Anthozoa

Some sea animals look like flowers.

They live in the ocean. Most stay on the sea floor.

These animals are called polyps. A polyp has a body like a tube. It has a mouth at the top. Many tiny arms surround the mouth.

They use these arms to catch food. Some live all alone. Others live in big groups. These groups are called colonies.

Some are soft and move in the water.

Others are hard and stay still. Hard corals build big reefs.

They can be many colors. They can be very small or very large. These animals are amazing to see.

Some sea animals look like flowers. These animals are called Anthozoa.

They live in salt water. Most adults stay on the sea floor.

The basic body part is a polyp. A polyp is a tube-shaped animal. It has a mouth at the top. Many arms, called tentacles, surround the mouth.

These animals use tentacles to catch food. Most are carnivores, which means they eat other animals.

Some Anthozoans live all alone. Others live in large groups called colonies.

In a colony, new polyps grow from one original animal. Stony corals make hard skeletons. These skeletons can look like bushy plants or flat plates.

There are two main groups. Hexacorallia have six-fold symmetry. This means their parts fit in groups of six. This group includes sea anemones and stony corals. Octocorallia have eight-fold symmetry. Their parts fit in groups of eight. This group includes soft corals and sea pens.

Some species live in shallow water. They get power from tiny algae living inside them. Other species live in deep, dark water.

Anthozoa are fascinating marine animals that often look like colorful flowers.

The name comes from Greek words meaning "flower animals." These creatures live only in salt water or brackish water. They belong to a large group of animals called cnidarians.

Most adult anthozoans stay attached to the seabed. However, they begin their lives as tiny drifting larvae called planula. These larvae float in the water as part of the plankton. Once they are ready, they settle on the ocean floor and change into adults.

The basic body of an anthozoan is called a polyp.

A polyp is a tube-shaped animal with a central mouth. Many tentacles surround this mouth to help catch food. Because they eat other animals, they are known as carnivores.

Some polyps live all by themselves, like many sea anemones. Other polyps live together in large groups called colonies.

In a colony, new polyps grow by budding from one original individual. Some corals even build hard skeletons made of aragonite. These skeletons can grow into huge, bushy, or plate-like shapes.

Scientists divide Anthozoa into two main groups based on their symmetry. The first group is Hexacorallia, which has six-fold symmetry.

This group includes stony corals and sea anemones. The second group is Octocorallia, which has eight-fold symmetry.

This group contains soft corals and sea pens. Some species in these groups can even make their own energy. They do this by using tiny algae that live inside their tissues. These algae use sunlight to help the animal grow in shallow water.

Researchers have studied these animals for a very long time. In 1995, a scientist named J. E. N. Veron led a group to study their DNA.

They found out how these different groups are related to each other. We also know about extinct groups like Rugosa and Tabulata.

These were older types of corals that lived a long time ago. Today, there are over six thousand known species of anthozoans. They can be tiny, less than half a centimeter across, or huge colonies over a meter wide.

You can see how these animals connect to the world around you. Many anthozoans are reef-builders that create homes for other sea life.

For example, deep-water corals provide habitats for fish like the alfonsino.

Even though some live in the dark, deep ocean, they are still part of a huge, connected system. Just like a garden needs many different plants, the ocean needs these animals to stay healthy. Their different shapes and colors help make the underwater world a very busy place.

Anthozoa is a large subphylum of Cnidaria containing over 6,000 described species.

The name comes from the Greek words for "flower animals."

This refers to the perennial polyp stage, which often resembles a flower.

These marine invertebrates live in salt or brackish water. They include sea anemones, stony corals, soft corals, and sea pens. Most adults are sessile, meaning they stay attached to the seabed. However, they begin life as drifting zooplankton called planula larvae.

The fundamental body unit of an anthozoan is the polyp.

A polyp consists of a cylindrical column and an oral disc. The oral disc features a central mouth surrounded by a ring of tentacles.

Inside the body, the mouth leads to a tubular pharynx. This pharynx opens into the coelenteron, or gastrovascular cavity. This internal space is divided by vertical partitions called mesenteries or septa. These septa are infoldings of the body wall. They consist of a mesogloea layer sandwiched between two layers of gastrodermis.

Anthozoans are carnivores that capture prey using their tentacles.

The tentacles contain specialized venom-containing cells called cnidocytes.

Many species also use photosynthesis to supplement their energy. They host single-celled algae known as zooxanthellae within their tissues.

These hermatypic, or reef-building, species must live in shallow, well-lit water. In contrast, azooxanthellate species lack these algae. They can thrive in deep-water locations where sunlight does not reach.

Scientists classify Anthozoa into two main extant classes. The first is Hexacorallia, which exhibits six-fold symmetry.

This class includes stony corals, sea anemones, and zoanthids. The second class is Octocorallia, which shows eight-fold symmetry.

This group includes soft corals, gorgonians, and sea pens.

Some species are currently listed as incertae sedis. This means their exact taxonomic position is not yet certain.

Research into the history of these animals involves studying DNA and fossils.

In 1995, J. E. N. Veron and colleagues analyzed ribosomal DNA.

They found that the order Ceriantipatharia was once thought to be the ancestral group. Newer studies show that Ceriantharia is actually a clade of Hexacorallia.

The reconstructed ancestor of Anthozoa likely lived during the Tonian period. This was between 1,000 and 720 million years ago.

This ancestor was likely a solitary polyp with bilateral symmetry. It lacked both a skeleton and photosymbiosis.

Anthozoans vary greatly in size and physical structure.

Some individuals are smaller than half a centimeter across. Large colonies can reach a diameter of one meter or more.

Many corals are colonial, growing through the budding of new polyps.

Stony corals build strong skeletons using aragonite. These can form massive, bushy, or leafy shapes.

Other groups, like sea pens, use different structural methods.

Some species also reproduce asexually through fragmentation. This occurs when a piece of the animal breaks off to form a new individual.

These animals play a vital role in marine ecosystems.

Reef-building corals create complex habitats for many other species.

For example, deep-water corals provide homes for fish like the alfonsino.

While shallow reefs are famous, more coral species live in deep water.

This diversity helps maintain the health of the entire ocean system. By building structures and providing food, anthozoans connect different levels of marine life.