The black swallower, ''Chiasmodon niger'', is a species of

deep sea fish Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep sea fishes include the flashlight ...

in the family

Chiasmodontidae The Chiasmodontidae, snaketooth fishes or swallowers, are a family of deep-sea percomorph fishes, part of the order Trachiniformes, known from oceans worldwide. Timeline ImageSize = width:1000px height:auto barincrement:15px PlotArea = l ...

. It is known for its ability to swallow fish larger than itself. It has a worldwide distribution in tropical and subtropical waters, in the mesopelagic and bathypelagic zones at a depth of . It is a very common and widespread ocean fish; of its genus, it is the most common species in the

North Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe and ...

Description

The black swallower is a small fish, averaging between 15 cm to 20 cm (6 to 8 in), with a maximum known length of . The body is elongated and compressed, without scales, and is a uniform brownish-black in color. Its

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...

is long, with a blunt

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is c ...

, moderately sized eyes, and a large

mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...

. The lower jaw protrudes past the

upper Upper may refer to: * Shoe upper or ''vamp'', the part of a shoe on the top of the foot * Stimulant, drugs which induce temporary improvements in either mental or physical function or both * ''Upper'', the original film title for the 2013 found fo ...

; both jaws are lined with a single row of sharp, depressible teeth, which interlock when the mouth is closed. The first three teeth in each jaw are enlarged into

canine Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** '' Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the ...

s. A small lower spine occurs on the preoperculum. The pectoral fins are long, with 12–15 (usually 13)

ray Ray may refer to: Fish * Ray (fish), any cartilaginous fish of the superorder Batoidea * Ray (fish fin anatomy), a bony or horny spine on a fin Science and mathematics * Ray (geometry), half of a line proceeding from an initial point * Ray (g ...

s; the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s are small and contain five rays. Of the two dorsal fins, the first is spiny with 10–12 spines, and the second is longer with one spine and 26–29 soft rays. The

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

contains one spine and 26–29 soft rays. The caudal fin is forked with 9 rays. The

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

is continuous with two pores per body segment.

Feeding

The black swallower feeds on bony fish, which are swallowed whole. With its greatly distensible stomach, it is capable of swallowing prey over twice its length and 10 times its mass. Its upper jaws are articulated with the skull at the front via the suspensorium, which allows the jaws to swing down and encompass objects larger than the swallower's head. Theodore Gill speculated that the swallower seizes prey fish by the tail, and then "walks" its jaws over the prey until it is fully coiled inside the stomach. Black swallowers have been found to have swallowed fish so large that they could not be digested before decomposition set in, and the resulting release of gases forced the swallower to the ocean surface. This is, in fact, how most known specimens came to be collected. In 2007, a black swallower measuring long was found dead off of Grand Cayman. Its stomach contained a

snake mackerel The snake mackerel (''Gempylus serpens'') is the sole species of fish in the monotypic genus ''Gempylus'', belonging to the family Gempylidae (which is also referred to generally as "snake mackerels"). It is found worldwide in tropical and sub ...

(''Gempylus serpens'') long, or four and a half times its own length.

Reproduction

Reproduction is

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...

; the eggs are pelagic and measure in diameter and contain a clear oil globule and six dark pigment patches, which become distributed along the newly hatched larva from in front of the eyes to the tip of the

notochord In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord consis ...

. These patches eventually disappear and the body darkens overall to black. The eggs are mostly found in winter off South Africa; juveniles have been found from April to August off Bermuda. The larvae and juveniles are covered in small, projecting spinules.

References

{{Taxonbar, from=Q142612 Chiasmodontidae Fish described in 1864 Taxa named by James Yate Johnson