Effects of clove oil concentrations on blood chemistry and stress-related gene expression in Siamese fighting fish (Betta splendens) during transportation.

Siamese fishing fish (Betta splendens) or betta are usually subjected to a special method of transportation for global trade, where they are individually conveyed in plastic bags containing just enough water to cover their bodies. This study aimed to investigate the effects of transportation on their stress response by measuring hematological values, stress hormone levels, glucose levels, and stress-related gene expression. Betta fish (average body weight 1.91 ± 0.42 g; n = 30) were exposed to simulated transport in a water volume of 40 mL for 12, 24, and 48 h. Baseline levels (pre-transport) were measured prior to the experiment. The control group was transported using water without adding clove oil. Two treatment groups were transported using water with the addition of 1 and 3 mg/L concentrations of clove oil, respectively. The results revealed that transportation can be a factor that affects water quality. The pH and dissolved oxygen levels were significantly lower than baseline, while nitrite and total ammonia concentrations significantly increased. Correlating to the stress responses, significantly increasing total red blood cell counts, plasma cortisol levels, and up-regulating the expression of stress-related genes, including HSP70, GR, MR, and HIF-1α. The addition of 1 mg/L clove oil was found to reduce stress during the transport simulation, as evidenced by a reduction in these stress parameters. Conversely, increasing the concentration of clove oil to 3 mg/L significantly increased plasma cortisol after 12 h of simulated transport, and up-regulated GR, MR, and HIF-1α expression. This study revealed that the transport process can stimulates stress in betta fish but adding a concentration of 1 mg/L clove oil to the transport water could mitigate this stress response and promote animal welfare during their transportation.

Genome-wide sequence divergence of satellite DNA could underlie meiotic failure in male hybrids of bighead catfish and North African catfish (Clarias, Clariidae).

Hybrid sterility, a hallmark of postzygotic isolation, arises from parental genome divergence disrupting meiosis. While chromosomal incompatibility is often implicated, the underlying mechanisms remain unclear. This study investigated meiotic behavior and genome-wide divergence in bighead catfish (C. macrocephalus), North African catfish (C. gariepinus), and their sterile male hybrids (important in aquaculture). Repetitive DNA analysis using bioinformatics and cytogenetics revealed significant divergence in satellite DNA (satDNA) families between parental species. Notably, one hybrid exhibited successful meiosis and spermatozoa production, suggesting potential variation in sterility expression. Our findings suggest that genome-wide satDNA divergence, rather than chromosome number differences, likely contributes to meiotic failure and male sterility in these catfish hybrids.

Quality control of fighting fish nucleotide sequences in public repositories reveals a dark matter of systematic taxonomic implication.

BACKGROUND: The number of nucleotide sequences in public repositories has exploded recently. However, the data contain errors, leading to incorrect species identification. Several fighting fish (Betta spp.) are poorly described, with unresolved cryptic species complexes masking undescribed species. Here, DNA barcoding was used to detect erroneous sequences in public repositories. OBJECTIVE: This study reflects the current quantitative and qualitative status of DNA barcoding in fighting fish and provides a rapid and reliable identification tool. METHODS: A total of 1034 barcode sequences were analyzed from mitochondrial cytochrome c oxidase I (COI) and cytochrome b (Cytb) genes from 71 fighting fish species. RESULTS: The nearest neighbor test showed the highest percentage of intraspecific nearest neighbors at 93.41% for COI and 91.67% for Cytb, which can be used as reference barcodes for certain taxa. Intraspecific variation was usually less than 13%, while most species differed by more than 54%. The barcoding gap, calculated from the difference between inter- and intraspecific sequence divergences, was negative in the COI data set indicating overlapping intra- and interspecific sequence divergence. Sequence saturation was observed in the Cytb data set but not in the COI data set. CONCLUSION: The COI gene should thus be used as the main barcoding marker for fighting fish.

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

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.

Complete mitochondrial genome of Mekong fighting fish, Betta smaragdina (Teleostei: Osphronemidae).

Mekong fighting fish (Betta smaragdina) are found in Northeast Thailand. A complete mitochondrial genome (mitogenome) of B. smaragdina was assembled and annotated. Mitogenome sequences were 16,372 bp in length, with slight AT bias (59.8%), containing 37 genes with identical order to most teleost mitogenomes. Phylogenetic analysis of B. smaragdina showed closer relationship with B. splendens and B. mahachaiensis as the bubble-nesting group, compared to the mouthbrooder group (B. apollon, B. simplex, and B. pi). Results will allow the creation of a reference annotated genome that can be utilized to sustain biodiversity and eco-management of betta bioresources to improve conservation programs.

Overview of the betta fish genome regarding species radiation, parental care, behavioral aggression, and pigmentation model relevant to humans.

BACKGROUND: The Siamese fighting fish (Betta splendens, also known as the betta) is well known in aquarium markets, and also presents an exciting new research model for studying parental care, aggressive behavior, and cryptically diverse pigmentation. However, concentrated efforts are required, both in the context of conservation biology and in its genetics, to address the problems of ongoing outbreeding depression, loss of biodiversity, and lack of scientific biological information. OBJECTIVE: The evolutionary dynamics of the betta must be better understood at the genomic scale in order to resolve the phylogenetic status of unrecognized species, develop molecular markers to study variation in traits, and identify interesting sets of genes encoding various bioresource functions. METHODS: The recent revolution in multi-omics approaches such as genomics, transcriptomics, epigenomics, and proteomics has uncovered genetic diversity and gained insights into many aspects of betta bioresources. RESULTS: Here, we present current research and future plans in an ongoing megaproject to characterize the betta genome as de novo assemblies, genes and repeat annotations, generating data to study diverse biological phenomena. We highlight key questions that require answers and propose new directions and recommendations to develop bioresource management to protect and enhance the betta genus. CONCLUSION: Successful accomplishment of these plans will allow the creation of a reference annotated genome and provide valuable information at the molecular level that can be utilized to sustain biodiversity and eco-management of the betta to improve breeding programs for future biomedical research.

Complete mitochondrial genome of Mahachai betta, Betta mahachaiensis (Teleostei: Osphronemidae).

Mahachai bettas (Betta mahachaiensis) are distributed in areas of brackish water with Nipa Palms in Samut Sakhon, Thailand but urbanization is restricting their biodiversity. A complete mitochondrial genome (mitogenome) of B. mahachaiensis was determined to support conservation programs. Mitogenome sequences were 16,980 bp in length with slight AT bias (61.91%), containing 37 genes with identical order to most teleost mitogenomes. Phylogenetic analysis of B. mahachaiensis showed a closer relationship with B. splendens. Results will allow the creation of a reference annotated genome that can be utilized to sustain biodiversity and eco-management of the betta to improve conservation programs.

Next-generation sequencing yields complete mitochondrial genome assembly of peaceful betta fish, Betta imbellis (Teleostei: Osphronemidae).

The complete mitochondrial genome (mitogenome) of the peaceful betta (Betta imbellis) was obtained using next-generation sequencing. The sample of B. imbellis was collected from its native habitat in Southern Thailand. The mitogenome sequence was 16,897 bp in length, containing 37 genes with identical order to most teleost mitogenomes. Overall nucleotide base composition of the complete mitogenome was determined as AT bias. Phylogenetic analysis of B. imbellis showed a closer relationship with bubble-nesting fighting fish. This annotated mitogenome reference can be utilized as a bioresource for phylogenetic studies to support betta conservation programs.