Eogammarus ryotoensis ( Uéno, 1940 )

Tomikawa, Ko, Morino, Hiroshi, Toft, Jason & Mawatari, Shunsuke F., 2006, A revision of Eogammarus Birstein, 1933 (Crustacea, Amphipoda, Anisogammaridae), with a description of a new species, Journal of Natural History (J. Nat. Hist.) 40 (17 - 18), pp. 1083-1148 : 1143

Eogammarus ryotoensis ( Uéno, 1940)

Anisogammarus (Eogammarus) ryotoensis Uéno 1940, p 70 –73, Figures 31 –48; Tzvetkova 1975, p 108 –109, Figure 39.

Eogammarus ryotoensis: Bousfield 1979, p 314 .

Material examined

No material of E. ryotoensis including type series could be obtained for this study.

Remarks

Eogammarus ryotoensis was originally described as Anisogammarus (Eogammarus) ryotoensis by Uéno (1940), but is currently placed in Eogammarus ( Bousfield 1979) . As shown in the figures and descriptions by Uéno (1940), E. ryotoensis has a pair of clusters of robust lateral setae and paired clusters of robust medial setae on the dorsal margin of urosomite 2. These are traits of Jesogammarus , Locustogammarus , and Spasskogammarus in the family Anisogammaridae , but not of Eogammarus . The accessory lobe formula of the coxal gills is a significant character of the family Anisogammaridae , but this character is not given in Uéno (1940). The decision whether E. ryotoensis belongs to Eogammarus should be postponed until the coxal gill feature of E. ryotoensis can be clarified. The taxonomic position of this species remains therefore uncertain.

Figures

Figure 31. Eogammarus possjeticus (Tzvetkova, 1967), Lake Akkeshi, Japan, male, 13.6 mm. (A, B) Pereopods 3 and 4; (C–E) coxa–ischium of pereopods 5–7; (F–H) epimeral plates 1–3; (I–K) uropods 1–3; (L) pleopod 1 (plumose setae on rami are omitted); (M) retinacula of pleopod 1; (N–P) dorsal margins of urosomites 1–3; (Q) telson (dorsal view). Scale bars: 0.1 mm.