Fabiola Sepulveda

A new genus and species of Clavella -like specimens parasitic on Macrourus holotrachys , previously reported as a host for Clavella adunca , clearly differ from the latter in the position and condition of the antennal sympod and rami, which are uniramous in C. adunca but biramous in the new species. Additional morphological traits, such as antennule armature, maxillary size, and the absence of basal swelling on the cephalothorax, support these differences. Molecular analyses corroborate these distinctions. The 28S rDNA sequences of Neoclavella holotrachia gen. nov. et sp. nov . show genetic divergence of 4.1–4.7% and 6.2–6.8% from those of C. adunca and Lernaeopodidae gen. sp., respectively, all of which cluster within a strongly supported clade. Clavellomimus macruri exhibits sequence divergence with Clavellotis girellae (15.3%) and with Clavellotis dilatata (15.5%), although the corresponding nodes in the phylogram are weakly supported. COI mtDNA sequences of Neoclavella holotrachia gen. nov. et sp. nov . grouped together with Clavella spp. in a strongly supported node, with genetic distances ranging from 17.3% to 18.2% between the new genus and the other species. These results suggest that Macrourus holotrachys and possibly other Macrourus species are not hosts for C. adunca , as previously reported. Alternatively, M. holotrachys may be parasitized by both C. adunca and the new species. These findings suggest that some previous records of C. adunca from fishes off Chile may have been misidentified.

The Yellowtail Kingfish ( Seriola lalandi ) is a widely distributed marine species of high commercial value for both fisheries and aquaculture. Although the taxonomic status of S. lalandi remains unresolved, this study examined its genetic structure across two Pacific Ocean regions and evaluated the genetic differentiation between wild and captive‐reared fish. Globally, our results demonstrated two genetically differentiated groups of S. lalandi : one restricted to the Temperate Northern Pacific (Mexico‐United States) and another to Temperate South America (Chile), with pronounced divergence ( F _ST = 0.208). Among wild populations, individuals from the Northern Hemisphere displayed greater heterozygosity compared to those from the Southern Hemisphere (Chile). We also detected fine‐scale population substructure within the Northern Pacific ( F _ST = 0.078), along with consistent genetic differentiation between wild fish and captive‐reared stocks in both Chile ( F _ST = 0.049) and Mexico ( F _ST = 0.120). Together, these findings support the hypothesis of two independent evolutionary lineages in S. lalandi and challenge the current notion that a single northern stock (referred to as Seriola dorsalis ) exists in the Temperate Northern Pacific, highlighting the need for region‐specific management strategies for fisheries and aquaculture.

Pseudosteringophorus profundissp. nov. a new species of deep-sea digenean, parasitizing the gallbladder of the “Bigeye grenadier” (Macrourus holotrachys Günther, 1878) in the deep waters of the southeastern Pacific Ocean is described on the basis of morphological and molecular (28S rRNA) data. The new species is distinguishable from Pseudosteringophorus hoplognathi Yamaguti, 1940, the only other member of the genus, by its subterminal oral sucker, the position of the ovary and testes, the larger anterior seminal vesicle compared to the posterior one, and its larger eggs. In addition, the new species is a parasite of a deep-sea fish, whereas P. hoplognathi is a parasite of shallow-water fish. A phylogenetic tree, based on 28S rDNA sequences, indicates that this species is included in a clade of deep-sea fellodistomid species (Steringophorus spp.). We provide the first molecular data on the genus Pseudosteringophorus Yamaguti, 1940 and expand the molecular database for the family Fellodistomidae. Further studies, including sequences from other fellodistomid taxa, are needed to more precisely infer relationships within this family.

Morphological and molecular methods were used to describe a new species of Trapania Pruvot-Fol, 1931 from shallow water kelp forests on the north-central coast of Peru. The new species, Trapania huarmeyana sp. nov., is distinguished from other species along the Eastern Pacific by external morphological characters such as its translucent white body with brown stripes and small spots on the dorsum, blotches on the base of the extra-branchial processes, extra rhinophoral processes and gill branches. Internally, T. huarmeyana sp. nov. is distinguishable by several morphological characteristics of the radula, jaws and genital organs. Phylogenetic trees recovered using Bayesian Inference and Maximum Likelihood analysis of DNA sequences support its distinct status and clarify its relationship to other species from the Eastern Pacific. This new species constitutes the first record of Trapania from the Humboldt Current Ecosystem, contributing to our understanding of the distribution of the genus in the South-eastern Pacific.

Currently, 24 species of Encotyllabe Diesing, 1850 (Monogenea: Capsalidae), are recorded as parasites on teleost fishes, but the validity of many species has been questioned due to deficient or incomplete descriptions. Almost all species in the genus have been described from one host species or closely related host species, suggesting host specificity, but some species, specifically Encotyllabe spari Yamaguti, 1934, have been reported from at least 19 species belonging to nine families in two orders (Perciformes and Scorpaeniformes) from Japan, Arabian Gulf and Brazil. Concerning Brazilian records of Encotyllabe spari and Encotyllabe cf. spari, seven species belonging to four families and two orders have been reported as hosts for this species. The aim of this study was to describe two new species of Encotyllabe from Brazil, previously considered as E. spari. Morphological and morphometric (multivariate analysis of proportional measurements standardized by total length) and molecular analysis (LSU rRNA and cox1 gene) were performed in order to identify the collected monogeneans. The description of two new species, namely Encotyllabe bifurcatum n. sp. and Encotyllabe parvum n. sp., parasitizing Pagrus pagrus and Orthopristis ruber, respectively, is the result of the three approaches. The main morphological differences from the most related species include a combination of body size, shape of the male copulatory organ, size and position of the testes. Our results suggest host specificity for members of Encotyllabe and specimens previously recorded as E. spari, other than those from the original description, must be revisited.

Blood flukes are digeneans that infect wild and farmed fish that can cause a severe and potentially lethal disease in farmed fish. These parasites are undetectable in the larval stage based on macroscopic observations in the definitive host with the infection becoming evident when eggs accumulate in the branchial vessels. There are nine known species of the genus Paradeontacylix and seven exclusively parasitize Seriola spp. from several geographical areas. Seriola lalandi aquaculture farms are emerging at various localities in northern Chile. Here, we report, for the first time, two blood fluke species parasitizing S. lalandi in the Southeastern Pacific (Chile). In the laboratory, the gills and heart of fish were removed. The retained blood flukes were separated according to the infection site, fixed in 70% or 95% ethanol for taxonomic and molecular analysis, respectively. Morphometrical differences among the fluke species were evaluated with a principal component analysis (PCA) using proportional body measurements. Phylogenetic trees were constructed based on 28S rDNA, cox1 mDNA using Bayesian inference (BI), and maximum likelihood (ML). Based on morphology, morphometry, and molecular analyses, two new species are proposed: P. humboldti n. sp. from the gills and P. olivai n. sp. from the heart of S. lalandi. Both were clearly distinguished from other species of Paradeontacylix by a combination of morphologic features (posterior tegumental spines, testes arrangement, body size). The genetic distance (based on cox1) among species was >10%. P. humboldti n. sp. and P. olivai n. sp. are sister species (with a common ancestor) independent of P. godfreyi from S. lalandi in Australia. The newly identified parasites may pose a risk to farmed S. lalandi as aporocotylids have been the cause of diseases in farmed fish from other geographical areas. In addition, some cages of S. lalandi are currently maintained in an open circulating system, which could favor the transmission of these parasites (if involved hosts are present in the environment).

Background: The monogenean Benedenia seriolae parasitizes fishes belonging to the genus Seriola, represents a species complex, and causes substantial impact on fish welfare in aquaculture systems worldwide. This study reports, for the first time, the complete mitochondrial genome of B. humboldti n. sp., a new cryptic species from the South-East Pacific (SEP). Methods: The mitogenome of B. humboldti n. sp. was assembled from short Illumina 150 bp pair-end reads. The phylogenetic position of B. humboldti n. sp. among other closely related congeneric and confamiliar capsalids was examined using mitochondrial protein-coding genes (PCGs). Morphology of B. humboldti n. sp. was examined based on fixed and stained specimens. Results: The AT-rich mitochondrial genome of B. humboldti is 13,455 bp in length and comprises 12 PCGs (atp8 was absent as in other monogenean genomes), 2 ribosomal RNA genes, and 22 transfer RNA genes. All protein-coding, ribosomal RNA, and transfer RNA genes are encoded on the H-strand. The gene order observed in the mitochondrial genome of B. humboldti n. sp. was identical to that of B. seriolae from Japan but different from that of B. seriolae from Australia. The genetic distance between B. humboldti n. sp. and B. seriolae from Japan was high. Minor but reliable differences in the shape of the penis were observed between Benedenia humboldti n. sp. and congeneric species. Conclusions: Phylogenetic analyses based on PCGs in association with differences in the shape of the penis permitted us to conclude that the material from the South-East Pacific represents a new species of Benedenia infecting S. lalandi off the coast of Chile. The discovery of this parasite represents the first step to improving our understanding of infestation dynamics and to develop control strategies for this pathogen infecting the farmed yellowtail kingfish, Seriola lalandi, in the South-East Pacific.

Little is known about the diversity of parasites of the deep-sea fish of the world's oceans. Here, a new species of monogenean parasite of the deep-sea skate Gurgesiella furvescens is described. Specimens of parasites were obtained from the skin of two specimens of the dusky finless skate, G. furvescens (Rajidae), in the vicinity of Valparaiso (33°S, 72°W), central Chile, from midwater trawl fishing at depths of 350–450 m. Both morphological and molecular analyses were conducted to provide a full description of the new species, named Acanthocotyle gurgesiella. For the molecular analyses, nuclear large subunit (LSU) rDNA and the mitochondrial gene cytochrome c oxidase 1 (COI) were used. From the morphological analysis and a comparison with the known species of the genus, A. gurgesiella can be identified by a combination of morphological characteristics, including the number of testes, number of radial rows of sclerites in the pseudohaptor, aperture of the genital pore and shape of the vitelline follicles. The results from the DNA analysis indicated that A. gurgesiella has a genetic divergence of 3.2–3.7% (LSU rDNA gene) from A. urolophi, the only congener species for which molecular data are available.