Cnidarian phylogeny
Recent molecular phylogenetic work by Zapata et al. (2015) supports the traditional view that the phylum Cnidaria should be divided between two major clades, Anthozoa and Medusozoa.
Phylogenetic relationships of major groups of cnidarians.
Anthozoa is represented by some 7,500 extant species (Zapata et al., 2015) and is divided into two major subgroupings, Octocorallia and Hexacorallia. Octocorallia is represented today by sea pens, gorgonian corals, and soft corals; the group is entirely soft-bodied and consequently has a very poor fossil record. Hexacorallia, however, includes several major groups of extinct and modern corals that produced calcium carbonate skeletons, resulting in a superb fossil record. Soft-bodied sea anemones and several other groups also belong to the Hexacorallia. Most of these groups have polyp-like adult forms.
There are around 3,700 extant species of Medusozoa (Zapata et al., 2015), which is divided into four major groups. The true jellyfish are assigned to the Scyphozoa, while the deadly box jellyfish belong to the Cubozoa. The stalked jellyfish are assigned to the Staurozoa. Finally,Hydra and related forms are assigned to the Hydrozoa. As their name implies, most Medusozoan have medusoid-like (or, jellyfish-like) adult forms, though this is not universally true (e.g., the polyp-like Hydra is an exception).
Most of this chapter focuses on the superb fossil records of members of the Hexacorallia, in particular the extinct rugose and tabulate corals and the extant scleractinian corals. Very brief overviews of the other major groups of cnidarians are also presented, though none have an especially significant fossil record (though some extraordinary fossils are known).
FAQs
The phylum Cnidaria (pronounced “nih DARE ee uh”) includes soft-bodied stinging animals such as corals, sea anemones, and jellyfish (Fig. 3.23 A). The phylum's name is derived from the Greek root word cnid- meaning nettle, a stinging plant. Cnidarians are found in many aquatic environments.
What are some examples of cnidarians answer? ›
cnidarian, any member of the phylum Cnidaria (Coelenterata), a group made up of more than 9,000 living species. Mostly marine animals, the cnidarians include the corals, hydras, jellyfish, Portuguese men-of-war, sea anemones, sea pens, sea whips, and sea fans.
What are 3 interesting facts about Cnidaria? ›
Facts about cnidarian
- The phylum cnidaria is invertebrates, and their size ranges from ¾ of an inch to 61/2 feet in diameter.
- These can grow to a length of 250 feet.
- The weight of the species can be around 440 pounds.
- The lifespan of Cnidaria is around 4000 years, and these live on a carnivore diet.
The phylum Cnidaria contains about 10,000 described species divided into four classes: Anthozoa, Scyphozoa, Cubozoa, and Hydrozoa. The anthozoans, the sea anemones and corals, are all sessile species, whereas the scyphozoans (jellyfish) and cubozoans (box jellies) are swimming forms.
Are sexes separate in Cnidaria? ›
Cnidarians exhibit a range of sexual strategies, including gonochorism (separate sexes), simultaneous hermaphroditism, and sequential hermaphroditism [12].
What is the largest cnidarian? ›
The largest non-colonial cnidarian is the lion's mane jellyfish. As mentioned above, the tentacles are thought to stretch more than 100 feet. The bell of this jellyfish can be over 8 feet across. Of colonial cnidarians, the longest is the giant siphonophore, which can grow to over 130 feet.
How many hearts do cnidarians have? ›
Cnidarian Body Forms
These creatures contain two tissue layers (which is known as diploblastic) but no organs. While these organisms contain no heart, brain or lungs, they do use their internal cavity as a means for respiration.
What is unique to cnidarians? ›
All Cnidarians have tentacles with stinging cells in their tips which are used to capture and subdue prey. In fact, the phylum name "Cnidarian" literally means "stinging creature." The stinging cells are called cnidocytes and contain a structure called a nematocyst. The nematocyst is a coiled thread-like stinger.
What do cnidarians eat? ›
All cnidarians are carnivores, meaning that some form of meaty food is the basis of their diet. The meat consumed varies depending on the size of the species eating it, from microscopic zooplankton (animal larvae) and phytoplankton (plant larvae) to small fish.
Which class of cnidarians can sting you? ›
A group of cnidarians known as box jellies and sea wasps represent the biggest “stinging” threat to divers and swimmers. While many divers think of these animals as types of jellyfish, there are enough differences between the two groups that scientists place the box jellies and sea wasps in a separate class.
Cnidarians are early-branching animals in the eukaryotic tree of life. The phylum Cnidaria are divided into five classes: Scyphozoa (true jellyfish), Cubozoa (box jellyfish), Hydrozoa (species, Hydra and Hydractinia), Anthozoa (sea anemone, corals, and sea pen), and Staurozoa (stalked jellyfish).
What are the 4 groups of animals in the phylum Cnidaria? ›
Modern cnidarians are generally classified into four main classes: sessile Anthozoa (sea anemones, corals, sea pens); swimming Scyphozoa (jellyfish) and Cubozoa (box jellies); and Hydrozoa, a diverse group that includes all the freshwater cnidarians as well as many marine forms, and has both sessile members such as ...
Why is the phylum Cnidaria important? ›
Cnidarians play an important role in ecosystem functioning, in the competition among species, and for possible utilization of several active compounds against cardiovascular, nervous, endocrine, immune, infective, and inflammatory disorders or having antitumoral properties, which have been extracted from these ...
Why are jellyfish in the phylum Cnidaria? ›
Cnidarians are soft-bodied animals that include corals, jellyfish, and sea anemones. These soft-bodied animals have saclike digestive cavities and tentacles containing rows or stinging cells used for defense and capture of food.
