Usually, when the word “shark” is mentioned, an image of a large formidable predator arises in the head, meeting with which carries a danger to humans. However, in this superclass of cartilaginous fish there is a unique group of truly miniature species (up to 50 cm). In the list of sharks with the smallest sizes, the second place is occupied by dwarf (Latin Euprotomicrus bispinatus). The length of her body is only 22-27 cm, that is, the predator can easily be placed in the palm of your hand.
The first scientific description of a dwarf shark dates from 1824. Currently, the species lives not only in the wild, but also at home. The miniature and original appearance of Euprotomicrus bispinatus made this predator a popular object for decorative aquarium breeding.
general characteristics
The dwarf (or pygmy) shark belongs to the dalatian family and is the only representative of the genus Euprotomicrus. The species belongs to the katraiform order. This taxon also includes the smallest shark in the world - Etmopterus perryi. However, Euprotomicrus bispinatus is only a couple of centimeters larger than it.
The dwarf shark is not only remarkable for its miniature. This fish has one of the unique natural phenomena - bioluminescence. Because Euprotomicrus bispinatus is sometimes called a dwarf luminous shark.
The animal uses the luminescence mechanism for protective purposes. The miniature size of the pygmy shark makes it vulnerable to larger predators. The blue glow spreading along the abdomen has a good masking effect in the water column, since it effectively reflects light rays. This makes the shark virtually invisible to predators swimming from below. Luminescence also helps fish to hunt. Soft flickering is an excellent way to attract prey.
The maximum recorded length of the dwarf shark was 27 cm. The females of these fish are larger in comparison with males.
Features of the structure and appearance
The dwarf shark has a miniature dark brown (almost black) elongated body of a conical shape, tapering towards the tail. The head of this fish is very large, and the muzzle is blunt and compressed, moderately long.
The eyes of a pygmy shark are large, round and able to glow green in the dark. Behind them are sprinklers. Gill slits very small and evenly wide. The snout accounts for 2/5 of the length of the head.
The mouth of the pygmy shark is rounded, framed by thin fleshy lips, with no fringe. The teeth on the upper and lower jaws are very different. Their structure corresponds to the characteristics of all deep-sea sharks of the Dalatian family. For the latter, the following tooth structure is characteristic:
- the upper ones are smaller, with narrow, sharp, straight tips, have a curved awl-shaped shape;
- the lower ones are large, with a high, wide, almost vertical tip, the cutting edge is triangular in shape, the bases close together, forming a continuous blade.
The pygmy shark has smooth teeth. On the upper jaw they are laid in 29 rows, and on the lower - in 34 rows.
The body of Euprotomicrus bispinatus in appearance resembles a tadpole. Dorsal fins are very small, while the second is much larger than the first. They are located closer to the tail of the body.
On the back of this fish there is no “triangle” typical of sharks. The pectoral fins are rounded, and the anal is completely absent. The caudal fin of Euprotomicrus bispinatus differs from the heterocircular sickle-shaped structure habitual for sharks. In a pygmy, it is asymmetric, but not lobed. The upper and lower parts are rounded and almost identical (close to the homocercal type). The subterminal notch on the fin is well developed. The precadal pits and subterminal carinae on the caudal stem are absent.
The entire lower body of the shark is covered with bioluminescent organs - photophores. Their size is very small (0.3-0.8 mm), however, together they give a very powerful glow. Photophores do not burn continuously, but only when the shark is in an excited state.
Habitat
The habitat of the dwarf shark is very extensive. It covers tropical and temperate waters. Within the Southeast Atlantic, this fish inhabits:
- not far from Ascension Island;
- heading west from Cape of Good Hope;
- in the region of South Africa;
- in the waters located east of the island of Fernando de Noronha.
Distribution in the Indian Ocean covers the open waters of Madagascar and Western Australia.
In the North Pacific, the pygmy shark inhabits the following areas:
- USA;
- Hawaiian Islands;
- Midway Island.
In the southern part of the same ocean, the distribution area occupies the space between New Zealand, southern Chile and the Phoenix island.
Lifestyle
Despite its miniature size, the dwarf shark is a real predator. She preys on smaller fish, crustaceans, mollusks, and sometimes even attacks relatively large prey. In the latter case, the pygmy shark clings to the victim’s torso and rotates, bites off pieces of it.
Euprotomicrus bispinatus usually hunts at night, sinking in search of food to a depth of one and a half kilometers. In the daytime, this predator keeps closer to the surface of the water. However, even in the afternoon, the pygmy sharks are at a depth of at least 200 meters.
Breeding
Euprotomicrus bispinatus propagates by ovum. The number of cubs in the litter does not exceed 8. The length of the body of sharks that are born is about 6 cm. They become adult mature when their body reaches 17-19 cm (in males) and 22-23 cm (in females).
Another species of shark called dwarf
The dwarf spiny shark (Latin Squaliolus laticaudus) is slightly larger than the pygmy shark (body length up to 28 cm). This miniature predator is notable for the presence of a spike on the anterior dorsal fin, for which it received the corresponding Russian name.
The distribution area of Squaliolus laticaudus covers all oceans, with the exception of the Arctic. However, this species is currently poorly understood.
This predator has an elongated spindle-shaped body with a long conical muzzle, on which large round eyes are located. Unlike Euprotomicrus bispinatus, in a dwarf prickly shark, the snout is not blunt, but pointed. The head of the fish is disproportionately large in relation to the body.
Miniature shark for aquarium
One of the most popular modern areas of aquarium is the home content of sharks. Of course, only small fish are suitable for this purpose. The best choice in terms of ease of care and reservoir capacity will be miniature decorative sharks. The latter are distinguished not only by compactness, but also by their original appearance.
Species Euprotomicrus bispinatus is ideal for the role of an aquarium. The dwarf shark is very unpretentious and tolerates captivity. In addition, it is a very beautiful fish, the aggressiveness of which is much lower than that of larger counterparts. One of its most valuable decorative qualities is the ability to glow in the dark.
The content of the pygmy shark must take into account 4 important features:
- proper selection of temperature conditions;
- effective aeration;
- sufficient aquarium volume (at least 200 liters).
With all the advantages of Euprotomicrus bispinatus, this decorative predator is an expensive pleasure. Prices for dwarf sharks for an aquarium start at 150 thousand rubles.