Chordata
Chordates are a diverse phylum of animals that includes all vertebrates, along with several groups of invertebrates. They are characterized by the presence of a notochord, a flexible rod that supports the body. Chordates also have a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some point in their development. Chordates are found in a wide variety of marine environments, from the shallow intertidal zone to the deep sea.
Common Names
Chordates are sometimes referred to as vertebrates because this subphylum contains all the animals with backbones. However, there are also many invertebrate chordates, such as tunicates and cephalochordates.
Characteristics
The defining characteristics of chordates are:
- Notochord: A flexible rod that supports the body. In vertebrates, the notochord is replaced by the vertebral column (backbone).
- Dorsal hollow nerve cord: A tube of nerve tissue that runs along the back of the body. In vertebrates, this develops into the brain and spinal cord.
- Pharyngeal slits: Openings in the throat that are used for filter feeding in some chordates. In vertebrates, these slits are modified to form parts of the head and neck.
- Post-anal tail: A tail that extends beyond the anus. In some chordates, the tail is used for swimming, while in others it is reduced or absent.
Environments
Marine chordates can be found in a wide variety of environments, including:
- Intertidal zone: The area between high and low tide marks.
- Coastal waters: The shallow waters near the shore.
- Open ocean: The vast expanse of water that is far from land.
- Deep sea: The ocean floor and the water column below 200 meters.
References
Wikipedia: Chordate
Britannica: Chordate
Biology Reference: Chordata