Eosymtes Bousfield & Hendrycks, 1994

Labay, Vjacheslav S., 2022, 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 & Hendrycks, 1994, Zootaxa 5125 (5), pp. 547-562 : 548-549

Genus Eosymtes Bousfield & Hendrycks, 1994

Eosymtes Bousfield & Hendrycks, 1994: 43 .— Hendrycks & Bousfield 2004: 49.

Type species. Eosymtes minutus Bousfield & Hendrycks, 1994 .

Species. Including the new species described here, Eosymtes contains two species: E. minutus Bousfield & Hendrycks, 1994 ; E. magnumoculis sp. nov.

Diagnosis (from Bousfield & Hendrycks 1994 with additions). Body smooth. Rostrum short. Lateral head lobe rounded. Eyes rounded or reniform. Antenna 1, peduncle 1 without antero-distal process. Antenna 2, peduncular segments 4 and 5 setose.

Mandible, row of raker setae short, with 4–7 pectinate blades; left lacinia 6–7-dentate; right lacinia blade-like. Maxilla 1, inner plate with two stout plumose apical setae. Maxilla 2, inner plate with two strong submarginal setae. Maxilliped, inner plate with 2–4 apical button spine-like setae; palp segment 3 not produced distally, broadened, dactylus slender, curved, micro-pectinate.

Coxal plates 1–4 medium, increasing posteriorly; posterodistally with one small cusp. Coxal gills medium, sac-like.

Pereopods 1 & 2 (gnathopods 1 & 2) medium, subsimilar; carpus shorter than propodus, posterodistal lobe shallow; palmar margin of propodus oblique, without medium tooth.

Pereopods 3–7 slender, medium long, dactylus elongate. Pereopods 5–7, coxae shallow, lobes rounded; bases broadly rounded behind, increasing in size posteriorly, hind margin serrate.

Epimeral plates 1–3, posterior corners acuminate, not produced. Uropod 3 slender, outer ramus not more than 2/3 the length of the inner ramus.

Telson linguiform, apex subtruncate or rounded, incised; with proximal keel.

Distribution. Marine waters of boreal part of Pacific Ocean ( Bousfield & Hendrycks 1994, Hendrycks & Bousfield 2004, Labay 2018).

Relationships. Eosymtes differs from Cognateosymtes by the following combination of character states ( Figs. 1 , 2 ): antenna 1, peduncular segment 1 without strong anterodistal processes; coxae 1–3, posterodistal cusps posterodistally with one small cusp, not multiple; maxilliped, palp segment 2 linear, inner margin densely setose; dactylus of pereopods 3–7 medium in length ( Labay 2018).

Remarks. Labay (2018) pointed out as one of the signs the setulation of outer and inner plates of maxilla 2: “ Cognateosymtes differs from Eosymtes by … outer and inner plates of maxilla 2 with numerous apical setae”. The following description of the new species Eosymtes magnumoculis sp. nov. shows that this feature is invalid.

Figures

FIGURE 1. Eosymtinae Bousfield & Hendrycks, 1994, lateral view: a—Eosymtes minutus Bousfield and Hendrycks, 1994 (from Bousfield and Hendrycks 1994: fig. 7), b—Eosymtes magnumoculis sp. nov., c—Cognateosymtes serraticoxae Labay, 2018 (from Labay 2018: fig. 2a)

FIGURE 2. Eosymtinae Bousfield & Hendrycks, 1994: a–c—peduncle of antenna 1; d–f—maxilla 2; g–i—palp of maxilliped; j–l—coxal plates 1–3 posteroventrally; m, n, o—propodus and dactylus of pereopods 3–7; a, d, g, j, m—Eosymtes minutus Bousfield and Hendrycks, 1994 (from Bousfield and Hendrycks 1994), b, e, h, k, n—Eosymtes magnumoculis sp. nov., c, f, i, l, o—Cognateosymtes serraticoxae Labay, 2018 (from Labay 2018)