Systematic revision of the Potamotrygon motoro (Müller & Henle, 1841) species complex in the Paraná-Paraguay basin, with description of two new ocellated species (Chondrichthyes: Myliobatiformes: Potamotrygonidae)
Abstract:A systematic revision of the Potamotrygon motoro (Müller & Henle, 1841) species complex in the Paraná-Paraguay basin based on morphological characters was undertaken. Morphological systems analyzed include external morphology, coloration, dermal denticles, and spines, canals of the ventral lateral-line system, and skeletal components. Potamotrygon motoro is widely distributed in the Paraná-Paraguay basin and some of its diagnostic characters are: ocelli present on dorsal disc tricolored, well-defined and evenl… Show more
“…Skeletal components of the pelvic girdle, fin and clasper in the adult abnormal specimen of Potamotrygon sp. (Figure ) differ from the conspecific non‐deformed specimen (Figure ) and other members of Potamotrygon (Carvalho et al, ; Fontenelle, Silva, & Carvalho, ; Loboda & Carvalho, ; Nishida, ; Rosa, ; Silva & Carvalho, , b; Silva & Carvalho, ; Silva & Loboda, ; Taniuchi & Ishihara, ) (Figure ). In the adult specimen the pelvic radials fail to reach the fin margins, are unsegmented and barely branched (Figure ) a condition also observed in the deformed juvenile (MZUSP 124856, Figure ).…”
Section: Discussionmentioning
confidence: 74%
“…In the adult specimen the pelvic radials fail to reach the fin margins, are unsegmented and barely branched (Figure ) a condition also observed in the deformed juvenile (MZUSP 124856, Figure ). The lateral pre‐pelvic processes (lpp) of pelvic girdle are greatly reduced and almost undiscernible (Figure ) and the right dorsal terminal 2 (dt2) is horizontally folded, a condition distinct from the observed in members of the genus that may bear a marked medial longitudinal groove in this cartilage, but which is always unfolded horizontally (Figure ) (see also Fontenelle et al, ; Loboda & Carvalho, ; Silva & Carvalho, , b; Silva & Carvalho, ; Silva & Loboda, ). The proximal portion of dorsal marginal (dm) is fused to the axial cartilage (Figure ), different from the typical condition in which this cartilage is detached from the axial cartilage but connected to the beta cartilage dorsally (Figure b).…”
We report deformities in the pelvic fin and clasper skeleton in specimens of Potamotrygon marquesi from Acre, Northwestern Brazil. The malformations involve skeletal deformities in the pelvic girdle, right clasper skeleton, and severe muscular and skeletal deformities in the left or right pelvic fin and clasper, including the loss of all of its terminal components. Descriptions of malformations dealing with elasmobranchs are extensive in the literature and are important for future studies dealing with their probable causes. Nevertheless, although the reasons of these deformities are herein possibly linked to malformation (as a result of stress or chemical contaminants) or predation, the anomalies in the muscular and skeletal components of the pelvic fin and clasper are described in detail and compared to a non‐deformed specimen.
“…Skeletal components of the pelvic girdle, fin and clasper in the adult abnormal specimen of Potamotrygon sp. (Figure ) differ from the conspecific non‐deformed specimen (Figure ) and other members of Potamotrygon (Carvalho et al, ; Fontenelle, Silva, & Carvalho, ; Loboda & Carvalho, ; Nishida, ; Rosa, ; Silva & Carvalho, , b; Silva & Carvalho, ; Silva & Loboda, ; Taniuchi & Ishihara, ) (Figure ). In the adult specimen the pelvic radials fail to reach the fin margins, are unsegmented and barely branched (Figure ) a condition also observed in the deformed juvenile (MZUSP 124856, Figure ).…”
Section: Discussionmentioning
confidence: 74%
“…In the adult specimen the pelvic radials fail to reach the fin margins, are unsegmented and barely branched (Figure ) a condition also observed in the deformed juvenile (MZUSP 124856, Figure ). The lateral pre‐pelvic processes (lpp) of pelvic girdle are greatly reduced and almost undiscernible (Figure ) and the right dorsal terminal 2 (dt2) is horizontally folded, a condition distinct from the observed in members of the genus that may bear a marked medial longitudinal groove in this cartilage, but which is always unfolded horizontally (Figure ) (see also Fontenelle et al, ; Loboda & Carvalho, ; Silva & Carvalho, , b; Silva & Carvalho, ; Silva & Loboda, ). The proximal portion of dorsal marginal (dm) is fused to the axial cartilage (Figure ), different from the typical condition in which this cartilage is detached from the axial cartilage but connected to the beta cartilage dorsally (Figure b).…”
We report deformities in the pelvic fin and clasper skeleton in specimens of Potamotrygon marquesi from Acre, Northwestern Brazil. The malformations involve skeletal deformities in the pelvic girdle, right clasper skeleton, and severe muscular and skeletal deformities in the left or right pelvic fin and clasper, including the loss of all of its terminal components. Descriptions of malformations dealing with elasmobranchs are extensive in the literature and are important for future studies dealing with their probable causes. Nevertheless, although the reasons of these deformities are herein possibly linked to malformation (as a result of stress or chemical contaminants) or predation, the anomalies in the muscular and skeletal components of the pelvic fin and clasper are described in detail and compared to a non‐deformed specimen.
“…This led to an invasion of the Upper Paraná by multiple fish species of the more diverse (Albert et al 2011) Lower Paraná ecoregion (Júlio Júnior et al 2009Vitule et al 2012). Two or three species of Potamotrygon have established viable populations in the newly invaded ecoregion (Garrone-Neto et al 2007da Graça and Pavanelli 2007;Loboda and de Carvalho 2013). However, P. brachyura has been unable to reach the Upper Paraná ecoregion so far, despite having been recorded close to the Itaipú dam (Fig.…”
Section: Summary Of Maxlike and Generalised Additive Models (Gam) Umentioning
Freshwater elasmobranchs are threatened but little is known about them. Potamotrygon brachyura is the world's largest obligate freshwater elasmobranch. This makes it popular among fishermen and suggests a susceptibility to anthropogenic threats. We collected records of P. brachyura (n ¼ 70) from media, fishermen and scientific sampling, to estimate its global geographic distribution (using both generalised additive and MaxLike models). Then, we estimated the species' exposure to habitat modification and fishing pressure, by applying multinomial ordinal models with threat levels as response and the presence or absence of P. brachyura as an independent variable. Distance to coast, depth, water temperature range, salinity range and mean water temperature were the main determinants of the distribution in the Río de la Plata. This resulted in a narrow coastal distribution. In the Uruguay and Paraná River basins, the probability of occurrence was positively associated with flow accumulation, percentage of open water and submerged vegetation, and lowland ecoregions, and negatively to wetness index and altitude. This limited the distribution to large lowland rivers. Approximately 41% of the range of P. brachyura in the Río de la Plata was subject to high habitat modification. In the Uruguay and Paraná River basins, this percentage reached 7%; however, the overlap with high fishing pressure was 59%. For conservation purposes, P. brachyura may function as an umbrella species.
“…Four genera are presently recognised as valid within the subfamily (Carvalho et al, ; Carvalho & Lovejoy, ): Potamotrygon Garman 1877, Paratrygon Duméril 1865, Plesiotrygon Rosa et al, and Heliotrygon Carvalho & Lovejoy, . Paratrygon is currently monotypic (although a recent taxonomic revision recognised seven new species within the genus) (Loboda, ), Heliotrygon and Plesiotrygon have two valid species each (Carvalho & Lovejoy, ; Carvalho & Ragno, ; Rosa et al, ) and Potamotrygon is the most diverse genus, including 35 valid species (Carvalho et al, , ; Silva & Carvalho, , ; Loboda & Carvalho, ; Fontenelle et al, ; Silva & Carvalho, , Carvalho, 2016a,b; Fontenelle & Carvalho, ).…”
Potamotrygon marquesi, sp. nov., is described and compared with other species of Potamotrygon occurring in the Amazon Basin. The identity of this new species is supported by an extensive external and internal morphological study including coloration pattern, squamation, skeleton and ventral lateral‐line canals. Morphometrics and meristics were used to further distinguish P. marquesi from congeners. Potamotrygon marquesi was first considered to fall within the range of variation found in P. motoro. However, even with an extensive variation in coloration observed in P. motoro, this new species presents a series of autapomorphies that confidently distinguishes it from what is understood as the morphological variation found in P. motoro. Additional morphological characters that diagnose P. marquesi include three angular cartilages, asymmetrical star‐shaped denticles, a single regular row of spines on tail dorsum, lateral row of caudal spines near the sting insertion, dorsal disc background in beige and grey mixed with shades of grey and bearing open and closed bicolored rings, among others. Although presenting a gap of distribution along the west–east extension of the Amazon Basin, its diagnostic charactistics are consistent in both recorded regions. Our study supports the need for many morphological characters to robustly distinguish members of Potamotrygoninae considering their extremely variable dorsal disc color pattern.
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