Salinity‐induced transcriptome profiles in marine and freshwater threespine stickleback after an abrupt 6‐hour exposure

Abstract

Saltwater and freshwater environments have opposing physiological challenges, yet, there are fish species that are able to enter both habitats during short time spans, and as individuals they must therefore adjust quickly to osmoregulatory contrasts. In this study, we conducted an experiment to test for plastic responses to abrupt salinity changes in two populations of threespine stickleback, Gasterosteus aculeatus, representing two ecotypes (freshwater and ancestral saltwater). We exposed both ecotypes to abrupt native (control treatment) and non‐native salinities (0‰ and 30‰) and sampled gill tissue for transcriptomic analyses after 6 h of exposure. To investigate genomic responses to salinity, we analyzed four different comparisons; one for each ecotype (in their control and exposure salinity; (1) and (2), one between ecotypes in their control salinity (3), and the fourth comparison included all transcripts identified in (3) that did not show any expressional changes within ecotype in either the control or the exposed salinity (4)). Abrupt salinity transfer affected the expression of 10 and 1530 transcripts for the saltwater and freshwater ecotype, respectively, and 1314 were differentially expressed between the controls, including 502 that were not affected by salinity within ecotype (fixed expression). In total, these results indicate that factors other than genomic expressional plasticity are important for osmoregulation in stickleback, due to the need for opposite physiological pathways to survive the abrupt change in salinity.

Genomic insights into the seawater adaptation in Cyprinidae

“…Previous reports have indicated adverse effects of hypotonic stress on various developmental stages of Macrobrachium rosenbergii larvae; the expression of the autophagy-related gene atg7 showed significant changes under hypotonic stress [76]. In salinity-induced transcriptome studies of marine and freshwater threespine stickleback, a decrease in usp45 expression was observed 6 h after the sudden exposure to seawater [77]. Notably, our genomic analyses found that there were CNEs loss near the atg7 and obtain close to usp45 (Fig.…”

Alternative splicing plays a nonredundant role in greater amberjack (Seriola dumerili) in the adaptation to ambient salinity fluctuations

“…Moreover, alcohol metabolism was also enhanced in the gills. For most saltwater fish, a decrease in water salinity alters their oxygen requirements in gills, thus may increase the production of lactate (Ern et al, 2014; Taugbøl et al, 2022). To combat the adverse impact of lactate buildup, crucian carp and goldfish ( Carassius , Cyprinidae) can further covert lactic acid to ethanol and excrete it into ambient water via the special coupling of pyruvate dehydrogenase complex (PDC) and alcohol dehydrogenase (ADH) in gills, which largely improve their tolerance to low oxygen environment (Fagernes et al, 2017).…”

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

“…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). KCNN3 is a potassium-activated channel that has been proven to be differentially expressed in euryhaline fish exposed to osmotic stress (Bonzi et al, 2021).…”