J. M. Díaz de Astarloa

DNA barcoding highlights a cryptic species of grenadier Macrourus in the Southern Ocean.

Although three species of the genus Macrourus are recognized in the Southern Ocean, DNA sequencing of the mitochondrial COI gene revealed four well-supported clades. These barcode data suggest the presence of an undescribed species, a conclusion supported by meristic and morphometric examination of specimens.

Fish composition in a south-western Atlantic temperate coastal lagoon: spatial–temporal variation and relationships with environmental variables

Mar Chiquita, an irregularly shaped brackish-water coastal lagoon, is located in the Buenos Aires province of Argentina and considered since 1996 by the Coordination Council of the Man and Biosphere Program of UNESCO as a World Reserve of Biosphere. The present paper aims to study both the spatial and temporal variation of fish composition in this coastal lagoon and the influence of some environmental variables on the relative abundance of the main fish species. Monthly sampling surveys over a two-year period in three different areas were conducted, using a beach-seine net and three monofilament-gill nets with different mesh size. Twenty-eight species belonging to four bio-ecological categories were identified, five of them are new records for Mar Chiquita fish community. The correspondence analysis showed strong relationships between high salinity range and the abundance of Brevoortia aurea, Cynoscion guatucupa and Pomatomus saltatrix. Conversely, low salinity range corresponded to high abundance of Mugil platanus and Odontesthes argentinensis. High temperatures were corresponded with abundance of Micropogonias furnieri and Brevoortia aurea. In contrast, high abundance of both Odontesthes argentinensis and Oligosarcus jenynsii were corresponded to low temperatures. Brevoortia aurea, Mugil platanus and Odontesthes argentinensis were the most abundant species, representing more than 80% of the total capture. The group of estuarine-nondependent-marine fish presented the highest species richness. Estuarine-dependent-marine species presented for both juveniles and adults specimens the highest abundance values.

Chondrichthyan egg cases from the south-west Atlantic Ocean

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.

Morphological, morphometric, meristic and osteological evidence for two species of hake (Actinopterygii: Gadiformes: Merluccius) in Argentinean waters

Morphologically, both classic and landmark-based morphometry and meristic analyses of 241 specimens of Merluccius, along with the re-examination of six paratype specimens of Merluccius hubbsi, the holotype and three paratypes of Merluccius patagonicus and the syntype of Merluccius australis revealed the presence of only two species of Merluccius in Argentinean waters. Internal structures (hyomandibula, urohyal and sagitta otolith) of M. hubbsi were compared to those reported for M. patagonicus and were shown to have identical morphology. Type specimens of M. patagonicus showed a complete overlap in morphometric and meristic characters with M. hubbsi, whereas M. australis had a greater number of second dorsal and anal-fin rays, and more lateral-line scales. In addition, M. australis had a smaller eye and longer snout than M. hubbsi and M. patagonicus. The results indicate that there is no evidence for a third hake species in Argentinean waters. Merluccius patagonicus is a synonym of M. hubbsi.

First record of Callorhinchus callorynchus and Trachurus lathami , in a south-western Atlantic coastal lagoon

*Laboratorio de Ictiologia, Departamento de Ciencias Marinas, Universidad Nacional de Mar del Plata (UNMdP), Argentina. †Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET). ‡Museo del Mar, Mar del Plata, Argentina. ∫Comision de Investigaciones Cientificas de la Provincia de Buenos Aires (CIC). §Instituto Nacional de Investigacion y Desarrollo Pesquero (INIDEP). ¶Corresponding author, e-mail: blasina@mdp.edu.ar

Barcoding Antarctic Fishes: Species Discrimination and Contribution to Elucidate Ontogenetic Changes in Nototheniidae

Fish species richness in the Southern Ocean accounts for approximately 2 % of the world’s ocean species, with more than 370 species registered and several awaiting for formal description. Here we explore on the use of DNA barcoding to discriminate fishes from Antarctic Peninsula by compiling our results and placing them into a comparative framework with other previous studies to provide a comprehensive review of available barcodes for Antarctic fishes. A total of 275 specimens, belonging to 36 different putative species were barcoded. Nearly all species exhibit unique barcodes or clusters of closely related haplotypes, and only four species lacked genetic resolution using Barcode Index Numbers (BINs). Thus, ~90 % of the species barcoded in this study could be identified at species level with accuracy using BINs. However the use of nucleotic diagnostic character allowed us to discriminate the remaining species. Compiling our results with previous studies, about 80 species inhabiting the Antarctic Peninsula were already barcoded, representing approximately 60 % of the species occurring in the area. Finally, we highlighted ontogenetic morphological traits observed in some Notothenidae, which may lead to misidentification of juveniles. DNA Barcoding was a cornerstone element for obtaining a reliable identification of these specimens. These results are crucial for management and conservation purposes since an accurate species-level resolution of juveniles is necessary to determine nursery areas and to clarify species distributions.