Saccopharyngiformes is an order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 of unusual ray-finned fish superficially similar to eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...

s, but with many internal differences. Most of the fish in this order are deep-sea types known from only a handful of specimens such as the Umbrella Mouth Gulper Eel. Saccopharyngiformes are also bioluminescent in several species. Some, such as the swallowers, can live as deep as 10,000 feet (3,000 m) in the ocean, well into the aphotic zone
Aphotic zone
The aphotic zone is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1% of sunlight penetrates. Consequently, bioluminescence is essentially the only light found in this zone...


Saccopharyngiforms lack several bones, such as the symplectic bone, the bones of the opercle
Operculum (fish)
The operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body....

, and ribs. They also have no scale
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...

s, pelvic fins, or swim bladder. The jaws are quite large, and several types are notable for being able to consume fish larger than themselves. Their myomere
Myomere are the blocks of skeletal muscle tissue found commonly in chordates. They are commonly zig-zag, "W" or "V"-shaped muscle fibers. The myomeres are separated from adjacent myomere by connective tissues and most easily seen in larval fishes or in the olm...

s (muscle segments) are V-shaped instead of W-shaped like in all other fish, and their lateral line has no pores, instead being modified to groups of elevated tubules.


There are four families in two suborders in the order:
  • Suborder Cyematoidei
    • Cyematidae (bobtail snipe eels)
  • Suborder Saccopharyngoidei
    • Eurypharyngidae (pelican eel)
    • Monognathidae (onejaws)
    • Saccopharyngidae (swallowers, gulpers or gulper eels)


The gulper eel eats fish, copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...

s, shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

, and plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

. It uses its mouth like a net by opening its large mouth and swimming at its prey. Due to the gulper eel's specialised body shape, it is a poor swimmer and relies on the luminescent organ at the tip of its tail to attract prey.

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