Similar to corals, sponges can be found along the bottom of the sea. Scuba divers and snorkelers love seeing the variety of shapes and colors that sponges produce. The most characteristic shape is the tubular sponge with a couple of branches that have openings at the end. They look like colored rock formations or maybe a hardened plant. They don’t have eyes, ears, nostrils, and a mouth and don’t look like any animals common to us. So, are sponges animals? Let’s find out!
What are sponges?
There are 5,000-8,500 species of sponges, but the most common ones are hollow tubular shaped, with a large opening at one end. You can find them attached to rocks or mixed in with corals. If you think of a large coral reef, you will have sponges mixed in with all of the coral. Sponges found in shallower water are very colorful and can be bright orange, yellow, purple, and red. The ones found deep in the ocean are usually more neutral in color, like gray and brown. They vary in shape and size as well.
What are some examples of sponges?
- Branching vase sponge: This type of sponge looks like a grouping of vases. It has a long tubular opening at the end of each tube. It is found in the waters around Bermuda, Bahamas, Florida, and the Caribbean. This sponge has a variety of colors, and some are three feet tall and two feet wide.
- Yellow tube sponge: This type of sponge is long, skinnier tube-shaped, with openings at the top. It is bright yellow and found in clusters. It is located in the Caribbean and can grow to be three feet tall.
- Fan sponge: This type of sponge looks like a handheld fan with variegated edges. It is usually singular but around other sponges. It can get to be three feet wide and attached to reefs and rocks. The orange fan sponge is one of the most common.
- Barrel sponge: This type of sponge looks like a giant barrel, and it is attached to a coral or rock base. It is reddish-brown and also the largest sponge species in the Caribbean. This sponge is found at about 30-390 feet deep. Some are so big you can fit a human diver inside, with an opening six feet across!
Are sponges animals?
Yes, sponges are animals. Scientists were not sure how to categorize these creatures. Some thought they were plants because they do not have any internal organs and can’t move. Some thought they should be put in a new category all of their own. The more research done on them, the more proof was found that they are actually animals. Sponges are made of cells and fibers. The pores on the side of the sponge draw in water. The cells filter the water for nutrients, and the opening at the top expels the waste. Sponges may be very primitive or simple creatures, but they have the same characteristics as animals.
Are sponges alive?
Yes, sponges are living animals that need food, water, and oxygen to live. They get their food by filtering the water they live in. Their diet is very simple and includes plankton, detritus, viruses, fungi, and bacteria. You might not spend hours watching a “Sponge Cam” since they don’t move, but it would be interesting to see all that goes around the sponges in their coral reef ecosystem.
What is in the ocean that is not alive?
Examples of things in the ocean that are not alive are seashells. Seashells may look similar to some sponges, but shells are made by mollusks. Sponges are like our fingernails; we make them, but they are not alive. Shells are made by mollusks, like clams, oysters, zebra mussels, and snails, that live inside the shells. The shells are left empty when they die. Starfish are animals and are alive, but when they die, they leave the hard starfish “shell” behind. Other non-living things in the ocean are rocks, sand, boulders, and sea glass.
What is the difference between a plant and an animal?
One of the main differences between plants and animals is that animals typically have the ability to move to get food, water, and oxygen. Plants are usually stationary. While sea sponges were thought to be completely stationary, recent research has shown that some species are capable of movement. When you compare plant cells with animal cells, you will find that plant cells have a cell wall and contain chloroplasts. This is important! Plants get energy from sunlight by using photosynthesis to convert sunlight into energy. Animals need nutrients from other animals and plants to get energy. Sea sponges do not have cells with chloroplasts, and they do not use sunlight to make energy, so they are animals.
Do some sponges move?
In 2016, scientists studying sponges in the Arctic discovered that sea sponges might actually move; not far, but they may be capable of moving. Sending a camera to depths of 580-1000 meters, they observed trails of sponges where they leave behind parts of their body, or spicules, as they crawl to a new location, sometimes only a few inches away. As humans, we may pick up and move because we have annoying neighbors, but for the sea sponge, it is unclear why they move. The scientists speculated that they were relocating to find more food or creating a trail that roughs up the surface for juvenile sea sponges to grow better.
What other animals live with sponges?
A large variety of other species live inside sponges. We all know the importance of keeping our kitchen sponges clean so that bacteria don’t grow inside them. The same thing happens thousands of feet under the sea. Other animals that live inside sponges include:
- Shrimp (like the snapping shrimp)
- Amphipod crustaceans (less than 10mm, don’t have a shell, and look like tiny shrimp)
- Polychaeta worms (like bristle worms)
- Brittle stars (sometimes called serpent stars, have a small circular body with five skinny arms branching out like a starfish)
Can sponges be kept as pets?
You could care for a sea sponge if you maintained a seawater aquarium. Sea sponges need to have water at the correct salinity and temperature and need a moving current to filter the water. Sponges also require lots of planktonic foods that need to be added daily to their environment in order to survive. They are somewhat challenging to keep alive in captivity, but if you want a brightly colored addition to your aquarium, you might want to add this “pet” (since sponges are animals).
The photo featured at the top of this post is © iStock.com/dsabo
FAQs (Frequently Asked Questions)
How old do sponges get?
Incredibly, some sponge species can live to be 10,000 or more years old! That makes them the oldest known living animals on Earth. The oldest sponge species are generally those that live in the coldest water.
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