Éditeur(s) : Elsevier
Résumé : The individual food-demand behavior of juvenile European sea bass (Dicentrarchus labrax, L.) reared in groups under self-feeding conditions was investigated. The triggering activity on self-feeder, i.e. index of the food-demand activity, agonistic interactions and territorial behavior were monitored for periods of 42 to 68 days in six groups of 50 fish. The specific growth rate was calculated and the brain serotonergic activity was used as a stable index of social stress. Inter-individual differences appeared in triggering activity and three groups were distinguished: 3-5 high-triggering fish, 17-30 low-triggering fish and the remaining individuals were null-triggering fish. There were no significant differences in specific growth rates calculated at the end of the experiment (day 42 or day 68) between individuals with high, low, and null food-demand (ANOVA, p > 0.05). No territorial or agonistic behaviors were observed, however, there were significant differences in brain scrotonergic activity between the three triggering groups (ANOVA, p=0.050 in telencephalon and p=0.004 in cerebellum). Specifically, high-triggering fish had lower serotonergic turnover than low or null-triggering fish. We put forth the hypothesis that fish with low or null-triggering activity could be stressed by the high activity of high-triggering individuals. (c) 2006 Elsevier Inc. All rights reserved.
Physiology & Behavior (0031-9384) (Elsevier), 2007-03 , Vol. 90 , N. 4 , P. 559-566

Droits : 2006 Elsevier Inc. All rights reserved
http://archimer.ifremer.fr/doc/2007/publication-2637.pdf
DOI:10.1016/j.physbeh.2006.11.005
http://archimer.ifremer.fr/doc/00000/2637/

Éditeur(s) : NRC
Résumé : In self-feeding conditions, a few individual sea bass (Dicentrarchus labrax (L., 1758)) display strong activity in striking the food dispenser, whereas the remaining individuals of the group actuate the feeder weakly or never. Here, we investigated the effects of removal of the individuals showing dominant activity on the social and feeding behaviours in groups of juvenile sea bass. Following removal, new fish showing a dominant self-feeding activity quickly appear. They always come from the group of fish that have a low number of triggering actuations. This observation shows that it takes less time, about 5 days after the removal of dominant triggerers vs. 14 days at the beginning, for the re-establishment of the behavioural structure, suggesting the possibility of social transmission between individuals. The fish that show weak triggering activity seem to reach the high-food triggering level without obvious signs of competition. This experiment reveals the importance of the food-demand behavioural structure: the fish displaying the highest activity lead to a general food distribution and play a dominant role in feeding the entire group. Functional plasticity in this role within individuals is also demonstrated, indicating that the high-triggering function is essential for the group and not for the individual themselves.
Au sein d'un groupe de bars (Dicentrarchus labrax (L., 1758)) placés en auto-nourrissage, quelques individus disposent d'une activité forte de déclenchement volontaire du distributeur d'aliments. Les autres poissons du groupe disposent d'une activité de demande faible voire nulle. Ici, nous avons étudié l'impact du retrait des poissons à forte activité sur le comportement alimentaire et social de groupes de bars juvéniles. De nouveaux individus à forte activité réapparaissent rapidement, provenant exclusivement de la classe de poissons de faible demande. Cinq jours en moyenne suffisent après le retrait, contre 14 jours au début de l'expérience, pour que la structure comportementale se rétablisse suggérant l'existence d'une transmission sociale entre les individus. Ces poissons de faible activité semblent de plus atteindre leur nouvelle fonction sans aucun signe de compétition. Cette expérience révèle d'abord l'importance de la structure de la demande alimentaire puisqu'elle réapparaît après le retrait. Elle montre également que l'activité des forts manipulateurs conduit à une distribution générale de l'aliment et contribue à nourrir le groupe en entier. L'étude montre enfin une plasticité fonctionnelle indiquant que seule la fonction de manipulateur fort est essentiel pour la stabilité du groupe, non l'identité des individus par elle-même.
Canadian journal of zoology (0008-4301) (NRC), 2008-09 , Vol. 86 , N. 9 , P. 1015-1023

Droits : 2008 NRC Canada
http://archimer.ifremer.fr/doc/2008/publication-4766.pdf
DOI:10.1139/Z08-077
http://archimer.ifremer.fr/doc/00000/4766/

Éditeur(s) : HAL CCSD Landes Bioscience
Résumé : International audience
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
Autophagy

hal-00735751
https://hal.archives-ouvertes.fr/hal-00735751
PUBMED : 22966490