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Fisheries statistics of many countries are still limited by the use of common names in multispecific captures, where little is known about the correct taxonomic identification of captured species. Homonymy is a known obstacle for commercially exploited Pleuronectiformes, traditionally grouped as flatfishes in Brazilian fisheries statistics. The present study was based on visits to 14 artisanal fish landing points and four industrial landing sites along the coast of Rio de Janeiro, in the southwestern Atlantic, between 2013 and 2016. A total of 176 Pleuronectiformes specimens were collected under the flatfish category. Standardized and scaled images were used for a geometric morphometric analysis based on anatomical landmarks in order to identify how species were distributed in the morphospace and to point out diagnostic character not used by the known literature for the group. A total of four different groups were identified as the main target for the commercial flatfish category, being associated with four species of Paralichthyidae: Paralichthys isosceles Jordan, 1891, P. patagonicus Jordan, 1889, P. orbignyanus (Valenciennes, 1839) and Xystreurys rasile (Jordan, 1891). A canonical analysis independently isolated P. isosceles and X. rasile, while strongly associating P. patagonicus and P. orbignyanus. These results were corroborated by an UPGMA analysis of Procrustes distances based on the consensus form. The analysis identified that tail shape and relative eye and jaw positions are of significant importance for species separation. The combination of the results of the analysis and specific ocelli positioning allowed for the selection of diagnostic characters for all species without the need for laboratory examinations. Conflicts between the literature and the specific composition of flatfish landings are also discussed. Geometric morphometrics were demonstrated herein as useful not only in quantifying differences in scarcely studied body parts, but also as a tool able to identify the consistency of a multispecies commercial category used by the fishery statistics, as well as useful in pointing out characteristics capable of dismembering flatfishes into monospecific categories.

Five adult paralichthyid specimens with various kinds of abnormalities are reported from the south-west Atlantic Ocean. These abnormal flatfish specimens represent the first records of wholly ambicoloured Paralichthys orbignyanus specimens having a deep notch between the eye and dorsal fin and a partially albinistic specimen having skeletal deformities and only the second record of an almost totally ambicoloured specimen. We also report the first observation of reversal in Paralichthys patagonicus and an almost totally ambicoloured, reversed Xystreurys rasile.

Flounders are commercially and economically important fish. A total of 120 specimens of flounders (60 Paralichthys isosceles, 30 Paralichthys patagonicus and 30 Xystreurys rasile) were collected off the coast of the state of Rio de Janeiro, Brazil. The fish were measured, necropsied and filleted, and then had their organs investigated for acanthocephalans. Taxonomic identification of the parasites was based on morphological, morphometric and genetic characters. Paralichthys isosceles and P. patagonicus were parasitized by juveniles of Serrasentis sagittifer, Bolbosoma turbinella, Corynosoma australe and C. cetaceum; Xystreurys rasile was parasitized by C. australe. Genetic characterization confirmed the identification of specimens of Bolbosoma turbinella and Corynosoma australe, as demonstrated by phylogenetic analyses using both ITS and cox1 molecular targets. Parasite indices of prevalence, intensity, mean intensity, abundance, mean abundance, and range of infection, as well as infection site, were evaluated for each parasite species. This is the first report of S. sagittifer parasitizing P. isosceles and P. patagonicus, and B. turbinella parasitizing P. patagonicus. Resumo Os linguados são peixes comercial e economicamente importantes. Um total de 120 espécimes de linguados (60 Paralichthys isosceles, 30 P. patagonicus e 30 Xystreurys rasile) foram coletados no litoral do estado do Rio de Janeiro, Brasil. Os peixes foram medidos, necropsiados, filetados e tiveram seus órgãos investigados para a presença de acantocéfalos. A identificação taxonômica foi baseada em caracteres morfológicos, morfométricos e genéticos. Paralichthys isosceles e P. patagonicus estavam parasitados por acantocéfalos juvenis de Serrasentis sagittifer, Bolbosoma turbinella, Corynosoma australe e C. cetaceum; Xystreurys rasile estava parasitado com C. australe. A caracterização genética confirmou a identificação dos espécimes de Bolbosoma turbinella e Corynosoma australe, como demonstrado por análises filogenéticas usando ambos marcadores moleculares ITS e cox1. Foram analisados os índices parasitários: prevalência, intensidade, intensidade média, abundância, abundância média, amplitude de variação da infecção e sítio de infecção de cada espécie de parasito. Este é o primeiro registro de S. sagittifer parasitando P. isosceles e P. patagonicus, e de B. turbinella parasitando P. patagonicus.

The aims of this study were (1) to compare the structure and composition of parasite assemblages of the flounder Xystreurys rasile in two regions of the Argentine Sea in order to evaluate the hypothesis for the existence of different stocks, and (2) to test the hypothesis for X. rasile migration from the Argentine-Uruguayan Common Fishing Zone (AUCFZ) towards more southern waters during spring. Parasitological evidence shows that at least two stocks of X. rasile inhabit the coastal and shelf waters of the northern Argentine Sea, one in El Rincon and the other in the AUCFZ. These stocks should be considered as discrete entities in management plans to ensure a sustainable use of these resources. The results also confirm the existence of migratory patterns in the northern stock.

Thirty-six Paralichthys patagonicus and 30 Xystreurys rasile were collected in the state of Rio de Janeiro, Brazil to investigate the presence of anisakid and raphidascaridid nematodes. Anisakis typica, Terranova sp., Contracaecum sp., Hysterothylacium deardorffoverstreetorum, and Raphidascaris sp. were identified using integrative taxonomy of morphological and genetic data. Morphological and morphometric analysis was conducted using bright field microscopy with scanning electron microscopy for topographic characterization of the cuticular surface. Phylogenetic analysis, using ITS and cox2 molecular targets, clearly demonstrated the species identification of A. typica and H. deardorffoverstreetorum and the high diversity of H. deardorffoverstreetorum. This is the first report of A. typica, H. deardorffoverstreetorum, and Raphidascaris sp. parasitizing P. patagonicus and X. rasile.

From February 2007 to July 2010, 27 specimens of Paralichthys patagonicus, and from September to December 2010, 30 specimens of Xystreurys rasile were purchased from fish markets in the municipalities of Cabo Frio and Rio de Janeiro, State of Rio de Janeiro, Brazil. The fishes were measured, necropsied, filleted, and further had their organs investigated. In P. patagonicus, 19 (70, 3 %) were parasitized with metacestodes of Trypanorhyncha species: Nybelinia erythraea, N. lingualis, Heteronybelinia nipponica, Pterobothrium crassicolle, Grillotia carvajalregorum, and Callitetrahynchus gracilis. In X. rasile, 17 (56, 6 %) were parasitized with metacestodes: N. erythraea, N. lingualis, H. nipponica, and G. carvajalregorum. The parasitological indices of prevalence, intensity, mean intensity, abundance, mean abundance, range of infection, and infection sites of each parasite species are presented. This is the first report of Trypanorhyncha cestodes parasitizing specimens of P. patagonicus and X. rasile. These cestodes were studied due to their importance during fish sanitary inspection, if one considers the harm that the repulsive aspect of infected meat causes to consumers.

Además de sus conocidos aportes a la geología, la paleontología y la biogeografía de ecosistemas terrestres de la región pampeana y la Patagonia (Argentina), Darwin realizó notables y poco difundidas contribuciones al conocimiento de los ambientes marinos costeros del actual territorio argentino y de los organismos que habitan en ellos. La intimidad de Darwin con el mar se advierte en toda su obra: en el Viaje y en el Origen igual que en numerosos trabajos de investigación realizados y publicados a su regreso a Inglaterra. Entre 1846 y 1854 dio a conocer una extensa obra sobre cirrípedos o cirripedios, que sentó las bases del estudio de esos crustáceos y, aún hoy, es bibliografía obligada de los taxónomos. Su trabajo sobre la estructura y distribución de los arrecifes coralinos de 1842, es considerado un documento fundacional del conocimiento sobre el origen de los atolones. Los moluscos fueron igualmente objeto de publicaciones y cartas entre 1848 y 1871. La difundida imagen de Darwin sentado ante un escritorio escribiendo sus libros lleva a olvidar que pasaba también mucho tiempo con el microscopio. En el Viaje del Beagle incluyó párrafos sobre aves marinas, lo mismo que sobre briozoos o briozoarios, y en El origen, explicó sus pensamientos acerca de la migración de los ojos en los lenguados. Dedicó especial atención a las algas gigantes o sargazos marinos de Tierra del Fuego (donde se los conoce por cachiyuyos). Se incluyen los siguientes trabajos de divulgación científica -Darwin y los briozoos; -Darwin y el desarrollo larval de crustáceos; -Sobre Cirripedios; De Darwin a los acelerómetros; -Los peces de cara torcida; -La incursión en la costa sur de Buenos Aires. Reprinted as: pp.145-154 in, Ciencia del Mar. Volumen temático 1, 12/2014; Asociación Ciencia Hoy. ISBN: 978-987-45584-0-4 (Special issue dedicated to 'Marine Sciences: 1988-2014')

RESUMEN. La estructura poblacional de Xystreurys rasile varía estacionalmente, debido principalmente a la reproducción. Se identificaron grupos segregados por tamaños en el área estudiada (34°-40°S), los ejemplares más pequeños, por lo general, se encontraron en aguas más costeras y al norte, principalmente durante la primavera, y se observó una tendencia de aumento de la longitud media con la latitud. En cuanto a la abundancia, se identificaron dos grupos, uno al norte de los 36ºS y otro al sur de los 37ºS, el primero mucho menos abundante que el segundo. Durante el otoño los especímenes se desplazan hacia aguas más profundas para alimentarse y crecer. En primavera los ejemplares maduros migran hacia la costa y hacia el sur. Tanto el grupo norteño como el sureño, convergen al sur de Mar del Plata (38ºS) para reproducirse. La talla de primera madurez sexual se estimó en 20,0 cm en los machos y 21,2 cm en las hembras, con uno y dos años de edad respectivamente. Los adultos se reclutan al área de pesca entre el segundo y tercer año de vida y existen fuertes evidencias que los juveniles no están accesibles a la flota pesquera ABSTRACT. The present paper deals with the dynamic population of the flatfish Xystreurys rasile on the Southwest Atlantic between 34º and 40ºS. Increase of mean size of Xystreurys rasile`s shoals was observed to the south. The smallest specimens were found in coastal waters in Spring. Two groups were identified according to the abundance, one northern than 36ºS, characterized with very low captures and the other southern than 37ºS, characterized with higher yields. In Spring mature individuals of X. rasile migrate to shallow waters at 38ºS and southwards for spawning. On the contrary, in autumn they migrate offshore for feeding and growing. First sexual maturity length was estimated in 20.0 cm for males and 21.2 cm for females, corresponding to one and two years respectively. Adult recruitment to the fishing area is around the second and third years of age. Strong evidences enforce that juveniles are not available to the fishing fleet