Hypothesis: Using macroporous jellyfish mesoglea which consists of nano-sized layers and fibers as a matrix, metal nanoparticles with different morphologies might be formed in it. Experiment: Hierarchical silver dendrites are prepared by in situ reduction of silver nitrate (AgNO3) in the jellyfish mesoglea. Findings: The formation of silver dendrites is affected by the concentration of AgNO3. The biogel-metal nanoparticles hybrid materials with silver dendrites show an extremely high solid content of silver dendrites and good catalytic activity as well as excellent recyclability for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). (C) 2015 Elsevier Inc. All rights reserved.