Insight into seawater acclimation of cartilage fish from ionocytes of catshark embryo

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K20590
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0603:Forestry and forest products science, applied aquatic science, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Inokuchi Mayu 東京大学, 大学院農学生命科学研究科(農学部), 助教 (90778549)
• Project Period (FY): 2021-08-30 – 2023-03-31
• Keywords: 軟骨魚類 / 浸透圧調節 / 環境適応 / 塩類細胞 / 胚

Outline of Final Research Achievements

In elasmobranch fish, the ionoregulatory function of the gills is still poorly understood. The present study investigated the development of gill ionocytes in the embryo of cloudy catshark. We first observed ionocyte distribution by immunohistochemical staining with anti-Na+/K+-ATPase (NKA) and anti H+-ATPase (V-ATPase) antibodies. The single NKA- and V-ATPase-rich ionocytes appeared in the filament from stage 31. The ionocytes on the body skin and yolk-sac membrane were immunoreactive to anti-NKA and their apical membrane is open with microvilli. Since stage 32, some NKA-rich-cell aggregates were developed on the gill septa. The ionocytes aggregates possess NKA in the basolateral membrane and NHE3 in the apical membrane. Three-dimensional analysis revealed that the distribution of ionocyte aggregate was limited to the cranial side of gill septum. Our findings indicate that ionocyte aggregates contribute efficient body fluid homeostasis regulation in the gills of catshark embryo.

Free Research Field

魚類生理学

Academic Significance and Societal Importance of the Research Achievements

世界のサメ類の漁獲量は増加の一途をたどり、その水揚げ量は現在では1950年の約3倍を示す。発生・成熟に多くの年数を要するサメ類が過剰な漁獲から受ける影響は大きく、資源量の回復は容易ではない。このように海洋生態系の頂点に立つ捕食者の個体数変動は、食物連鎖を通して生態系全体に大規模な変化をもたらすことが危惧される。軟骨魚の環境適応機構を解明する本研究は、環境変動が海洋生態系に及ぼす影響を評価すると共に生態系維持への解決策を提唱する重要な研究になることが期待される。