Sex Control in Tilapias

Baroiller, Jean‐François; D'Cotta, Hélèna

doi:10.1002/9781119127291.ch9

Cited by 17 publications

(24 citation statements)

References 150 publications

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“…Fry were collected from the mother’s mouth at 3 days post-fertilisation (dpf), transferred to McDonald jars for incubation until 9 or 10 dpf, and then reared in 40 L aquaria at 27 ± 1 °C. At 90 dpf, fish were euthanised with 2-phenoxyethanol (1 mL/L) and 100 randomly sampled individuals per group were sexed by microscopic observation of the gonads [ 28 ] to determine the phenotypic sex and define the sex ratios of the progenies. Fin clips from the parents, and from 14 females and 15 males per family were collected and stored in 100% ethanol until DNA extraction.…”

Section: Methodsmentioning

confidence: 99%

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Structure and Sequence of the Sex Determining Locus in Two Wild Populations of Nile Tilapia

Triay

Conte

Baroiller

et al. 2020

Genes

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In domesticated strains of the Nile tilapia, phenotypic sex has been linked to genetic variants on linkage groups 1, 20 and 23. This diversity of sex-loci might reflect a naturally polymorphic sex determination system in Nile tilapia, or it might be an artefact arising from the process of domestication. Here, we searched for sex-determiners in wild populations from Kpandu, Lake Volta (Ghana-West Africa), and from Lake Koka (Ethiopia-East Africa) that have not been subjected to any genetic manipulation. We analysed lab-reared families using double-digest Restriction Associated DNA sequencing (ddRAD) and analysed wild-caught males and females with pooled whole-genome sequencing (WGS). Strong sex-linked signals were found on LG23 in both populations, and sex-linked signals with LG3 were observed in Kpandu samples. WGS uncovered blocks of high sequence coverage, suggesting the presence of B chromosomes. We confirmed the existence of a tandem amh duplication in LG23 in both populations and determined its breakpoints between the oaz1 and dot1l genes. We found two common deletions of ~5 kb in males and confirmed the presence of both amhY and amh∆Y genes. Males from Lake Koka lack both the previously reported 234 bp deletion and the 5 bp frameshift-insertion that creates a premature stop codon in amh∆Y.

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Section: Methodsmentioning

confidence: 99%

“…Due to economic interest in producing fast-growing all-male stocks for aquaculture, numerous studies have examined the sex-determining system in the Nile tilapia ( Oreochromis niloticus ) [ 28 ]. These studies have revealed a complex sex-determining system, involving both genetic and environmental factors [ 12 , 29 , 30 , 31 ].…”

Section: Introductionmentioning

confidence: 99%

Structure and Sequence of the Sex Determining Locus in Two Wild Populations of Nile Tilapia

Triay

Conte

Baroiller

et al. 2020

Genes

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“…Oreochromis (Baroiller and D'Cotta, 2019). Nonetheless, a remarkable conservation of SD has also been reported in other groups, such as the genus Seriola (Koyama et al, 2019) or the order Salmoniformes (Yano et al, 2016).…”

Section: Introductionmentioning

confidence: 74%

Multiple evidences suggest sox2 as the main driver of a young and complex sex determining ZW/ZZ system in turbot (Scophthalmus maximus)

Martı́nez

Robledo

Taboada

et al. 2019

Preprint

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A major challenge in evolutionary biology is to find an explanation for the variation in sex-determining (SD) systems across taxa and to understand the mechanisms driving sex chromosome differentiation. We studied the turbot, holding a ZW/ZZ SD system and no sex chromosome heteromorphism, by combining classical genetics and genomics approaches to disentangle the genetic architecture of this trait. RAD-Seq was used to genotype 18,214 SNPs on 1,135 fish from 36 families and a genome wide association study (GWAS) identified a ~ 6 Mb region on LG5 associated with sex (P < 0.05). The most significant associated markers were located close to sox2, dnajc19 and fxr1 genes. A segregation analysis enabled narrowing down the associated region and evidenced recombination suppression in a region overlapping the candidate genes. A Nanopore/Illumina assembly of the SD region using ZZ and WW individuals identified a single SNP fully associated with Z and W chromosomes. RNA-seq from 5-90 day-old fish detected the expression along the gonad differentiation period of a short non-coding splicing variant (ncRNA) included in a vertebrate-conserved long non-coding RNA overlapping sox2. qPCR showed that sox2 was the only differentially expressed gene between males and females at 50-55 days post fertilization, just prior the beginning of gonad differentiation. More refined information on the involvement of secondary genetic and environmental factors and their interactions on SD was gathered after the analysis of a broad sample of families. Our results confirm the complex nature of SD in turbot and support sox2 as its main driver.

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“…Sex determination and sex differentiation in fish are of major interest for both basic and applied research since some species require sex control in order to inhibit reproduction, improve growth and/or flesh quality (Baroiller & D’Cotta, 2016; Baroiller & D’Cotta, 2018). In gonochoristic fish, an individual retains a unique sex throughout its life.…”

Section: Introductionmentioning

confidence: 99%

“…The Nile tilapia O. niloticus (Linnaeus, 1758) is a major world aquaculture species where sex determination has been abundantly studied for sex control because males grow faster than females and mixed-sex farming leads to unwanted reproduction when fish become sexually mature (Beardmore, Mair & Lewis, 2001; Baroiller & D’Cotta, 2018). Previous studies revealed a complex sex determining system governed by interactions between genetic factors and temperature.…”

Section: Introductionmentioning

confidence: 99%

Mismatches between the genetic and phenotypic sex in the wild Kou population of Nile tilapia Oreochromis niloticus

Sissao

D'Cotta

Baroiller

et al. 2019

PeerJ

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Sex determination and sex chromosomes can be very diverse between teleost species. The group of tilapias shows a polymorphism in sex determination not only between closely related species but also between domestic strains within a species. In the Nile tilapia, the major effect genes and therefore the Y chromosome have been located on either linkage group 1 (LG1) or LG23 depending on the strains. In a Japanese strain, the sex determinant of LG23 (the amhY gene) has been identified as a duplicated amh (anti-Müllerian hormone) gene, with its gametolog found on the X chromosome (amhX). AmhY is located in tandem with the amhΔY gene (a truncated form) on the Y chromosome. X and Y chromosome markers based on the amh genes have been validated only on a few domestic strains but not in wild populations. Here, we used four of these markers in order to examine (1) the possible variation in sex determination of a wild population of Nile tilapia living in Lake Kou (Burkina Faso), (2) putative polymorphisms for these amh copies and (3) the existence of sex reversed individuals in the wild. Our genotyping of 91 wild Kou individuals with the amh sex-diagnostic markers of LG23 showed that while phenotypic females were all XX, phenotypic males were either XY or XX. Progeny testing of eight of these XX males revealed that one of these males consistently sired all-female progenies, suggesting that it is a wild sex reversed male (which could result from high temperature effects). The other XX males gave balanced sex ratios, suggesting that sex is controlled by another locus (possibly on another LG) which may be epistatically dominant over the LG23 locus. Finally, identification of unexpected amh genotypes was found for two individuals. They produced either balanced or female-biased sex ratios, depending on the breeder with whom they were crossed, suggesting possible recombination between the X and the Y chromosomes.

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Sex Control in Tilapias

Cited by 17 publications

References 150 publications

Structure and Sequence of the Sex Determining Locus in Two Wild Populations of Nile Tilapia

Structure and Sequence of the Sex Determining Locus in Two Wild Populations of Nile Tilapia

Multiple evidences suggest sox2 as the main driver of a young and complex sex determining ZW/ZZ system in turbot (Scophthalmus maximus)

Mismatches between the genetic and phenotypic sex in the wild Kou population of Nile tilapia Oreochromis niloticus

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