Mariano González-Castro

Morphometric and genetic assessment of the Cynoscion guatucupa population structure from Buenos Aires coast, Argentine Sea

This study analyzed the morphometric, microsatellite loci and mitochondrial control region variation of the striped weakfish from two feeding and spawning grounds in the coastal area of Buenos Aires province. The characterization of the body shape proved to be different between sites. Genetic structure analysis showed that the main source of genetic variation was within populations rather than among populations and low genetic differentiation was observed between sites. The striped weakfish inhabiting the coastal areas of Buenos Aires would exhibit two management units in agreement with other fishes studied in both areas.

Transcriptomic differentiation underlying marine‐to‐freshwater transitions in the South American silversides Odontesthes argentinensis and O. bonariensis (Atheriniformes)

Abstract Salinity gradients are critical habitat determinants for freshwater organisms. Silverside fishes in the genus Odontesthes have recently and repeatedly transitioned from marine to freshwater habitats, overcoming a strong ecological barrier. Genomic and transcriptomic changes involved in this kind of transition are only known for a few model species. We present new data and analyses of gene expression and microbiome composition in the gills of two closely related silverside species, marine O. argentinensis and freshwater O. bonariensis and find more than three thousand transcripts differentially expressed, with osmoregulatory/ion transport genes and immune genes showing very different expression patterns across species. Interspecific differences also involve more than one thousand transcripts with nonsynonymous SNPs in the coding sequences, most of which were not differentially expressed. In addition to characterizing gill transcriptomes from wild‐caught marine and freshwater fishes, we test experimentally the response to salinity increases by O. bonariensis collected from freshwater habitats. Patterns of expression in gill transcriptomes of O. bonariensis exposed to high salinity do not resemble O. argentinensis mRNA expression, suggesting lack of plasticity for adaptation to marine conditions in this species. The diversity of functions associated with both the differentially expressed set of transcripts and those with sequence divergence plus marked microbiome differences suggest that multiple abiotic and biotic factors in marine and freshwater habitats are driving transcriptomic differences between these species.

Surfing among species, populations and morphotypes: Inferring boundaries between two species of new world silversides (Atherinopsidae).

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.

External morphology, postcranial and appendicular osteology of three southwestern Atlantic flatfishes ( Paralichthys , Paralichthyidae), and comparisons with other congeneric species

Comparisons of the external morphology and analysis of osteological features of the postcranial and appendicular skeletons of three southwestern Atlantic flatfish species of the genus Paralichthys (P. isosceles, P. orbignyanus and P. patagonicus) were carried out. Bones are described, and detailed morphological, morphometric and meristic characteristics of these flounders are given in order to provide information about the external and internal morphology of three species of Paralichthys occurring in the south-west Atlantic waters that add new information and will help regarding within the framework of a phylogenetic study of the group. Interspecific differences were found in the number of vertebrae and intermuscular bones, as well as in the morphology and morphometry of vertebrae, caudal skeletons, pectoral and pelvic girdle bones. Relationships between bones are discussed and bone characteristics compared with those found in other species of Paralichthys and in other pleuronectiform species. The position of Paralichthys isosceles within Paralichthys is discussed, along with other congeners such as P. triocellatus and P. oblongus.(AU)

Juveniles recruitment and daily growth of the southern stock of Mugil liza (Actinopterygii; Fam. Mugilidae): new evidence for the current life-history model

Fil: Castellini, Damian Luis. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

Reproduction of Brevoortia aurea (Spix & Agassiz, 1829) (Actinopterygii: Clupeidae) in the Mar Chiquita Coastal Lagoon, Buenos Aires, Argentina

Reproductive biology of the Brazilian menhaden, Brevoortia aurea (Clupeiformes), was studied in Mar Chiquita Coastal Lagoon. Its abundance was analysed in relation to environmental variables, and the main biological-reproductive parameters were estimated: size at first maturity, batch and relative fecundity, frequency distribution of oocyte diameters and gonadosomatic index (GSI). Moreover, its reproductive cycle was analysed histologically. Samples were collected from May 2012 to April 2013. Once the spawning period was detected, extra samples were added (October and November 2013). The specimens were caught with gillnets, at a distance of 2,300 meters from the mouth of the lagoon. The highest abundances were observed in the months of October and November. Both macroscopic and microscopic analysis allowed to confirm that in these months the saraca spawn in the mixo-eurihaline area of the lagoon. Females were recorded in the five phases of ovarian development. Histological and frequency distribution of oocyte diameters characterized this species as a batch spawner with undetermined fecundity. The fecundity varied between 19,900 and 178,508 oocytes/female. Relative fecundity ranged between 41 and 381 oocytes/g female ovary free. The size at first maturity was estimated on 277 and 265 mm total length for females and males, respectively.

El uso de otolitos y huesos de la cabeza para la identificación de dos especies del género Merluccius, en estudios de predador-presa

A comparative osteological analysis of 6 bones and the sagitta otolith in Merluccius hubbsi and M. australis, two species that live in Southwest Atlantic, has been carried out. The objective was to contribute to identifying these two species as prey in the diet studies, and further description of these bony elements for a better taxonomic identification. Fresh bones disarticulation techniques were used. Potentially diagnostic features were observed for discrimination of species in the following elements: urohyal, maxilla, premaxilla, dentary, quadrate, hyomandibular, and the sagitta otolith.