Gammarus parvioculus, Hou & Li, 2010
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2009.00603.x |
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persistent identifier |
https://treatment.plazi.org/id/AD798550-F105-FF85-FF39-D4B9FAD2BCD7 |
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Valdenar |
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scientific name |
Gammarus parvioculus |
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sp. nov. |
GAMMARUS PARVIOCULUS SP. NOV. ( FIGS 19–23 View Figure 19 View Figure 20 View Figure 21 View Figure 22 View Figure 23 )
Synonymy: Gammarus sp4 Hou et al., 2007: 599.
Material examined: Holotype (IZCAS-I-A318), male, Tongdong Cave (39°42′N, 115°42′E), Sihe Village, Xiayunling Town , Fangshan District , Beijing City; collected by X. Xu and Q. Wang, 13.iv.2005 GoogleMaps . Paratypes (from IZCAS-I-A318-2 to IZCAS-I-A318-23), 16 males and six females, same locality as holotype GoogleMaps .
Etymology: The specific name is from the Latin ‘parvi-’ and ‘-oculus’, referring to the vestigial eyes.
Diagnosis: Eyes small; pereopods 3–7 slender, with few long setae on anterior and posterior margins; inner ramus less than half of outer ramus, outer margin of outer ramus with simple setae.
Description
Holotype: male
Body length: 12.5 mm.
Head ( Fig. 19A View Figure 19 ): eyes relatively small, about onesixth of head depth, 1.2 times as long as wide; inferior antennal sinus distinct, projection on the anterodistal corner shorter.
Antenna 1 slender ( Fig. 19B View Figure 19 ), peduncular articles 1–3 in length ratio 1: 0.8: 0.4, with distal setae; flagellum with 32 articles, most with aesthetascs; accessory flagellum with five articles.
Antenna 2 ( Fig. 19C View Figure 19 ): peduncular article 5 a little longer than article 4, with groups of short setae along anterior and posterior margins; flagellum with 14 articles, calceoli present.
Upper lip subrounded ( Fig. 19D View Figure 19 ), with minute setae.
Mandibles ( Fig. 19F View Figure 19 ): left incisor with five teeth; lacinia mobilis with four teeth; spine row with eight pairs of plumose setae; article 2 of palp with 12 marginal setae, article 3 with a group of four A-setae, a group of three B-setae, a row of plumose D-setae, and five E-setae. Right incisor with four teeth ( Fig. 19E View Figure 19 ); lacinia mobilis bifurcate, with dentitions at edge.
Lower lip ( Fig. 19G View Figure 19 ): inner plate absent.
Maxilla 1 asymmetric ( Fig. 19H, I, M View Figure 19 ), inner plate with a row of 14 plumose setae; outer plate with 11 serrated spines; article 2 of left palp with seven slender spines accompanied by three stiff setae; article 2 of right palp with five stout spines and one slender spine accompanied by one seta.
Maxilla 2 ( Fig. 19J View Figure 19 ): inner plate with a diagonal row of 15 plumose setae; outer plate with apical setae.
Maxilliped ( Fig. 19K, L View Figure 19 ): inner plate with three apical spines and one to two subapical spines; outer plate with a row of 15 spines on inner margin and six apical pectinate spines; palp with four articles.
Gnathopod 1 ( Fig. 20A, C View Figure 20 ): coxal plate with two and one setae on anterior and posterior corners, respectively, lower margin with setules; basis with long setae on anterior and posterior margins; carpus 1.6 times as long as wide, about 0.75 times as long as propodus; propodus ovate, with one stout spine on medial palmar margin, posterior margin with one single and four pairs of spines, inner surface with three groups of three, three, and two spines; dactylus with one seta on outer margin.
Gnathopod 2 ( Fig. 20B, D, E View Figure 20 ): coxal plate with three setae on anterior corner and one seta on posterior corner; carpus with parallel sides, 1.6 times as long as wide, about 0.83 times as long as propodus; propodus palm subacute, with one stout medial palmar spine and two pairs of spines on posterodistal corner, inner surface with groups of long setae; dactylus with one seta on outer margin and several short setae at hinge of unguis.
Pereopod 3 ( Fig. 21A, F View Figure 21 ): coxal plate subrectangular, with two setae on lower margin; basis with long setae on posterior margin; merus and carpus densely set with long and straight setae on posterior margin; propodus with long setae accompanied by spines; dactylus with one plumose seta on outer margin and two setae at hinge of unguis.
Pereopod 4 ( Fig. 21B, G View Figure 21 ): coxal plate excavated on posterior margin, with setae on anterior corner and posterior margin; basis with long setae on posterior margin; merus to propodus with groups of setae on posterior margin accompanied by spines; dactylus with one plumose seta on posterior margin and two setae at hinge of unguis.
Pereopod 5 ( Figs 21C View Figure 21 , 22A View Figure 22 ): coxal plate with one seta on anterior corner and two setae on posterior margin; basis with six single spines on anterior margin, posterior margin straight with a row of short setae, posterior corner subquadrate; merus and carpus with two groups of spines on anterior and posterior margins; propodus with three groups of spines on anterior margin; dactylus with one plumose seta on outer margin and two stiff setae at hinge of unguis.
Pereopod 6 ( Figs 21D View Figure 21 , 22B View Figure 22 ): slender, basis elongate, posterior margin weakly expanded, inner surface with one seta; merus to propodus with spines and few short setae, carpus longer than merus and propodus; dactylus with one plumose seta on outer margin and two stiff setae at hinge of unguis.
Pereopod 7 slender ( Figs 21E View Figure 21 , 22C View Figure 22 ), coxal plate with five setae on posterior margin; posterior margin of basis weakly sinuate, inner surface with one spine accompanied by one seta; merus to carpus similar to those of pereopod 6.
Coxal gills present on gnathopod 2 and pereopods 3–7.
Epimeral plates ( Fig. 22D–F View Figure 22 ): epimeron 1 with ten long setae on anteroventral corner, posterior margin with four setules; epimeron 2 posterior margin nearly straight, bearing two setae and three spines on ventral margin and five setae on posterior margin; epimeron 3 posterodistal corner weakly produced, bearing four long setae on anterior margin, three spines on ventral margin, and three setae on posterior margin.
Pleopods 1–3 subequal ( Fig. 22G View Figure 22 ), peduncle with two retinacula accompanied by one to three plumose setae on anterior corner; outer ramus a little shorter than inner ramus, both rami fringed with plumose setae.
Urosomites 1–3 dorsally flat, with four groups of spines and setae.
Uropod 1 ( Fig. 22H View Figure 22 ): peduncle with one basofacial spine, outer margin with three spines and inner margin with one spine; inner ramus with one spine on inner margin; outer ramus with one spine on inner and outer margins, both rami with five distal spines.
Uropod 2 ( Fig. 22I View Figure 22 ): peduncle longer than both rami, with two spines on outer margin and one spine on inner margin; outer ramus with one spine on inner and outer margins; inner ramus with one spine on inner margin.
Uropod 3 ( Fig. 22J View Figure 22 ): peduncle with one spine accompanied by one seta on lateral surface; inner ramus nearly the same length as peduncle, about 0.4 times as long as outer ramus, inner and outer margins with plumose and simple setae; article 1 of outer ramus with two pairs of spines and long simple setae on outer margin, inner margin densely set with long simple and plumose setae on inner margin, terminal article shorter than adjacent spines.
Telson cleft ( Fig. 22K View Figure 22 ), length same as width, each lobe with one basolateral spine accompanied by long facial setae, with two distal spines accompanied by long setae.
Female: paratype (IZCAS-I-A318-2)
Body length: 9 mm.
Gnathopod 1 ( Fig. 23A View Figure 23 ): propodus oval, palm not as oblique as that of male, without palmar medial spine, with four spines on posterodistal corner.
Gnathopod 2 ( Fig. 23B View Figure 23 ): propodus longer than that of male, with three spines on posterodistal corner.
Uropod 3 ( Fig. 23C View Figure 23 ): inner ramus about 0.44 times as long as outer ramus; outer ramus with two pairs of spines and long simple setae on outer margin, inner margin with simple and plumose setae, terminal article shorter than adjacent spines; inner ramus with simple and plumose setae on both margins.
Telson cleft ( Fig. 23D View Figure 23 ), 0.8 times as long as wide, each lobe with basofacial and distal spines accompanied by long setae.
Oostegites 2–5 progressively reduced ( Fig. 23E–H View Figure 23 ), with long marginal setae.
Habitat: The examined specimens were collected 15 m away from the entrance of cave. This entrance is halfway up the hill, and there is a crystal-clear underground river running throughout the year.
Remarks: Gammarus parvioculus sp. nov. is very similar to G. nekkensis in antenna 2 with calceoli, epimeral plates 2 and 3 posterodistal corners weakly produced, and uropod 3 with long simple setae on outer margin of outer ramus. Gammarus parvioculus differs from G. nekkensis (state in parentheses) in smaller eyes, about one-sixth of head (one-quarter), pereopod 3 with long, straight setae on posterior margin (curled setae), pereopods 5–7 very slender, inner ramus of uropod 3 about 0.4 times the length of outer ramus (0.5 times as long as outer ramus). The comparisons with the other three new species are presented in Table 2.
This taxon may have adapted to a cave-entrance existence relatively recently and therefore is intermediate between a common freshwater species with large eyes and a cave species without eyes.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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