Idotea ochotensis

The body is very elongated, narrow, in a male with almost parallel lateral edges; its length in males is from 4.2 to 5.8 (on average 5.0) times the width. The head has a rounded shape, more or less convex, with a slightly concave frontal margin, posteriorly slightly expanding, the posterior margin almost straight; its width is slightly less than 1.5 times the length along the medial line. The frontal process is rather narrow, elongated-triangular in shape, with a bluntly pointed apex; dorsal extension of scutellum significantly shorter than frontal process, with wide base rather narrow, strongly convex apex. Eyes of moderate size, slightly convex, rounded triangular in shape, markedly elongated in the transverse direction, with an almost straight front and angular convex posterior edge, located on the sides of the head in the middle of the distance between the front and rear edges of the head. The male appendix of the II pleopod is relatively narrow and long, slightly extends beyond the distal end of the endopodite, with a slightly curved pointed end; its lateral edges for a considerable extent carry a series of tiny spines. Females are distinguished by a relatively shorter and wider, elongated-oval body, whose length is on average about 4.3–4.5 times greater than the largest width in the III – IV thoracic segments.

The color of I. ochotensis is very diverse and adaptive, since it usually corresponds to the color of the substrate or the predominant vegetation in the habitat of a particular population. I. ochotensis is a predominantly herbivorous species, most of the food lump is made up of particles of thalli of brown algae. Single fertility in I. ochotensis is significantly higher than in other studied Idotea species . According to O. G. Kusakin, in 56 females of I. ochotensis, the number of eggs or embryos in the bag of one individual ranged from 24 to 217 and averaged 103 embryos per female. In the examined samples of the studied regions, the number of embryos varied from 18 to 134, with an average of 56 specimens per female.

West Pacific widespread boreal species. From southern Hokkaido and southern Primorye to the northern part of the Sea of ​​Okhotsk and the Olyutor Bay in the Bering Sea with a break in the range of the middle and northern Kuril Islands. It lives on the littoral and in the upper sublittoral to a depth of 20 m. I. ochotensis tolerates strong desalination, occurring in bays of bays, and according to published data, even in estuaries of rivers. In different parts of its vast range, I. ochotensis is either predominantly littoral or now mainly sublittoral.

Dwells in various biocenoses of rocky, rocky and silty-sandy soils among the most diverse algae (Pelvetia, fucus, Dictyosiphon, Cystoseira, Corallina, Iridaea, Ptilota, Kjellmaniella, Arthrothamnus, Alaria, Laminospae, Zarythophyllus, bathtub, Phara zostraphythamnus, Phyllosophyta, Pharynophyta , clefts, puddles, less often on the surface of reefs, but most often settles between boulders and especially beneath them, where it can accumulate in large numbers on littoral at low tide. Length up to 67 mm, average length of sexually mature males 30–40, females 25–30 mm. Most individuals of I. ochotensis live for more than 1, and possibly more than 2 years.

Kusakin O.G. Marine and brackish-water isosomes of crustaceans. - "Science", 1982. - 436 p. with.