These interesting marine organisms belong to the order Amphioxiformes, and there are about 25 species in the genera Branchiostoma and Epigonichthys. They are usually up to 10 cm long and have a physique without a simple head, a vertebrate but with head-like tentacles in Branchiostoma species. They have hollow dorsal filaments (notocord) similar to dorsal nerve cords found in vertebrates. Their bodies have prominent muscle blocks and their gills are well developed.
The sexes of these organisms are separate, and fertilization occurs by releasing the eggs and sperm into open water. They are known for their free-floating planktonic tornaria larvae, which they consume by filtering food particles through seawater. They live in coastal shallows and are commonly found in temperate and tropical seas.
Amphioxus are known for their very slender bodies and a profile that is pointed at both ends. Hence the name "amphioxus", meaning opposite end. They can reach up to 10 cm in length and have an appearance reminiscent of spears, harpoons, pikes or miniature blades.
Interestingly, rats have some characteristics similar to fish. Their bodies are similar to those of small snakes and they have fins. They have a dorsal fin that runs from the back of their head to the tail, and they have a ventral fin that extends from the underside of the body to the beginning of the anus. Having an atriopore is a structure that regulates the excretion of water.
Although they have the ability to move like fish, they are distinguished from fish by the lack of skulls and jaws. Also, they have no mouths and water enters the throat and is filtered by multiple gill filters, separating food particles. Food is mixed with the fluid secreted by a structure called the endostyle and transmitted to the small intestines to be digested.
The swamps have many similarities with seaweeds and primitive vertebrates, and are therefore considered representatives of the link between vertebrates and invertebrates. Although they have many features in common with dorsal bony animals, they share some, such as jawless fish. Some larvae obtain food by filtering water, and their simple fins are reminiscent of features of the most primitive vertebrates.
Bags begin as free-swimming larvae as a stage of their life cycle and complete as adult swamp fish, often living in small tunnels or near the bottom of the sea, and roaming quickly. These organisms serve as a fascinating scientific bridge, providing important information about vertebrates.
