Jesogammarus (Annanogammarus) debilis, Hou & Li, 2005

Hou, Zhong-E & Li, Shuqiang, 2005, Amphipod crustaceans (Gammaridea) from Beijing, P. R. China, Journal of Natural History 39 (36), pp. 3255-3274 : 3262-3271

publication ID	https://doi.org/ 10.1080/00222930500289590
persistent identifier	https://treatment.plazi.org/id/0336445B-FFE8-FFD0-B01E-FF60FC8E71F3
treatment provided by	Felipe
scientific name	Jesogammarus (Annanogammarus) debilis
status	sp. nov.

Treatment

Jesogammarus (Annanogammarus) debilis View in CoL sp. nov.

( Figures 1–6 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 )

Type material examined

One male holotye (IZCAS-I-A0115), Beixinzhuang Village, Hebei Town, Fangshan District, 15 September 2001, collected by Yuezhao Wang and Shuqiang Li; one female allotype (IZCAS-I-A0116) and 10 males and 12 females paratypes, same data as holotype .

Other material

Beixinzhuang Village, Hebei Town, Fangshan District: one male, 15 September 2001, collected by Lihong Tu. Jiudaohe Village, Fangshan District : one female, 15 September 2001, collected by Yuezhao Wang and Shuqiang Li. Beiganchi Village, Changgou Town, Fangshan District : three males and one female, 15 September 2001, collected by Yuezhao Wang and Shuqiang Li. Fengsui Relic, Xiabanquan Village, Yanqing County : 15 males, 54 females and three juveniles, 7 April 2004, collected by Shuqiang Li and Zhong-E Hou. Huamu Spring, Huamu Village, Huairou District : eight males, seven females and three juveniles, 2 June 2001, collected by Shuqiang Li. Beijing (10147), no detailed locality: 26 males and 23 females, 21 November 1928. Beijing (BJ0141), no detailed record on the label: three males and four females.

Etymology

This specific name debilis alludes to the body shape, which seems slender.

Diagnosis

Peduncular article 1 of antenna 1 lacking a distal spine; mandibular palp articles with setae alone; propodus of male gnathopod 2 slender; propodus palmar margin of female gnathopod 2 with weakly pectinated stiff setae; outer ramus of uropod 2 marginally bare; uropod 3 with more than three plumose setae; telson longer than maximum basal width.

Description

Male. Body length 10.5 mm.

Head as long as deep ( Figure 1A View Figure 1 ), eyes medium in size, subreniform.

Antenna 1 ( Figure 1B, D View Figure 1 ): peduncular articles 1–3 in length ratio 1:0.77:0.53, peduncular article 1 lacking posterodistal spine, with distal setae, peduncular articles 2 and 3 bearing setae on posterior margin; flagellum with 26 articles, most of which with aesthetascs; accessory flagellum with five articles.

Antenna 2 ( Figure 1C, E View Figure 1 ): peduncular article 4 about as long as article 5, with two to four groups of setae along anterior and posterior margins; flagellum with 14 articles, proximal nine articles with cup-calceoli.

Upper lip ( Figure 1F View Figure 1 ): convex, with minute setae.

Mandibles ( Figure 1G, H, O, P View Figure 1 ): left and right incisor with five and four teeth, respectively; left lacinia mobilis with four dentitions, right lacinia mobilis bifurcate; article 1 of palp unarmed, article 2 with seven marginal and nine submarginal setae, article 3 reaching 89% of length of article 2, with two cluster of A-setae and one B-seta.

Lower lip ( Figure 1I View Figure 1 ): inner lobes absent.

Maxilla 1 ( Figure 1J, K, N View Figure 1 ): asymmetrical, inner plate with 16 plumose setae medially; outer plate with 11 serrated spines apically, outer margin with setules; article 2 of left palp with six spines and four setae apically; article 2 of right palp with six spines and five setae apically.

Maxilla 2 ( Figure 1L View Figure 1 ): inner plate with a diagonal row of 16 plumose setae.

Maxilliped ( Figure 1M View Figure 1 ): inner plate with one subapical spine and three apical spines; outer plate with 13 spines on medial margin and three pectinate setae apically.

Gnathopod 1 ( Figure 2A, C, E View Figure 2 ): coxal plate lower and anterodistal margins setose, posterodistal corner with one stiff seta; anterior and posterior margins of basis setose; propodal palmar margin bearing seven inner and nine outer striated peg-spines, anterior margin with three groups of setae; dactylus with posterior accessory blade longer than nail, bearing one seta on outer margin and two setae on inner margin.

Gnathopod 2 ( Figure 2B, D, F, G View Figure 2 ): coxal plate lower and anterodistal margins setose, posterodistal corner with one stiff seta; anterior and posterior margins of basis setose; propodus more slender than in gnathopod 1, palmar margin bearing eight inner and eight outer striated peg-spines; dactylus with posterior accessory blade longer than nail, bearing one seta on outer margin and two setae on inner margin.

Pereopod 3 ( Figures 2H View Figure 2 , 3A, J View Figure 3 ): coxal plate subrectangular, anterodistal margin with two setae, posterodistal margin with one seta and one stiff seta; basis with long setae on anterior and posterior margins; merus with three groups of long stiff setae on posterior margin; carpus with spines accompanied by setae on posterior margin; propodus with four single spines accompanied by setae on posterior margin; dactylus with one plumose seta on outer margin and two setae at hinge of nail.

Pereopod 4 ( Figures 2I View Figure 2 , 3B View Figure 3 ): coxal plate excavated on posterior margin, anterodistal margin with one seta, posterodistal margin with seven setae; basis with long setae on posterior margin; merus with three groups of stiff setae on posterior margin; carpus with one spine accompanied by setae; propodus with spines accompanied by setae; dactylus similar to that of pereopod 3.

Pereopod 5 ( Figures 2J View Figure 2 , 3C, I View Figure 3 ): coxal plate with one distal seta on anterior lobe, posterodistal corner of posterior lobe with one spine; basis with one group of setae on anteroproximal margin, anterodistal margin spinose, posterior margin nearly straight, with stiff setae; merus to propodus with marginal spines; dactylus with one plumose seta on outer margin and one seta at hinge of nail.

Pereopod 6 ( Figures 2K View Figure 2 , 3D View Figure 3 ): longer than pereopod 5, coxal plate with one spine on posterodistal corner; basis with one group of setae on anteroproximal margin and spines on anterodistal margin, posterior margin weakly sinuate, with a row of setae associated with short spines; merus to propodus with marginal spines; dactylus similar to that of pereopod 5.

Pereopod 7 ( Figures 2L View Figure 2 , 3E View Figure 3 ): coxal plate with a group of long setae on anterior margin and three short setae on posterior margin; basis with two long setae on anteroproximal margin and spines on anterodistal margin, posterior margin expanded, with short spines and setae, inner surface bearing one posterodistal spine and one seta; merus to propodus with marginal spines; dactylus similar to that of pereopod 5.

Coxal gills of gnathopod 2 and pereopods 3 and 4 subequal to their bases in length ( Figure 2G–I View Figure 2 ), anterior accessory lobe of each gill larger than posterior lobe, about onequarter of main gill in length. Gill of pereopod 5 ( Figure 2J View Figure 2 ) longer than basis, anterior accessory lobe larger than posterior lobe, about one-third of main gill. Gill of pereopod 6 ( Figure 2K View Figure 2 ) shorter than basis, accessory lobe about half of main gill. Gill of pereopod 7 ( Figure 2L View Figure 2 ) a little longer than half of basis, accessory lobe less than one-quarter of main gill.

Pereonite 6 ( Figure 4A View Figure 4 ): posterodorsal margin bare.

Pereonite 7 ( Figure 4B View Figure 4 ): posterodorsal margin with six setae.

Pleonites 1–3 ( Figure 4C–E View Figure 4 ): posterodorsal margins with 11 marginal setae, 16 marginal setae, and 17 marginal and two submarginal setae, respectively; lateral plate 1 with about 10 long setae on anteroventral corner and six setules on posterior margin; lateral plate 2 with three anteroventral marginal spines and two submarginal spines, posterior margin with a row of seven setules; lateral plate 3 with three spines on anteroventral margin and six setules on posterior margin.

Pleopods 1–3 ( Figure 3F–H View Figure 3 ): subequal in length, peduncle with long setae on outer margin, bearing two retinacula accompanied by three or four plumose setae on anterodistal corner; outer ramus a little shorter than inner ramus, both rami armed with plumose setae.

Urosomites ( Figure 4F View Figure 4 ): urosomites 1 and 2 bearing a pair of dorsomarginal lateral spines and medial spine-clusters associated with setae; urosomite 3 with a pair of dorsomarginal lateral spines and two medial setae.

Uropod 1 ( Figure 3K View Figure 3 ): basofacial spine in peduncle present or absent, outer and inner margins with two or three spines, respectively; outer ramus with three spines on inner margin; inner ramus with two spines on inner margin.

Uropod 2 ( Figure 3L View Figure 3 ): peduncle with marginal spines on inner and outer margins; outer ramus marginally bare; inner ramus with one spine on outer margin and two spines on inner margin.

Uropod 3 ( Figure 3M View Figure 3 ): peduncle with short setae on inner margin; outer ramus with two articles, outer margin of proximal article with one spine and two pairs of spines sequentially, inner margin with seven plumose setae and a pair of spines; terminal article distinct, 18% of length of proximal article, longer than distal spines of proximal article; inner ramus about one-third of proximal article, with one spine and two plumose setae on inner margin, and one apical spine accompanied by one plumose seta.

Telson ( Figure 4G View Figure 4 ): medially cleft for 72% of its length, basal maximum width 90% of length, with apical and distolateral spines.

Female. Body length 8.2 mm.

Gnathopod 1 ( Figure 5A, C, E, G, H View Figure 5 ): coxal plate with setae on lower and posteroproximal margins; basis with numerous long setae on anterior and posterior margins; propodus oval, bearing two spines on inner posterodistal corner and two spines on outer posterodistal corner, and five pectinate stiff setae; dactylus with posterior accessory blade shorter than nail, bearing one seta on outer margin.

Gnathopod 2 ( Figure 5B, D, F, I View Figure 5 ): coxal plate with one seta on anterodistal corner and 15 setae on posterior margin; basis with setae along anterior and posterior margins; carpus and propodus slender, propodus parallel-sided, palmar margin with five simple spines on inner margin and three simple spines and two weakly pectinate stiff setae on outer margin; dactylus with posterior accessory blade shorter than nail, bearing one seta on outer margin.

Pereopod 3 ( Figures 5J View Figure 5 , 6A View Figure 6 ): coxal plate with setae on posterior margin; basis with long setae on anteroproximal and posterior margins; merus and carpus with long stiff setae on posterior margin; propodus with spines on posterior margin.

Pereopod 4 ( Figure 6B View Figure 6 ): coxal plate with setae on posterior margin; basis with long setae on posterior margin; merus with stiff setae on posterior margin.

Pereopod 5 ( Figure 6C View Figure 6 ): basis with one seta on posterodistal margin of inner surface; merus to propodus spinose.

Pereopod 6 ( Figure 6D View Figure 6 ): coxal plate with long setae on anterior margin; basis with two groups of setae and one posterodistal seta on inner surface.

Pereopod 7 ( Figure 6E, I View Figure 6 ): coxal plate with two groups of long setae on anterior margin; basis with numerous long setae and one posterodistal spine on inner surface.

Accessory gills: anterior lobe of accessory gills of gnathopod 2 and pereopod 3 much larger than posterior lobe; anterior lobe of accessory gill of pereopod 4 a little larger than posterior lobe; anterior lobe of accessory gill of pereopod 5 about one-third of main gill; accessory gill of pereopod 6 about half of main gill; accessory gill of pereopod 7 about onethird of main gill.

Oostegites on gnathopod 2 to pereopod 5 progressively attenuated ( Figure 4H–K View Figure 4 ), fringed with many marginal setae.

Uropod 1 ( Figure 6F View Figure 6 ): peduncle with or without basofacial spine, bearing marginal spines; outer ramus with one spine on inner margin; inner ramus with two spines on inner margin.

Uropod 2 ( Figure 6G View Figure 6 ): peduncle with marginal spines; outer ramus marginally bare; inner ramus with two spines on inner margin.

Uropod 3 ( Figure 6H View Figure 6 ): proximal article of outer ramus with two groups of spines on outer margin, inner margin with three plumose setae and one spine, and bearing two pairs of distal spines, reaching half of terminal article length; terminal article 23% of length of proximal article; inner ramus 40% of length of proximal article, with one spine and two plumose setae on outer margin.

Telson ( Figure 4L View Figure 4 ): medially cleft 72% of length, basal maximum width 87% of length, with apical and distolateral spines.

Variation

Basofacial spine on peduncle uropod 1 present or absent in males and females.

Remarks

This subgenus contains five species: J. (A.) annandalei ( Tattersall, 1922) , J. (A.) naritai Morino, 1985 , J. (A.) fluvialis Morino, 1985 , J. (A.) suwaensis Morino, 1986 , and J. (A.) koreaensis Lee and Seo, 1990 . Jesogammarus (A.) debilis is closely related to J. (A.) annandalei in peduncular article 1 of antenna 1 without posterodistal spine, many setae on pleonites, and antenna 2 with short setae; it differs from J. (A.) annandalei in having bases of pereopods 6–7 without long setae, inner ramus of uropod 3 elongate and both rami with more plumose setae. Jesogammarus (A.) debilis can be distinguished from J. (A.) koreaensis and J. (A.) fluvialis by peduncular article 1 of antenna 1 without posterodistal spine and propodus palmar margin of female gnathopod 2 with weakly pectinate stiff setae. Jesogammarus (A.) debilis differs from J. (A.) naritai and J. (A.) suwaensis by pleonites without spines on dorsal margins.

This discovery of a new Annanogammarus species from a suburb of Beijing is interesting from a zoogeographical viewpoint. It is probable that Annanogammarus has invaded from the continent, through the Korean Peninsula to Japan.