Researchers publish chromosome-level genome of invasive Australian eastern mosquitofish
Researchers at the Okinawa Institute of Science and Technology and James Cook University have published a fully phased, chromosome-level genome of the eastern mosquitofish (Gambusia holbrooki), sampled from Townsville, Queensland, in the journal Scientific Data. The authors say the 24-chromosome assembly of two haplotypes, each about 676 Mb, is intended as a reference for studying invasion biology and local adaptation in a species they describe as one of the world's most invasive freshwater fish. A separate assembly of a European population from Padua, Italy, was published as a data note by the ERGA-BGE project, which reports 674.6 Mb and 21,050 protein-coding genes.
Bottom line — Two independent chromosome-level mosquitofish genomes, from Australia and Italy, now give invasion biologists comparable references for a species introduced in the 1920s.
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The Australian authors say the species was introduced to Europe, Asia, Africa, the Caribbean and Australia in the 1920s, originally as a mosquito control measure that they describe as ineffective.
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The Australian paper reports a 2n = 48 karyotype and a genome of roughly 676 Mb per haplotype, against a single-haplotype estimate of 589.97 Mb from k-mer analysis.
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The ERGA-BGE data note says the Italian specimens were sampled in July 2024 from the Piovego canal in Padua, and that the species was first introduced to Spain and Italy in 1921.
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The Italian note's assembly is 674.6 Mb with a scaffold N50 of 29.6 Mb, against 30.2 Mb for the Australian HAP1 haplotype, and the Australian authors report comparable gene counts across the two assemblies.
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Both papers report a lower BUSCO completeness for gene annotation (99.3% and 88.5% respectively) than for assembly, and the ERGA-BGE authors attribute the gap to the conservative filtering of the automated Ensembl pipeline, which both reviewers asked the authors to explain.
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Reviewers of the ERGA-BGE note asked for more context on South American records and comparison with recent Poeciliidae genomes; the authors say they added the Argentine introduction and cited the 2025 Genome Biology and Evolution paper.