Molecular characterisation of Sardina pilchards larvae diet in Málaga Bay (SW Mediterranean Sea)

The study of predation in the early life stages of fish by direct observation of their stomach content is very difficult, mostly because prey lose all identifiable characteristics. We developed a multiplex-PCR based method, which detected within the gut of the larvae the presence/absence of the five main species of copepods that live in Malaga Bay: Clausocalanus parapergens, Oncaea waldemari, Paracalanus indicus, Temora stylifera and Acartia clausi. A set of five species-specific primers were designed and combined in a single multiplex PCR system, which allowed a time and cost effective screening of the samples. The method detected as little as 0.09 ng/μL of copepod DNA without cross-reactions with Sardina pilchardus DNA

First estimates of metabolic rate in Atlantic bluefin tuna larvae

Author's accepted manuscript.Available from 26/07/2021.This is the peer reviewed version of the following article: Blanco, E., Reglero, P., Ortega, A., Folkvord, A., de la Gándara, F., Hernández de Rojas, A. & Moyano, M. (2020). First estimates of metabolic rate in Atlantic bluefin tuna larvae. Journal of Fish Biology, 97(5), 1296-1305, which has been published in final form at https://doi.org/10.1111/jfb.14473. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.acceptedVersio

The effect of nutritional condition on the growth to post-flexion of bluefin tuna larvae under cultured condition

These findings indicate that protein synthesis increase in proportion to the flexion stage which is strongly associated with the development of the digestive system and therefore the increase in the nutritional condition. Ontogenetic differences in the RNA and DNA content will be discussed in more detail. Also, the pattern obtained for Atlantic bluefin tuna larva will be compared with those of other species

Metabolic rates in Atlantic bluefin tuna larvae: first data and methodological challenges

Atlantic bluefin tuna is an emblematic scombrid species, but many physiological aspects during the larval stages are still unknown. The mechanisms of how fish larvae balance growth and activity are of great interest since metabolic costs are very high compared to juveniles and adults. However, there is a lack of information about metabolic costs in scombrid larvae. This lack of data is probably related to the challenges associated to larval handling before and during respirometry trials. In this study for the first time, we: i) estimate the relationship between routine metabolic rate and the larval dry weight (mass scaling exponent) at 26°C, ii) measure metabolism under light and darkness and iii) explore the influence of nutritional status (RNA:DNA ratio) on the inter-individual variability in metabolic rates. The relationship between metabolism and size (ranging from 0.6 to 23 mg) was near isometric (slope, b=0.99), in contrast to the allometric relationship observed in most species (b=0.87). Our results show no significant differences in oxygen consumption under light and darkness. A possible regulation (decrease) of their swimming activity with the consequent decrease in the oxygen consumption in light situations is discussed. Nutritional condition did not explain the inter-individual differences in oxygen consumption. This study first reports metabolic rates of Atlantic bluefin tuna larvae and discusses the challenges of performing bioenergetics studies with early life stages of Scombrids

Propuesta de desarrollo de una aplicación web para la sugerencia de horarios y salas basado en algoritmos genéticos para el Juzgado de Control y Enjuiciamiento Penal del Estado de Guerrero

El artículo presenta una propuesta para solucionar la problemática de visualizar y proporcionar sugerencias de fechas para asignar horarios y salas para las audiencias de un Juzgado de Control, poder modelar y resolver este problema de una manera más concisa permitirá lograr mejoras significativas al proceso actual. Se plantea un modelo donde los recursos, en este caso salas, horarios y Jueces, no pueden compartirse en un momento determinado, es aquí donde se ven reflejadas las restricciones de tiempo, espacio y recursos para el correcto funcionamiento del proceso. Se plantea utilizar algoritmos genéticos para intentar reducir la incidencia de errores causados por la distribución manual de los recursos y a su vez disminuir el tiempo que esto conlleva dentro del Juzgado de Control y Enjuiciamiento Penal del Estado de Guerrero

Long-term effect of a short pulse of dietary supplementation with algae on the quality of turbot (Scophthalmus maximus) frozen fillets

This study raises the question of the potential long-term effects of a feeding pulse with diets containing algal biomass on the quality of frozen turbot (Scophthalmus maximus) fillets. A feeding trial was carried out with this aim, in which juvenile turbot were fed during 60 d with six different experimental diets, two of which were enriched with the macroalgae Ulva rigida (U diets), the other two with a microalgae blend (M diets), plus a non-supplemented control diet (CT), and finally, a commercial aquafeed (COM). Two inclusion levels were considered in algae-enriched diets (50 and 100 g kg-1) so that they were designed as U5 and U10 for U. rigida, and M5 and M10 for microalgae-enriched diets. The duration of the feeding pulse with the functional diets was 60 days, and then, all specimens were fed with a COM diet for a further 150-d period until reaching a body size close to the commercial standard (approximately 750 g). Subsequently, fish were sacrificed; fillets were removed from the pigmented flank and kept at -20 °C for 5 months. Then, fillets were thawed and the muscle proximal composition and fatty acid profile were analyzed, and fillet quality parameters were assessed during a 10-d co\ld storage period at 4°C. The possible deferred effects of algae-enriched diets on fillet quality were compared with a control diet without algae (CT) and with a commercial diet (COM). Roughly, the results obtained indicated that a 60-d administration pulse of algae-enriched diets induced some long-term changes in both the nutritional and organoleptic quality of turbot fillets. In this regard, the algae-enriched aquafeeds improved the muscle antioxidant response throughout the cold storage period, prolonging the shelf life of thawed turbot fillets. In addition, in terms of consumers’ acceptability, this feeding pulse on pre-growing stage of the productive cycle was able to modify the skin and muscle pigmentation of fish of commercial size. Namely, the U10 diet increased the protein content, improved muscle texture, reduced fillet total lipid content, and favored muscle selective retention of n-3 polyunsaturated fatty acids. On the other hand, the strategy based on the early administration of a diet rich in fishmeal (CT) for 60 d, followed by feeding with commercial feed, also affected positively the quality of fillets, with values comparable to U10 specimens. Thus, the results obtained indicate that a two-month feeding pulse with algae-supplemented diets during pre-growing phase may represent a promising strategy to improve the nutritional and organoleptic quality of frozen turbot fillet, as well as to extend their shelf life during the post-thawing cold storage

Seasonal variability of oceanographic conditions off NW Galician waters influencing the early life trophic ecology of European hake Merluccius merluccius by stable isotope analysis

Stable isotopes of nitrogen (δ15N) and carbón (δ13C) have been used as tracers for analyzing the trophic ecology of European hake larvae collected during the winter and summer of 2012 off NW Galicia. The sampling times correspond to periods of high and low hake spawning activity, respectively. Trophic enrichment was analyzed using as baseline two different plankton size fractions, corresponding to micro- (55-200μm) and mesozooplankton (>200μm). During both seasons, the δ15N signatures of hake larvae showed higher values than the zooplankton fractions. The first survey carried out in late February was characterized by a preceding marked upwelling, low geostrophic velocities in the hydrographic circulation and an intense mixing of the water column. This environmental scenario is hypothesizing that originated a great nutrient availability for primary consumers showed its effect in the low δ15N values observed in plankton and hake larvae. During July, the environmental setting corresponded to period where the water column was stratified, an anticyclonic gyre was formed in the center of the study area that concentrated particles and weak upwelling conditions and strong geostrophic currents where found. This scenario was characterized hypothetically by low nutrient availability in which production is mainly based on regenerated nutrients which would explain the higher δ15N values found during this period. On the other hand, the greater δ13C values observed in summer in comparison to winter suggest differences in the energetic sources of carbon (Fig. 1). The discussion of results is centered in how oceanographic variability conditions signatures of stable isotope fractionation in the early life trophic food web influencing the variable trophic pathways of larval hake subject to contrasting environmental conditions, thereby affecting their larval nutritional condition as estimated by RNA/DNA ratios and the Fulton index. This study was financed by the projects: CRAMER-CTM2010-21856-CO3 y ECOPREGA-10MMA602021P

POTENCIAL PROBIÓTICO DE CEPAS DE BACILLUS CON PROPIEDADES ANTIMICROBIANAS FRENTE A PATÓGENOS DE PECES

El objetivo de este trabajo ha sido aislar, identificar y caracterizar cepas bacterianas procedentes de ambiente marino, fitoplancton, zooplancton, huevos, larvas de lenguado y diferentes juveniles (branquias, intestino, piel), que pudieran tener actividad probiótica y actividad antibacteriana frente a distintos patógenos de peces. Se aislaron un total de 217 cepas bacterianas. Tras un primer cribado mediante ensayos de inhibición en placa frente a patógenos, se seleccionaron 9 cepas y se identificaron utilizando la secuenciación de su rRNA 16S. Los resultados mostraron que las mejores candidatas eran cepas del género Bacillus. Varios de estas posibles cepas candidatas se caracterizaron in vitro para determinar su potencial probiótico, mediante ensayos de inhibición en co-cultivo con V. anguillarum, resistencia a bilis de pez, y adherencia a mucus intestinal de pez. Nuestros resultados mostraron que algunas de las cepas seleccionadas pertenecientes al género Bacillus, podrían ser consideradas como potenciales probióticos frente a patógenos de peces, por lo que el beneficio de la administración de estas cepas a cultivos de peces será posteriormente estudiada