Microscopic images and 2D-MALDI-images of the sponge Aplysina aerophoba in response to grazing and video recording of grazing behavior

We aimed to investigate the cellular and chemical response of the chemically defended sponge Aplysina aerophoba (Phylum Porifera: Class Demospongiae) to grazing by its specialist Tylodina perversa (Phylum Mollusca: Class Opistobranchia). Three treatments were applied: control, grazing, and mechanical damage. Samples were collected 3 hours, 1 day, 3 days, and 6 days after treatment. The behavior of sea slugs after directly contact with sponge specimen was recorded by using a GoPro Hero 4 camera with the program time lapse (1 picture every 5 sec) for 1.5 to 2 hours. Our results showed that spherulous cells were recruited to the wounded site in a time-dependent manner. MALDI-imaging MS showed that both brominated compounds (aerophobin-2 and aeroplysinin-1) localized usually at the sponge surface and accumulated at the damaged surface upon wounding. As spherulous cells are common in many members of the class Demospongiae, the recruitment of defensive cells may also occur in other sponges for protecting these filter-feeders. Our study contributes to understanding the evolutionary mechanisms in sponges for facing grazing and wounding.