Abstract
The mechanism of osmoregulation is crucial for maintaining growth, development, and life activities in teleosts. Takifugu obscurus, the only euryhaline species in the genus Takifugu, is a proper model organism for studying the mechanism of low-salt tolerance and hypoosmotic regulation. In this study, whole-genome sequencing data were obtained from 90 pufferfish representing five species within this genus, T. rubripes, T. obscurus, T. flavidus, T. niphobles, and T. bimaculatus. Using a phylogeny, PCA, and population structure analyses, we observed similar amounts of population genetic differentiation among species. The five species are closely related to each other and have differentiated within a relatively short period, while T. bimaculatus and T. flavidus shared the most similar genetic backgrounds. We further identified hundreds of genes under selection related to hypoosmotic regulation between T. obscurus and other Takifugu species, including 16 representative genes involving ion transporters (atp1a3, atp2a2, atp2a3, slc13a1, slc5a8, slc12a2, slc12a4, slc26a2, scn1b, and kcna2/3/10), genes involved in hormone regulation (fyn, prlr, and grb2), and a gene associated with water absorption (aqp3). Our findings provide preliminary insight into the mechanism of osmoregulation and will facilitate follow-up validation of candidate genes related to osmoregulation in T. obscurus.
Highlights
Pufferfish are a group of migratory benthic teleost fishes belonging to the genus Takifugu (Tetraodontiformes, Tetraodontidae)
The samples of T. rubripes, T. flavidus, and T. bimaculatus were from the Tanghai breeding base, Beidaihe Central Experiment Station, Chinese Academy of Fishery Sciences (119°31′32′′ E, 39°48′58′′ N)
The water salinity for T. obscurus was 6 ppt, while the water salinity for the other Takifugu species was equivalent to the natural salinity of seawater, 30 ppt
Summary
Pufferfish are a group of migratory benthic teleost fishes belonging to the genus Takifugu (Tetraodontiformes, Tetraodontidae). They are naturally distributed in the Western Pacific Ocean, spanning the Bohai Sea, Yellow Sea, East China Sea, and the Sea of Japan. E.g., Takifugu rubripes, Takifugu flavidus, are commercially important fish in China, Japan, and Korea due to their high nutritional value and extraordinary flavor (Song et al 2001). The genus Takifugu includes 25 species, most of which are closely related, that are able to produce fertile hybrids (e.g., T. rubripes × T. niphobles, T. rubripes × T. flavidus) (Hosoya et al 2013). The extensive existence of hybrids is mainly due to the relatively recent evolutionary time scale of Takifugu species diversification.
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