An optimized whole-body corticosteroid hormones quantification method by LC-MS/MS for assessing stress levels in European glass eels (Anguilla anguilla).

The European eel (Anguilla anguilla) juvenile stage exhibits facultative estuarine migration. The causes of this behavior are yet unknown but it may have an impact on the population's fate by altering the sex ratio of the population. Recent studies have highlighted potential stress-related issues in glass eels settling in estuaries but studying stress response in small organisms requires sensitive, accurate and precise analytical methods.

Unravelling the metabolomic signatures of migrant and non-migrant glass eels (Anguilla anguilla) and their response to diazepam exposure.

Understanding the migratory cycle of the European eel is crucial for implementing effective conservation measures. The reasons why some glass eels settle in lower estuaries rather than migrating upriver remain unclear. This study aims to identify metabolomic signatures that distinguish active (migrant) from inactive (non-migrant) glass eels.

A psychiatric drug found in waste-water plant effluents alters the migratory behavior of critically endangered Anguilla anguilla juveniles.

Migratory fishes cross or settle in several environments potentially polluted. Psychiatric drugs, which represent one growing pollution and are found in discharges from waste-water treatment plants, may alter individual behaviors. Here, we assessed behavioral alterations in the upstream migratory behavior of Anguilla anguilla caused by diazepam, an anxiolytic.

Metabolomics to study the sublethal effects of diazepam and irbesartan on glass eels (Anguilla anguilla).

Since glass eels are continuously exposed to contamination throughout their migratory journey in estuaries, to a certain extent the fall in the population of this endangered species might be attributed to this exposure, which is especially acute in estuaries under high urban pressure. In this work, metabolomics was used to address the main objective of this study, to evaluate the effects of two pharmaceuticals previously identified as potential concerning chemicals for fish (diazepam and irbesartan) on glass eels. An exposure experiment to diazepam, irbesartan and their mixture was carried out over 7 days followed by 7 days of depuration phase.

Prioritization based on risk assessment to study the bioconcentration and biotransformation of pharmaceuticals in glass eels (Anguilla anguilla) from the Adour estuary (Basque Country, France).

The presence of contaminants of emerging concern in the aquatic environment directly impacts water-living organisms and can alter their living functions. These compounds are often metabolized and excreted, but they can also be accumulated and spread through the food chain. The metabolized contaminants can also lead to the formation of new compounds with unknown toxicity and bioaccumulation potential.

Modulation of Energy Metabolism and Epigenetic Landscape in Rainbow Trout Fry by a Parental Low Protein/High Carbohydrate Diet.

It is now recognized that parental diets could highly affect offspring metabolism and growth. Studies in fish are, however, lacking. In particular, the effect of a parental diet high in carbohydrate (HC) and low in protein (LP) on progeny has never been examined in higher trophic level teleost fish.

New insights into methylmercury induced behavioral and energy-related gene transcriptional responses in European glass eel (Anguilla anguilla).

The effect of methylmercury (MeHg) was investigated in glass eel migration behavior and metabolism. To migrate up estuary, glass eels synchronize their swimming activity to the flood tide and remain on or in the substratum during ebb tide. Following seven days of exposure to MeHg (100 ng L), glass eels migration behavior was expressed by their swimming synchronization to the water current reversal every 6.

Modeling of autophagy-related gene expression dynamics during long term fasting in European eel (Anguilla anguilla).

Autophagy is an evolutionary conserved cellular self-degradation process considered as a major energy mobilizing system in eukaryotes. It has long been considered as a post-translationally regulated event, and the importance of transcriptional regulation of autophagy-related genes (atg) for somatic maintenance and homeostasis during long period of stress emerged only recently. In this regard, large changes in atg transcription have been documented in several species under diverse types of prolonged catabolic situations.

Migratory behavior, metabolism, oxidative stress and mercury concentrations in marine and estuarine European glass eels (Anguilla anguilla).

The relationships between the migratory behavior, methylmercury (MeHg) concentrations, oxidative stress response and detoxification processes were investigated in glass eels collected in marine (Molliets) and estuarine (Urt) waters (Adour estuary, South West France) at the end of the fishing season (April). Glass eel migratory behavior was investigated in an experimental flume according to their response to dusk. Fish responding to the decrease in light intensity by ascending in the water column and moving with or against the flow were considered as having a high propensity to migrate (migrant).

No early gender effects on energetic status and life history in a salmonid.

Throughout an organism's early development, variations in physiology and behaviours may have long lasting consequences on individual life histories. While a large part of variation in critical life-history transitions remains unexplained, a significant proportion may be caused by early gender effects as part of gender-specific life histories shaped by sexual selection. In this study, we investigated the presence of early gender effects on the timing of emergence from gravel and the energetic status of brown trout (Salmo trutta) early stages.

Kleptoparasitism and aggressiveness are influenced by standard metabolic rate in eels.

Kleptoparasitism refers to either interspecific or intraspecific stealing of food already procured by other species or individuals. Within a given species, individuals might differ in their propensity to use such a tactic, in a similar manner to which they differ in their general level of aggressiveness. Standard metabolic rate is often viewed as a proxy for energy requirements.

Methylmercury effects on migratory behaviour in glass eels (Anguilla anguilla): an experimental study using isotopic tracers.

The effect of methylmercury (MeHg) on glass eels' propensity to migrate, mitochondrial activity and antioxidative defence systems was investigated. Marine glass eels were first sorted in an experimental flume according to their response to dusk. Fish responding to the decrease in light intensity by ascending in the water column and moving with or against the flow were considered as having a high propensity to migrate (migrant).

Spatial and seasonal variations of methylmercury in European glass eels (Anguilla anguilla) in the Adour estuary (France) and relation to their migratory behaviour.

Overall recruitment of European glass eels (Anguilla anguilla) has decreased significantly since the early 1980s. Due to their long life cycle, benthic/demersal habits and high lipid content, eels might accumulate high concentrations of contaminants, but data concerning glass eels are still scarce. This study provides original data on methylmercury (MeHg) concentrations in glass eels at spatial (marine and estuarine), annual and seasonal scales.

Female effects on offspring energetic status and consequences on early development in yolk feeding brown trout (Salmo trutta).

Energetic status can be defined as the interaction between energy stores and metabolic rate. In salmonids, it is variable and influences the timing of emergence, and therefore may have strong effects on both juvenile and maternal fitness. The aim of this study is to (i) describe the ontogeny of energy use for different brown trout clutches to understand how such a variability of energetic status is developed at the end of incubation and (ii) to estimate maternal influences over offspring physiological processes.

Influence of energetic status on ontogenetic niche shifts: emergence from the redd is linked to metabolic rate in brown trout.

Ontogenetic niche shift should occur when the ratio of growth opportunities to mortality risk becomes higher in the subsequent habitat. While most studies have focused on size to understand the timing of these shifts, an endogenous factor like energetic status (interaction between energy available and energy requirements) appears as a natural candidate to integrate and analyze the growth trade-off between habitats. In this study, we measure energetic content and metabolic rate of individual brown trout (Salmo trutta) fry at emergence from gravel to investigate the influence of energetic status on the timing of this critical ontogenetic niche shift.

Video tracking in the extreme: a new possibility for tracking nocturnal underwater transparent animals with fluorescent elastomer tags.

Initially developed so that an individual could be recognized in mark-recapture studies of aquatic animals, fluorescent visible implant elastomer (VIE) tags are used here for a new application in ethometry: the study of the behavior of transparent animals in dim light or in darkness using automatic tracking technology. The application and validation of this multitracking method is tested in the context of research on the estuarine migratory behavior of the glass eel (Anguilla anguilla), a crucial point to better understand the dynamics of this endangered species. The method makes it possible to measure the activity (notably the distance and speed) of four individuals as a function of tidal and nycthemeral rhythms in the same flume (a circular aquarium simulating river or estuarine conditions) across a wide time scale (from seconds to weeks).

Assessing maternal effects on metabolic rate dynamics along early development in brown trout (Salmo trutta): an individual-based approach.

Routine metabolic rate (oxygen consumption) of individual eggs and larvae of brown trout (Salmo trutta) originating from different families were monitored from fertilisation to the onset of emergence by means of flow through micro-respirometry. This measuring system revealed an accurate tool to measure oxygen consumption on small organisms at the individual level, and daily consumption proved to be very stable. The mass-specific metabolic rate remained low from fertilisation to hatching, and then increased quickly until the age of emergence.

Endocrine control of Anguilla anguilla glass eel dispersal: effect of thyroid hormones on locomotor activity and rheotactic behavior.

Dispersal, one of the most important processes in population ecology, is an issue linking physiological and behavioral features. However, the endocrine control of animal dispersal remains poorly understood. Here, we tested whether and how thyroid hormones may influence dispersal in glass eels of Anguilla anguilla, by testing their influence on locomotor activity and rheotactic behavior.