Latin name

Chionobathyscus dewitti

Other name

Глубинная белокровка

Identification

Chionobathyscus dewitti is characterised by the absence of scales on its body and possesses a unique phenomenon among all vertebrates, shared by only 25 species of fish in this family - the presence of "white" blood, a slightly yellowish plasma devoid of red blood cells and haemoglobin. This phenomenon is explained by the adaptation of ancestral forms of white-blooded fish to the harsh conditions of Antarctica and the negative water temperature of the Southern Ocean, which is close to freezing.

There are 122-132 pores in the dorsal lateral line of these fish, 9-13 pores in the medial line and 64-82 pores in the anal line. There are 2-12 gill stamens in the lower part of the first gill arch. The total number of vertebrae is 59-61, of which 23-28 in the trunk and 32-36 in the tail. Jaws have up to 3-4 rows of teeth.

The rostral spike is greatly reduced and button-shaped. The supraorbital ridges (outer edges of the frontal bones) are smooth (not indented). The apex of the lower jaw is level with the apex of the upper jaw, or the lower jaw is slightly shorter than the upper jaw. The mouth is large, the posterior edge of the upper jaw passing behind the vertical of the posterior edge of the pupil. Eye large, orbital diameter 18-22% of head length. The interorbital space (skin) is wide (29-31% of head length) and flat. The body has three lateral lines without bony segments. 

Features of fish fins

The first dorsal fin has 5-6 flexible barb rays, the second dorsal fin has 39-42 rays, the anal fin has 33-35 rays, the pectoral fin has 24-26 rays and the caudal fin has 11 rays. The first dorsal fin is relatively low (9-11% of standard body length) and short. Both dorsal fins are well separated by an interdorsal space. The pelvic fins are elongated with the second ray being the longest (24-28% of standard body length).

Fish colouring

The overall colouration of the body and fins is greyish in immature fish, dark grey in adults and charcoal black (mating season) in pre-spawning and spawning fish. There is a silvery white patch at the base of the pectoral fin. There are five broad blackish stripes on the sides of the body, which become almost invisible during spawning and blend into the overall black colouration of the body.

Distribution

The distribution of Chionobathyscus dewitti is circumpolar-Antarctic. It is known only from the high latitudes of Antarctica. 

Habitat

The marine bathydemersal is an endemic deep-water species. Habitat depths range from 500 to 2000 m. 

Size

The largest known length of Chionobathyscus dewitti is 50 cm for females and 40 cm for males. 

Behavior

Juveniles of this species have been observed on the shelf at depths of about 500 m, while adults are permanently found near the bottom in the deep-water zone of the bathyal slope at depths of about 600-2000 m.

Food and feeding habits

Predators that feed on Antarctic krill and fish.

Reproduction

Spawning occurs during the southern hemisphere summer period, December-February. The gonadosomatic index (the ratio of gonad weight to body weight, in percent) in mature pre-spawning females reaches 24%. The diameter of mature eggs is approximately 3.8 mm. The absolute fecundity counted in females with a total length of 41-46 cm was 3385-5499 eggs.

Fishing

Chionobathyscus dewitti is often caught as by-catch in the Antarctic toothfish bottom longline fishery.

Relationship with a person

Harmless.