Balanoglossus gigas: example of hemicordate animal
Introduction (what they are)
The hemicordates are small marine animals. They belong to the Hemichordata Phylum. They have many physiological characteristics in common with chordates. However, they are not chorded, as they do not present notochord.
About 100 species of hemicordates are currently known.
The word originates in Greek and hemi means half and chord means cord.
Main characteristics of hemicordates:
- The body of the hemicordates has bilateral symmetry and shape similar to that of worms, ie it is cylindrical and soft.
- They have a stomach, a tubular structure that is an extension of the digestive tract.
- Most of these animals live in shallow water.
- Body composed of three parts: proboscis, necklace and trunk.
- Size varies greatly from species to species. Some can be up to one meter long, while others are only 10 cm long.
- Most species feed on organic matter present in the ocean substrate.
- They have pharynx with slits. This pharynx is used as a kind of filter for ingested foods.
- Have circulatory system, excretory system and heart.
- The cardiovascular system of the hemicordates is open.
- Depending on the species, reproduction may be sexual or asexual (mainly by budding).
Examples of hemicorded animal species
- Balanoglossus gigas
- Schizocardium brasiliensis
- Glossobalanus crozieri
- Balanoglossus clavigerus
- Saccoglossus sp.
- Graptolithine (extinct)