Fig. 10

Schematic model of Na trapping by specific binding molecules in mucus and sequential events that leads to the delay biphasic change in plasma Na⁺ in eels following FW to SW transfer. Mucus cells were activated after SW transfer and produced mucus containing Na-binding molecules rapidly, which trapped ionic Na⁺ to reduce the osmotic potential of imbibed SW. The Na-binding and ion absorption/excretion mechanisms were recruited at different time points after SW transfer, and interplayed each other to resolve the salt stress in a specific order, resulting in the signature delay of plasma Na⁺ changes. The circle region indicates desquamated cells containing high bound Na content revealed by EPMA scanning