Temporal variability of the effects of embryonic exposure of Japanese medaka (Oryzias latipes) to waters from the spawning grounds of the European shad (Alosa alosa) in Golfech (Garonne) and consequences for development and reproduction

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INRAE presentation

The French National Research Institute for Agriculture, Food, and Environment (INRAE) is a major player in research and innovation. It is a community of 12,000 people with 272 research, experimental research, and support units located in 18 regional centres throughout France. Internationally, INRAE is among the top research organisations in the agricultural and food sciences, plant and animal sciences, as well as in ecology and environmental science. It is the world’s leading research organisation specialising in agriculture, food and the environment. INRAE’s goal is to be a key player in the transitions necessary to address major global challenges. Faced with a growing world population, climate change, resource scarcity, and declining biodiversity, the Institute has a major role to play in building solutions and supporting the necessary acceleration of agricultural, food and environmental transitions.

Work environment, missions and activities

You will join the research unit “Aquatic Ecosystems and Global Change” (EABX), which focuses on how aquatic biodiversity in estuarine and freshwater systems responds to global changes (climate change, human pressures, etc.).

Within this unit, you will be part of the team “Functioning and Restoration of Estuarine Ecosystems and Populations of Amphihaline Migratory Species” (FREEMA). This team is particularly interested in the functioning of estuarine ecosystems and in migratory fish populations of conservation importance.

This thesis aims to evaluate the long-term effects of embryonic exposure to potentially contaminated river water using an ex situ experimental setup (Bancel et al., 2025) and a model fish, the Japanese medaka (Oryzias latipes), combining morphometric, physiological and behavioural markers. Chosen as a model species, medaka allows for a relevant assessment of the ecotoxicological risks affecting the Allis shad (Alosa alosa), a diadromous species in critical danger of extinction. According to Bancel (2025), these two species have a similar sensitivity to the toxicity of the water in the Garonne River, particularly in the Golfech spawning ground.

It is structured around two complementary areas: (1) characterising the seasonal toxicity of the water and (2) studying the delayed effects of this early exposure on the development and reproduction of individuals.

The first area explores the seasonal variability of toxicity by continuously exposing medaka embryos to water from the Golfech spawning ground under controlled conditions at different times of the year (spring, summer, autumn) and at different dilutions (25%, 50% and 100%). The survival and development of the embryos will be monitored daily. Standardised ecotoxicological tests (bioaccumulation and toxicity in gammarids) and targeted chemical analyses (using passive samplers) will enable the quality of the environment to be characterised in detail.

The second area focuses on the long-term consequences of this exposure during embryonic development, by maintaining and monitoring individuals until adulthood under controlled and uncontaminated conditions. Their growth, metabolism (respirometry), behaviour (swimming, activity) and reproductive success will be assessed to identify sublethal effects that could alter population dynamics, particularly in migratory species.

In parallel, collaborations with Master's students will enrich this study through molecular analyses (lipidomics, proteomics and transcriptomics) designed to assess the metabolic effects of exposure. These complementary approaches will provide a better understanding of the mechanisms underlying the observed impacts. Ultimately, these results will provide key data for the environmental management of contaminated environments, particularly for critical spawning grounds such as Golfech.

More information is available on the website of the Doctoral School “Sciences and Environment”:

https://adum.fr/as/ed/voirproposition.pl?langue=&site=ed_se&matricule_prop=70215

PhD project combining fieldwork and laboratory work.

Training and skills

Recommended training: Master’s degree (or equivalent) in ecology, ecotoxicology, environmental sciences, or a related field

Knowledge required: Strong background in ecophysiology, ecotoxicology, and ecology, with an understanding of environment effects on aquatic organisms.

Appreciated experience: Experience in laboratory work is highly valued, as well as fieldwork experience.

Skills sought: Ability to work under sometimes demanding field and laboratory conditions, problem-solving skills and capacity to work effectively both independently and as part of a collaborative, multidisciplinary team.

INRAE's life quality

By joining our teams, you benefit from (depending on the type of contract and its duration):

- up to 30 days of annual leave + 15 days "Reduction of Working Time" (for a full time);
- parenting support: CESU childcare, leisure services;
- skills development systems: training, career advise;
- social support: advice and listening, social assistance and loans;
- holiday and leisure services: holiday vouchers, accommodation at preferential rates;
- sports and cultural activities;
- collective catering;

-partial coverage of home/work subscription (TER, TBM).

How to apply

You must apply on the  the website of the Doctoral School “Sciences and Environment”:

https://adum.fr/as/ed/voirproposition.pl?langue=&site=ed_se&matricule_prop=70215