Eogammarus possjeticus ( Tzvetkova, 1967 )

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 : 1131-1136

publication ID	https://doi.org/ 10.1080/00222930600828859
publication LSID	lsid:zoobank.org:pub:41F5583D-BD6D-4FFF-961F-39AA6A6ECCE8
persistent identifier	https://treatment.plazi.org/id/BF741C1D-B220-570F-FE14-84BAFDDDAF75
treatment provided by	Felipe
scientific name	Eogammarus possjeticus ( Tzvetkova, 1967 )
status

Treatment

Eogammarus possjeticus ( Tzvetkova, 1967) View in CoL

[Japanese name: Poshietto togeo yokoebi, new]

( Figures 30–32 View Figure 30 View Figure 31 View Figure 32 )

Anisogammarus (Eogammarus) possjeticus Tzvetkova 1967, p 176 View in CoL –181, Figures 5–7 View Figure 5 View Figure 6 View Figure 7 ; 1972, p 214; 1975, p 109–114, Figures 40–42.

Eogammarus possjeticus: Bousfield 1979, p 314 View in CoL ; Hirayama 1993, p 156 –160, Figures 12–14 View Figure 12 View Figure 13 View Figure 14 . Eogammarus sinensis Ren 1992, p 307 View in CoL –308, Figures 12 View Figure 12 , 13 View Figure 13 , new synonymy.

Material examined

Japan. „, 13.6 mm, ♀, 9.3 mm, Lake Akkeshi (43 ° 019550N, 144 ° 539100E), Akkeshi Town, Akkeshi County, Hokkaido, 10 May 1994, collected by H. Mukai. „, 13.5 mm, ♀, 9.1 mm, ovigerous, Lake Saroma (44 ° 089280N, 143 ° 489290E), Saroma Town , Tokoro County , Hokkaido, 13 August 1982, collected by A. Ohtaka. 3 „, 13.1–18.1 mm, Notsuke Bay (43 ° 359300N, 145 ° 139370E), Nakashibetsu Town, Shibetsu County, Hokkaido, 28 May 2002, collected by K. Wada. „, 14.5 mm, ♀, 10.9 mm, ovigerous, Origasa River (39 ° 269550N, 141 ° 579430E), Yamada Town , Shimoheii County , Iwate Prefecture, 5 June 1992, collected by H. Morino. „, 7.9 mm, ♀, 9.1 mm, ovigerous, Gamo Lagoon (38 ° 159190N, 141 ° 009420E), Sendai City, Miyagi Prefecture, 16 June 1997, collector unknown. 3 „, 11.1–13.0 mm, ♀, 9.1 mm, ovigerous, Lake Hinuma (36 ° 169440N, 140 ° 319580E), Oarai Town , Higashiibaraki County, Ibaraki Prefecture, 17 June 1987, collected by H. Morino. 2 „, 16.5 mm, 18.0 mm, ♀, 13.7 mm, ovigerous, Higashi River (34 ° 199160N, 135 ° 079130E), Misaki Town, Sennan County, Osaka Prefecture, 25 May 1987, collected by H. Ariyama. „, 17.9 mm, Yamato River (34 ° 269280N, 135 ° 269560E), Sakai City , Osaka Prefecture, 13 April 2000, collected by H. Ariyama. ♀, 7.8 mm, ovigerous, Sumoto River (34 ° 209540N, 134 ° 539410E), Sumoto City , Hyogo Prefecture, 27 April 1986, collected by H. Ariyama. „, 6.9 mm, Lake Nakaumi , Shimane Prefecture, August 2000 (day unknown) , collected by T. Yamauchi. Ten juveniles, 4.0– 6.9 mm, Wajiro Lagoon (33 ° 419100N, 130 ° 259410E), Fukuoka City , Fukuoka Prefecture, 12 May 1995 , collected by T. Kikuchi . Russia. Three juveniles, 6.9–7.9 mm, Uryum River (46 ° 329590N, 143 ° 239210E), north of Kirillovo , Sakhalin Island , 19 July 2002, collected by J. Toft.

Description of male (13.6 mm from Lake Akkeshi)

Antenna 1 ( Figure 30A View Figure 30 ): peduncular articles 1:2: 3 in ratio of 1.0:0.7:0.3; article 1 with slender posterodistal seta in place of robust seta, posterior margin with pair of setae; article 2 posterior margin with two pairs of setae; article 3 posterior margin bare; accessory flagellum six-articulate; primary flagellum 20-articulate, each article with one long aesthetasc ( Figure 30B View Figure 30 ). Antenna 2 ( Figure 30C View Figure 30 ): peduncular article 1 without robust setae; articles 4: 5 in ratio of 1.0:0.9, posterior margin of article 4 with pair and cluster of setae and minute setae, posterior margin of article 5 with two clusters of setae; flagellum 16-articulate, with cup-calceoli ( Figure 30D View Figure 30 ).

Mandible ( Figure 30G, H View Figure 30 ): palp article 2 with six marginal and 12 submarginal setae; article 3 length 0.9× article 2 length, with two clusters of A-setae. Maxilla 1 ( Figure 30I View Figure 30 ): inner plate with 17 plumose setae medially; palp article 1 with seta on outer margin; article 2 with three setae on outer margin, and seven robust and eight slender setae apically. Maxilla 2 ( Figure 30J View Figure 30 ): inner plate with 17 facial setae. Maxilliped ( Figure 30K–M View Figure 30 ): 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 cluster of slender setae.

Gnathopod 1 ( Figure 30N View Figure 30 ): basis without medial setae; anterior margin of propodus with two short setae, palmar margin ( Figure 22P View Figure 22 ) lined with 14 inner and seven outer robust, striated peg setae. Gnathopod 2 ( Figure 30Q View Figure 30 ): basis without medial setae; anterior margin of propodus with two pairs of short setae, palmar margin ( Figure 30S View Figure 30 ) lined with six inner and six outer robust, striated peg setae and three stiff inner pectinate setae.

Pereopod 3 ( Figure 31A View Figure 31 ): merus, carpus, and propodus in ratio of 1.0:0.7:0.8. Pereopod 4 ( Figure 31B View Figure 31 ): merus, carpus, and propodus in ratio of 1.0:0.8:1.0. Pereopods 6–7 ( Figure 31D, E View Figure 31 ): posterior margin of basis with very short setae.

Epimera 1–3 ( Figure 31F–H View Figure 31 ): with setose anterior margin. Epimeron 2 ( Figure 31G View Figure 31 ): ventral margin and submargin with three and four robust setae, respectively. Epimeron 3 ( Figure 31H View Figure 31 ): ventral margin with four robust setae.

Uropod 1 ( Figure 31I View Figure 31 ): inner and outer ramus length 0.8× 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 31J View Figure 31 ): inner ramus length 0.9×, outer ramus length 0.7× peduncle, latter with robust marginal setae; inner ramus with two inner and one outer robust marginal setae; outer ramus with outer robust marginal seta. Uropod 3 ( Figure 31K View Figure 31 ): inner ramus length 0.2× outer ramus length; outer margin of outer ramus with four clusters of robust setae, a few simple and plumose setae, inner margin with three clusters of robust setae, a few simple and numerous plumose setae; terminal article length 0.2× proximal article length. Telson ( Figure 31Q View Figure 31 ): length 1.1× width, with robust apical and distolateral setae, slender apical setae, and penicillate apical and distolateral setae; cleft 71%.

Description of female (9.3 mm from Lake Akkeshi)

Antenna 1 ( Figure 32A View Figure 32 ): peduncular articles 1:2: 3 in ratio of 1.0:0.6:0.3; article 1 posterior margin with three setae; article 2 posterior margin with cluster of setae; article 3 posterior margin bare; accessory flagellum four-articulate; primary flagellum 20-articulate, each article with one aesthetasc. Antenna 2 ( Figure 32B View Figure 32 ): peduncular articles 4: 5 in ratio of 1.0:0.9; posterior margin of article 4 with pair of setae and three setae, posterior margin of article 5 with cluster of setae and two setae; flagellum 12-articulate, lacking cup-calceoli.

Gnathopod 1 ( Figure 32C View Figure 32 ): basis with medial setae; anterior margin of propodus with two clusters of setae and a single seta, palmar margin ( Figure 32E View Figure 32 ) with four robust simple setae on inner distal part and three robust simple setae on outer distal part. Gnathopod 2 ( Figure 32F View Figure 32 ): basis with medial setae; anterior margin of propodus with cluster and pair of setae, palmar margin ( Figure 32H View Figure 32 ) with two simple and two pectinate setae, all robust, on inner distal part and four robust pectinate setae on outer distal part.

Uropod 3 ( Figure 32M View Figure 32 ): inner ramus length 0.3× outer ramus length; outer margin of outer ramus with three clusters of robust setae and a few simple setae, inner margin with two clusters of robust setae, a few simple setae 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 two. The number of clusters of robust setae on the outer margin of the ramus of uropod 3 varies from three to four.

Remarks

The incisor of the left mandible is five-dentate for all specimens of E. possjeticus examined, except for the one illustrated (male, 13.6 mm from Lake Akkeshi, 10 May 1994, collected by H. Mukai), which possesses a six-dentate incisor on its left mandible, possibly an aberration.

Ren (1992) described a new species under the name of E. sinensis based on the material from Jiaozhou Bay (Yellow Sea coast of China). He remarked on the differences between his new species and two Eogammarus species : E. kygi and E. annandalei . Since we could not find any critical differences between the descriptions and figures of E. sinensis and our material of E. possjeticus , we here assign E. sinensis to be a junior synonym of E. possjeticus .

Eogammarus possjeticus is similar to E. tiuschovi , but is distinguished from the latter by the following characters (character states of E. tiuschovi in parentheses): (1) zero or one posteromarginal setal pairs or clusters are present on peduncular article 1 of antenna 1 (three or four); (2) on antenna 1, the aesthetasc is longer than the surrounding setae (shorter); (3) on antenna 2, the calceolus is wider than 0.25× the article width (about 0.25×); and (4) pleonites are dorsally smooth (carinate) (see Table I).

Distribution

Possjet Bay (Sea of Japan coast of Russia), Kuril Islands, Hokkaido, Honshu, Kyushu, Jiaozhou Bay (Yellow Sea coast of China).

Habitat

River mouths, brackish lakes, estuaries.