Eogammarus oclairi 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 : 1114-1119

Eogammarus oclairi Bousfield, 1979

[Japanese name: Okurea togeo yokoebi, new]

( Figures 18–21 ) Eogammarus oclairi Bousfield 1979, p 319 –321, Figure 5 .

Material examined

Canada. Paratypes: „, 12.0 mm, CMNC 1980-0459 , ♀, 13.5 mm, ovigerous, CMNC 1982-323 , Mouth of Gold River (49 ° 429N, 126 ° 07.59W), Muchalet Inlet, Vancouver Island , British Columbia, 13 June 1976, collected by R. M. O’Clair .

Description of male (12.0 mm, paratype, CMNC 1980-0459)

Antenna 1 ( Figure 18A ): peduncular articles 1:2: 3 in ratio of 1.0:0.9:0.4; article 1 with robust seta posterodistally, posterior margin with three pairs of setae and a single seta, article 2 posterior margin with two clusters and two pairs of setae; article 3 posterior margin with one cluster and one pair of setae; accessory flagellum six-articulate; primary flagellum 23+ articulate, each article with one long aesthetasc ( Figure 18B ). Antenna 2 ( Figure 18C ): peduncular article 1 with robust seta; article 4 length 0.9× article 5 length; posterior margin of article 4 with four clusters and one pair of setae and a single seta; posterior margin of article 5 with four clusters and one pair of setae; flagellum 14+ articulate, with cup-calceoli ( Figure 18D ).

Mandible ( Figure 18G, H ): palp article 2 with seven marginal and 14 submarginal setae; article 3 length 0.9× article 2 length, with two clusters of A-setae and a B-seta. Maxilla 1 ( Figure 18I ): inner plate with 12 plumose setae medially; palp article 1 marginally bare; article 2 with six setae on outer margin and six stout and six slender setae apically. Maxilla 2 ( Figure 18J ): inner plate with 10 facial setae. Maxilliped ( Figure 18K ): inner plate with three apical and two medial bent, stout setae; outer plate beyond middle of palp article 2; outer distal corner of palp article 2 with robust seta and slender seta.

Gnathopod 1 ( Figure 18L ): anterior margin of propodus with cluster of setae and two setae, palmar margin ( Figure 18M ) lined with 16 inner robust striated peg setae. Gnathopod 2 ( Figure 18N ): anterior margin of propodus with seta, palmar margin ( Figure 18O ) lined with 15 inner robust, striated peg setae.

Pereopod 3 ( Figure 19A ): merus, carpus, and propodus in ratio of 1.0:0.8:0.6. Pereopod 4 ( Figure 19B ): merus, carpus, and propodus in ratio of 1.0:0.9:1.0. Pereopod 6 ( Figure 19D ): longest posteromarginal seta of basis 0.3× width of ischium. Pereopod 7 ( Figure 19E ): posterodistal margin of basis with robust seta, longest posteromarginal seta 0.6× width of ischium.

Pleopods ( Figure 19F ): retinacula paired ( Figure 19G ). Epimera 1–3 ( Figure 20A–C ): with setose anterior margin. Epimeron 2 ( Figure 20B ): ventral margin and submargin with two robust setae and slender seta, respectively. Epimeron 3 ( Figure 20C ): ventral margin with four robust setae.

Uropod 1 ( Figure 20D ): inner and outer ramus length 0.7× peduncle length, latter with robust marginal setae and robust basofacial seta; inner ramus with three inner and one outer robust marginal setae; outer ramus with two inner and two outer robust marginal setae. Uropod 2 ( Figure 20E ): inner ramus length 0.9×, outer ramus length 0.7× peduncle length, latter with robust marginal setae; inner ramus with three inner and one outer robust marginal setae; outer ramus with one inner and two outer robust marginal setae. Uropod 3 ( Figure 20F ): inner ramus length 0.2× outer ramus length; outer margin of outer ramus with three clusters of robust setae, a few simple and plumose setae; inner margin with three robust setae, a few simple and numerous plumose setae; terminal article length 0.2× proximal article length. Telson ( Figure 20G ): as long as wide, without robust distolateral setae, robust apical setae longer than slender apical setae.

Description of female (13.5 mm, paratype, CMNC 1982-323)

Antenna 1 ( Figure 21A ): peduncular articles 1:2: 3 in ratio of 1.0:0.8:0.3; article 1 posterior margin with pair of setae; article 2 posterior margin with four clusters of setae and a single seta; article 3 posterior margin with cluster of setae; accessory flagellum four-articulate; primary flagellum 10+ articulate, each article with one aesthetasc. Antenna 2 ( Figure 21B ): peduncular articles 4 and 5 about equal in length, posterior margin of article 4 with two clusters and one pair of setae and a single seta; posterior margin of article 5 with three clusters of setae; flagellum 11+ articulate, lacking cup-calceoli.

Gnathopod 1 ( Figure 21C ): anterior margin of propodus with one cluster and two pairs of setae, palmar margin ( Figure 21D ) with six inner and nine outer robust simple setae and weakly serrate inner seta. Gnathopod 2 ( Figure 21E ): anterior margin of propodus with two clusters and one pair of setae, palmar margin ( Figure 21F ) with four simple and three robust pectinate setae on inner margin, five simple and three robust pectinate setae on outer margin.

Pereopod 6 ( Figure 21I ): longest posteromarginal seta of basis 0.3× width of ischium. Pereopod 7 ( Figure 21J ): longest posteromarginal seta of basis 0.6× width of ischium.

Uropod 3: missing.

Variation

The number of clusters of setae on peduncular articles of both antennae 1 and 2 varies from one 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 oclairi is similar to E. confervicolus in having two characters in common, as mentioned in the remarks for E. confervicolus (see above). Eogammarus oclairi is also similar to E. kygi , but is distinguished from the latter by the following characters ( E. kygi in parentheses): (1) in antenna 1, the aesthetasc on the flagellum is longer than the surrounding normal setae (shorter); (2) calceoli are absent on female antenna 2 (present); and (3) on the telson, the robust apical setae are longer than the slender apical setae (shorter) (see Table I).

Distribution

Southern British Columbia, Vancouver, Washington.

Habitat

River mouths, estuaries, intertidal zone.

Figures

Figure 5. Eogammarus barbatus (Tzvetkova, 1965), Makinouchi, Nemuro, Japan, male, 20.2 mm. (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) palp of maxilliped; (L) inner plate of maxilliped; (M) outer plate of maxilliped; (N) gnathopod 1; (O) dactylus of gnathopod 1; (P) palm of gnathopod 1 (slender setae are omitted); (Q) gnathopod 2; (R) dactylus of gnathopod 2; (S) palm of gnathopod 2 (slender setae are omitted). Scale bars: 0.1 mm.

Figure 18. Eogammarus oclairi Bousfield, 1979, Muchalet Inlet, British Columbia, paratype, male, 12.0 mm, CMNC 1980-0459. (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; (L) gnathopod 1; (M) dactylus and palm of gnathopod 1 (slender setae on palm are omitted); (N) gnathopod 2; (O) dactylus and palm of gnathopod 2 (slender setae on palm are omitted). Scale bars: 0.1 mm.

Figure 19. Eogammarus oclairi Bousfield, 1979, Muchalet Inlet, British Columbia, paratype, male, 12.0 mm, CMNC 1980-0459. (A, B) Pereopods 3 and 4; (C–E) coxa–ischium of pereopods 5–7; (F) pleopod 2 (plumose setae on rami are omitted); (G) retinacula of pleopod 2. Scale bars: 0.1 mm.

Figure 20. Eogammarus oclairi Bousfield, 1979, Muchalet Inlet, British Columbia, paratype, male, 12.0 mm, CMNC 1980-0459. (A–C) Epimeral plates 1–3; (D–F) uropods 1–3; (G) telson (dorsal view). Scale bars: 0.1 mm.

Figure 21. Eogammarus oclairi Bousfield, 1979, Muchalet Inlet, British Columbia, paratype, female, 13.5 mm, CMNC 1982-323. (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) brood plate of gnathopod 2; (H–J) coxa–ischium of pereopods 5–7. Scale bars: 0.1 mm.