The time course of molecular acclimation to seawater in a euryhaline fish

Abstract

The Arabian pupfish, Aphanius dispar, is a euryhaline fish inhabiting both inland nearly-freshwater desert ponds and highly saline Red Sea coastal lagoons of the Arabian Peninsula. Desert ponds and coastal lagoons, located respectively upstream and at the mouths of dry riverbeds (“wadies”), have been found to potentially become connected during periods of intense rainfall, which could allow the fish to migrate between these different habitats. Flash floods would therefore flush Arabian pupfish out to sea, requiring a rapid acclimation to a greater than 40 ppt change in salinity. To investigate the molecular pathways of salinity acclimation during such events, a Red Sea coastal lagoon and a desert pond population were sampled, with the latter exposed to a rapid increase in water salinity. Changes in branchial gene expression were investigated via genome-wide transcriptome measurements over time from 6 h to 21 days. The two natural populations displayed basal differences in genes related to ion transport, osmoregulation and immune system functions. These mechanisms were also differentially regulated in seawater transferred fish, revealing their crucial role in long-term adaptation. Other processes were only transiently activated shortly after the salinity exposure, including cellular stress response mechanisms, such as molecular chaperone synthesis and apoptosis. Tissue remodelling processes were also identified as transient, but took place later in the timeline, suggesting their importance to long-term acclimation as they likely equip the fish with lasting adaptations to their new environment. The alterations in branchial functional pathways displayed by Arabian pupfish in response to salinity increases are diverse. These reveal a large toolkit of molecular processes important for adaptation to hyperosmolarity that allow for successful colonization to a wide variety of different habitats.

Thermal optima of cercarial emergence in trematodes from a marine high-temperature ecosystem, the Persian Gulf

“…The establishment and subsequent flourishment of trematodes outside their current range will depend on the presence of the host species needed to complete the life cycle. While knowledge about other intermediate hosts of the studied trematodes is limited, the first intermediate host P. cingulata of both trematode species and the second intermediate host of A. tridactyla , the fish A. dispar 40 , 41 , are both eurytherms with vast geographic distributions 34 , 58 , 59 (see the Supplementary Fig. S1 ).…”

Unravelling the molecular mechanisms of fish salinity adaptation in the face of multiple stressors: A comparative multi-tissue transcriptomic study in the Llobregat River, Barcelona, Spain

“…In our study, the brain exhibited transport enrichment and overall osmoregulation, evident through the differential expression of genes like CLCN2, ANO1, KCNN3, KCNT1, KCNT2, RYR2 , and RYR3 . Chloride channels play a key role in the osmoregulatory physiology of all animals, with CLCN2 differentially expressed in euryhaline fish exposed to osmotic stress (Bonzi et al, 2021; Su et al, 2020b). Another member of the anoctamin family, ANO1 , related to osmoregulation, was differentially expressed in fish under osmotic stress (Taugbøl et al, 2022).…”

“…Another member of the anoctamin family, ANO1, related to osmoregulation, was differentially expressed in fish under osmotic stress (Taugbøl et al, 2022). KCNN3 is a potassiumactivated channel that has been proven to be differentially expressed in euryhaline fish exposed to osmotic stress (Bonzi et al, 2021). The potassium channels KCNT1 and KCNT2 are activated under high concentrations of chloride and be differentially expressed in euryhaline fish exposed to osmotic stress (Blondeau Bidet et al, 2023;Lüscher et al, 2020).…”

Influences of Salinity on Embryonic and Larval Development of Striped Catfish Pangasianodon hypophthalmus

“…Thus, salt ions producing toxicity have direct negative impacts not only on physiology of the individual species but also on species population (Nielsen et al, 2003). Salinity adaptation in fully euryhaline species is reliant on the gene expression of compounds that are involved directly and indirectly in ion transport (Lee et al, 2020;Bonzi et al, 2021). A comparison of closely related medaka species revealed a relationship of cotransporter gene expression with the ability to tolerate osmotic challenges (Juo et al, 2016).…”