Pacific hagfish (Eptatretus stoutii), also known as slime eel―incorrectly though―is a jawless fish that inhabits the depths of the Pacific Ocean. It is mostly found in muddy bottom areas and rock crevices at considerable depths. Hagfish belong to the agnathans group of fish, which are considered the earliest species of all living fish.
Pacific hagfish have eel-like bodies, a cartilaginous skeleton, five hearts, and 10 to 14 pairs of gill pores. However, they lack scales, jaws, paired fins, and stomach. Their eyes are rudimentary and appear as small spots on their lightly shaded skin.
They are virtually blind, and can visualize an object with their keenly developed senses of smell and touch. Hagfish anatomy resembles that of many of the prehistoric species of fish.
Pacific hagfish are unsavory to their predators, as they produce a large amounts of slime when disturbed. The slime, which is a combination of proteins mixed with salt water, expands to create a protective layer around them. It works as an anti-predatory mechanism and keeps them safe from being eaten by predatory species.
Pacific hagfish prefer to live in areas with soft mud at the deep-sea bottom, where they can burrow when predators are lurking around.
Hunting and Diet
Burrowing doesn't just keep them off the predator's radar, but also complements their unique hunting style. They swim in snake-like manner and attack their prey by making a hole into its body. Then they actually slither into the dead fish and consume its flesh and internal organs from inside with the help of their 'rasping tongue'.
Being opportunistic feeders, they even feed on dead rotten animals that are available at the bottom of the ocean. Besides, they are also known to feed on crustaceans and worms. In the absence of well-developed eyesight, they rely on their nasal organs to find their prey.
The Pacific hagfish has a prolonged spawning period. The females carry an average of 28 eggs. Eggs are laid once in a year and when they hatch, the young ones emerge as small hagfish―not larvae. While they can lay eggs during any season, the same is usually seen in spring or during the early summer season.
Relationship with Humans
Pacific hagfish--and their eggs--are consumed in Japan and several other Asian countries. They are caught using rakes and plastic baited traps. In some parts of the world, fishermen use chemicals to anesthetize the fish immediately after catching them. Additionally, their skin is processed into various leather goods and sold throughout the world.
Though they are known as "slime-eels", they are not true eels―nor are related to the eel family in any way. Studies have revealed that the origin of this creature can be traced back to the Paleozoic era, which is also considered the evolving era of fish.
Their unusual feeding habits and their slime-producing abilities have led scientists to recognize them as the most 'disgusting' of all sea creatures.