Time‐course changes in the regulation of ions and amino acids in the hard clam Meretrix lusoria upon lower salinity challenge

Abstract

In this study, we examined ion and amino acid regulation in the gill and mantle of the hard clam Meretrix lusoria. We found that the osmolality and Na + and Clconcentrations of hard clam hemolymph were significantly reduced after transferring clams from the salinity of their natural habitat [20‰ saltwater (SW)] to a lower salinity environment (10‰ SW). Specific activities of Na + , K + -ATPase (NKA), which provides the driving force for the secondary ion transport associated with cell osmoregulation in gills and mantles, were unaffected during the acclimation to lower salinity. In contrast, there was a significant decline in the contents of free amino acids (FAAs) in the gills and mantles of hard clams during lower salinity acclimation.

Dynamic Regulation of Ions and Amino Acids in Adult Asian Hard Clams Meretrix lusoria Upon Hyperosmotic Salinity

“…However, the mantle NKA activity of those exposed to SW was significantly upregulated compared to those exposed to 20 BW, while no differences were found between those exposed to 20 BW and 10 BW (Lin et al, 2016). Although mantle NKA activity of Asian hard clams did not change upon exposure to 10 BW, we found that it was temporarily increased after the individuals were transferred to this environment (Lin et al, 2021).…”

“…The shortterm response of TAUT mRNA and protein expression in the gills and mantle of Asian hard clams to exposure to high-salinity SW is unknown. However, our previous study on this species revealed that gill TAUT mRNA expression was upregulated, whereas mantle TAUT mRNA expression was downregulated, and TAUT protein expression in the gills and mantle increased after the individuals were transferred from 20 to 10 BW (Lin et al, 2021). Accordingly, the transcription and/or translation of TAUT in bivalve tissues is regulated in response to salinity stress.…”

“…Our previous study found that taurine is the predominant FAA in Asian hard clams (Lin et al, 2016). When Asian hard clams are transferred from 20 BW to 10 BW, the amino acid content (e.g., taurine, glutamate, glycine, and/or alanine) in their gills and mantle decreases (Lin et al, 2021). Moreover, the reduction of the taurine content in tissues is greater than that of the other amino acids (Lin et al, 2021).…”

“…When Asian hard clams are transferred from 20 BW to 10 BW, the amino acid content (e.g., taurine, glutamate, glycine, and/or alanine) in their gills and mantle decreases (Lin et al, 2021). Moreover, the reduction of the taurine content in tissues is greater than that of the other amino acids (Lin et al, 2021). This indicates that the taurine content plays an important role in the osmoregulation of this species tissues after exposure to a low-salinity environment (Lin et al, 2021).…”

“…Moreover, the reduction of the taurine content in tissues is greater than that of the other amino acids (Lin et al, 2021). This indicates that the taurine content plays an important role in the osmoregulation of this species tissues after exposure to a low-salinity environment (Lin et al, 2021). Nevertheless, the change in taurine content in the gills and mantle of Asian hard clams after exposure to a high-salinity environment remains unclear.…”