Sebastián Sánchez

Migration and brackish environment use of Prochilodus lineatus (Characiformes: Prochilodontidae) inferred by Sr:Ca ratio transects of otolith

otolith sections were analyzed for Sr:Ca with laser ablation-inductively coupled plasma-mass spectrometry (LA ICP-MS) to infer habitat use of fish. To the interpretation of transects, a threshold that represents the transition between freshwater and brackish environments was calculated using the Sr:Ca ratio of the otolith edge of specimens captured in the first section of the La Plata Estuary (salinity ≥ 0.5 PSU). The percentage of fish using the estuary was higher in the Parana (37%) than the Uruguay River (5%). Change-point analysis showed that fish entered the estuary between 1 and 3 times throughout life at a wide range of ages (0-15 years). These incursions had no obvious periodicity. This information should be integrated into future management actions, which should also be specific to each area since migration patterns differ between the major rivers of the basin.

Desarrollo Ontogénico de la Columna Vertebral y del Esqueleto Caudal en Larvas de Rhamdia quelen en Condiciones de Larvicultura Intensiva

Se analiza por primera vez el desarrollo osteologico de la columna vertebral y del esqueleto caudal en larvas de Rhamdia quelen mantenidas bajo condiciones controladas y con alimentacion artificial. Entre los dias 1 a 20 posteriores a la eclosion (dpe) se muestrearon a intervalos regulares 400 larvas, que se colorearon y transparentaron siguiendo la tecnica de Taylor & Van Dike. En los primeros dias de vida, las larvas presentan una notocorda recta en toda su longitud. El inicio de la formacion de la columna vertebral fue observado a los 7 dpe con la aparicion de las espinas neurales y hemales, y entre los 9 y 10 dpe para las tres primeras vertebras. La osificacion de la columna vertebral ocurrio en sentido craneo-caudal y fue completa a los 20 dpe. El esqueleto caudal inicia su desarrollo entre los 3 y 4 dpe, con la formacion de los hipurales (H), parahipural (PH) y los radios caudales. Los H 1 al 4 se formaron como primordios cartilaginosos en la cara ventral de la porcion distal de la notocorda, mientras que posteriormente lo hicieron el H 5 y el PH en el extremo distal y proximal del esqueleto caudal, respectivamente. El complejo centro ural (CCU) se osifico inicialmente en dos partes, una anterior que resulta de la combinacion del centro preural 1 y el ural 1 y una posterior con el ural 2. Los primeros radios de la aleta caudal aparecieron en larvas en flexion, mientras que despues de los 13 dpe, todos los ejemplares presentaron los radios principales osificados (ocho en la parte superior y ocho en la inferior). El desarrollo de la columna vertebral y del esqueleto caudal en R. quelen muestra patrones similares a los descriptos en otros peces teleosteos aunque con algunas particularidades que lo diferencian de los grupos relacionados.

Development of the Vertebral Column and Caudal Skeleton in Prochilodus lineatus Larvae under Laboratory Conditions

Se describe el desarrollo osteologico de la columna vertebral y del esqueleto caudal en larvas de sabalo (Prochilodus lineatus) bajo condiciones controladas hasta los 30 dias posteriores a la eclosion (dpe). El inicio de la formacion de la columna vertebral fue observado entre los 10-12 dpe (8,3 mm de longitud estandar, LE) con la aparicion de los primeros procesos neurales, hemales y cuerpos vertebrales pre-caudales. La osificacion de la columna vertebral ocurrio en sentido craneo-caudal y fue completa a los 28 dpe (22,6 mm LE). El esqueleto caudal inicio su desarrollo entre los 6 y 8 dpe con la formacion de los hipurales (H), parahipural (PH) y los radios caudales principales y secundarios. Los H 1 al 3 se formaron como primordios cartilaginosos en la cara ventral de la porcion distal de la notocorda, mientras que posteriormente se formaron los H 4 al 6 y el PH. Los primeros radios de la aleta caudal fueron observados en correspondencia con la formacion de los H 2 y 3, mientras que a los 28 dpe se observo la completa formacion de los mismos, existiendo 10 radios en el lobulo dorsal y 9 en el lobulo ventral. Los epurales, en numero de tres, fueron evidentes como elementos cartilaginosos en dorsal de la notocorda y distalmente a los arcos neurales, permaneciendo sin osificarse hasta los 25 dpe. El complejo centro ural se constituyo por la fusion de tres estructuras, el centro preural 1, el ural 1 y 2. El desarrollo de la columna vertebral y del esqueleto caudal muestran patrones similares a los descriptos en otros teleosteos.

Sensory and instrumental textural changes in fillets from Pacú (Piaractus mesopotamicus) fed different diets

The influence of two dietary treatments on quality properties, like textural parameters, sensory profile, and nutritional composition of Pacú fillets (Piaractus mesopotamicus) were studied. Pacú were fed diets based on plant-meals containing 13 g 100 g-1 fish meal (FMD) or bovine plasma protein concentrate (BPPD) as a complete replacement of fish meal. Harvested fish were filleted, kept frozen at -20C for 7 days before analysis. Chemical composition, amino acid and fatty acid profiles, and CIE-Lab parameters of fillets were measured. Sensory characteristics and texture profile analysis (TPA) were conducted for cooked portions. Average values of TPA hardness, chewiness, and deformability modulus were higher in BPPD samples but there was no significant difference in cohesiveness between samples. In accordance with TPA, higher values of firmness and chewiness as well as less flaky muscle were detected in BPPD samples by sensory panel. However, there was no significant difference in the characteristics associated with higher freshness between samples. Total color difference was lower in BPPD samples. Differences in protein, lipid, ash, and moisture content of FMD or BPPD fillets were not found (p > .05). BPPD fillets showed higher basic and sulfur amino acids. Saturated and polyunsaturated fatty acid contents were higher in FMD fillets than BPPD. However, a significantly higher n-6/n-3 ratio for FMD fillets was observed. The higher values of textural parameters observed for BPPD cooked fillets and the lower n-6/n-3 ratio imply a better sensory and nutritional quality of fillets from fish fed with BPPD. PRACTICAL APPLICATIONS: A complete study is presented on how the source of protein and lipids in feed affect both the sensory profile and the nutritional composition of fillets of Pacú (omnivorous temperate freshwater fish) cultivated in the second stage of fattening. Instrumental texture analysis of the fillets is presented, identifying the indicators that match with sensorial analysis. This analysis can help the industry of aquaculture in the evaluation of new ingredients or diets for fish feeding with impact in the quality of fillets.

Administration of Three Autochthonous Bacillus subtilis Strains Induce Early Appearance of Gastric Glands and Vestiges of Pylorus in Piaractus mesopotamicus Larvae

Autochthonous microorganisms as probiotics are a novel alternative to antibiotics. The genus Bacillus is highly used by its ability to survive on adverse conditions. Piaractus mesopotamicus, a native fish, is the most produced specie in Argentinian aquaculture. The low level of knowledge, high stress conditions and demand of animals led to a deficit in the number of larvae and fry. The aim of this study was to evaluate the probiotic effect of previously selected autochthonous Bacillus on biometrical parameters of P. mesopotamicus larvae when administered together in a combined suspension in different doses and stages. Results showed that the bacterial administration did not cause significant effects on the variables evaluated. However, the dose containing 6 × 107 CFU L-1 of each strain showed the highest average values of P. mesopotamicus biological parameters, regardless the stage of administration. Histological evaluations of animals administered with this dose did not showed adverse effects and indicated the capability of this dose, administered in a particularly period of time, to stimulate the early appearance of gastric glands, vestiges of what would be the pylorus and a higher development of liver. Thus, we proposed the safe use of this dose in a combined probiotic mixture to be studied in further assays.

Factor de condición relativo de Leporinus Acutidens (v alenciennes, 1837) (pisces, anostomidae) en el Alto Rio Paraná, aguas abajo de la Represa Yacyretá

Leoporinus. Acutidens (Valenciennes, 1837) es una de las especies mas abundantes del Alto rio Parana. El objetivo del presente trabajo fue evaluar los cambios espacio-temporales en el estado de bienestar de sus poblaciones en un tramo de este rio, aguas abajo de la represa Yacyreta. Los peces fueron colectados, desde julio de 2009 a junio de 2013, con una bateria de redes agalleras en dos sitios seleccionados en relacion con su distancia a la represa (Ituzaingo = 1 km aguas abajo; Ita Ibate = 90 km aguas abajo). Se aplico un analisis factorial de la covarianza a fin de evaluar el efecto del sexo, sitios y ciclo hidrologico (2009/10, 2010/11, 2011/12, 2012/13) sobre el factor de condicion relativo Kn, de los peces. Los resultados mostraron que el factor fue siempre superior en las hembras. Las diferencias entre sitios de muestreo no fueron significativas, aunque se registraron valores de Kn, mas elevados en Ita Ibate. Ademas, se detecto un efecto significativo del ciclo hidrologico (p < 0,05), con valores de Kn, mayores en ciclos con inundaciones mas pronunciadas. Los resultados obtenidos demuestran el fuerte efecto modelador del regimen hidrologico sobre las poblaciones de L. acutidens en este tramo del rio Parana.

Isolation and Selection of Potentially Beneficial Autochthonous Bacteria for Piaractus mesopotamicus Aquaculture Activities

Piaractus mesopotamicus is the most produced specie in Argentinian fish culture with an annual production of 2,017 tons. The high demands of specimens generated a deficit of larvae, juveniles and sexually mature adults. The high stress conditions and the incidence of diseases had intensified this deficit. Probiotics are proven to increase survival and growth rates in aquaculture. The first step in the design of a putative probiotic is the selection of adequate microorganisms to boost fish health. Lactic Acid Bacteria and Bacillus are generally accepted as probiotics in aquaculture. In this work we obtained 522 isolates from different anatomical parts of P. mesopotamicus, with a total of 30 lactic acid bacteria (LAB) and 8 Bacillus strains submitted for the evaluation of their beneficial properties. Only eight of these strains were selected for further “in vivo” assays based on following criteria: production of inhibitory metabolites and biosurfactants, screening of antagonistic activity against foodborne and pathogenic microorganisms, ability to emulsify polar solvents and compatibility between strains. All selected microorganisms were identified by sequencing 16S RNA gene. Pure cultures of all strains herein studied are preserved in Centro de Referencia de Lactobacilos (CERELA-CONICET) and Laboratorio de Sanidad Animal of the Estacion Experimental Agropecuaria Rafaela, Instituto Nacional de Tecnologia Agropecuaria (INTA) culture collections.