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Ferrari, S., Rey, S., Hoglund, E., Overli, O., Chatain, B., MacKenzie, S., et al. (2020). Physiological responses during acute stress recovery depend on stress coping style in European sea bass, Dicentrarchus labrax. Physiol. Behav., 216, 112801.
Résumé: Individual stress coping style (reactive, intermediate and proactive) was determined in 3 groups of 120 pit tagged European seabass using the hypoxia avoidance test. The same three groups (no change in social composition) were then reared according to the standards recommended for this species. Then, 127 days later, individuals initially characterized as reactive, intermediate or proactive were submitted to an acute confinement stress for 30 min. Blood samples were taken to measure plasma cortisol levels 30 min (Stress30) or 150 min (Stress150) after the end of the confinement stress. Individuals were then sacrificed to sample the telencephalon in order to measure the main monoamines and their catabolites (at Stress30 only). Individuals from Stress150 were sampled for whole brain for a transcriptomic analysis. The main results showed that reactive individuals had a lower body mass than intermediate individuals which did not differ from proactive individuals. The physiological cortisol response did not differ between coping style at Stress30 but at Stress150 when intermediate and proactive individuals had recovered pre stress levels, reactive individuals showed a significant higher level illustrating a modulation of stress recovery by coping style. Serotonin turnover ratio was higher in proactive and reactive individuals compared to intermediate individuals and a significant positive correlation was observed with cortisol levels whatever the coping style. Further, the confinement stress led to a general increase in the serotonin turnover comparable between coping styles. Stress150 had a significant effect on target mRNA copy number (Gapdh mRNA copy number decreased while ifrd1 mRNA copy number increased) and such changes tended to depend upon coping style.
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Gueroun, S. K. M., Molinero, J. C., Piraino, S., & Daly Yahia, M. N. (2020). Population dynamics and predatory impact of the alien jellyfish Aurelia solida (Cnidaria, Scyphozoa) in the Bizerte Lagoon (southwestern Mediterranean Sea). Mediterr. Mar. Sci., 21(1), 22–35.
Résumé: Understanding the life cycle strategies and predatory impact of alien jellyfish species is critical to mitigate the impact that these organisms may have on local populations, biodiversity, and ultimately on the functioning of food webs. In the Mediterranean Sea, little is known about the dynamics of alien jellyfish, despite this biodiversity hotspot being one of the most threatened areas by increasing numbers of alien jellyfish. Here, we investigated the population dynamics and predatory impact of a non-indigenous scyphomedusa, Aurelia solida Browne 1905, in the Bizerte Lagoon, Tunisia. The study was based on bimonthly surveys performed over two consecutive years, from November 2012 to August 2014. Field observations showed that the planktonic phase of A. solida occurs from winter to early summer. Prey composition was investigated by means of gut content and field zooplankton analyses. Calanoid copepods, mollusc larvae, and larvaceans represented the main food items of A. solida. To determine the jellyfish feeding rate and their predatory impact on zooplankton populations, the digestion time for zooplankton prey was assessed at three different temperatures: 13, 18, and 23 degrees C in laboratory conditions, corresponding to the average range of temperatures encountered by A. solida in the Bizerte Lagoon. We found that A. solida consumed 0.5-22.5% and 0.02-37.3% of the daily zooplankton standing stock in 2013 and 2014, respectively. These results indicate a non-negligible but restricted seasonal grazing impact on some mesozooplankton groups, explained by the relatively short lifespan of the medusa stage (5-6 months).
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Guilhaumon, F., Basset, A., Barbone, E., & Mouillot, D. (2012). Species–area relationships as a tool for the conservation of benthic invertebrates in Italian coastal lagoons. Estuarine Coastal and Shelf Science, 114, 50–58.
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Guinand, B., Chauvel, C., Lechene, M., Tournois, J., Tsigenopoulos, C. S., Darnaude, A. M., et al. (2016). Candidate gene variation in gilthead sea bream reveals complex spatiotemporal selection patterns between marine and lagoon habitats. Marine Ecology Progress Series, 558, 115–127.
Résumé: In marine fishes, the extent to which spatial patterns induced by selection remain stable across generations remains largely unknown. In the gilthead sea bream Sparus aurata, polymorphisms in the growth hormone (GH) and prolactin (Prl) genes can display high levels of differentiation between marine and lagoon habitats. These genotype-environment associations have been attributed to differential selection following larval settlement, but it remains unclear whether selective mortality during later juvenile stages further shapes genetic differences among habitats. We addressed this question by analysing differentiation patterns at GH and Prl markers together with a set of 21 putatively neutral microsatellite loci. We compared genetic variation of spring juveniles that had just settled in 3 ecologically different lagoons against older juveniles sampled from the same sites in autumn, at the onset of winter outmigration. In spring, genetic differentiation among lagoons was greater than expected from neutrality for both candidate gene markers. Surprisingly, this signal disappeared completely in the older juveniles, with no significant differentiation for either locus a few months later in autumn. We searched for signals of haplotype structure within GH and Prl genes using next-generation amplicon deep sequencing. Both genes contained 2 groups of haplotypes, but high similarities among groups indicated that signatures of selection, if any, had largely been erased by recombination. Our results are consistent with the view that differential selection operates during early juvenile life in sea bream and highlight the importance of temporal replication in studies of post-settlement selection in marine fish.
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Haffray, P., Enez, F., Bugeon, J., Chapuis, H., Dupont-Nivet, M., Chatain, B., et al. (2018). Accuracy of BLUP breeding values in a factorial mating design with mixed families and marker-based parentage assignment in rainbow trout Oncorhynchus mykiss. Aquaculture, 490, 350–354.
Résumé: Marker-based parentage assignment provides the opportunity to investigate factors of efficiency for mixed-family designs and factorial mating. In such designs, family size is both uncontrolled and small, which may be thought to limit the accuracy of estimated breeding values (EBVs). The objective of this work was to estimate the accuracy of EBVs of growth and quality traits in a large factorial mating design and in commercial breeding conditions. An expected six hundred full-sib families of rainbow trout Oncorhynchus mykiss (2042 fish in total) were produced by ten factorial matings of six dams with ten sires. Fish were phenotyped for body weight, carcass yield, fillet yield, fillet fat content and fillet colour, and family information was recovered using microsatellite markers. The accuracy of EBVs was estimated using or removing individual performance to mimic combined family selection (with individual phenotype) or sib selection (without individual phenotype). The traits investigated had medium to high heritability (0.17–0.58). High to very high accuracy (0.630–0.817) was estimated for combined family selection. The accuracy of sib selection (not using individual phenotype) was 18–22% lower (0.542–0.638), but remained in the upper range reported for such traits. This level of accuracy was higher than those reported in conventional breeding programs using separate family rearing. This was true even for families with a very low number of full-sibs. Individual EBV accuracy was more closely linked to the total number of full- and half-sibs of each fish than to its number of full-sibs. We hypothesize that this was due to the factorial mating, which led to a high number of the genetic ties between sibs. These results highlight the possibility of introducing precise estimated breeding values for quality traits into combined or sib selection in breeding programs when using mixed families from factorial designs and marker-based parentage assignment in aquaculture species.
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