Disruption of endogenous tidal rhythms of larval release linked to food supply and heat stress in an intertidal barnacle

The timing of larval release may greatly affect the survivorship and distribution of pelagic stages and reveal important aspects of life history tactics in marine invertebrates. Endogenous rhythms of breeding individuals and populations are valuable indicators of selected strategies because they are free of the neutral effect of stochastic environmental variation. The high-shore intertidal barnacle Chthamalus bisinuatus exhibits endogenous tidal and tidal amplitude rhythms in a way that larval release would more likely occur during fortnightly neap periods at high tide. Such timing would minimize larval loss due to stranding and promote larval retention close to shore. This fully explains temporal patterns in populations facing the open sea and inhabiting eutrophic areas. However, rhythmic activity breaks down to an irregular pattern in a population within the São Sebastião Channel subjected to large variation of food supply around a mesotrophic average. Peaks of chl a concentration precede release events by 6 d, suggesting resource limitation for egg production within the channel. Also, extreme daily temperatures imposing mortality risk correlate to release rate just 1 d ahead, suggesting a terminal reproductive strategy. Oceanographic conditions apparently dictate whether barnacles follow a rhythmic trend of larval release supported by endogenous timing or, alternatively, respond to the stochastic variation of key environmental factors, resulting in an erratic temporal pattern.

Mecanismos divergentes de regulação do assentamento larval: estudo de caso em caranguejos e cracas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Interações alelopáticas reguladoras do assentamento larval do coral sol Tubastrea coccinea

CAPES

Culex quinquefasciatus storage proteins

Insect storage proteins accumulate at high levels during larval development of holometabolous insects. During metamorphosis they are degraded, supplying energy and amino acids for the completion of adult development. The genome of Culex quinquefasciatus contains eleven storage protein-coding genes. Their transcripts are more abundant in larvae than in pupae and in adults. In fact, only four of these genes are transcribed in adults, two of which in blood-fed adult females but not in adult males. Transcripts corresponding to all Cx. quinquefasciatus storage proteins were detected by RT-PCR, while mass spectrometric analysis of larval and pupal proteins identified all storage proteins with the exception of one encoded by Cq LSP1.8. Our results indicate that the identified Cx. quinquefasciatus storage protein-coding genes are candidates for identifying regulatory sequences for the development of molecular tools for vector control

Temporal and along-shelf distribution of the larval fish assemblage at Gran Canaria, Canary Islands

Temporal and spatial variations of the larval fish community off the island of Gran Canaria (Canary Islands) were studied in weekly surveys from October 2005 to June 2006. A total of 156 taxa, belonging to 51 families and 15 orders, were identified. Myctophidae was by far the most abundant family (30%), followed by Sparidae (11%), Clupeidae (9%) and Gonostomatidae (7%). As expected for an oceanic island, neritic and oceanic taxa contributed in similar proportions. Leeward and windward retention areas were found for total egg and neritic larval abundance. However, seasonality showed a stronger influence on the annual larval assemblage than sampling site, as the latter was not significant on a long time scale. Results suggest that there are two seasonal larval assemblages corresponding to the two main characteristic periods of the water column in these waters: mixing (winter) and stratification (summer). In addition, a significant relationship was recorded between lunar illumination and small mesozooplankton biomass, suggesting that this relationship may be extended to certain neritic families. The most abundant neritic larvae (Sparidae) showed this lunar pattern, which partially supports a recent hypothesis about the effect of lunar illumination on larval fish survival and development in subtropical waters.

Importance of the proportions of dietary polyunsaturated fatty acids and antioxoidants in larval development of marine fish

La acuicultura es uno de los sectores con mayor crecimiento en la producción animal mundial, con una tasa superior al 5% anual en la última década (Izquierdo et al., 2008). En la acuicultura, el éxito del cultivo de cualquier especie de peces marinos está limitado por la cantidad y la calidad de la producción en masa de sus alevines (Izquierdo y Fernández - Palacios, 1997). Por lo tanto, para cubrir las crecientes demandas de la producción de semillas, es necesario mejorar la calidad nutritiva de sus larvas, lo cual todavía constituye una de las principales limitaciones para el desarrollo del cultivo de especies de peces marinos (Watanabe et al., 1983; Yúfera y Pascual, 1984; Sargent et al. 1997; Izquierdo et al., 2000). Aunque la producción Mediterránea del cultivo de peces marinos se ha incrementado en varias especies, la dorada Sparus aurata continúa siendo la especie mas cultivada (Izquierdo, 2005), con una producción anual de alevines que supera los 120 millones/ año. La demanda de alevines de buena calidad está aumentando a un ritmo del 10% anual, pero el éxito de la producción de los juveniles se ve muy afectado por la eficacia de la primera alimentación y la calidad nutricional de la dieta de arranque (Kolkovski et al., 1993; Sargent et al., 1997; Izquierdo et al., 2000). En general, la dorada y la lubina europea (Dicentrarchus labrax) son las especies más importantes de peces marinos criados en la región mediterránea y han caracterizado el desarrollo de la acuicultura marina en esta región en las últimas tres décadas (FAO, 1999). Además, en la producción, de ambas especies, se prevee una mayor expansión (Basurco y Abellán, 1999). Sin embargo, a pesar de que el engorde de estas especies está bien controlado, el conocimiento de sus necesidades nutricionales, en comparación con otras especies como salmónidos y carpas, sigue siendo incompleto (NRC, 1993). Por lo tanto, para obtener un mejor crecimiento y una mayor tasa de supervivencia, es esencial una dieta que responda a las necesidades nutricionales de las larvas, tanto cualitativas como cuantitativas (Kolkovski et al., 1993; Sargent et al., 1997). Además, incluso antes de que comience el desarrollo larvario, los huevos de los peces deben contener todos los nutrientes que cubran los requerimientos adecuados para el desarrollo del embrión (Izquierdo y Fernández - Palacios, 1997). En los últimos años, las investigaciones han prestado gran atención a la importancia de los lípidos dietéticos para larvas de peces marinos (Izquierdo et al., 2003), puesto que son esenciales para el crecimiento y el desarrollo de los mismos (Watanabe, 1982; Sargent et al., 1999a). Como reflejo de esta importancia, la dieta para dorada y lubina se ha convertido en una dieta altamente energética (25% de lípidos) en comparación con la década anterior (12% de lípidos) (Izquierdo et al., 2003). Los lípidos dietéticos proporcionan una fuente rica de energía y fosfolípidos y son fundamentales para la estructura de las biomembranas. Los lípidos dietéticos también sirven como vehículos para la absorción de otros nutrientes, como las vitaminas liposolubles A, D, E, y K, y pigmentos naturales o sintéticos. Los lípidos son componentes de las hormonas y precursores para la síntesis de diversos metabolitos funcionales, como las prostaglandinas y otros eicosonoides. Además, los lípidos dietéticos son reconocidos como uno de los factores nutricionales más importantes que afectan el crecimiento y la supervivencia de las larvas (Watanabe et al., 1983), porque constituyen materiales esenciales para la formación normal de célula, las membranas de los tejidos y el desarrollo de órganos (Izquierdo et al., 1998, 2003; Pousaò et al., 2003). Sin embargo, la utilización de los lípidos dietéticos por las larvas puede verse afectada directa o indirectamente por varios cambios morfológicos y fisiológicos que ocurren durante el desarrollo larvario. En los últimos años ha habido más interés en todos estos aspectos nutricionales de los lípidos en las larvas de peces, debido a la importancia de utilización de los lípidos dieteticos para el óptimo crecimiento y supervivencia larvaria (Izquierdo et al., 2000).

Enhancement of gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) larval growth by dietary vitamin E en relation to diffetent levels of essential fatty acids

[EN]Most marine fish larvae require high amounts of n-3 HUFA (highly unsaturated fatty acids) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (Watanabe, 1982; Izquierdo, 1996). Fish larvae tissue lipids are also very high in n-3 HUFA, what implies a higher risk of peroxidation (Sargent et al. 1999) and cellular damage (Kanazawa, 1991), requiring then antioxidants to protect them intra- and extra-cellularly from free radical compounds. Vitamin E (Vit E) functions as a chain breaking antioxidant, reacting with the lipid peroxide radical produced and preventing the further reaction with a new PUFA. Hence their requirements are related with the dietary and tissue PUFA contents. The objective of the present study was to determine the effect of dietary Vit E on gilthead sea bream and sea bass survival, growth and stress, at different n-3 HUFA levels.

Effect of larval density and feeding sequence on meagre (Argyrosomus regius Asso, 1801) larval rearing

[EN] Meagre, has been proposed as a candidate for marine finfish diversification on commercial aquaculture (Quémèner, 2002, Mateos, 2007). Despite of the elevated on growing potential, the most important bottleneck of this specie is related to the limited production of fry. Larval rearing of this species, is performed mainly adapting seabream culture techniques with different success (Roo et al., 2007) However, since limited information about the optimal feeding sequences and nutritional requirements of meagre is available, more research is needed on larval rearing protocols and nutrition. Present results (elevated larval growth rate, high survival, short rotifers period) are very promising for a successful implementation at industrial scale, which helps to solve the continues lack of fry of this specie in the Mediterranean and Canary islands.

Effect of rearing system intensiveness on biological features, culture performance and larval quality of meagre (Argyrosomus regius Asso, 1801) larvae

[EN]Meagre, Argyrosomus regius A., is a new species for aquaculture in south Atlantic and Mediterranean regions, that can reach a mean fresh weight of 8.02±2.51g. at 95dah. However, hatchery techniques must be improved to optimize culture performance and larval quality. Eggs of meagre were cultured under intensive (75 indv.l-1 in 2m3 tanks) and semi-intensive system (7.5 indv.l-1 in 40m3 tanks) to evaluate the effect of the intensification on biological features, stress resistance and skeletal deformities. At 30dah, despite in semi-intensive system reared larvae a higher total length (19.08± 2.3mm vs 16.00±1.54mm), dry body weight (13.09± 2.43mg vs 6.46±0.52mg), and survival after the activity test (75.0± 13.8% vs 53.3±11.5%) was found, the use of intensive systems were also very suitable and cost-effective for larval rearing of this species

Long-term variability and effects on larval fish distribution of the Gulf of Mexico Loop Current and Rings

Programa de doctorado: Oceanografía