Purple tunicates | Tunicates are a subphylum of the phylum Chordata. They are marine filter feeders with a saclike morphology. In respiration and feeding they take in water through an incurrent siphon and expel the filtered water through an excurrent siphon. Most adult tunicates are sessile and attached to surfaces on the ocean floor. Various species are known as sea squirts or sea pork. [Wikipedia.]
Coral symbolizes Competition; Calcium crystals are the building blocks for both shells and coral. Live Coral compete with Molluscs for the dissolved calcium in their immediate surroundings. Scientists believe that to aid this competition, Coral release a substance that is repugnant to Mollusks. Although many species of Mollusks find shelter in Coral graveyards, few coexist with living Coral colonies.