Review of amphipods of the family Pleustidae Buchholz, 1874 (Amphipoda) from the coastal waters of Sakhalin Island (Far East of Russia). III. Subfamily Pleustoidinae Bousfield & Hendrycks, 1994.

The taxonomic analysis of subfamily Pleustoidinae Bousfield & Hendrycks, 1994 is performed. A review of subfamily Pleustoidinae from the shelf of Sakhalin Island and adjacent water area based on all literature and own data is provided. The diagnoses of the subfamily Pleustoidinae and the genus Pleustoides Gurjanova, 1972 have been clarified. Based on new material, the new species Pleustoides tridens sp. nov. is described from the shelf of Sakhalin Island. The species P. ochoticus Gurjanova, 1972 is re-described and its status is clarified. A key to the amphipod of the genus Pleustoides is given.

A new deep-sea species of Renella (Amphipoda: Lysianassida: Pakynidae) from the Sea of Okhotsk.

A new amphipod species, Renella lowryi sp. nov., from the north-eastern slope of the Sea of Okhotsk (Russian Far East) is described. The new species is assigned to the genus Renella Lowry & Stoddart, 2012 because it is similar to the species of this genus in the main characters: in the structure of the mouthparts, the structure of gnathopods 1 and 2, corner of palm of gnathopod 1 with the complex of robust seta, pereopods 37, the shape of epimeron 3, uropods and telson. The new species similar to Renella sculptidentata (Ren, 1991) by the structure of antennae 1 and 2, mandible, maxilla 2 and maxilliped, but differs from it by the missing eyes, by the morphology of maxilla 1 outer plate: with 9 setal-teeth in 6/3 arrangement (in R. sculptidentata with 11 setal-teeth in 7/4 arrangement), by the shape of propodus of gnathopod 1 with medially convex anterior margin (in R. sculptidentata anterior margin straight medially), by the shape of propodus of gnathopod 2 with oblique distal margin (in R. sculptidentata distal margin is perpendicular), by the shape of basis of pereopod 5 with rounded posterior wing (in R. sculptidentata posterior wing subrectangular), by the weak armament of the anterior margin of the basis of pereopod 5 and anterior margin of merus of pereopods 57 (in R. sculptidentata anterior margins with few long setae), by the length of inner ramus of uropod 3 which subequal to proximal segment of outer ramus in length (in R. sculptidentata inner ramus shorter than proximal segment of outer ramus). Keys to the world species of the genus Renella is provided.

Review of amphipods of the family Pleustidae Buchholz, 1874 (Amphipoda) from the coastal waters of Sakhalin Island (Far East of Russia). II. Subfamily Eosymtinae Bousfield amp; Hendrycks, 1994.

A taxonomic analysis of subfamily Eosymtinae Bousfield Hendrycks, 1994 is performed. A review of subfamily Eosymtinae from the shelf of Sakhalin Island and adjacent area based on all literature and own data is provided. Based on new material, the new species Eosymtes magnumoculis sp. nov. is described from the shelf of Sakhalin Island and Kamchatka Peninsula. The range of Cognateosymtes serraticoxae Labay, 2018 is expanded. A key to the amphipod genera of the subfamily Eosymtinae is given. The key to the species of genus Eosymtes is provided.

Desdimelita spicatimanus a new species of Melitidae Bousfield, 1973 (Crustacea: Amphipoda: Hadziida) from the Sea of Okhotsk.

A new amphipod species, Desdimelita (?) spicatimanus sp. nov., from the north-eastern slope of the Sea of Okhotsk (Russian Far East) is described. The new species is tentatively assigned to the genus Desdimelita because it is similar to females of the species of this genus in most of the characters: in the structure of the mouthparts, the armament of the dactylus of pereopod 2 (gnathopod 2), the anterior and posterior margins of the propodus of pereopods 1 and 2 (gnathopods 1 and 2), pereopods 37, uropods and telson. The new species differs from other Desdimelita species by the morphology of propodus of pereopod 2: broadened; palm with a row of 56 rare strong long robust setae). It also differs from D. microphthalma Jarrett Bousfield, 1996 in larger eyes; from D. barnardi Jarrett Bousfield, 1996 and D. transmelita Jarrett Bousfield, 1996 it differs by the presence of a postero-dorsal tooth (teeth) on urosome 1; from D. californica (Alderman, 1936) it differs by the presence only a single postero-dorsal tooth on urosome 1; from D. desdichada (J.L. Barnard, 1962) and D. microdentata Jarrett Bousfield, 1996 it differs by the long dactylus of pereopods 57. Keys to the world species of the genus Desdimelita is provided.

Review of amphipods of the family Pleustidae Buchholz, 1874 (Crustacea: Amphipoda) from the coastal waters of Sakhalin Island (Far East of Russia). I. Subfamily Neopleustinae Bousfield amp; Hendrycks, 1994.

Taxonomic analysis of the subfamily Neopleustinae Bousfield Hendrycks, 1994, is performed. Cladistic analysis of morphological relationships within the genera Hendrycksopleustes gen. nov., Neopleustes Stebbing, 1906, and Shoemakeroides Hendrycks Bousfield, 2004, is performed. A new genus Hendrycksopleustes gen. nov. is described. A review of the subfamily Neopleustinae from the shelf of Sakhalin Island and adjacent water area, based on all literature and own data, is provided. Based on new material, a new species Hendrycksopleustes neimanii sp. nov. is described from the shelf of Sakhalin Island. Status of the species Neopleustes euacanthus (G. Sars, 1877) is restored. New subspecies Neopleustes boecki pacifica ssp. nov. and Neopleustes pulchellus asiaticus ssp. nov. are described from the shelf of Sakhalin Island. Keys to the amphipod genera of the subfamily Neopleustinae and to the world species of the genera Neopleustes and Shoemakeroides are provided.

Review of amphipods of the genus Cryptodius Moore, 1992 (Amphipoda: Ochlesidae) from the coastal waters of Sakhalin Island (Far East of Russia).

Based on new material, the new species of the genus Cryptodius is described: C. sakhalinensis sp. nov. from north-east shelf of Sakhalin Island. Keys to the world species of the genus Cryptodius is provided. Cladistic analysis of morphological relationships within genera Cryptodius and Odius are implemented.

Cognateosymtes serraticoxae, new genus, new species, a pleustid amphipod from the Sea of Japan (Crustacea: Amphipoda: Gammaridea: Pleustidae: Eosymtinae).

The new genus Cognateosymtes gen. nov. and new species C. serraticoxae sp. nov. are described from the shelf of western Sakhalin Island. The new genus has a set of features specific to the subfamily Eosymtinae: strongly ridged molar grinding surface of mandible and presence of a medial seta; inner plate of maxilla 1 with 2 strong apical plumose setae; inner plate of maxilla 2 with 2 strong submarginal setae, positioned subapically; pereopods 1 and 2 (gnathopods), propodal palmar margins lacking submedial tooth. Cognateosymtes differs from Eosymtes by the combination of character states: antenna 1, peduncular segment 1 with strong anterodistal processes; outer and inner plates of maxilla 2 with numerous apical setae; maxilliped, palp segment 2 linear, inner margin densely setose; coxae 1-3, posterodistal cusps multiple; dactylus of pereopods 3-7 the short. The key to the amphipod genera of the subfamily Eosymtinae Bousfield Hendrycks, 1994 is given.

Vinogradovopleustes punctatum, new genus, new species, a pleustid amphipod from the Okhotsk Sea (Crustacea: Amphipoda: Gammaridea: Pleustidae: Pleusymtinae).

The new genus Vinogradovopleustes gen. nov. and new species V. punctatum sp. nov. are described from the shelf of northern Sakhalin Island. A key to the amphipod genera of the subfamily Pleusymtinae Bousfield Hendrycks, 1994 is given.

A new species of Sextonia Chevreux, 1920 (Crustacea: Amphipoda: Liljeborgiidae) from the Okhotsk Sea.

A new amphipod species, Sextonia caecus sp. nov., from the shelf of northern Sakhalin Island (Russian Far East) is described. A key to the amphipod species of the genus Sextonia is given.

Review of amphipods of the Melita group (Amphipoda: Melitidae) from the coastal waters of Sakhalin Island (Far East of Russia). III. Genera Abludomelita Karaman, 1981 and Melita Leach, 1814.

The taxonomic analysis of Melita group is performed. The revision of the genus Melita Leach, 1814 was held on the basis of analysis of morphological characters. Cladistic analysis of morphological relationships within genera Abludomelita and Melita is performed. Status of the genus Paraniphargus Tattersall, 1925 restored. New genera Barnardomelita gen. nov. and Ledoyeromelita gen. nov. are described and removed from the composition of the genus Melita. A review of Melita group (fam. Melitidae) from the shelf of Sakhalin Island based on all literature and own data is provided. Based on new material, two new species of the genus Abludomelita Karaman, 1981 are described: A. klitinii sp. nov. and A. okhotensis sp. nov. from the shelf of Sakhalin Island. Megamoera aequidentatum Labay, 2013 is transferred to the genus Abludomelita as A. rotundactyla (Ren, 2012) on the basis of additional morphological description of male. The new subspecies Melita shimizui sakhalinensis ssp. nov. is described from estuaries of Sakhalin Island. The keys to the world species of genera Abludomelita and Melita are provided.

Review of amphipods of the Melita group (Amphipoda: Melitidae) from the coastal waters of Sakhalin Island (Far East of Russia). II. Genera Quasimelita Jarrett & Bousfield, 1996 and Melitoides Gurjanova, 1934.

Based on new material, three new species of the genus Quasimelita are described: Q. tolyza sp. nov., Q. jarettii sp. nov. and Q. serraticoxae sp. nov. from northern shelf of Sakhalin Island and contiguous area. The new species of the genus Melitoides, M. kawaii sp. nov. is described from north-east shelf of Sakhalin Island. Keys to the world species of genera Quasimelita and Melitoides are provided. Cladistic analysis of morphological relationships within genera Quasimelita and Melitoides are implemented.

Review of amphipods of the Melita group (Amphipoda: Melitidae) from the costal waters of Sakhalin Island (Far East of Russia). I. Genera Megamoera Bate, 1862 and Armatomelita gen. nov.

A review of Melita group (fam. Melitidae) from the shelf of Sakhalin Island based on literature and own data is provided. Based on new material, four new species of the genus Megamoera are described: M. similidentata sp. nov. and M. striata sp. nov. from north-east shelf of Sakhalin Island; M falsomikulitschae sp. nov. and M. aequidentatum sp. nov. from Aniva Bay (southern Sakhalin). The new genus Armatomelita gen. nov. and new species A. tshayensis sp. nov. are described from Aniva Bay (southern Sakhalin). A key to the world species of the genus Megamoera is provided. Cladistic analysis of morphological relationships within the genus Megamoera is implemented.