The gulper eel, known scientifically as Eurypharynx pelecanoides, is one of the most bizarre looking creatures in the deep sea. Its most notable attribute is the large mouth. This enormous mouth is much larger than the eel’s body. The mouth is loosely hinged, and can be opened wide enough to sᴡᴀʟʟᴏᴡ an animal much larger than itself. The hapless fish is then deposited into a pouch-like lower jaw, which resembles that of a pelican. In fact, this eel issometimes referred to as the pelican eel. The gulper’s stomach can also stretch to accommodate its large meals. This giant mouth gives the eel its other common name of umbrella mouth gulper.
In spite of its gigantic mouth, it is believed that the Umbrella Mouth Gulper Eel’s diet consists mainly of small crustaceans. Since the eel has very tiny teeth, it probably does not eat large fish on a regular basis. The large mouth may be an adaptation to allow the eel to eat a wider variety of ᴘʀᴇʏ when food is scarce. It can also be used like a large net. They are hypothesized to exhibit ʟᴜɴɢᴇ-ꜰᴇᴇᴅɪɴɢ through the expansion of their mandible and upper jaw. Furthermore, their stomach can stretch and expand to accommodate large meals, although analysis of stomach contents suggests they primarily eat small crustaceans.
Like most eels, Gulper Eel lacks pelvic fins and scales. Otherwise, the pelican eel is very different in appearance from typical eels. Instead of having a swim bladder, the pelican eel has an aglomerular kidney that is thought to have a role in maintaining the gelatinous substance filling the “lymphatic spaces” that are found around the vertebrae. It has been hypothesized that these gelatinous substance filled “lymphatic spaces” could function in a similar way to a swim bladder. Furthermore, the muscle segment shape of the pelican eel is different. Its muscle segments have a “V-shape”, while other fish have “W-shaped” muscle segments. Pelican eels are also unusual because the ampullae of the lateral line system projects from the body, rather than being contained in a narrow groove; this may increase its sensitivity.
Unlike many other deep sea creatures, the pelican eel has very small eyes. For reference, the horizontal eye size diameter of a male pelican eel specimen was measured to be 2.6 mm. It is believed that the eyes evolved to detect faint traces of light rather than form images.
The pelican eel also has a very long, whip-like tail that it uses for movement and for communication via bioluminescence. Specimens that have been brought to the surface in fishing nets have been known to have their long tails tied into several knots. The end of the tail bears a complex organ with numerous tentacles, which glows pink and gives off occasional bright-red flashes. The colors on its tail are displayed through its light-emitting photophores. This is presumably a lure to attract ᴘʀᴇʏ, although its presence at the far end of the body from the mouth suggests the eel may have to adopt an unusual posture to use it effectively.
Not much is known about the reproductive habits of the pelican eel. Similar to other eels, when pelican eels are first born, they start in the leptocephalus stage, meaning that they are extremely thin and transparent. Until they reach their juvenile stage, they interestingly have very small body organs and do not contain any red blood cells. Many researchers believe that the eels ᴅɪᴇ shortly after reproduction.