Hagfish Anatomy

The hagfish are a very rare species of fish, due to the many strange and outstanding habits. Among marine life animals, hagfish are titled as 'fish', however, they do not fulfill many conventional characteristics that are found in common fish. Hagfish are also known by many names like 'slime eels' or 'jaw-less fish'. It must be noted that these fish are not eels and their classification as fish is still debatable.

Hagfish Anatomy

Physical Appearance
Average hagfish have a length of about half a meter, which is equivalent to 18 inches. The Eptatretus goliath is the longest ever recorded specie of hagfish, which has a length of about 127 cm. Other species that grow up to a rather significant length are Myxine kuoi and Myxine pequenoi, which grow about 18 cm long. For an animal that is classified as a fish, the hagfish does not look like a fish at all. The body of the hagfish is large and elongated. It has the physical appearance like that of an eel, hence the nickname, 'slime eel'. These fish have a group of 4 hearts and are empowered with 2 brains. The movement of hagfish is enabled by tails, that are shaped like paddles. The skeleton has a very wired construction. These fish, are the only animals which have a skull but do not have a vertebra (spine). The skulls of hagfish are cartilaginous in nature, where Keratin based tooth-like structures are attached for consumption of food. The color of the skin differ from specie to specie. It often ranges from pink to blue-gray. The eyes are not very well developed and are very simple eye spots. The underdeveloped eyes or rather eye spots also cannot revolve or resolve complex images which make hagfish almost blind. The sense of smelling, on the other hand, is very well developed. The fins are not present, instead six to eight barbels that surround a single nostril are seen. These barbels help the hagfish in locomotion. The hagfish do not have jaws like rest of the fish. Instead these fish have two structures that move horizontally. These tentacles have a tooth like structure attached to the end that pull pieces of food.

Circulatory System
The circulatory system of the hagfish is also not very well developed, and is similar to the respiration of worms. The circulatory system is made up of open and closed blood vessels. The 4 hearts are brachial in nature and act as pumps. The first three hearts fulfill the function of the circulation of blood. The fourth heart, however, is used to circulate the blood only between the intestines and livers.

Defense Mechanism
While studying the anatomy of a hagfish, it is important to study it's defense mechanism. As compared to other marine animals it's defense mechanism is very different. If a hagfish is in danger or is caught by a predator, it secretes a huge amount of mucus. This mucus reacts with water and forms a micro fibrous slime. This slime makes the body of the hagfish extremely slippery. The slime also confuses the predator, giving the fish, time to escape. Hagfish get rid of the slime on their body by tying themselves into a knot and again slowly coming back to their initial position. An average adult hagfish is capable of secreting such an amount of mucus, that it can turn 20 liters of water slime.

Though the hagfish is often considered as a gorse and disgusting creature by marine life experts, its study has helped the marine scientists to know more about ancient and prehistoric marine life. This is due to the fact that the anatomy of hagfish is very similar to prehistoric species of fish. Many organs of the hagfish such as eyes or feeding mechanism have remained primitive and underdeveloped even today.