Latin name

Rhodichthys regina

Other name

Rhodichthys regina

Identification

The head of the Threadfin seasnail is large, thick, and compressed at the sides. The cheeks are vertical. The body is compressed at the sides and tapers sharply to the tail. The snout is slightly forward. Both pairs of nostrils have the appearance of open pores. The gill openings are very large, reaching to the base of the abdominal filaments. Vertebrae: 62-69. They have broad and flat dental plates, and the teeth are very fine, slightly protruding, and uniform in size. The posterior edge of the gill cover is rounded.

Features of fish fins

Dorsal soft rays (total): 56 - 60. The upper pectoral fin blade of these fishes is formed by 11-12 rays. The lower lobe is filiform, two- or three-branched. It begins on the thorax and is formed by 5 rays - 2 long and 3 lower rudimentary.

Fish colouring

The body of a live fish is translucent and varies in color from light red to light purple. Fry are colorless. The belly is black. The skin on the head, including the lower part, is pale (bright red when alive). Mouth pale, gill cavity grayish.

Distribution

Threadfin seasnails are widely distributed from the Arctic to the Northeast Atlantic: Central Arctic Basin, Norwegian and Greenland Seas; including north of the Wyvill-Thomson Ridge and the Iceland-Faroe Rise. They can be found in the depths of the Scandinavian Basin as well as in the Central Arctic Ocean, extending into some marginal seas.

Habitat

Marine species. Lives at great depths (1390-2365 m) over muddy substrates with negative bottom temperatures and high salinity (about 35 ‰). Leads a bathydemersal lifestyle in intermediate layers of water above great depths.

Size

The length of adult fish of this species is 25-28 cm, the maximum length is 29.7 cm. The preanal distance is 34.3-34.5% of the body length, the head distance is 23.4-23.9%. The post-orbital distance is short, 12.7-13.0% of the length.

Behavior

All trawl catches of Rhodichthys regina were made at great depths on muddy substrate at negative bottom temperatures and high salinities. There is reason to believe that this species is not only found near the bottom, but also has a bathypelagic lifestyle in the intermediate water layers above the deep water. This is indicated by the good preservation of specimens collected during trawling at a depth of about 2000 m (live specimens are also found), as well as by the diet composition - a number of bathypelagic and planktonic crustaceans (Hymenodora glacialis, Pseudomysis abissi, Bythocaris leucopis, Calanus hyperboreus, etc.) have been found in the stomachs of Rhodichthys regina.

Food and feeding habits

The Threadfin seasnail feeds on bathypelagic and planktonic crustaceans.

Reproduction

These fish spawn in the summer. Female fecundity ranges from 44 to 59 large eggs (5.5 mm in diameter).

Fishing

This species is not commercially important.

Relationship with a person

Harmless.