Cyclostomatida facts for kids
Quick facts for kids Cyclostomatida |
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| Tubulipora flabellaris | |
Scientific classification  |
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| Unrecognized taxon (fix): | Cyclostomatida |
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See List of Cyclostomatida families. |
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Cyclostomatida, also known as cyclostomes, are a group of tiny sea animals called bryozoans. They are an ancient order that first appeared a very long time ago, in the Lower Ordovician period. Imagine them as small, tube-shaped creatures living in colonies.
Today, there are many different kinds of cyclostomes. Scientists have identified over 7 subgroups, more than 59 families, 373 genera, and 666 species. These creatures were once very common in the Mesozoic Era, but their numbers have decreased since then. Now, cyclostomes usually make up less than 20% of the bryozoan species found in different ocean areas.
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What Are Cyclostomatida?
Bryozoans are small, invertebrate animals that live in colonies. They are often called "moss animals" because their colonies can look like moss or small plants. Cyclostomatida are a special type of bryozoan. They are known for their unique tube-like structures. These animals are important for understanding ancient ocean life.
How Are They Classified?
Scientists classify cyclostomes into two main groups based on their outer body structure. Think of it like having different types of houses.
- Free-walled cyclostomes: These have soft, uncalcified outer walls on their individual animals (called zooids). The openings for these zooids can be shaped like polygons or circles.
- Fixed-walled cyclostomes: These have much harder, calcified outer walls. Their zooids usually have circular openings that are part of the hard outer wall.
Inside a Cyclostome: Their Body Structure
Cyclostomes have fascinating body structures that help them live and grow in colonies.
Their Tiny Skeletons
The hard, protective outer layer of a cyclostome is called a skeleton. It's usually made of a material called calcite. This skeleton is often made of tiny, flat crystals stacked together.
The individual feeding animals, or zooids, are typically long, curved tubes. They have openings at the end that can be circular or polygonal. Cyclostome colonies come in many shapes. Some grow flat against hard surfaces like rocks or shells, forming circular patches or branching patterns. Others grow upright, forming bushy colonies with thin, branching arms. New zooids usually form in special growth areas, like the edges of flat colonies or the tips of branching ones.
Connecting Zooids
All cyclostomes that lived after the Palaeozoic Era have tiny connections between their zooids. These connections are like small pores in the walls that separate each individual animal. In fixed-walled forms, these pores are the only way the internal body cavities connect. However, in free-walled forms, the outer walls are soft, allowing for wider connections between the zooids.
Special Zooids for Life Cycle
Cyclostome colonies have different types of zooids, though not as many as some other bryozoans.
- Gonozooids: These are larger zooids specially designed for brooding (protecting) their young larvae.
- Kenozooids: These are non-feeding zooids that help fill spaces and provide structural support for the colony.
Modern cyclostomes have a unique way of reproducing called polyembryony. This means that one fertilized egg can divide to produce many genetically identical larvae. These larvae are kept safe inside the gonozooid. After a while, they are released, swim for a short time, and then settle down. Once settled, they change (this is called metamorphosis) and start new colonies. Gonozooids are very important for identifying different types of cyclostomes. However, not all colonies develop gonozooids, which can make identification tricky.
How New Colonies Grow
Every cyclostome colony starts from a single larva. This larva settles onto a surface and changes into the very first zooid of the new colony, called the ancestrula.
This first zooid then begins to create new generations of zooids. This process of colony growth is called astogeny. The zooids can change slightly in appearance as the colony grows. In all species, the first few generations of zooids might look a bit different. After that, most zooids in the colony will look very similar. Some colonies can also develop new branches from the side of an existing branch, starting a new growth pattern.
Where Cyclostomes Live and How They Survive
Cyclostome bryozoans live only in the ocean. They need salty water and are mostly found in the deeper parts of the continental shelf.
Their Ocean Home
While some cyclostomes can attach to soft algae, most prefer hard surfaces. They often colonize rocks and shells. You might find many encrusting species in hidden spots, like inside empty bivalve shells. They seem to be less common in warm tropical waters. Instead, you'll find most of the larger species in cooler, temperate, and arctic environments.
Facing Challenges in the Sea
Cyclostomes are not very good at competing for space with other sea creatures. Larger animals like sponges and ascidians (sea squirts) often grow over them. They also tend to lose battles for space against other types of bryozoans.
Their feeding tentacles are generally smaller and fewer than those of other bryozoans. This means they create weaker water currents to catch food. Many encrusting species have small colonies, suggesting they live a "weedy" lifestyle. This means they grow quickly and might not live for a very long time, perhaps less than a year. However, some of the larger colonies, both flat and upright, can live for many years. Scientists still don't know much about how fast cyclostomes grow.
Who Eats Cyclostomes?
Although specific studies on cyclostome predators are rare, it's likely they are eaten by the same animals that prey on other marine bryozoans. These predators include nudibranchs (sea-slugs), pycnogonids (sea-spiders), echinoids (sea urchins), and various fish.
Their Life Cycle and Reproduction
Scientists are still learning a lot about how cyclostomes reproduce. We know that sperm is released from the tips of their tentacles, similar to other bryozoans. However, the actual fertilization of eggs has never been directly observed.
It's also unclear if each gonozooid (the special zooid for babies) produces one group of larvae or many. We also don't know if one or more groups of genetically identical larvae are present in each gonozooid. The exact length of time the larvae spend developing inside the gonozooid is another mystery.
