Eogammarus psammophilus Bousfield, 1979

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 : 1119-1125

Eogammarus psammophilus Bousfield, 1979

( Figures 22–25 ) [Japanese name: Sunaji togeo yokoebi, new] Eogammarus psammophilus Bousfield 1979, p 315 –316, Figure 3 .

Material examined

USA. Paratype: 1♀, 16.0 mm, CMNC 1982-0321 , Southwestern Constantine Harbor (51 ° 249N, 179 ° 179E), Amchitka Island, Aleutian Islands , 30 October 1971, collected by P. N. Slattery. 1 „, 20.0 mm, CMNC 2004-1029 , Kenai Peninsula Borough (65 ° 459N, 167 ° 519W), Alaska, USA, 16 July 1984, collected by P. N. Slattery.

Description of male (20.0 mm from Alaska, CMNC 2004-1029)

Antenna 1 ( Figure 22A ): peduncular articles 1:2: 3 in ratio of 1.0:0.8:0.4; article 1 with long posterodistal seta in place of robust seta, posterior margin with two setae; article 2 posterior margin with three clusters of setae; article 3 posterior margin with cluster and pair of setae; accessory flagellum five-articulate; primary flagellum 20-articulate, each article with one short aesthetasc ( Figure 22B ). Antenna 2 ( Figure 22C ): peduncular article 1 with long slender setae; articles 4: 5 in ratio of 1.0:1.1; posterior margin of article 4 with three clusters and one pair of setae; posterior margin of article 5 with five clusters of setae; flagellum 12- articulate, with calceoli, width of calceoli 0.4× width of flagellar article ( Figure 22D ).

Coxae 1–4 ( Figure 23A, C, E, F ): with long, setose lower margins.

Mandible ( Figure 22G, H ): palp article 2 with numerous marginal and submarginal setae; article 3 length 0.8× article 2 length, with four clusters of A-setae and cluster of B-setae. Maxilla 1 ( Figure 22I ): inner plate with 17 plumose setae medially; palp article 1 with plumose seta on outer margin; article 2 with six plumose setae on outer margin, eight stout and 10 slender setae apically. Maxilla 2 ( Figure 22J ): inner plate with 17 facial setae. Maxilliped ( Figure 22K ): 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 23A ): anterior margin of propodus with four clusters of setae, palmar margin ( Figure 23B ) lined with 19 inner and 10 outer robust, striated peg setae. Gnathopod 2 ( Figure 23C ): anterior margin of propodus with three clusters of setae, palmar margin ( Figure 23D ) lined with nine inner and nine outer robust, striated peg setae.

Pereopods 3–7: both margins of basis–carpus with long plumose setae. Pereopod 3 ( Figure 23E ): merus, carpus, and propodus in ratio of 1.0:0.7:0.7. Pereopod 4 ( Figure 23F ): merus, carpus, and propodus in ratio of 1.0:0.7:0.7. Pereopod 6 ( Figure 23H ): longest posteromarginal seta of basis 1.1× width of ischium. Pereopod 7 ( Figure 23I ): longest posteromarginal seta of basis 1.2× width of ischium.

Pleopods ( Figure 24D ): retinacula triplicated ( Figure 24E ). Epimera 1–3 ( Figure 24E–G ): with plumose setose anteroventral margins, posterior margins with numerous simple setae.

Uropod 1 ( Figure 24A ): inner ramus length 0.7×, outer ramus length 0.8× peduncle length, latter with robust and slender marginal setae and robust basofacial seta; inner ramus with one robust and two slender setae on inner margin; outer ramus with one inner and one outer robust marginal seta. Uropod 2 ( Figure 24B ): inner ramus length 0.8×, outer ramus length 0.7× peduncle length, latter with robust and slender marginal setae; inner ramus with one robust and one slender seta on inner margin; outer ramus with margin bare. Uropod 3 ( Figure 24C ): inner ramus length 0.3× outer ramus length; outer margin of outer ramus with one cluster and three pairs of robust setae, a single robust seta, and a few simple and 10 plumose setae; inner margin with two pairs of robust setae, a few simple and numerous plumose setae; length of terminal article of outer ramus 0.2× proximal article length. Telson ( Figure 24I ): length 0.9× width, with robust apical and distolateral setae, slender apical setae, and penicillate distolateral setae, robust apical setae about as long as slender apical setae; cleft 65%.

Description of female (16.0 mm from Amchitka Island, paratype, CMNC 1982-0321)

Antenna 1 ( Figure 25A ): peduncular articles 1:2: 3 in ratio of 1.0:0.7:0.5; article 1 posterior margin with two clusters and one pair of setae and a single seta; article 2 posterior margin with two clusters and one pair of setae and a single seta; article 3 posterior margin with one cluster and one pair of setae; accessory flagellum five-articulate; primary flagellum 24-articulate, each article with one aesthetasc. Antenna 2 ( Figure 25B ): peduncular articles 4: 5 in ratio of 1.0:1.2; posterior margin of article 4 with four clusters of setae; posterior margin of article 5 with five clusters of setae; flagellum 14-articulate, lacking cupcalceoli.

Coxa 1 ( Figure 25C ): with densely setose inner face.

Gnathopod 1 ( Figure 25C ): anterior margin of propodus with four clusters of setae and a single seta, palmar margin ( Figure 25D ) with 10 robust simple setae on inner part and three robust simple setae on outer distal part. Gnathopod 2 ( Figure 25E ): anterior margin of propodus with three clusters of setae, palmar margin ( Figure 25F ) with five simple and five robust pectinate setae on inner part, five simple and three stiff pectinate setae on outer part.

Pereopod 6 ( Figure 25H ): longest posteromarginal seta of basis 1.3× width of ischium. Pereopod 7 ( Figure 25I ): longest posteromarginal seta of basis 1.1× width of ischium.

Uropod 3 ( Figure 25K ): inner ramus length 0.3× outer ramus length; outer margin of outer ramus with one cluster and two pairs of robust setae, a few simple and numerous plumose setae; inner margin with robust seta and 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 zero to five. The number of clusters of robust setae on the outer margin of the ramus of uropod 3 varies from three to four.

Remarks

Eogammarus psammophilus is similar to E. schmidti ( Derzhavin, 1927) , as Bousfield (1979) mentioned. These two species are distinct from their congeners by their thick antennae; densely setose gnathopods, pereopods, and epimeron; and the triplicated retinacula on pleopods. Eogammarus psammophilus is distinguished from E. schmidti by the following features ( E. schmidti in parentheses): (1) on antenna 1, the aesthetasc is shorter than the surrounding setae (longer) and (2) on antenna 2, the calceolus is wider than 0.25× the article width (narrower) (see Table I).

Distribution

Amchitka Island ( Aleutian Islands ), Kenai Peninsula Borough (Alaska) .

Habitat

Intertidal zone.

Figures

Figure 3. Eogammarus kygi (Derzhavin, 1923), Naibetsu River, Chitose, Japan, male, 17.0 mm. (A–C) Uropods 1–3; (D–F) dorsal margins of urosomites 1–3; (G) telson (dorsal view). Scale bars: 0.1 mm.

Figure 22. Eogammarus psammophilus Bousfield, 1979, Kenai Peninsula, Alaska, male, 20.0 mm, CMNC 2004- 1029. (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) right mandible; (H) incisor and lacinia mobilis of left mandible; (I) maxilla 1 (robust apical setae on outer plate are shown enlarged); (J) maxilla 2; (K) maxilliped. Scale bars: 0.1 mm.

Figure 23. Eogammarus psammophilus Bousfield, 1979, Kenai Peninsula, Alaska, male, 20.0 mm, CMNC 2004- 1029. (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 24. Eogammarus psammophilus Bousfield, 1979, Kenai Peninsula, Alaska, male, 20.0 mm, CMNC 2004- 1029. (A–C) Uropods 1–3; (D) pleopod 1 (plumose setae on rami are omitted); (E) retinacula of pleopod 1; (F–H) epimeral plates 1–3; (I) telson (dorsal view). Scale bars: 0.1 mm.

Figure 25. Eogammarus psammophilus Bousfield, 1979, Amchitka Island, Aleutian Islands, paratype, female, 16.0 mm, CMNC 1982-0321. (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.