A pair of white squirrels [1] ( lat. Channichthys velifer ) is a species of marine subantarctic bottom fish from the family of white squirrel (Channichthyidae) perciform order. As a new species for science, it was described in 1974 by the Ukrainian ichthyologist E.E. Meisner. The name of the species comes from the Latin word (adjective) “sailing” ( velifer ) and is associated with the unusual shape of the first dorsal fin, which is very wide for most rhinoceroses , has a very wide base, trapezoidal shape and a high fin fold, reaching the tips of flexible spiny rays [2] [ 3] .
| Sailing Whitefish |
Channichthys velifer , female |
| Scientific classification |
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| No rank : | Bilateral symmetrical |
| Family: | White-blooded fish |
| Gender: | Rhinoceros squirrels |
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| International scientific name |
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Channichthys velifer Meissner, 1974 |
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Kerguelen Islands - a typical habitat for sailing whitefish
C. velifer is a large-sized coastal and thalassobatial fish with a total length of up to 54 cm. It is endemic to the waters of the Indian Ocean washing the islands of the Kerguelen archipelago and a series of underwater uplifts - guyots (cans) in the area of the underwater ridge Kerguelen in the Indian Ocean sector of the Subantarctic . Perhaps also lives in the area of the Heard and McDonald Islands , located at the southern tip of the Kerguelen submarine ridge. In addition to C. velifer, the genus of rhinoceros whitefish ( Channichthys ) includes another 8 species of albino fish endemic for Kerguelen [4] .
According to the scheme of zoogeographic zoning for bottom fish proposed by A.P. Andriyashev and A.V. Neyelov [5] [6] , the above region is within the boundaries of the zoogeographic district of Kerguelen-Hurd, Indo-Oceanic province of the Antarctic region.
Like other rhinoceros whitefish , C. velifer has a well-developed rostral spike (“horn”) in the anterior part of the snout. For it, as for all other white-headed fish, the absence of scales on the body (except for the lateral lines ) and the unique phenomenon among all vertebrates , characteristic of only 25 species of fish of this family, are also characteristic — the presence of “white” blood , which is a slightly yellowish plasma deprived of red blood cells and hemoglobin . This phenomenon is explained by the adaptation of the ancestral forms of white-blood fish to the harsh conditions of the Antarctic and, accordingly, a decrease in the water temperature in the Southern Ocean to negative values close to the freezing point (–1.9 ° C) [2] [7] .
Sailing whitefish can be found as by- catch when fishing in the Kerguelen Islands for the pike-shaped whitefish Chamsocephalus gunnari Lönnberg, 1905, better known under the trade name “ icefish ”.
Content
It differs from other species of the genus Channichthys in the following set of characters. In the first dorsal fin there are 10-11 flexible spiny rays, of which the 5th or 4th largest; in the second dorsal fin 30–33 rays; in the anal fin 29-30 rays; pectoral fin 20-21 ray; in the dorsal (upper) lateral line of 56–72 tubular bone segment ( scales ), in the back of the medial (median) lateral line of 5–16 tubular bone segment (scales), in the front of the medial line, rounded perforated bone plaques, as a rule, absent or occasionally up to 3-8 plaques; in the lower part of the gill arch 11-13 stamens located only in the outer row; There are 55–56 vertebrae, of which 22–24 are trunk and 31–33 are caudal [2] [4] [7] .
The first dorsal fin is high, its height is 3.7–5.1 times the standard length of the fish, trapezoidal in shape, with a high fin fold reaching the tips of the flexible spiny rays. The first and second dorsal fins, as a rule, are in contact with their bases or are sometimes separated by a narrow inter-dorsal gap. The eye is small (15–20% of the length of the head or 30–39% of the length of the snout). The interorbital space is relatively wide (16-19% of the length of the head), usually larger than the diameter of the orbit, concave, with the outer edges of the frontal bones moderately elevated above the orbit. The posterior edge of the jawbone extends backward to the vertical through the middle of the orbit.
Granulation (tuberculosis) moderate; bone granules smoothed or less often in the form of small spines cover the frontal bones in the occipital and orbital regions, are well defined on the infraorbital bones (postlacrimalia) and gill covers, as well as on the bone segments (scales) of the lateral line, sometimes found on the rays of the ventral fin and rays of the gill membranes; granulation on the rays of the first dorsal fin is rather weak and usually occurs no further than the 2nd ray.
The intravital general color of the fish varies from light gray and light green to brownish-olive with small dark rounded spots, sometimes merging into a kind of delicate moire pattern. Under the dorsal fins, 3-4 vertical wide dark stripes, tapering downward. The bottom of the head, chest and body sections adjacent to the anal fin are light, with small golden spots, sometimes with weak dark pigmentation. Golden spots are usually also found on the rays of paired and unpaired fins. The rays and fin fold of the first dorsal fin are gray or dark gray, sometimes yellowish-gray (golden), with numerous, larger than the body, dark spots. The rays of the pectoral, caudal, and second dorsal fins are gray, in some fish with small dark spots; fin folds are light. Anal fin light. Abdominal fins are yellowish brown on top, in some fish with small dark spots. In formalin or alcohol-fixed fish, the general body color is dark gray or grayish-brown with dark brown or blackish spots.
The well-known range of the species covers the coastal sea waters surrounding the Kerguelen Islands ( endemic ) and individual underwater elevations (banks) of the Kerguelen submarine ridge. A relatively shallow species, observed at depths of 95-310 m [2] [3] [7] .
Belongs to the group of large species of the genus Channichthys . The largest females reach 538 mm of total length and 490 mm of standard length. The dimensions of the largest known male are 325 mm of total length and 290 mm of standard length [3] .
Leads a bottom lifestyle. It occurs on the bottom with thickets of brown algae with a large biomass of bottom fauna - echinoderms and glass sponges . Predator-ichthyophagous and benthophagous, feeding, obviously, on the surface of the soil and in the bottom layer. In the stomachs of fish, pike-like whitefish and cephalopods were found. As in other predatory rhinoceros squirrels, in sailing squirrel, gill stamens are few and arranged in a row on the bottom of the first gill arch [1] [2] [3] .
Puberty first occurs with a total length of about 33–35 cm (30–32 cm of standard length). Spawning apparently occurs in the winter-spring period of the southern hemisphere . Absolute fecundity , calculated for a female with a total length of 418 mm (378 mm standard length), with gonads at the maturity stage III-IV, amounted to 7155 eggs.
