Black swallower
Encyclopedia
The black swallower, Chiasmodon niger, is a species of deep sea fish
in the family Chiasmodontidae
, notable for its ability to swallow fish larger than itself (for which it is sometimes named the "great swallower").
It has a worldwide distribution in tropical and subtropical waters, in the mesopelagic
and bathypelagic zones at a depth of 700-2,745 meters (2,300-9,000 ft).
, and is a uniform brownish black in color. The head
is long, with a blunt snout
, moderately sized eyes, and a large mouth
. The lower jaw 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 canine
s.
There is a small lower spine on the preoperculum. The pectoral fins are long, with 12-15 (usually 13) rays; the pelvic fins are small and contain 5 rays. There are two dorsal fin
s; the first is spiny with 10-12 spines, and the second is longer with 1 spine and 26-29 soft rays. The anal fin contains 1 spine and 26-29 soft rays. The caudal fin is forked with 9 rays. The lateral line
is continuous with 2 pores per body segment.
, it is capable of swallowing prey over twice its length and ten 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 fishes by the tail, and then "walks" its jaws over the prey until it is fully coiled inside the stomach.
Black swallowers have been found that had 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 19 cm (7.4 in) long was found dead off Grand Cayman
. The stomach of the swallower contained a snake mackerel (Gempylus serpens) 86 cm (34 in) long, or four times its length. It is unclear how the swallower managed to avoid being eaten by the larger snake mackerel, itself an aggressive predator.
from in front of the eyes to the tip of the notochord
. 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.
Deep sea fish
Deep sea fish is a term for any fish that lives below the photic zone of the ocean. The lanternfish is, by far, the most common deep sea fish. Other deep sea fish include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, and viperfish....
in the family Chiasmodontidae
Chiasmodontidae
Chiasmodontidae, the snaketooth fishes, is a family of deep-sea fishes in the order Perciformes.-Species:There are 22 species in four genera:* Genus Chiasmodon Johnson, 1864 ** Chiasmodon bolangeri Osório, 1909....
, notable for its ability to swallow fish larger than itself (for which it is sometimes named the "great swallower").
It has a worldwide distribution in tropical and subtropical waters, in the mesopelagic
Mesopelagic
The mesopelagic is that part of the pelagic zone that extends from a depth of 200 to 1000 metres below the ocean surface. It lies between the photic epipelagic above and the aphotic bathypelagic below, where there is no light at all...
and bathypelagic zones at a depth of 700-2,745 meters (2,300-9,000 ft).
Description
This is a small fish, with a maximum known length of 25 cm (10 in). The body is elongated and compressed, without scalesScale (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...
, and is a uniform brownish black in color. The head
Head
In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....
is long, with a blunt snout
Snout
The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
, moderately sized eyes, and a large mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
. The lower jaw 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 canine
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
s.
There is a small lower spine on the preoperculum. The pectoral fins are long, with 12-15 (usually 13) rays; the pelvic fins are small and contain 5 rays. There are two dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s; the first is spiny with 10-12 spines, and the second is longer with 1 spine and 26-29 soft rays. The anal fin contains 1 spine and 26-29 soft rays. The caudal fin is forked with 9 rays. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
is continuous with 2 pores per body segment.
Feeding
The black swallower feeds on bony fishes, which are swallowed whole. With its greatly distensible stomachStomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
, it is capable of swallowing prey over twice its length and ten times its mass. Its upper jaws are articulated with the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
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 Gill
Theodore Nicholas Gill was an American ichthyologist, mammalogist, malacologist and librarian.Born and educated in New York City under private tutors, Gill early showed interest in natural history. He was associated with J...
speculated that the swallower seizes prey fishes by the tail, and then "walks" its jaws over the prey until it is fully coiled inside the stomach.
Black swallowers have been found that had swallowed fish so large that they could not be digested before decomposition
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
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 19 cm (7.4 in) long was found dead off Grand Cayman
Grand Cayman
Grand Cayman is the largest of the three Cayman Islands and the location of the nation's capital, George Town. In relation to the other two Cayman Islands, it is approximately 75 miles southwest of Little Cayman and 90 miles southwest of Cayman Brac.-Geography:Grand Cayman encompasses 76% of...
. The stomach of the swallower contained a snake mackerel (Gempylus serpens) 86 cm (34 in) long, or four times its length. It is unclear how the swallower managed to avoid being eaten by the larger snake mackerel, itself an aggressive predator.
Reproduction
Reproduction is oviparous; the eggs are pelagic and measure 1.1-1.3 mm (0.04-0.05 in) in diameter and contain a clear oil globule and six dark pigment patches, which become distributed along the newly hatched larvaLarva
A larva 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...
from in front of the eyes to the tip of the notochord
Notochord
The notochord is a flexible, rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes...
. These patches eventually disappear and the body darkens overall to black. The eggs are mostly found in winter off South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
; juveniles have been found from April to August off Bermuda
Bermuda
Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...
.
The larvae and juveniles are covered in small projecting spinules.