Both sea anemones and corals are marine invertebrates belonging to the phylum Cnidaria. These organisms are quite similar and share many common characteristics. They both have tentacles with stinging cells, also known as nematocysts, and a cylindrical body with a central mouth.
They also have a symbiotic relationship with algae called zooxanthellae. And above all else, they both play an essential role in providing food and habitat to many marine animals.
While they share many similarities, there are significant differences between these two creatures. This article will dive more into the main differences between sea anemones and corals.
Left image credit: Bernard Spragg
Main Differences Between Sea Anemone vs Coral
- Appearance: In terms of appearance, both animals are pretty similar. Generally, they are cylindrical, with a mouth at the center and surrounded by tentacles. However, corals are more complex animals with a well-developed external skeleton which is made of calcium carbonate. Sea anemones, on the other hand, do not have a skeleton. Instead, they have soft bodies covered in a sticky mucus layer.
- Habitat: Sea anemones are found in all of the world’s oceans, especially in tidal pools, rocky shorelines, and on the ocean floor. Corals, on the other hand, mainly occur in shallow and warm tropical and subtropical waters.
- Size: Sea anemones are generally smaller than sea corals, with most species measuring between a few centimeters to a few feet long. On the other hand, sea corals vary greatly in size, with some species growing several feet long.
- Social behavior: Another main difference between sea anemones and corals is their social behavior. Sea anemones are generally solitary animals and do not form colonies. Conversely, corals are colonial organisms that form extensive reefs of thousands of polyps.
- Ecological importance: Both sea anemones and corals are important components of marine ecosystems, providing habitat for various fish and other organisms. However, coral reefs play a more critical role. They provide a diverse range of habitats and also act as natural barriers that protect coastlines from storm surges and erosion.
Let’s explore more on these main differences between sea anemones and corals.
Sea Anemone
A sea anemone is a predatory marine animal belonging to the phylum Cnidaria, which includes corals and jellyfish. They are named after the terrestrial flower, anemone, because of their colorful and flower-like appearance. They are sedentary and anchor themselves to hard substrates such as rocks and shells.
There are about 1000 species of sea anemones found in all of the world’s oceans.
Appearance
Sea anemones are generally cylindrical with a central mouth. Their mouth is usually surrounded by long, stingy tentacles that capture prey.
Since they are sessile, they attach themselves to a hard surface using a basal disk. The basal disc is a circular flattened structure usually located at the base of the anemone’s body. Typically, it has a sticky substance known as “pedal mucus” that the anemone uses to adhere to the substrate.
Like the anemone flower found on land, sea anemones are also very bright and colorful, coming in various colors, such as green, purple, red, and blue.
Habitat
Sea anemones are found in all the world’s oceans, thriving in shallow and deep waters. As mentioned above, they are sessile and often attach to rocks, shells, or other hard surfaces. However, there are some species, such as the burrowing sea anemone, that burrow into soft sediments.
In most cases, they are commonly found in intertidal zones, tidal pools, and coral reefs. Although they thrive well in warm tropical waters, some species are adapted to live in extreme environments such as the Arctic and the Antarctic.
Size
The size of sea anemones varies greatly, with some species measuring just a few millimeters in length while others grow over a meter. However, their size varies greatly depending on the species’ habitat and the animal’s age.
For example, the giant green anemone is the largest sea anemone and can grow over three feet long.
Social Behavior
Sea anemones are solitary animals, meaning that they do not form colonies. However, they create symbiotic relationships with various marine organisms, including fish, crabs, shrimp, and certain species of algae.
One of the most well-known symbiotic relationships is with clownfish. Clownfish are immune to their stinging cells and use the anemone’s tentacles to protect themselves from predators. In return, the clownfish provides the sea anemone with food scraps and help circulate water around its body with oxygen and nutrients.
Ecological Importance
Sea anemones play a vital role in marine ecosystems by providing shelter to various marine organisms. They are also a food source for many animals, such as sea stars and sea turtles.
Corals
At first glance, corals look like colorful plants growing on the ocean floor. But these colorful creatures are not plants but marine invertebrates belonging to the phylum Cnidaria.
They come in various shapes, sizes, and colors and are generally classified as hard coral or soft coral. Hard corals are also known as stony corals. They are reef builders and have a hard exoskeleton that is made of calcium carbonate.
Soft corals, on the other hand, do not form reefs and lack a hard exoskeleton. Instead, they have a flexible skeleton made of a protein known as gorgonin.
Appearance
Corals are colonies of tiny animals known as polyps that come in various shapes, sizes, and colors. Each polyp has a sac-like shape and is attached to a substrate at one end and open at the other. A ring of stinging tentacles surrounds the open end, which is the mouth of the polyp. They use these tentacles to catch prey and protect themselves.
Since they are classified as either hard or soft corals, hard corals have a hard exoskeleton made of calcium carbonate, while soft corals tend to have a feathery appearance, such as sea feathers and sea fans.
They also come in various colors, from shades of blue, purple, brown, and even pink. They get most of their colors from the microscopic algae inside their tissues.
Habitat
Although corals are found in all the world’s oceans, they are more prolific in warm, shallow tropical waters. Because of their symbiotic relationship with zooxanthellae algae, they occur near the water surface, where the sun’s rays can reach the algae.
In addition, they are sessile organisms and attach themselves to substrates made of calcium carbonates, such as rocks or old coral skeletons.
Size
Individual coral polyps are often quite small, with a diameter of less than half an inch. However, since they live in colonies, the size of a single colony can range from small clusters to massive reef structures covering hundreds of miles. The largest coral colony on record is the Great Barrier Reef in Australia, which covers approximately 2600 kilometers.
Social Behavior
Corals are colonial organisms and form large colonies that look like plants or trees. However, some species occur in small clusters or even singularly.
They are also well-known for their symbiotic relationships with microscopic algae, zooxanthellae, which live inside their tissues. The relationship between them is mutually beneficial and essential for both parties to survive.
Ecological Importance
Although coral reefs cover only 0.1% of the ocean, 25% of marine life depends on them. Animals of many kinds and sizes, including starfish, clownfish, and cuttlefish, rely on coral reefs for various needs, such as food, habitat, spawning, and breeding grounds.
Coral reefs also act as natural barriers that protect coastlines from the damaging effects of storm surges and erosion. They also help reduce the effects of waves and currents, thus providing a stable environment for other marine life to thrive.
FAQs
Are sea anemones and corals endangered?
Yes, sea anemones and corals are endangered. They face various threats, such as climate change, pollution, and overfishing, with some species listed as threatened by the IUCN.
Can sea anemones and corals live in aquariums?
Yes, sea anemones and corals can live in aquariums. However, to survive, it is important to note that they have specific water temperature, salinity, and pH requirements.
Are sea anemones harmful to humans?
Most sea anemones are harmless to humans, but some species have a powerful sting that can cause a painful reaction. The degree of harm depends on the species, the location of the sting, and the individual’s sensitivity to the venom.
What threats do corals face?
Corals are threatened by climate change, ocean acidification, overfishing, and pollution. These threats lead to coral bleaching, where corals expel their zooxanthellae and become vulnerable to disease and death.
