Consecutive underwater mappings of specimens of the calcareous sponge Clathrina cerebrum were performed within a plastic quadrat (1 m‐side) fixed to a cliff wall of the Portofino Promontory (Ligurian Sea, Italy) at a depth of 4 m. The typical clathrate

A homogeneous population of gram-negative elongated bacteria grows within the canal system of the calcareous sponge Clathrina cerebrum (Haeckel). The location of symbionts is probably related to the ascon organization of the host sponge. Bacteria have

To study interactions between sponge cells and components of the extracellular matrix (ECM), cells of the calcareous sponge Clathrina cerebrum were investigated in vitro by scanning electron microscopy. Cells were settled on glass coverslips, used as