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 The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

and subtropical waters, in the

mesopelagic The mesopelagic zone (Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light, and begins ...

and

bathypelagic zone The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagic ...

s 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 Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

, 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 Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conve ...

, 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 In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

protrudes past the upper; 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 canines. A small lower spine occurs on the preoperculum. The

pectoral 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 ...

s 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 fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s, 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 The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

, it is capable of swallowing prey over twice its length and 10 times its mass. Its upper jaws are articulated with the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

at the front via the suspensorium, which allows the jaws to swing down and encompass objects larger than the swallower's head.

Theodore Gill Theodore Nicholas Gill (March 21, 1837 – September 25, 1914) was an American ichthyologist, mammalogist, malacologist and librarian. Career Born and educated in New York City under private tutors, Gill early showed interest in natural histor ...

speculated that the swallower seizes

prey fish Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food ...

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 Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...

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 Grand Cayman is the largest of the three Cayman Islands and the location of the territory's capital, George Town. In relation to the other two Cayman Islands, it is approximately 75 miles (121 km) southwest of Little Cayman and 90 miles ( ...

. 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 The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

and measure in diameter and contain a clear oil globule and six dark pigment patches, which become distributed along the newly hatched

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

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 South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

; juveniles have been found from April to August off

Bermuda ) , anthem = "God Save the King" , song_type = National song , song = " Hail to Bermuda" , image_map = , map_caption = , image_map2 = , mapsize2 = , map_caption2 = , subdivision_type = Sovereign state , subdivision_name = , e ...

. 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