Eogammarus confervicolus ( Stimpson, 1856 )

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 : 1108-1114

Eogammarus confervicolus ( Stimpson, 1856)

[Japanese name: Moba togeo yokoebi, new]

( Figures 14–17 )

Maera confervicola Stimpson 1856, p 90 .

Gammarus confervicolus: Stimpson 1857, p 520 –521; Bate 1862, p 218, Plate 38, Figure 9 ; Holmes 1904, p 239.

Melita confervicola: Stebbing 1906 , 428.

Anisogammarus confervicolus: Shoemaker 1964, p 423 –427, Figures 14 , 15 .

Anisogammarus (Eogammarus) confervicolus: Barnard 1954, p 9 –12, Plates 9, 10; Bousfield 1958, p 86, Figure 10 ; Tzvetkova 1975, p 145 –147, Figure 57.

Eogammarus confervicolus: Bousfield 1979, p 315 , 317–319, Figure 4 .

Material examined

USA. „, 13.0 mm, CMNC 2004-1028 , Malibu Lagoon (34 ° 029N, 118 ° 419W), Los Angeles, California, 25 January 1984, collected by D. Galli. „, 15.5 mm, ♀, 12.0 mm, CMNC 2004-1027 , Malibu Lagoon (34 ° 009N, 118 ° 489W), Los Angeles , California, 6 February 1984, collected by D. Galli. Canada. 2 „, 17.0 mm, 15.5 mm, 1♀, 13.0 mm, CMNC 1980-0427 , Alberni (49 ° 149N, 124 ° 489W), British Columbia, 4 May 1970, collected by B. Bravender. „, 13.0 mm, ♀, 9.5 mm, CMNC 1980-0401 , Brady Beach (48 ° 509N, 125 ° 89W), Barclay Land , British Columbia, 26 June 1976, collected by E. L. Bousfield and F. Rafi. 3♀, 6.5–9.0 mm, CMNC 1980-0376 , Sayward Land (50 ° 219N, 125 ° 299W), 26 June 1959, collected by E. L. Bousfield. ♀, 11.0 mm, CMNC 1980-0150 , Knight Inlet , British Columbia, 25 July 1959, collected by E. L. Bousfield.

Description of male (13.0 mm from Malibu Lagoon, CMNC 2004-1028)

Antenna 1 ( Figure 14A ): peduncular articles 1:2: 3 in length ratio of 1:0.7:0.3; article 1 with robust seta posterodistally, posterior margin with two setae; article 2 posterior margin with two clusters of setae and a single seta; article 3 posterior margin with cluster of setae; accessory flagellum five-articulate; primary flagellum 24-articulate, each article with one aesthetasc ( Figure 14B ). Antenna 2 ( Figure 14C ): peduncular article 1 with robust setae; peduncular articles 4: 5 in length ratio of 1.0:0.9; article 4 posterior margin with two clusters of setae; article 5 posterior margin with two clusters of setae and pair of setae; flagellum 14-articulate, with cup-calceoli ( Figure 14D ).

Mandible ( Figure 14G–I ): palp article 2 with one marginal and eight submarginal setae; article 3 length 0.8× article 2, with two clusters and one pair of B-setae. Maxilla 1 ( Figure 14J ): inner plate with 14 plumose setae medially; palp article 1 marginally bare; article 2 with four setae on outer margin and six robust and slender setae apically. Maxilla 2 ( Figure 14K ): inner plate with 12 facial setae. Maxilliped ( Figure 14L ): inner plate with three apical and two medial bent, stout setae; outer plate beyond middle of palp article 2, outer distal corner with robust seta and slender seta.

Gnathopod 1 ( Figure 14M ): anterior margin of propodus with two setae, palmar margin lined with 13 inner and six outer robust striated peg setae ( Figure 14N ). Gnathopod 2 ( Figure 14O ): anterior margin of propodus with cluster of setae and a single seta, palmar margin ( Figure 14P ) lined with seven inner and six outer robust, striated peg setae.

Pereopods 3–4 ( Figure 15A ): merus, carpus, and propodus in ratio of 1.0:0.8:0.8. Pereopod 6 ( Figure 15D ): longest posteromarginal seta of basis 0.5× width of ischium. Pereopod 7 ( Figure 15E ): longest posteromarginal seta of basis 0.7× width of ischium.

Pleopods ( Figure 15F ): retinacula paired ( Figure 15G ). Epimeron 1 ( Figure 16A ): with setose anteroventral margin, posterior margin with seta, posterodistal corner with seta. Epimeron 2 ( Figure 16B ): with setose anterior margin, ventral margin with slender seta and four robust setae. Epimeron 3 ( Figure 16C ): with setose anterior margin, ventral margin with two slender and six robust setae.

Uropod 1 ( Figure 16D ): inner ramus length 0.7×, outer ramus length 0.6× peduncle length, latter with robust marginal and slender setae and robust basofacial seta; inner ramus with three inner and two outer robust marginal setae; outer ramus with two inner and two outer robust marginal setae. Uropod 2 ( Figure 16E ): inner ramus length 0.6×, outer ramus length 0.6× peduncle length; inner ramus with two inner and one outer robust marginal setae; outer ramus with one inner and one outer robust marginal setae. Uropod 3 ( Figure 16F ): inner ramus length 0.3× outer ramus length; outer margin of outer ramus with two clusters and two pairs of robust setae and simple and plumose setae; inner margin with two robust, a few simple, and numerous plumose setae; terminal article length 0.2× proximal article length. Telson ( Figure 16G ): as long as wide, apical robust seta shorter than slender seta; cleft 58%.

Description of female (immature, 12.0 mm from Malibu Lagoon, CMNC 2004-1027)

Antenna 1 ( Figure 17A ): peduncular articles 1:2: 3 in length ratio of 1.0:0.6:0.3; article 1 posterior margin with seta; article 2 posterior margin with pair of setae and a single seta; article 3 marginally bare; accessory flagellum five-articulate; primary flagellum 22- articulate, each article with one aesthetasc. Antenna 2 ( Figure 17B ): peduncular articles 4: 5 in length ratio of 1.0:0.9, posterior margins of articles 4 and 5 with cluster and pair of setae; flagellum 14+ articulate.

Gnathopod 1 ( Figure 17C ): palmar margin of propodus ( Figure 17D ) with five robust inner and outer setae. Gnathopod 2 ( Figure 17E ): palmar margin of propodus ( Figure 17F ) with three pectinate and four robust simple setae on inner margin, two pectinate and two robust simple setae on outer margin.

Pereopod 6 ( Figure 17H ): longest posteromarginal seta 0.3× width of basis. Pereopod 7 ( Figure 17I ): longest posteromarginal seta of basis 0.6× width of ischium.

Uropod 3 ( Figure 17K ): inner ramus length 0.3× outer ramus length; outer margin of outer ramus with two clusters and one pair of robust setae, and simple and plumose setae; inner margin with two pairs of robust setae and a single robust seta, and a few simple 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 0 to three. The number of clusters of robust setae on the outer margin of the ramus of uropod 3 varies from three to four.

Remarks

Eogammarus confervicolus and E. oclairi are distinct from their congeners by the presence of robust setae on the peduncular article 1 of antenna 2, and the absence of outer marginal setae on palp article 1 of maxilla 1. Eogammarus confervicolus is distinguished from E. oclairi by the following characters ( E. oclairi in parentheses): (1) the aesthetasc on the antenna 1 flagellum is about equal to the surrounding setae in length (longer); (2) calceoli are absent on female antenna 2 (present); (3) the longest posteromarginal seta on the basis of male pereopod 6 is about equal to half the ischium width (shorter); and (4) the robust apical setae on the telson are about equal to or shorter than the slender apical setae (longer) (see Table I).

Distribution

Pacific coasts of USA and Canada.

Habitat

Intertidal zone, estuaries.

Figures

Figure 4. Eogammarus kygi (Derzhavin, 1923), Naibetsu River, Chitose, Japan, female, 12.5 mm. (A) Antenna 1; (B) antenna 2; (C) gnathopod 1; (D) dactylus of gnathopod 1; (E) palm of gnathopod 1 (slender setae are omitted); (F) gnathopod 2; (G) dactylus of gnathopod 2; (H) palm of gnathopod 2 (slender setae are omitted); (I– K) coxa–ischium of pereopods 5–7; (L) brood plate of gnathopod 2; (M) uropod 3. Scale bars: 0.1 mm.

Figure 9. Eogammarus itotomikoae sp. nov., Masuhoro River, Wakkanai, Japan, holotype, male, 18.9 mm, NSMT- Cr. 16678. (A) Habitus (lateral view); (B) antenna 1; (C) flagellar article of antenna 1 (some setae are omitted); (D) antenna 2; (E) flagellar article of antenna 2 (some setae are omitted); (F) upper lip; (G) lower lip; (H) right mandible; (I) incisor and lacinia mobilis of left mandible; (J) maxilla 1 (robust apical setae on outer plate are shown enlarged); (K) maxilla 2; (L) palp of maxilliped; (M) inner plate of maxilliped; (N) outer plate of maxilliped. Scale bars: 0.1 mm unless indicated otherwise.

Figure 10. Eogammarus itotomikoae sp. nov., Masuhoro River, Wakkanai, Japan, holotype, male, 18.9 mm, NSMT-Cr. 16678. (A) Gnathopod 1; (B) dactylus of gnathopod 1; (C) palm of gnathopod 1 (slender setae are omitted); (D) gnathopod 2; (E) dactylus of gnathopod 2; (F) palm of gnathopod 2 (slender setae are omitted); (G) pereopod 3; (H) pereopod 4; (I) coxa–ischium of pereopod 5. Scale bars: 0.1 mm.

Figure 14. Eogammarus confervicolus (Stimpson, 1856), Malibu Lagoon, California, male, 13.0 mm, CMNC 2004- 1028. (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) palp of right mandible; (I) incisor and lacinia mobilis of left mandible; (J) maxilla 1 (robust apical setae on outer plate are shown enlarged); (K) maxilla 2; (L) maxilliped; (M) gnathopod 1; (N) dactylus and palm of gnathopod 1 (slender setae on palm are omitted); (O) gnathopod 2; (P) dactylus and palm of gnathopod 2 (slender setae on palm are omitted). Scale bars: 0.1 mm.

Figure 15. Eogammarus confervicolus (Stimpson, 1856), Malibu Lagoon, California, male, 13.0 mm, CMNC 2004- 1028. (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 16. Eogammarus confervicolus (Stimpson, 1856), Malibu Lagoon, California, male, 13.0 mm, CMNC 2004- 1028 and male, 17.0 mm, CMNC 1980-0427. (A–C) Epimeral plates 1–3; (D–F) uropods 1–3; (G) telson (male, 13.0 mm, dorsal view); (H) telson (male, 17.0 mm, dorsal view). Scale bars: 0.1 mm.

Figure 17. Eogammarus confervicolus (Stimpson, 1856), Malibu Lagoon, California, female, 12.0 mm, CMNC 2004-1027. (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.