Phylum Chordata: Characteristics

Welcome to the World of Chordates

In the next few posts we will delve deeper into the world of chordates, but before we get started, what actually is a chordate?  Chordates are animals that have enormous diversity!  There are animals that can fly, swim, have scales, have shells, and even flippers!  Despite all of these differences, all chordates have four characteristics that are exhibited at some point in their lifetimes: Dorsal hollow nerve chord, notochord, pharyngeal pouches/slits, and a post-anal tail.



Chordate Embryo

The dorsal hollow nerve chord is placed on the dorsal side (back) of the animal.  Most chordates' dorsal hollow nerve chords form into a brain and spinal chord, creating the central nervous system.  Nerves develop from this chord and then go to other parts of the body.

The notochord protects and supports the dorsal hollow nerve chord.  In vertebrates, the notochord is only present during embryonic development; it forms into the vertebral column after birth.  

Pharyngeal pouches/slits are openings located in the pharynx.  In some chordates these pouches/slits help them to breathe and filter out food.  In tetrapods (amphibians, reptiles, birds, and mammals), pharyngeal pouches/slits develop into components ears and tonsils.  

The post-anal tail is a posterior extension of the body that goes past the anus.  Post-anal tails in fish and other aquatic chordates help with locomotion.  In some terrestrial chordates, their tails are used for balance, communication, and mating.