Wild Betta fighting fish species in Thailand and other Southeast Asian countries

Panijpan, Bhinyo; Sriwattanarothai, Namkang; Laosinchai, Parames

doi:10.2306/scienceasia1513-1874.2020.064

Cited by 17 publications

(15 citation statements)

References 34 publications

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“…We separately genotyped the transposon drbx1 , a candidate driver for the emergence of the SD system, in six wild B. splendens including two females and four males, and a pair of female and male B. smaragdina and B. imbellis that diverged from B. splendens within the last five million years (Additional file 1 : Table S1) [ 35 ]. All these species belong to the Betta splendens complex [ 36 , 37 ].…”

Section: Resultsmentioning

confidence: 99%

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Transposon-induced epigenetic silencing in the X chromosome as a novel form of dmrt1 expression regulation during sex determination in the fighting fish

et al. 2022

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Background Fishes are the one of the most diverse groups of animals with respect to their modes of sex determination, providing unique models for uncovering the evolutionary and molecular mechanisms underlying sex determination and reversal. Here, we have investigated how sex is determined in a species of both commercial and ecological importance, the Siamese fighting fish Betta splendens. Results We conducted association mapping on four commercial and two wild populations of B. splendens. In three of the four commercial populations, the master sex determining (MSD) locus was found to be located in a region of ~ 80 kb on LG2 which harbours five protein coding genes, including dmrt1, a gene involved in male sex determination in different animal taxa. In these fish, dmrt1 shows a male-biased gonadal expression from undifferentiated stages to adult organs and the knockout of this gene resulted in ovarian development in XY genotypes. Genome sequencing of XX and YY genotypes identified a transposon, drbx1, inserted into the fourth intron of the X-linked dmrt1 allele. Methylation assays revealed that epigenetic changes induced by drbx1 spread out to the promoter region of dmrt1. In addition, drbx1 being inserted between two closely linked cis-regulatory elements reduced their enhancer activities. Thus, epigenetic changes, induced by drbx1, contribute to the reduced expression of the X-linked dmrt1 allele, leading to female development. This represents a previously undescribed solution in animals relying on dmrt1 function for sex determination. Differentiation between the X and Y chromosomes is limited to a small region of ~ 200 kb surrounding the MSD gene. Recombination suppression spread slightly out of the SD locus. However, this mechanism was not found in the fourth commercial stock we studied, or in the two wild populations analysed, suggesting that it originated recently during domestication. Conclusions Taken together, our data provide novel insights into the role of epigenetic regulation of dmrt1 in sex determination and turnover of SD systems and suggest that fighting fish are a suitable model to study the initial stages of sex chromosome evolution.

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Section: Resultsmentioning

confidence: 99%

“…In the six wild B. splendens, the presence of drbx1 noticeably deviated from the expectation of association with sex, in contrast to the situation in most domesticated fish (Additional file 1 : Fig. S10) [ 35 ].…”

Section: Resultsmentioning

confidence: 99%

Transposon-induced epigenetic silencing in the X chromosome as a novel form of dmrt1 expression regulation during sex determination in the fighting fish

et al. 2022

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“…This presents a problem for academic research because genetic profiles of Siamese fighting fish from wild or commercial breeds are no longer stable or pure. Perhaps the dynamics of SDS in different populations is nothing more than chance in the admixture within sampled populations, as observed in several local studies in Thailand or international parties, following both official and unofficial research protocols [ 138 ]. Unofficial research protocols might also encourage people in the local community to perform different actions such as capture fish from newer locations to receive extra payment.…”

Section: Discussionmentioning

confidence: 99%

Something Fishy about Siamese Fighting Fish (Betta splendens) Sex: Polygenic Sex Determination or a Newly Emerged Sex-Determining Region?

Panthum

Jaisamut

Singchat

et al. 2022

Cells

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Fishes provide a unique and intriguing model system for studying the genomic origin and evolutionary mechanisms underlying sex determination and high sex-chromosome turnover. In this study, the mode of sex determination was investigated in Siamese fighting fish, a species of commercial importance. Genome-wide SNP analyses were performed on 75 individuals (40 males and 35 females) across commercial populations to determine candidate sex-specific/sex-linked loci. In total, 73 male-specific loci were identified and mapped to a 5.6 kb region on chromosome 9, suggesting a putative male-determining region (pMDR) containing localized dmrt1 and znrf3 functional sex developmental genes. Repeat annotations of the pMDR revealed an abundance of transposable elements, particularly Ty3/Gypsy and novel repeats. Remarkably, two out of the 73 male-specific loci were located on chromosomes 7 and 19, implying the existence of polygenic sex determination. Besides male-specific loci, five female-specific loci on chromosome 9 were also observed in certain populations, indicating the possibility of a female-determining region and the polygenic nature of sex determination. An alternative explanation is that male-specific loci derived from other chromosomes or female-specific loci in Siamese fighting fish recently emerged as new sex-determining loci during domestication and repeated hybridization.

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“…The fighting fish B. splendens is a freshwater fish species, which is naturally distributed in Thailand, Laos, Vietnam, Indonesia and other Southeast Asian countries 1,2 . It has been domesticated for 1000 years in Southeast Asia 3 .…”

Section: Introductionmentioning

confidence: 99%

The ornamental fighting fish is the next model organism for genetic studies

Yue

Wang

Sun

et al. 2022

Reviews in Aquaculture

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The fighting fish Betta splendens is a freshwater species from Thailand and other Southeast Asian countries. This fish has been domesticated for 1000 years and bred for fighting, various colours, body size and fin types for 600 years. It is one of the most important fish species cultured for the world ornamental fish market. This fish is easy to culture, highly fecund and displays great morphological diversity. Its biology has been studied for over 100 years. Recently, its compact genome and transcriptomes have been sequenced. Genome editing with CRISPR/cas9 has been applied to knock out genes in this fish. Its diverse phenotypes, including colours, colour patterns, fin types, and aggressive behaviour, are complementary to those of other model animals.Therefore, this fish could be the next important model organism for studying phenotypic variation and aggressive behaviour. In this paper, we synthesized knowledge about its aquaculture, biology, genetics, genomic tools, phenotypes and novel insights on phenotypic variation, sex determination and aggression. We hope that the information described in this paper will facilitate genetic studies on phenotypic variations in aquaculture and aggressive behaviour in other species, including humans.

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Wild Betta fighting fish species in Thailand and other Southeast Asian countries

Cited by 17 publications

References 34 publications

Transposon-induced epigenetic silencing in the X chromosome as a novel form of dmrt1 expression regulation during sex determination in the fighting fish

Transposon-induced epigenetic silencing in the X chromosome as a novel form of dmrt1 expression regulation during sex determination in the fighting fish

Something Fishy about Siamese Fighting Fish (Betta splendens) Sex: Polygenic Sex Determination or a Newly Emerged Sex-Determining Region?

The ornamental fighting fish is the next model organism for genetic studies

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