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Prolactin (Prl) and growth hormone (Gh) as well as insulin-like growth factor 1 (Igf1) are involved in the physiological adaptation of fish to varying salinities. The Igfs have been also ascribed other physiological roles during development, growth, reproduction and immune regulation. However, the main emphasis in the investigation of osmoregulatory responses has been the endocrine, liver-derived Igf1 route and local regulation within the liver and osmoregulatory organs. Few studies have focused on the impact of salinity alterations on the Gh/Igf-system within the neuroendocrine and immune systems and particularly in a salinity-tolerant species, such as the blackchin tilapia Sarotherodon melanotheron. This species is tolerant to hypersalinity and saline variations, but it is confronted by severe climate changes in the Saloum inverse estuary. Here we investigated bidirectional effects of increased salinity followed by its decrease on the gene regulation of prl, gh, igf1, igf2, Gh receptor and the tumor-necrosis factor a. A mixed population of sexually mature 14-month old blackchin tilapia adapted to freshwater were first exposed to seawater for one week and then to fresh water for another week. Brain, pituitary, head kidney and spleen were excised at 4 h, 1, 2, 3 and 7 days after both exposures and revealed differential expression patterns. This investigation should give us a better understanding of the role of the Gh/Igf system within the neuroendocrine and immune organs and the impact of bidirectional saline challenges on fish osmoregulation in non-osmoregulatory organs, notably the complex orchestration of growth factors and cytokines.

Sex-determining regions have been identified in the Nile tilapia on linkage groups (LG) 1, 20 and 23, depending on the domesticated strains used. Sex determining studies on wild populations of this species are scarce. Previous work on two wild populations, from Lake Volta (Ghana) and from Lake Koka (Ethiopia), found the sex-determining region on LG23. These populations have a Y-specific tandem duplication containing two copies of the Anti-Müllerian Hormone amh gene (named amhY and amhΔY). Here, we performed a whole-genome short-reads analysis using male and female pools on a third wild population from Lake Hora (Ethiopia). We found no association of sex with LG23, and no duplication of the amh gene. Furthermore, we found no evidence of sex linkage on LG1 or on any other LGs. Long read whole genome sequencing of a male from each population confirmed the absence of a duplicated region on LG23 in the Lake Hora male. In contrast, long reads established the structure of the Y haplotype in Koka and Kpandu males and the order of the genes in the duplicated region. Phylogenies constructed on the nuclear and mitochondrial genomes, showed a closer relationship between the two Ethiopian populations compared to the Ghanaian population, implying an absence of the LG23Y sex-determination region in Lake Hora males. Our study supports the hypothesis that the amh region is not the sex-determining region in Hora males. The absence of the Y amh duplication in the Lake Hora population reflects a rapid change in sex determination within Nile tilapia populations. The genetic basis of sex determination in the Lake Hora population remains unknown.

Ce volume regroupe les textes issus du programme Casdar "Innovation et Partenariat" et "Recherche finalisée et innovation" de 2013. Le colloque de restitution s’est déroulé le 6 février 2019 sous l’égide du GIS Relance Agronomique; National audience; Aquaponics is based on the integration of aquaculture and hydroponics production process making it possible the recycling and recovery of nutrients rejected by fish farming through vegetable production. This innovative approach is attractive for the aquaculture sectors as this co-production facilitates the recirculation of water with a minimal opening rate of the system, but also for the horticulture sector as it reduces totally or partially the needs of chemical inputs in soilless plant production. APIVA®’s project (“Aquaponics: Plant Innovation and Aquaculture”) aims to develop functional aquaponic pilot systems and to study the economic feasibility of such systems, but also their impact on the environment and on the quality of products, while modelling the flow occurring between the different compartments (fish farming, soilless culture, biological filter).After a brief presentation of the origin of aquaponics, this article aims to identify advantages and drawbacks of this innovative practice, but also the different forms it can take and the possible design methods and technical aspects to apprehend. In France, very few commercial aquaponics systems are already in activity, but many projects have been emerging in recent years, especially in urban areas. Some examples of commercial aquaponics companies abroad are presented before giving a typology of French project holders; L’aquaponie repose sur l’intégration de process de production aquacole et hydroponique permettant le recyclage et la valorisation des nutriments émis par l’élevage aquacole par des cultures végétales. Cette démarche innovante attire à la fois les filières aquacoles, car la co-production permet de réutiliser l’eau en permanence pour l’élevage ; mais également les filières horticoles en réduisant l’emploi d’intrants chimiques dans la conduite de production végétale. Le projet APIVA® (Aquaponie Innovation Végétale et Aquaculture) a permis de développer et de caractériser des pilotes aquaponiques fonctionnels, d’étudier leur faisabilité économique, leur impact environnemental et la qualité des produits obtenus, tout en modélisant les flux se produisant entre les compartiments (bassins d’élevage, surfaces de culture, filtre biologique). Après une rapide présentation de l’origine de l’aquaponie, cet article vise à définir les avantages et les inconvénients de cette pratique innovante, les différentes formes qu’elle peut prendre, les diverses modalités de conception envisageables, ainsi que les aspects techniques à appréhender. En France, très peu de systèmes d’aquaponie commerciale sont actifs, mais beaucoup de projets émergent depuis quelques années, notamment en milieu urbain. Des exemples d’entreprises d’aquaponie commerciale à l’international sont présentés, avant de définir une typologie des porteurs de projet français

We now know that early environmental conditions can influence an individual's future phenotype. As a mediator between environmental signals and phenotypic responses, epigenetics raises many hopes but also many questions in aquaculture, as in most agricultural production sectors. We will present the main principles regarding the Maternal & Paternal transmission of epigenetic patterns and the transgenerational epigenetic inheritance. Epigenetic mechanisms can be in the form of DNA methylation, Histone variants, chromatin remodelling and post-translational modifications with non-coding RNA. We will show from recent fish examples, how it should be quickly used and taken into account especially for sex control in aquaculture. The first potential application of epigenetics in aquaculture is by environmental manipulation of the fry or bloodstock. It relies on studies carried out on 3 species. In sea bass, Dicentrarchus labrax, high temperatures applied at early stages of development induce hyper-methylation in the promoter region of the aromatase gene (cyp19a1a), which inhibits the expression of this gene and leads to fry masculinization (Navarro-Martin et al., 2011). In the half-smooth tongue sole, Cynoglossus s emilaevis, the pseudo-male testes induced by early treatment of genetic females at high temperatures exhibit methylation patterns comparable to those of genetic males, but different from those encountered in the ovaries of genetic females. The pseudomale phenotype and its methylation patterns are found in F1 resulting from crosses between pseudomales and normal females, suggesting a transgenerational effect of masculinization induced by high temperatures in this species (Shao et al., 2014). The third species studied has been the Nile tilapia where temperature treatments can induce masculinization of XX individuals resulting in higher levels of DNA methylation in both promoters and gene bodies (Sun et al., 2016). The second approach, validated on oil content in oil palm, consists in integrating the presence or absence of epigenetic marks in epigenetic selection programmes. Epigenetics is involved in the development and maintenance of the phenotype, including a sexual phenotype. A better understanding of epigenetic mechanisms will allow a functional annotation of genomes, but also to anticipate and probably to select (via epigenetic markers) the phenotypes induced by certain early environmental conditions. Epigenetics should be rapidly integrated into aquaculture practices and selection schemes, especially for sex control purposes.

Tilapia is now the second most produced group of fish in the world. With the exception of a few very specific culture conditions, the use of monosex male populations makes it possible to optimize the profitability of tilapia production, on the one hand by preventing reproduction, and on the other hand by taking advantage of the best growth rate of males. Two main approaches are used to produce these monosex populations: a genetic approach based on the use of YY males (or ZZ females in blue tilapia) or on hybridization between certain tilapia species, and a sexual inversion approach induced by hormonal or thermal treatments. The advantages and disadvantages of each of these methods are presented. The ease of implementation, efficiency and low cost of hormonal treatments make this approach the most widespread for the production of male monosex populations. However, at a worldwide scale, large amounts of hormones are consequently used, which raises debates on the sustainability of tilapia farms using such treatments, and on their consequences at least on water quality and biodiversity. Indeed, data on the accumulation of 17α-methyltestosterone (MT) in water and sediment are few and sometimes contradictory. In ponds, under very specific conditions, certain bacteria are capable of degrading MT. More sustainable alternative approaches are now proposed. These include the use of genetic markers linked to sex chromosomes or the thermosensitivity of sex differentiation