Figure 2.

An ion transport model depicting the cellular transport processes of membrane‐bound ion transport proteins exhibiting elevated expression during Mytilus edulis‐like larval development. The Na⁺/K⁺ ATPase (NKA) provides the electrochemical gradient for secondary ion transport via proteins such as the Na⁺/H⁺ exchanger (NHE, SLC9), sodium bicarbonate cotransporters (NBC, SLC4), and Na⁺/Ca²⁺ exchangers (NCX, SLC8). Additionally, septate junctions may regulate the permeability of ions via the paracellular pathway (Jonusaite, Kelly, Donini, 2017). The putative precipitation of calcium carbonate in an extracellular calcification space is described in gray. The precise cellular location (apical/basolateral) and distribution of these ion transport proteins are unknown. In situ hybridization studies are necessary to ascertain the expression of these transporters calcifying epithelia