Response to Commentary on “Are some invertebrates exquisitely sensitive to the human pharmaceutical fluoxetine?”

International audienceWe appreciate the commentary made by Sumpter and Margiotta-Casaluci (in this issue) who are participating in the brainstorming around the effects of antidepressants on non-target aquatic organisms based on two recent articles published in Aquatic Toxicology, our paper Di Poi et al. (2013) and Franzellitti's article (Franzellitti et al., 2013)

Déterminisme de la structure sociale chez le bar juvénile Dicentrarchus labrax en conditions d'auto-nourrissage (approches neuro-éthologique et physiologique)

Ce travail avait pour objectif de déterminer, par une approche multidisciplinaire, la structure sociale émergente au sein de groupes de bars juvéniles Dicentrarchus labrax en conditions d'auto-nourrissage. Les résultats montrent que seuls quelques individus, les manipulateurs principaux, sont particulièrement actifs vis-à-vis du distributeur à la demande, alors que le reste du groupe reste peu, voire totalement inactif. Une telle structuration sociale semble pérenne et particulièrement robuste. Les manipulateurs principaux ne présentent aucun bénéfice en termes de prise alimentaire et de croissance, ils ne démontrent pas non plus de comportement agressif pour défendre l'accès au levier ou à l'aliment. Néanmoins, l'activité du manipulateur principal semble ajustée sur les besoins du groupe qui bénéficie de sa production. Ce modèle social ressemble à de nombreux égards au modèle de producteur / profiteur , dans lequel les profiteurs usurpent la nourriture trouvée par le (ou les) producteur(s). Si aucun bénéfice apparent n'est décelable pour les manipulateurs principaux, en revanche, ces individus présentent une bonne efficacité alimentaire. Il reste à déterminer si cette différence d'efficacité alimentaire est une conséquence de leur fonction ou une cause qui les prédisposerait à devenir les manipulateurs principaux. Nos résultats démontrent également une corrélation négative entre les niveaux physiologiques de stress (5-HIAA/5-HT), expression ARNm POMC, cortisol plasmatique) et le statut de demande alimentaire des individus. Ces différences de stress peuvent s'expliquer par les différences inter-individuelles dans le contrôle du système de nourrissage et la possibilité d'anticiper ou non l'heure et la fréquence des repas. Enfin, ces travaux montrent que les canaux de communication visuels et chimiques sont la base de systèmes de communication chez le bar, et que ce dernier dispose de capacités cognitives relativement élaborées pour la transmission sociale et pour la reconnaissance conspécifiques familiers (individus du même groupe social). Cette capacité de reconnaissance module les réponses comportementales mais également l'expression neurale du neuropeptide arginine vasotocine (AVT) au niveau de l'aire préoptique de l'hypothalamus. Au-delà de la contribution de ces travaux dans la connaissance du comportement social du bar juvénile, nos résultats sont susceptibles d'intéresser les pisciculteurs. Il contribue à la mise en évidence d'indicateurs éthologiques et physiologiques dans le cadre de l'amélioration du bien être des poissons au sein des élevagesBy a multidisciplinary approach, this PhD work aimed to determine the social structure underlying the individual differences in self-feeding behaviour within juvenile sea bass Dicentrarchus labrax groups. The results show that a few individuals, the high-triggering fish, within the group strongly operate the self-feeder, whereas the remaining individuals are composed of low- and null-triggering fish. Such triggering structure exhibits a high constancy and seems to be particulary robust. However, the high-triggering fish do not show direct benefits, neither in feed intake nor in growth rate. In addition, they do not exhibit agonistic behaviour for the food ressource or the trigger defence. Moreover, the activity of the high-triggering fish seems to be adjusted on the whole group food needs rather than on their own needs. Such social model looks like the producer / scrounger social model, in which the scroungers are individuals usurping the ressources found by producers. No visible benefits are noticed for the high-triggerers, however, they appear to be most feed efficient fish in the group. Then a question remains, whether such food efficiency differences are the consequence of their triggering function or the cause which lead one individual to achieve the high-triggering status. Our results also show a negative correlation between physiological stress levels (5-HIAA /5-HT, POMC mRNA expression, plasma cortisol) and the individual triggering behaviour. We assume that these differences may be linked to the individual differences in the control of the time and the frequency of the meal distribution, which permits to the high-triggering fish an advantage to anticipate the meal time. Finally, the last studies show that the visual and chemical sensory cues are the basis of conspecific communication in juvenile sea bass. In addition, this fish species exhibits cognitive abilities for social transmission and recognition of familiar conspecifies (based on a past experience). Such social recognition modulates behavioural responses, as well as, the neural expression of the neuropeptide arginine vosotocin (AVT) in the preoptic area of the hypothalamus. On one hand, this wotrk contributes to improve scientific knowledge on the social behaviour of sea bass ; on the other hand, our results may have a real interest for fish farmers to identify ethological and physiological indicators of sea bass welfare in aquacultureST ETIENNE-BU Sciences (422182103) / SudocSudocFranceF

Pacific oysters do not compensate growth retardation following extreme acidification events

International audienceOcean acidification caused by anthropogenic carbon dioxide emissions alters the growth of marine calcifiers. Although the immediate effects of acidification from global ocean models have been well studied on calcifiers, their recovery capacity over a wide range of pH has never been evaluated. This aspect is crucial because acidification events that arise in coastal areas can far exceed global ocean predictions. However, such acidification events could occur transiently, allowing for recovery periods during which the effects on growth would be compensated, maintained or amplified. Here we evaluated the recovery capacity of a model calcifier, the Pacific oyster Crassostrea gigas . We exposed juveniles to 15 pH conditions between 6.4 and 7.8 for 14 days. Oyster growth was retarded below pH 7.1 while shells were corroded at pH 6.5. We then placed the oysters under ambient pH > 7.8 for 42 days. Growth retardation persisted at pH levels below pH 7.1 even after the stress was removed. However, despite persistent retardation, growth has resumed rapidly suggesting that the oysters can recover from extreme acidification. Yet we found that the differences in individual weight between pH conditions below 7.1 increased over time, and thus the growth retardation cannot be compensated and may affect the fitness of the bivalves

Seawater carbonate chemistry and growth retardation of Pacific oyster Crassostrea gigas

We evaluated the recovery capacity of a model calcifier, the Pacific oyster Crassostrea gigas. We exposed juveniles to 15 pH conditions between 6.4 and 7.8 for 14 days. Oyster growth was retarded below pH 7.1 while shells were corroded at pH 6.5. We then placed the oysters under ambient pH > 7.8 for 42 days. The oysters from each pH condition were briefly dried with absorbent paper and the total wet body weight was measured with a Mettler precision balance (Mettler-Toledo) during the exposure period on days 6, 10 and 14, and then during the ambient pH period on days 4, 7, 9, 11, 14, 18, 22, 28, 36 and 42

Pacific oysters do not compensate growth retardation following extreme acidification events

Ocean acidification caused by anthropogenic carbon dioxide emissions alters the growth of marine calcifiers. Although the immediate effects of acidification from global ocean models have been well studied on calcifiers, their recovery capacity over a wide range of pH has never been evaluated. This aspect is crucial because acidification events that arise in coastal areas can far exceed global ocean predictions. However, such acidification events could occur transiently, allowing for recovery periods during which the effects on growth would be compensated, maintained or amplified. Here we evaluated the recovery capacity of a model calcifier, the Pacific oyster Crassostrea gigas. We exposed juveniles to 15 pH conditions between 6.4 and 7.8 for 14 days. Oyster growth was retarded below pH 7.1 while shells were corroded at pH 6.5. We then placed the oysters under ambient pH > 7.8 for 42 days. Growth retardation persisted at pH levels below pH 7.1 even after the stress was removed. However, despite persistent retardation, growth has resumed rapidly suggesting that the oysters can recover from extreme acidification. Yet we found that the differences in individual weight between pH conditions below 7.1 increased over time, and thus the growth retardation cannot be compensated and may affect the fitness of the bivalves

Seawater carbonate chemistry and effects of ocean acidification and wariming on life-history traits of the Pacific oyster Crassostrea gigas

Ocean acidification and warming (OAW) are pressing contemporary issues affecting marine life and specifically calcifying organisms. Here, we investigated the direct effects of OAW on life-history traits of the Pacific oyster Crassostrea gigas, the most cultivated bivalve species worldwide. We also tested whether parental conditioning history shaped the phenotypic characters of their progenies (intergenerational carryover effects). Adult oysters and their offspring were exposed to two temperatures (18°C, +3°C) under ambient pH conditions or under an end-of-century acidification scenario (−0.33 pH unit). In adults, we monitored standard biometric and reproductive parameters, stress response by quantifying neuroendocrine metabolites and gamete quality. In larvae, we measured hatching rate, size, biochemical quality, and behavior. We found that reducing pH reduced growth rate and activated the serotonin system, but increasing temperature attenuated these effects. There was no effect of pH on reproduction at either temperature, and no intergenerational carryover effects. Larval characteristics were similar between treatments, regardless of parental conditioning history. Thus, the Pacific oyster seems robust to changes in pH, and increasing temperature is not an aggravating factor. We emphasize that the use of neuroendocrine indicators holds promise for revealing sublethal impacts of environmental changes

Cryptic and biochemical responses of young cuttlefish Sepia officinalis exposed to environmentally relevant concentrations of fluoxetine

International audienceAntidepressants released in the environment have the potential to generate neural disrupting effects in non-target organisms, yet their putative effects on behaviors have never been studied in cephalopod molluscs. This study assessed the impact of the antidepressant fluoxetine (FLX) on the efficiency of cryptic behaviors (body patterns on uniform, checkerboard and sandy substrates), locomotor activity, and brain chemistry in young cuttlefish exposed to environmental concentrations (1 and 100 ng L−1 of FLX) during the perinatal period. Behavioral responses of cuttlefish were monitored at hatching and two weeks later, and brain monoamine contents were quantified at one month of age. FLX significantly altered the camouflage efficiencies on uniform and sandy backgrounds only at the lowest concentration, but not at 100 ng L−1. Hatchlings exposed to 1 ng L−1 of FLX exhibited a duration exposure-dependent decrease in the uniform camouflage. They also showed a significant increase of the frequency of sand digging behaviors which might make them highly visible to predators in nature. When tested again two weeks later, cuttlefish seemed to have recovered and no more behavioral alterations were observed showing a transitory effect of the antidepressant. FLX did not affect the levels of serotonin, norepinephrine and their metabolites; however, it seemed to influence dopaminergic activity between the two FLX-exposed groups. The results show for the time that environmentally realistic concentrations of a single SSRI significantly impair the cryptic performances of newly hatched cuttlefish, and may ultimately reduce their chance for survival

Seawater carbonate chemistry and reaction norms of two oyster species living in contrasting habitats

We deciphered the reaction norms of two oyster species living in contrasting habitats: the intertidal oyster Crassostrea gigas and the subtidal flat oyster Ostrea edulis, which are two economically and ecologically valuable species in temperate ecosystems. Six-month-old oysters of each species were exposed in common garden tanks for 48 days to a pH gradient ranging from 7.7 to 6.4 (total scale). The database contains data from: 1. seawater physico-chemical parameters during the acclimation period, 2. oyster survival during the acclimation period, 3. biometrics of oyster species, 4. shell coloration of oyster species, 5. composition of the membrane fatty acids of oyster species, 6. temporal evolution of the phytoplankton cell volume, 7. fatty acid composition of phytoplankton, 8. energy reserves of oyster species

Life-history traits in the Pacific oyster Crassostrea gigas are robust to ocean acidification under two thermal regimes

International audienceAbstract Ocean acidification and warming (OAW) are pressing contemporary issues affecting marine life and specifically calcifying organisms. Here, we investigated the direct effects of OAW on life-history traits of the Pacific oyster Crassostrea gigas, the most cultivated bivalve species worldwide. We also tested whether parental conditioning history shaped the phenotypic characters of their progenies (intergenerational carryover effects). Adult oysters and their offspring were exposed to two temperatures (18°C, +3°C) under ambient pH conditions or under an end-of-century acidification scenario (−0.33 pH unit). In adults, we monitored standard biometric and reproductive parameters, stress response by quantifying neuroendocrine metabolites and gamete quality. In larvae, we measured hatching rate, size, biochemical quality, and behavior. We found that reducing pH reduced growth rate and activated the serotonin system, but increasing temperature attenuated these effects. There was no effect of pH on reproduction at either temperature, and no intergenerational carryover effects. Larval characteristics were similar between treatments, regardless of parental conditioning history. Thus, the Pacific oyster seems robust to changes in pH, and increasing temperature is not an aggravating factor. We emphasize that the use of neuroendocrine indicators holds promise for revealing sublethal impacts of environmental changes