Genetic, abiotic and social influences on sex differentiation in cichlid fishes and the evolution of sequential hermaphroditism

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73799/1/j.1467-2979.2005.00184.x.pd

Étude des processus morphologiques et endocrinologiques de la différenciation naturelle du sexe chez Oreochromis niloticus, appliquée à la production de populations monosexes : intérêts et perspectives

Dans IDL-993

Tilapia sex determination: Where temperature and genetics meet

This review deals with the complex sex determining system of Nile tilapia, Oreochromis niloticus, governed by the interactions between a genetic determination and the influence of temperature, shown in both domestic and wild populations. Naturally sex reversed individuals are strongly suggested in two wild populations. This can be due to the masculinising temperatures which some fry encounter during their sex differentiation period when they colonise shallow waters, and/or to the influence of minor genetic factors. Differences regarding a) thermal responsiveness of sex ratios between and within Nile tilapia populations, b) maternal and paternal effects on temperature dependent sex ratios and c) nearly identical results in offspring of repeated matings, demonstrate that thermosensitivity is under genetic control. Selection experiments to increase the thermosensitivity revealed high responses in the high and low sensitive lines. The high-line showed ~ 90% males after 2 generations of selection whereas the weakly sensitive line had 54% males. This is the first evidence that a surplus of males in temperature treated groups can be selected as a quantitative trait. Expression profiles of several genes (Cyp19a, Foxl2, Amh, Sox9a,b) from the gonad and brain were analysed to define temperature action on the sex determining/differentiating cascade in tilapia. The coexistence of GSD and TSD is discussed

Genetic structure of domestic and natural populations of the Nile tilapia, <em>Oreochromis niloticus</em> in Burkina Faso, West Africa

National audienc

Temperature-induced masculinisation of Nile tilapia: effects seen in the adult gonad

International audienc

Identification of species-specific SNP markers in tilapia using double-digest RAD sequencing (ddRADseq)

International audienc

Effects of confinement stress of variable duration on the growth and microincrement deposition in the otoliths of Oreochromis niloticus (Cichlidae)

The effects of chronic confinement stress (1, 5 and 10 days) and of periodic blood sampling oil somatic growth and the structure and growth of otoliths was studied in Oreochromis niloticus. During the Study, the plasma concentrations of cortisol were measured at various times during the application of stress: they were significantly higher in confined fish than in control Fish (mean +/- S.D. 3.40 +/- 0.47 v. 1.26 +/- 0.62 ng ml(-1), P< 0.05) LIP to 5 days after the start of a 10 day stress period. The somatic growth (standard length, L-S, and mass) was affected by the confinement and by the sampling (from 16.21 +/- 1.07 to 14.64 +/- 1.15 cm for L-S, and from 173.31 +/- 33.14 to 110.50 +/- 29.48 g for mass). But the confinement masked the effect of the sampling on somatic growth. Tetracycline was injected at the start of the experiment to mark the otoliths, and showed that the short and long duration confinements led to,I clear check in the pattern of primary increments in the otoliths. The number of primary increments deposited during the resting periods that followed each period of confinement was always less than the number of days that these periods lasted. No relation was found between the duration of confinement and the structure of the resulting checks. These results Suggest that there is a disruption in the laying down of primary increments during periods of confinement resulting in an underestimation of their number compared to the actual number of days of growth. These results call into question the use of otolith primary increments as a means of estimating the age of Nile tilapia that have experienced periods of stress. (C) 2004 The Fisheries Society of the British Isles