Camallanidae, phylogenetic reconstructions using the 18S rRNA sequences were most consistent, due to the inclusion of higher number of taxa. Procamallanus (S.) huacraensis appeared as sister group of P. (S.) rarus, also isolated from a catfish in a neighbouring region. The order and habitat of hosts were also similar within some well-supported parasite lineages, but without common geographic origin. However, it is still premature to make definitive affirmations regarding the role of such features in the phylogenetic patterns of Camallanidae, given the scarcity of genetic data. The phylogenetic reconstructions also confirmed the artificiality of the morphology-based systematics of the family.

A new species of Hedruris Nitzsch, 1821 (Nematoda: Hedruridae) parasitic in eel Synbranchus marmoratus Bloch (Synbranchiformes: Synbranchidae) from Argentina, Neotropical Region.

During a parasitological survey, specimens belonging to the genus Hedruris (Nematoda: Hedruridae) were found in the stomach of Synbranchus marmoratus Bloch from the Paraná Guazú River, Paraná River basin (Argentina). Comparative morphological studies with its congeners showed that these nematodes belonged to a new species, herein described as Hedruris anguila sp. nov. The new species can be distinguished from remaining Hedruris species by the pseudolabia size, the morphology and size of spicules, the length of female caudal hook, the shape and size of eggs and the particular morphology of the male tail. Hedruris anguila sp. nov. closely resembles Hedruris bifida Rossin & Timi, 2016 and H. suttonae Brugni & Viozzi, 2010, both also described from fish hosts, in the arrangement of caudal papillae and morphology of eggs, but differ in the size of female hook and spicules, and the number of caudal papillae in males. The main morphological features, host range and geographical distribution of all species in the genus Hedruris species are analyzed and discussed. This is the first report of a representative of the family Hedruridae parasitizing a species of Synbranchidae and the eleventh report of the genus Hedruris for a fish host. The number of valid species of Hedruris described was increased to 26, including the new species; 11 for the Neotropical Region and represent the third species found in fish host from Argentina. Based on morphological analysis, the speciation process probably occurred first in Gondwana and the non-mammillated eggs could be an ancestral morphological character. The diet of Synbranchus marmoratus and values of prevalence and mean intensity could indicate that this host species is a true definitive host for this nematode.

Histopathological study of Corydoras micracanthus (Siluriformes: Callichthyidae) parasitized by the nematode Procamallanus (Spirocamallanus) pintoi (Camallanidae) from Lesser River, northwestern Argentina, South America

The nematode parasites can cause mechanical injuries such as irritation or atrophy of tissue and occlusions of the digestive tract, blood vessels or other ducts in their hosts. Some species belonging to the family Camallanidae have been the focus of histopathological studies because they lacerate the host´s intestinal wall with their buccal capsule. In this study, we describe the histopathological effects produced by Procamallanus (Spirocamallanus) pintoi in the small fish Corydoras micracanthus from Lesser River, in the northwest of Argentina, South America. The samples were processed with routine histology techniques. At light microscopy, specimens of P. (S.) pintoi were observed occupying the lumen of the gut. The histopathological sections revealed damage to the host intestine with the total destruction of the mucosa and submucosa, observed mainly in the region which is surrounding the buccal capsule of parasites. Moreover, an inflammatory reaction was observed with lymphatic accumulations in the affected tissue. This kind of degenerative and necrotic changes in the mucosa could affect negatively the absorption function of the host intestine, which may have adverse effects of the health status of fish. The present study provides the firs data about the histopathological effects of P. (S.) pintoi in C. micracanthus.

Further study on Procamallanus (Spirocamallanus) pintoi (Kohn et Fernandes, 1988) (Nematoda: Camallanidae) in Corydoras paleatus and Corydoras micracanthus (Siluriformes: Callichthyidae) from Salta, Argentina, with a key to congeneric species from Neotropical Realm.

This study describes the morphology of Procamallanus (Spirocamallanus) pintoi (Kohn et Fernandes, 1988), isolated from the intestine of Corydoras micracanthus Regan, 1912 and C. paleatus (Jenyns, 1842) (both Callichthyidae, Siluriformes) from Bermejo and Juramento River basins, respectively, province of Salta, Argentina. This is the first record of P. (S.) pintoi in C. micracanthus from Northwestern Argentina. The light and scanning electron microscopy observations of P. (S.) pintoi, revealed a few previously unreported morphological details of the cephalic region, vulva and caudal region of males. In addition, morphometric variability was observed in, mainly body size, glandular oesophagus length and position of the vulva between present specimens and those described in previous studies. A key to the species of Procamallanus (Spirocamallanus) from the Neotropical Realm is proposed.