Ferritin is an important hub of iron metabolism because it stores iron during times of iron overload and releases iron during iron deficiency. Here, we present the first crystal structure of ferritin from the marine invertebrate Dendrorhynchus zhejiangensis with a 2.3 angstrom resolution. D. zhejiangensis ferritin (DzFer) exhibits a common cage-shaped hollow sphere with 24 subunits containing the ferroxidase centers and 3-fold and 4-fold channels. The structure of DzFer shows highly conserved catalytic residues in the ferroxidase center. The metal wire formed by ferrous ions in the 3-fold channel reveals the path that iron ions use to enter and translocate into the ferroxidase site to be oxidized and finally arrive at the nucleation site. However, the electrostatic environment of the channels and pores exhibits significant and extensive variability, suggesting that ferritins execute diverse functions in different environments. (C) 2020 Elsevier Inc. All rights reserved.