Sex steroid dynamics during embryogenesis and sexual differentiation in Eurasian perch, Perca fluviatilis

It is widely accepted that sex steroid hormones play an important and a specific role during the process of sex differentiation in fish. In order to describe the role of the three main sex steroid hormones (testosterone--T, 17beta-estradiol--E2 and 11keto-testosterone--11KT) during embryogenesis and sex differentiation in Eurasian perch, Perca fluviatilis, eggs, larvae and juveniles originating from two mixed-sex and two all-female progenies were regularly sampled from fertilization to hatching (D0) and from hatching to day 70 post-hatching (D70). Just after spawning, a significant amount of sex steroids [T (1634.2pgg(-1)), E2 (554.4pgg(-1)) and 11KT (1513.2pgg(-1))] was measured in non-fertilised eggs suggesting a maternal transmission of these steroids. From D2 to D70 post-hatching, E2 levels were significantly higher in mixed-sex progenies (median: 725.7pgg(-1)) than in all-female progenies (156.2pgg(-1)) and significantly increased after the onset of the histological differentiation of the gonad in both progenies (D35). Levels of 11KT were significantly higher in mixed-sex (median: 431.5pgg(-1)) than in all-female progenies (below the limit of assay detection) and significantly increased at D35 in all-female progenies (median value: 343.2pgg(-1)). Mean 11KT to E2 ratio was six-fold higher in mixed-sex progenies (1.35) than in all-female progenies (0.24). The data suggest that the 11-oxygenated androgen (11KT) plays a major role in the male differentiation process, and that sex differentiation in Eurasian perch is probably determined by the 11KT to E2 ratio

Eco-designing Aquaponics: A Case Study of an Experimental Production System in Belgium

Aquaponics is receiving a growing interest as an emerging technology that combines recirculating aquaculture practices and hydroponics to produce fish and vegetables. However, a proper eco-design is essential to limit the environmental burdens and to enhance the economic profitability. Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) were here combined to estimate the environmental and economic impacts of a designed pilot indoor aquaponic system in Belgium. Results showed that energy consumption, infrastructure and water consumption represent the main critical issues to achieve both the environmental and economic sustainability of this aquaponic system

Effect of high temperatures on sex ratio and differential expression analysis (RNA-seq) of sex-determining genes in <i>Oreochromis niloticus</i> from different river basins in Benin

peer reviewedAbstract The high temperature sex reversal process leading to functional phenotypic masculinization during development has been widely described in Nile tilapia (Oreochromis niloticus) under laboratory or aquaculture conditions and in the wild. In this study, we selected five wild populations of O. niloticus from different river basins in Benin and produced twenty full-sib families of mixed-sex (XY and XX) by natural reproduction. Progenies were exposed to room temperature or high (36.5°C) temperatures between 10 and 30 days post-fertilization (dpf). In control groups, we observed sex ratios from 40 to 60% males as expected, except for 3 families from the Gobé region which showed a bias towards males. High temperature treatment significantly increased male rates in each family up to 88%. Transcriptome analysis was performed by RNA-sequencing (RNA-seq) on brains and gonads from control and treated batches of six families at 15 dpf and 40 dpf. Analysis of differentially expressed genes, differentially spliced genes, and correlations with sex reversal was performed. In 40 dpf gonads, genes involved in sex determination such as dmrt1, cyp11c1, amh, cyp19a1b, ara, and dax1 were upregulated. In 15 dpf brains, a negative correlation was found between the expression of cyp19a1b and the reversal rate, while at 40 dpf a negative correlation was found between the expression of foxl2, cyp11c1, and sf1 and positive correlation was found between dmrt1 expression and reversal rate. Ontology analysis of the genes affected by high temperatures revealed that male sex differentiation processes, primary male sexual characteristics, autophagy, and cilium organization were affected. Based on these results, we conclude that sex reversal by high temperature treatment leads to similar modifications of the transcriptomes in the gonads and brains in offspring of different natural populations of Nile tilapia, which thus may activate a common cascade of reactions inducing sex reversal in progenies

Physiological and proteomic responses to single and repeated hypoxia in juvenile Eurasian perch under domestication - clues to physiological acclimatation and humoral immune modulations.

peer reviewe

Influence of sexual genotype on the behaviour of females (genotype WZ) and pseudofemales (genotype ZZ) in the tilapia Oreochromis aureus

17alpha-ethynylestradiol sex-reversed males of Oreochromis aureus (pseudofemales, DeltaF, genotype ZZ) are used in aquaculture to produce a male monosex population by crossing with ZZ homogametic normal males. When placed with males (M) and females (F) in the same spawning tank, the spawning rate of F is higher than for DeltaF. In order to understand this phenomenon, comparisons were made between the behaviour of 18 F (446 +/- 96 mm) and 18 DeltaF (401 +/- 59 mm). DeltaF showed a more aggressive behaviour and were significantly more dominant than normal F in fighting pair experiments (F x DeltaF) or in fighting group experiments in four different stocking densities (8, 12, 16 and 83 fish 10(-3) l with F/DeltaF ratio = 1). DeltaF were also more aggressive towards males than F were. The results support the idea that behavioural differences exist between F and DeltaF These differences are probably due to the effect of the sexual genotype on behaviour. (C) 2002 Ifremer/CNRS/Inra/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS. All rights reserved