Difference between Sponge and Coral

Corals and sponges both are marine invertebrates that belong to different phyla, Cnidaria and Porifera respectively. Despite morphological similarities, corals and sponges are entirely different from each other. Let us study these creatures more closely to better understand the difference between corals and sponges!

Sponge:

Sponges belong to the phylum Porifera. They can survive in fresh water as well as in the salt water of the seas, and can be found in shallow water with few-feet-depth to a depth of around 29000 feet. They comprise two layers of cells with gelatinous matrix between them and have needle-like structures, made of calcium carbonate, that serve as an inner skeleton.

Sponges lack true tissues, organs and organ systems like the nervous system, digestive system and circulatory system. On the contrary, they have numerous pores lined with flagellated cells in order to facilitate extraction of food from the water. The circulatory water also provides the required oxygen and helps eliminate wastes from the body.

Their body cells totipotent, i.e. the functions of their cells can change as per the requirement. They produce toxins to protect themselves from the predators. They do not have a coelom (a cavity within the body).

Coral:

Corals belong to the phylum Cnidaria and are closely related to jellyfish and anemones. They are generally found in subtropical and tropical waters around the world. Their body structure is more complicated than that of sponges. The coral body is a hollow sac-like structure which is known as a polyp. It has a central opening at the top surrounded by a ring of tentacles and the other or opposite end of the body is called base and is attached to the substrate. The central opening which acts as a mouth is used for both feeding and eliminating the wastes from the body or polyp. The tentacles are used to sting the prey or predators.

Corals live in large colonies but look like a single organism. They can be of different types such as sea pens, sea fans, blue corals, soft corals, staghorn corals and clubbed finger corals. They secrete limestone (calcium carbonate) to form huge structures called coral reefs. The coral reef acts as a hard, durable exoskeleton that protects the soft, sac-like bodies of corals.

Furthermore, corals live in symbiotic association with algae. The algae provide food to the coral, produced by photosynthesis and the coral provides shelter, protection and nutrient-rich environment to algae for growth.

Based on the above facts, some of the key differences between sponge and coral are as follows: