In hilsa (Tenualosa ilisha), pseudobranch comprises a row of parallel filaments bear numerous leaf-like lamellae arranged on both sides throughout its length. The purpose of this study was to elucidate involvement of pseudobranchial Na⁺, K⁺-ATPase (NKA) 1 α-subunit, and carbonic anhydrase (CA) in concert with H⁺-ATPase (HAT) compared to their branchial counterparts in freshwater acclimation of hilsa during spawning migration from off-shore of the Bay of Bengal to the Bhagirathi-Hooghly zones of the Ganga river system in India. Adult hilsa fish were collected from seawater (SW), freshwater 1 (FW1), and freshwater 2 (FW2) locations, where the salinity level was 26–28‰, 1–5‰, and 0–0.04‰, respectively. Hilsa migrating through freshwater showed a consistent decrease in the plasma osmolality, sodium (Na⁺) and chloride (Cl⁻) ion levels indicates unstable ionic homeostasis. The mRNA expression and activity of NKA 1 α-subunit in pseudobranch as well as in true gills declined with the migration to upstream locations. The pseudobranchial CA activity almost mirrors its branchial counterpart most notably while hilsa entered the freshwater zone, in the upstream river suggesting its diverse role in hypo-osmotic regulatory acclimation. Nevertheless, the H⁺-ATPase activity of both the tissues increased with the freshwater entry and remained similar during up-river movement into the freshwater environment. The results confirm that the pseudobranchial NKA 1 α-subunit mRNA expression and activity mimic its branchial counterpart in the process of ionoregulatory acclimation during migration through salt barriers. Also, the increase in the activities of pseudobranchial and branchial CA in concert with H⁺-ATPase (HAT) during freshwater acclimation of hilsa suggests their critical involvement in ion uptake.

在hilsa（Tenualosa ilisha）中，假分支由一排平行的细丝组成，这些细丝在其整个长度的两侧均排列有无数叶状薄片。这项研究的目的是阐明假分支Na ⁺，K ⁺ -ATPase（NKA）1α亚基和碳酸酐酶（CA）与H ^{+的关系。}-ATPase（HAT）在从孟加拉湾近海向印度恒河水系的Bhagirathi-Hooghly区产卵迁移过程中的希尔沙河淡水适应过程中，与它们的分支对应物相比。成年的sa鱼是从海水（SW），淡水1（FW1）和淡水2（FW2）的位置采集的，它们的盐度分别为26-28‰，1-5％和0-0.04‰。Hilsa通过淡水迁移表明在血浆渗透压一致的降低，钠（Na ⁺）和氯化物（氯^-）离子水平表示不稳定的离子稳态。随着迁移到上游位置，假分支以及真实g中的NKA1α亚基的mRNA表达和活性下降。当hilsa进入上游河中的淡水区时，伪支气管CA活性几乎与它的支流对应，这表明其在低渗调节适应中的不同作用。尽管如此，H ⁺随着淡水的进入，两个组织的-ATPase活性均增加，并且在上游进入淡水环境的过程中保持相似。结果证实，在通过盐屏障迁移的离子调节驯化过程中，假支气管NKA 1α-亚基mRNA的表达和活性模仿其分支对应物。同样，在hilsa的淡水驯化过程中，假分支和分支CA与H ⁺ -ATPase（HAT）协同作用的活动增加，表明它们关键地参与了离子吸收。