Potenciales presas zooplanctónicas (Copepoda y Appendicularia) para Engraulis anchoita en relación con las distribuciones de larvas tempranas y de desove en la región frontal patagónica (océano Atlántico sudoccidental)

We investigated the spatial distribution of the abundance, biomass and size of zooplankton (nauplii, calanoids, cyclopoids and appendicularians) in relation to the distribution of first-feeding larvae and eggs of Engraulis anchoita across the frontal system of Peninsula Valdés. Twelve samples of zooplankton and ichthyoplankton were taken with small Bongo (67 μm) and Pairovet (200 μm) nets during the spring of 2004 along two transects. The total abundance of zooplankton and the chlorophyll a concentration were higher in homogeneous waters, while total biomasses were higher in stratified waters. Temperature was negatively correlated with biological variables and was the main factor affecting the zooplankton distribution. In both transects, abundance peaks of first-feeding larvae were detected at coastal stations along with the smallest fraction of zooplankton ( < 500 μm), while the largest fraction was dominant at the external stations, coinciding with the highest egg abundance. The physical structure of this front generates different levels of food availability for first-feeding larvae. Calanoids (southern transect) and cyclopoids (northern transect) are predominant followed by nauplii and appendicularians. The biomass of zooplankton preys contributes to the carbon transfer to the upper trophic levels and is probably important for the survival and growth of anchovy larvae in this frontal system.Se investigó la distribución espacial de la abundancia, biomasa y las tallas del zooplancton (nauplii, calanoideos, ciclopoideos y apendicularias) en relación con la distribución de las larvas en estadio de primera alimentación y los huevos de Engraulis anchoita en el sistema frontal de Península Valdés. Se tomaron 12 muestras de zooplancton e ictioplancton durante la primavera de 2004 a lo largo de dos transectos, mediante una red Minibongo (67 μm) y una Pairovet (200 μm) respectivamente. La abundancia total del zooplancton y la concentración de clorofila fue mayor en aguas homogéneas, mientras que la biomasa fue mayor en aguas estratificadas. La temperatura se correlacionó negativamente con las variables biológicas siendo ésta el principal factor que afectó la distribución del zooplancton. En las estaciones costeras de ambos transectos, se encontró la mayor abundancia de larvas en coincidencia con la fracción más pequeña de zooplancton ( < 500 μm), mientras que la fracción más grande fue dominante en las estaciones externas, en coincidencia con la mayor abundancia de huevos. La estructura física de este frente genera diferente disponibilidad de alimento para las larvas siendo los calanoideos (transecto sur) y los ciclopoideos (transecto norte) predominantes, seguidos por nauplii y apendicularias. La biomasa de dicho alimento zooplanctónico podría contribuir a la transferencia de carbono a los niveles tróficos superiores y esto sería importante para la supervivencia y crecimiento de la anchoita en este sistema frontal

Heritability of morphological and life history traits in a pelagic tunicate

Populations may adapt in response to selection pressures imposed by global environmental change. In marine zooplankton, measurements of the heritability of key life history characters, and thus the potential for evolution, are still rare. Here we demonstrate the feasibility of conducting controlled mating experiments with the dioecious appendicularian Oikopleura dioica to explore the narrow-sense heritability and genetic correlation among morphological and life history traits. At our standard laboratory conditions (15 ± 1°C, 100 μg C l–1), mature females were larger (1.213 ± 0.19 mm, mean ± SD) and lived longer (8.5 ± 2.18 d) than did males (1.115 ± 0.15 mm, 7.6 ± 2.07 d). The heritability (±SE) of morphological characters was low (trunk size, 0.37 ± 0.25; house size, 0.39 ± 0.23) to moderate (tail length, 0.50 ± 0.31). In contrast, an important life history trait, lifespan, showed high heritability (0.89 ± 0.47) and may therefore respond rapidly to selection pressure, either in the laboratory or in the wild.Fil: Lobon, Carla M.. Universidad de Oviedo; EspañaFil: Acuña, José L.. Universidad de Oviedo; EspañaFil: López Alvarez, Marcos. Universidad de Oviedo; EspañaFil: Capitanio, Fabiana Lia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Raman phonon spectrum of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O7

The Raman spectrum of Ba2CuGe2O7, a tetragonal insulator which develops Dzyaloshinskii-Moriya helical magnetism below TN=3.2K, has been detected at temperatures varying from 300 to 80 K in a single crystal, with the radiation polarized either in the ab plane or along the c axis of its tetragonal cell. Twenty-nine phonon lines out of the 35 allowed by the Raman selection rules for the present geometry were observed, and their vibrational frequencies were found in overall good agreement with those provided by shell-model calculations. Together with the previous report on the infrared-active phonons [A. Nucara, Phys. Rev. B 90, 014304 (2014)PRBMDO1098-012110.1103/PhysRevB.90.014304], the present study provides an exhaustive description, both experimental and theoretical, of the lattice dynamics in Ba2CuGe2O7.Fil: Capitanio, Fabiana Lia. Università degli studi di Roma ; ItaliaFil: Koval, Sergio Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Fittipaldi, Diego Rodrigo. Universita di Salerno; Italia. Consiglio Nazionale delle Ricerche; ItaliaFil: Caramazza, S.. Università degli studi di Roma ; ItaliaFil: Paris, E.. Istituto Italiano di Tecnologia. Center for Life Nano Science at Sapienza; ItaliaFil: Mohamed, W. S.. Università degli studi di Roma ; ItaliaFil: Lorenzana, J.. Consiglio Nazionale delle Ricerche; Italia. Università degli studi di Roma ; ItaliaFil: Nucara, A.. Consiglio Nazionale delle Ricerche; Italia. Università degli studi di Roma ; ItaliaFil: Rocco, L.. Consiglio Nazionale delle Ricerche; Italia. Universita di Salerno; ItaliaFil: Vecchione, A.. Consiglio Nazionale delle Ricerche; Italia. Universita di Salerno; ItaliaFil: Postorino, P.. Università degli studi di Roma ; ItaliaFil: Calvani, P.. Università degli studi di Roma ; Italia. Consiglio Nazionale delle Ricerche; Itali