Logistical ogives gave an estimated L T50 value (i.e. the total length at which 50% individuals are sexually mature) of 635 mm for female and 650 mm for male Sympterygia bonapartii. Mature individuals of both sexes had significantly larger livers than immature ones and females had a significantly heavier liver than males. Clasper elongation was the first step in male maturation, followed by clasper calcification and the development of alar thorns. In mature females, the right ovary was larger than the left, which was apparently due to differences in stroma tissue. Gonadosomatic index and diameter of ovarian follicles of mature females peaked in late spring and was at a minimum from late summer and through the winter. Juvenile S. bonapartii were more abundant near estuarine areas during winter, and adults appeared in estuaries by late spring and summer. Females carrying egg-cases were found near the shore in late spring and egg-cases were found in benthic samples only in shallow waters suggesting that S. bonapartii deposits egg-cases in shallow waters during late spring-summer and that nursery areas are in outer estuarine zones. In the southern part (38 -42 S) of the study area S. bonapartii showed a strong movement to shallow waters in late spring and summer, spreading over the entire coastal area in winter. These movements are discussed in relation to water temperature and trophic interactions.

BackgroundDNA barcoding has been advanced as a promising tool to aid species identification and discovery through the use of short, standardized gene targets. Despite extensive taxonomic studies, for a variety of reasons the identification of fishes can be problematic, even for experts. DNA barcoding is proving to be a useful tool in this context. However, its broad application is impeded by the need to construct a comprehensive reference sequence library for all fish species. Here, we make a regional contribution to this grand challenge by calibrating the species discrimination efficiency of barcoding among 125 Argentine fish species, representing nearly one third of the known fauna, and examine the utility of these data to address several key taxonomic uncertainties pertaining to species in this region.Methodology/Principal FindingsSpecimens were collected and morphologically identified during crusies conducted between 2005 and 2008. The standard BARCODE fragment of COI was amplified and bi-directionally sequenced from 577 specimens (mean of 5 specimens/species), and all specimens and sequence data were archived and interrogated using analytical tools available on the Barcode of Life Data System (BOLD; www.barcodinglife.org). Nearly all species exhibited discrete clusters of closely related haplogroups which permitted the discrimination of 95% of the species (i.e. 119/125) examined while cases of shared haplotypes were detected among just three species-pairs. Notably, barcoding aided the identification of a new species of skate, Dipturus argentinensis, permitted the recognition of Genypterus brasiliensis as a valid species and questions the generic assignment of Paralichthys isosceles.Conclusions/SignificanceThis study constitutes a significant contribution to the global barcode reference sequence library for fishes and demonstrates the utility of barcoding for regional species identification. As an independent assessment of alpha taxonomy, barcodes provide robust support for most morphologically based taxon concepts and also highlight key areas of taxonomic uncertainty worthy of reappraisal.

The total lengths (LT) at which 50% were mature of Psammobatis rudis and Psammobatis normani, in the south‐west Atlantic were: P. rudis, 428 mm for males and 414 mm for females and P. normani, 443 mm for males and 403 mm for females. Clasper length in mature males was greater in P. normani than in P. rudis, whereas oviducal gland width was not different between species. Females of P. normani with egg cases were found in every month sampled, and in January, March, April and July in P. rudis, although insufficient samples were available to identify peak oviposition times. Geographic variation in size frequency and maturity were found. The effects of oceanographic conditions and fishing pressure are discussed. Size at 50% maturity in both species was >74% of the maximum LT, indicating late sexual maturity and low potential stock recovery rate.

Egg cases of 21 oviparous chondrichthyan species from the south-west Atlantic Ocean are described and compared. The catshark Schroederichthys bivius has a cigar-shaped egg case with curled tendrils only at the posterior end. Egg cases of the elephant fish Callorhinchus callorynchus are spindle-shaped with anterior and posterior tubular extensions and lateral flanges. The skate Amblyraja doellojuradoi presents medium-sized egg cases (71 mm in length) with a lateral keel extending to the first portion of the horns. The endemic skate species of the genus Atlantoraja have medium to large egg cases (69-104 mm in length) and present relatively large posterior horns. Egg cases of the genus Bathyraja have a medium size, 75-98 mm in length, and are characterized by a very similar morphology, a relatively smooth to rough surface case and posterior horns strongly curved inwards. Egg cases of the genera Dipturus and Zearaja are very large, 115-230 mm in length, and have a well-developed posterior apron. Despite the problematical identification of skates at species level, the egg capsules of the endemic genus Psammobatis are easily diagnosed; the capsules are small (25-53 mm in length), those of Psammobatis rutrum being the smallest known to date in the world. Egg cases of Rioraja agassizi have a medium size, 61-68 mm in length, relatively straight sides, a smooth surface and silky attachment fibres placed in the lateral keel next to each horn. Those of the genus Sympterygia are small to medium sized, 51-86 mm in length, and display the thickest lateral keel and the longest posterior horns among the skates of the world. Egg cases can be a useful tool for identifying species and egg-laying areas; therefore, a provisional key for the south-west Atlantic Ocean chondrichthyan capsules is presented.

The fish fauna of the Pampa Plain, the southernmost distribution range of many Neotropical species, was barcoded in this study. COI sequences were analysed by means of distance (K2P/NJ) and character-based (ML) models, as well as the Barcode Index Number (BIN). K2P/NJ analysis was able to discriminate among all previously identified species while also revealing the likely occurrence of two cryptic species that were further supported by BIN and ML analyses. On the other hand, both BIN and ML were not able to discriminate between two species of Rineloricaria. Despite the small genetic divergence between A. cf. pampa and A. eigenmanniorum, a tight array of haplotypes was observed for each species in both the distance and character-based methods. Deep intraspecific divergences were detected in Cnesterodon decemmaculatus (5%) and Salminus brasiliensis (6%). For Salminus brasiliensis, these findings were further supported by character-based (ML) evidence and meristic and morphological data. Our results also showed that Pampa Plain representatives of Salminus brasiliensis, Rhamdia quelen, Hoplias malabaricus, Synbranchus marmoratus, Australoheros facetus, Oligosarcus jenynsii and Corydoras paleatus differed by more than 3% from their conspecifics from other parts of South America. Overall, this study was able to highlight the likely occurrence of a cryptic species in Salminus brasiliensis and also illustrate the strong geographical structure in the COI sequence composition of seven fish species from South America.

With an estimate of around 9,000 species, the Neotropical region hosts the greatest diversity of freshwater fishes of the world. Genetic surveys have the potential to unravel isolated and unique lineages and may result in the identification of undescribed species, accelerating the cataloguing of extant biodiversity. In this paper, molecular diversity within the valuable and widespread Neotropical genus Hoplias was assessed by means of DNA Barcoding. The geographic coverage spanned 40 degrees of latitude from French Guiana to Argentina. Our analyses revealed 22 mitochondrial lineages fully supported by means of Barcode Index Number, Automatic Barcode Gap Discovery and phylogenetic analyses. This mtDNA survey revealed the existence of 15 fully supported mitochondrial lineages within the once considered to be the continentally distributed H. malabaricus. Only four of them are currently described as valid species however, leaving 11 mitochondrial lineages currently “masked” within this species complex. Mean genetic divergence was 13.1%. Barcoding gap analysis discriminated 20 out of the 22 lineages tested. Phylogenetic analyses showed that all taxonomically recognized species form monophyletic groups. Hoplias malabaricus sensu stricto clustered within a large clade, excluding the representatives of the La Plata River Basin. In the H. lacerdae group, all species but H. curupira showed a cohesive match between taxonomic and molecular identification. Two different genetic lineages were recovered for H. aimara. Given the unexpected hidden mitochondrial diversity within H. malabaricus, the COI sequence composition of specimens from Suriname (the type locality), identified as H. malabaricus sensu stricto, is of major importance.

SUMMARY: The present paper analyses the diet, feeding strategy and niche width of B. macloviana in a sector of the Argentinean Continental Shelf (ACS). Individuals (n = 147) were collected from 43 sampling stations in late summer and autumn 2001. Thirty one alimentary items in the gut contents were found, with a clear dominance of polychaetes. Crustaceans were secondary alimentary items. The polychaete Travisia kerguelensis was the main food item ingested, followed by Nepthyidae, Sabellidae and Lumbrineridae, while Gammaridae and Cirolanidae were the main items among crustaceans. The niche width and feeding strategy displayed by B. macloviana support the specialisation towards polychaetes throughout this study. Slow motile and infaunal species constitute major preys. The results suggest that this skate actively selects worms, reflecting, in some sense, the composition of the polychaete assemblage, and allowing a low dietary overlap with other sympatric skates of the ACS.Keywords: skates, feeding strategy, polychaetes, niche width, specialist, Argentina. RESUMEN: ECOLOGÍA ALIMENTARIA DE BATHYRAJA MACLOVIANA (RAJIFORMES, ARHYNCHOBATIDAE): UNA RAYA CONSUMIDORA DE POLIQUETOS DEL ATLÁNTICO SUDOCCIDENTAL. -En el presente trabajo se analiza la dieta, estrategia alimentaria y amplitud del nicho trófico de Bathyraja macloviana en un sector de la Plataforma Continental Argentina (ACS). Los individuos (n = 147), fueron colectados en 43 estaciones de muestreo a fines de verano y otoño de 2001. Fueron encontrados 31 ítems en los contenidos estomacales con una clara dominancia de poliquetos. Los crustáceos constituyeron ítems secundarios. El poliqueto Travisia kerguelensis fue el principal ítem consumido seguido por Nepthyidae, Sabellidae y Lumbrineridae, mientras que Gammaridea y Cirolanidae fueron los ítems principales entre los crustáceos. En este estudio, la amplitud de nicho y la estrategia alimentaria de esta especie muestran su especialización hacia poliquetos. Especies de baja motilidad e infaunales constituyeron las presas fundamentales. Los resultados sugieren que esta raya selecciona activamente poliquetos, reflejando de algún modo las asociaciones de poliquetos, lo que permite un bajo solapamiento con otras especies de rayas simpátricas del Atlántico Sudoccidental.Palabras clave: rayas, estrategia alimentaria, poliquetos, amplitud de nicho, especialista, Argentina.

Atherinopsidae are widespread freshwater and shallow marine fish with singular economic importance. Morphological, genetical and life cycles differences between marine and estuarine populations were already reported in this family, suggesting ongoing speciation. Also, coexistence and interbreeding between closely related species were documented. The aim of this study was to infer boundaries among: (A) Odontesthes bonariensis and O. argentinensis at species level, and intermediate morphs; (B) the population of O. argentinensis of Mar Chiquita Lagoon and its marine conspecifics. To achieve this, we integrated, meristic, Geometrics Morphometrics and DNA Barcode approaches. Four groups were discriminated and subsequently characterized according to their morphological traits, shape and meristic characters. No shared haplotypes between O. bonariensis and O. argentinensis were found. Significative-meristic and body shape differences between the Mar Chiquita and marine individuals of O. argentinensis were found, suggesting they behave as well differentiated populations, or even incipient ecological species. The fact that the Odontesthes morphotypes shared haplotypes with both, O. argentinensis and O. bonariensis, but also possess meristic and morphometric distinctive traits open new questions related to the origin of this morphogroup.