Eogammarus schmidti ( Derzhavin, 1927 )

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 : 1125-1131

Eogammarus schmidti ( Derzhavin, 1927)

[Japanese name: Shumitto togeo yokoebi, new]

( Figures 26–29 )

Gammarus schmidti Derzhavin 1927, p 4 –6, Plate 2.

Anisogammarus schmidti: Gurjanova 1951, p 780 –781, Figure 544; Kurenkov and Mednikov 1959, p 82 –83.

Anisogammarus (Eogammarus) schmidti: Tzvetkova 1975, p 125 –127, Figure 48.

Eogammarus schmidti: Bousfield 1979, p 314 .

Material examined

Russia. 1 „, 16.0 mm, CMNC 1980-0461 , 1♀, 15.0 mm, ovigerous, CMNC 1980-0461 , Paramushir Island (50 ° 259N, 155 ° 509E), North Kuril Islands, 14 June 1954, collected by V. S. Korotkewitsch .

Description of male (16.0 mm, CMNC 1980-0461)

Antenna 1 ( Figure 26A ): peduncular articles 1:2: 3 in ratio of 1.0:0.7:0.4; article 1 with posterodistal slender seta in place of robust seta, posterior margin with seta; article 2 posterior margin with two clusters and two pairs of setae; article 3 posterior margin with two pairs of setae; accessory flagellum four-articulate; primary flagellum 24-articulate, each article with long and broad aesthetasc ( Figure 26B ). Antenna 2 ( Figure 26C ): peduncular article 1 with slender setae; articles 4: 5 in ratio of 1.0:1.2, posterior margin of article 4 with two clusters and two pairs of setae, posterior margin of article 5 with five clusters of setae; flagellum 8+ articulate, with cup-calceoli ( Figure 26D ), width of calceoli 0.2× width of flagellar article.

Coxae 1–4 ( Figure 27A, C, E, F ): with long setose lower margins.

Mandible ( Figure 26G, H ): palp article 2 with numerous marginal and submarginal setae; article 3 length 0.9× article 2 length, with five clusters of A-setae. Maxilla 1 ( Figure 26I ): inner plate with 15 plumose setae medially; palp article 1 with outer marginal seta, article 2 with six plumose setae on outer margin, seven robust and 11 slender setae apically. Maxilla 2 ( Figure 26J ): inner plate with 16 facial setae. Maxilliped ( Figure 26K ): inner and outer plate relatively short, not reaching distal end of palp article 1 and middle of palp article 2, respectively; inner plate with three apical and two medial bent, stout setae; outer distal corner of palp article 2 with cluster of slender setae.

Gnathopod 1 ( Figure 27A ): anterior margin of propodus with four clusters of setae, palmar margin ( Figure 27B ) lined with 14 inner and nine outer robust, striated peg setae. Gnathopod 2 ( Figure 27C ): anterior margin of propodus with two clusters and one pair of setae, palmar margin ( Figure 27D ) with eight inner and eight outer robust, striated peg setae and two inner stiff, pectinate setae.

Pereopods 3–7: both margins of basis–carpus with long plumose setae. Pereopod 3 ( Figure 27E ): merus, carpus, and propodus in ratio of 1.0:0.8:0.7. Pereopod 4 ( Figure 27F ): merus, carpus, and propodus in ratio of 1.0:0.7:0.7. Pereopod 6 ( Figure 27H ): longest posteromarginal seta of basis 1.1× width of ischium. Pereopod 7 ( Figure 27I ): longest seta of basis 1.3× width of ischium.

Pleopods ( Figure 28D ): retinacula triplicated ( Figure 28E ). Epimera 1–3: with plumose setose anteroventral margins, posterior margins with numerous simple setae.

Uropod 1 ( Figure 28F ): inner and outer ramus length 0.7× peduncle length, latter with marginal slender setae and robust seta and slender basofacial seta; inner ramus with one slender and one robust seta on inner margin; outer ramus with one inner and one outer robust marginal seta. Uropod 2 ( Figure 28G ): inner ramus length 0.8×, outer ramus length 0.7× peduncle length, latter with robust and slender marginal setae; inner ramus with robust inner marginal seta; margin of outer ramus bare. Uropod 3 ( Figure 28H ): inner ramus length 0.3× outer ramus length; outer margin of outer ramus with four clusters of robust setae and a few simple and plumose setae; inner margin with a few simple setae and numerous plumose setae; terminal article of outer ramus length 0.2× proximal article length. Telson ( Figure 28I ): length 0.9× width, with robust apical and distolateral setae, slender apical setae, and penicillate distolateral setae; robust apical setae about as long as simple apical setae; cleft 75%.

Description of female (15.0 mm, CMNC 1980-0461)

Antenna 1 ( Figure 29A ): peduncular articles 1:2: 3 in ratio of 1.0:0.7:0.5; article 1 posterior margin with one cluster and two pairs of setae and a single seta; article 2 posterior margin with two pairs of setae and a single seta, article 3 posterior margin with cluster of setae; accessory flagellum four-articulate; primary flagellum 19+ articulate, each article with one aesthetasc. Antenna 2 ( Figure 29B ): peduncular articles 4: 5 in ratio of 1.0:1.1; posterior margin of article 4 with four clusters of setae and a single seta; posterior margin of article 5 with five clusters of setae; flagellum 10-articulate, lacking calceoli.

Gnathopod 1 ( Figure 29C ): palmar margin of propodus ( Figure 29D ) with five inner and 10 outer robust simple setae. Gnathopod 2 ( Figure 29E ): palmar margin of propodus ( Figure 29F ) with three inner and one outer robust simple setae, four inner and six outer stiff pectinate setae.

Pereopod 6 ( Figure 29H ): longest seta of basis 1.1× width of ischium. Pereopod 7 ( Figure 29I ): longest seta of basis 1.3× width of ischium.

Uropod 3 ( Figure 29K ): inner ramus length 0.3× outer ramus length; outer margin of outer ramus with one cluster and three pairs of robust setae, with a few simple and eight plumose setae; inner margin with numerous plumose setae; terminal article of outer ramus length 0.2× proximal article length.

Variation

The number of clusters of setae on peduncular articles of both antennae 1 and 2 varies from 0 to five.

Remarks

As mentioned in the remarks for E. psammophilus (see above), E. schmidti is closely similar to E. psammophilus .

Distribution

Kamchatka, Kuril Islands .

Habitat

Intertidal zone.

Figures

Figure 26. Eogammarus schmidti (Derzhavin, 1927), Paramushir Island, Kuril Islands, male, 16.0 mm, CMNC 1980-0461. (A) Antenna 1; (B) flagellar article of antenna 1 (some setae are omitted); (C) antenna 2; (D) flagellar article of antenna 2 (some setae are omitted); (E) upper lip; (F) lower lip; (G) left mandible; (H) incisor and lacinia mobilis of right mandible; (I) maxilla 1 (robust apical setae on outer plate are shown enlarged); (J) maxilla 2; (K) maxilliped. Scale bars: 0.1 mm.

Figure 27. Eogammarus schmidti (Derzhavin, 1927), Paramushir Island, Kuril Islands, male, 16.0 mm, CMNC 1980-0461. (A) Gnathopod 1; (B) dactylus and palm of gnathopod 1 (slender setae on palm are omitted); (C) gnathopod 2; (D) dactylus and palm of gnathopod 2 (slender setae on palm are omitted); (E–I) pereopods 3–7. Scale bars: 0.1 mm.

Figure 28. Eogammarus schmidti (Derzhavin, 1927), Paramushir Island, Kuril Islands, male, 16.0 mm, CMNC 1980-0461. (A–C) Epimeral plates 1–3; (D) pleopod 2 (plumose setae on rami are omitted); (E) retinacula of pleopod 2; (F–H) uropods 1–3; (I) telson (dorsal view). Scale bars: 0.1 mm.

Figure 29. Eogammarus schmidti (Derzhavin, 1927), Paramushir Island, Kuril Islands, female, 15.0 mm, CMNC 1980-0461. (A) Antenna 1; (B) antenna 2; (C) gnathopod 1; (D) dactylus and palm of gnathopod 1 (slender setae on palm are omitted); (E) gnathopod 2; (F) dactylus and palm of gnathopod 2 (slender setae on palm are omitted); (G–I) coxa–ischium of pereopods 5–7; (J) brood plate of gnathopod 2; (K) uropod 3. Scale bars: 0.1 mm.