Inter-population differences in salinity tolerance of adult wild Sacramento splittail: osmoregulatory and metabolic responses to salinity

Abstract

The Sacramento splittail (Pogonichthys macrolepidotus) is composed of two genetically distinct populations endemic to the San Francisco Estuary (SFE). The allopatric upstream spawning habitat of the Central Valley (CV) population connects with the sympatric rearing grounds via relatively low salinity waters, whereas the San Pablo (SP) population must pass through the relatively high-salinity Upper SFE to reach its allopatric downstream spawning habitat. We hypothesize that if migration through SFE salinities to SP spawning grounds is more challenging for adult CV than SP splittail, then salinity tolerance, osmoregulatory capacity, and metabolic responses to salinity will differ between populations. Osmoregulatory disturbances, assessed by measuring plasma osmolality and ions, muscle moisture and Na+-K+-ATPase activity after 168 to 336 h at 11‰ salinity, showed evidence for a more robust osmoregulatory capacity in adult SP relative to CV splittail. While both resting and maximum metabolic rates were elevated in SP splittail in response to increased salinity, CV splittail metabolic rates were unaffected by salinity. Further, the calculated difference between resting and maximum metabolic values, aerobic scope, did not differ significantly between populations. Therefore, improved osmoregulation came at a metabolic cost for SP splittail but was not associated with negative impacts on scope for aerobic metabolism. These results suggest that SP splittail may be physiologically adjusted to allow for migration through higher-salinity waters. The trends in interpopulation variation in osmoregulatory and metabolic responses to salinity exposures support our hypothesis of greater salinity-related challenges to adult CV than SP splittail migration and are consistent with our previous findings for juvenile splittail populations, further supporting our recommendation of population-specific management.

Responses to saltwater exposure vary across species, populations and life stages in anuran amphibians

“…Changes in salinity can be physiologically stressful to freshwater organisms that even modest increases in salinity can generate consequences that cascade throughout entire ecosystems ( Jones et al ., 2017 ; Verhille et al ., 2020 ; Arnott et al ., 2023 ). Anuran amphibians (frogs and toads) are osmotically sensitive due to highly permeable ectodermal membranes, although there is more variation in salinity tolerance across amphibia than is commonly appreciated ( Hopkins and Brodie, 2015 ; Albecker and McCoy, 2017 ).…”

Diverse Transcriptome Responses to Salinity Change in Atlantic Cod Subpopulations

“…In general, teleosts use similar strategies to maintain osmotic homeostasis; however, there are also some differences in the regulation of internal water and solute homeostasis [41]. Furthermore, recent studies revealed inter-population differences in fish responses to salinity [42,43]. To address this problem in the present study, cod individuals derived from the western and eastern subpopulations were kept in tanks, where salinity was gradually changed, and then gene expression was measured using a genome-wide DNA oligonucleotide microarray to characterize the putative salinity-regulated genes and the biological and molecular processes involved in salinity adaptation.…”