Gammarus kesanensis, Özbek, Murat & Çamur-Elipek, Belgin, 2010

Özbek, Murat & Çamur-Elipek, Belgin, 2010, Gammarus kesanensis, a new blind amphipod species from Turkey (Amphipoda, Gammaridae), with a key to eyeless Gammarus species of Europe, Zootaxa 2399, pp. 51-60 : 52-60

Gammarus kesanensis n. sp.

( Figs. 1–7 )

Material examined. Holotype male, 10.1 mm (ESFM-MALI/90-01); Balcı Yalak, Erikli, Keşan, Edirne, Turkish Thrace; 0 1 March 1990; collected by Prof. Dr. Timur Kirgiz. Allotype female, 8.3 mm (ESFM- MALI /90-02), same data as holotype ( Fig. 1 ).

Diagnosis. A medium to large species similar to Gammarus pulex polonensis G. Karaman & Pinkster, 1977 except for the presence of setae on the inner surface of basal segment of pereopod 7 and the presence of long setae along the lower margin of the second epimeral plate. Second antenna bears more setae both in peduncle and flagellum segments. Pereopods 5 to 7 bearing long setae (longer than the spines) along the anterior margins of their third and fourth (ischium and merus) segments. The postero-inferior corner of first epimeral plate not rounded as in G. pulex pulex . Third uropod less setose, only a few simple and plumose setae occur along outer margin of its outer lobe.

Description. Head (fig. 6H): inferior antennal sinus deep. Eyes absent.

Antenna 1 (figs. 3D, E): shorter than half the body length; setation weak, peduncular segments bearing a few distal setae shorter than the diameter of the segment where they are implanted; article 1 stout; primary flagellum with 20-22 articles; accessory flagellum with 3 articles.

Antenna 2 (figs. 3A, B): antennal gland-cone short, not reaching to distal end of third peduncular segment; peduncular segments 4 and 5 armed with 4–5 groups of setae shorter than the diameter of segment on which they insert; setae on dorsal side of the peduncular segments shorter; flagellum comprising up to 11 segments; flagellar segments with many longer setae (as long as or slightly longer than the diameter of the segments where they are implanted) on their ventral sides; flagellar segments swollen; calceoli on 2–6th segments.

Upper lip (fig. 2B): convex, with minute setae on distal part.

Left mandible (fig. 2A): incisor with 5 teeth; lacina mobilis 4 dentate; molar triturative; second article of palp bearing 13 setae; third segment armed with 13 D-setae, 4–5 E-setae; one group of A-setae, and 1–2 groups of B-setae; C-setae absent.

Right mandible (fig. 2C): incisor 4-dentate, lacina mobilis bifurcate.

Lower lip (fig. 2G): inner lobe absent.

Maxilla 1 (figs. 2D, E): inner plate with 12 plumose setae, outer plate with 11 serrated spines, article 2 of palp with 7 sharp spines and 3 stiff setae; article 2 of right palp stout, with 5 blunt spines in distal part and 1 stiff seta on outer margin.

Maxilla 2 (fig. 2F): inner plate with diagonal row of 13 plumose setae.

Maxilliped (fig. 4G): inner plate with 3 apical spines and 1 subapical spine; outer plate with row of 9–10 spines on medial margin and 4–6 pectinate apical setae.

Coxal plate 1 (fig. 4C) not dilated on distal margin, with 2–4 setae on both the anterodistal and posterodistal margins. Coxal plates 2 and 3 subrectangular (figs. 4A, I). Coxal plate 2 with 3 short setae on anterodistal corner and 1 seta on posterodistal corner. Coxal plate 3 with 3 short setae on anterodistal corner and 1 seta on posterodistal corner. Ventral margin of coxal plate 4 slightly convex (fig. 5A), with 4 setae on anterodistal corner and 5–6 setae on posterior margin. Coxal plates 5–6 (figs. 5C, E) bilobate. Anterior lobe of coxal plate 5 small with 1 seta, posterior lobe with 6 setae on posterodistal corner. Coxal plate 6 with 1 seta on anterodistal and 4 setae on posterodistal corner. Coxal plate 7 (fig. 5G) with 5 setae on posterior margin. Coxal gills 2–7 present.

Gnathopod 1 (figs. 4C, D): basis with long setae (up to 1.2 times longer than diameter of the segment) on both anterior and posterior margins; carpus and propodus elongate; propodus with two groups of setae on anterior margin, palm oblique, bearing 1 blunt median spine and 6 (4+2) palmar angle spines in addition to some small spines on posterodistal margin of the segment; dactylus with one seta on its outer margin.

Gnathopod 2 (figs. 4A, B): basis with long setae (up to 1.5 times longer than diameter of the segment) on anterior and posterior margins; carpus and propodus elongate; anterior margin of carpus with three groups of long setae (not curled); propodus subrectangular, with 3 groups of setae on anterior margin; median spine present, with 3 spines on posterodistal margin; dactylus with 1 seta on outer margin. Inner side of propodus bearsing 4 groups of setae.

Pereopod 3 (figs. 4I, J): slender; posterior margins of basis bearing many long setae (up to 1.7 times longer than the diameter of the segment); merus and carpus densely setose along their posterior margins, the setae on posterior margins are long (longer than 1.5 times of the diameter of the segment where they are implanted) and some of them curled; dactylus slender, with 1 serrated seta on outer margin and 2 setae at joint of unguis.

Pereopod 4 (figs. 5A, B): slender; anterior and posterior margins of basis with many long setae; posterior margins of merus and carpus bearing many setae (slightly longer than the segment where they are implanted, not curled); dactylus slender, with 1 serrated seta on outer margin and 2 setae at joint of unguis.

Pereopods 5–7 (figs. 5C–H): subequal in length; basis of pereopod 5 is subrectangular; bases of pereopods 6 and 7 are quadrangular, anterior margins with 4–5 short spines, posterior margins with 10–13 short setae; basis of pereopod 7 bearing 2–4 setae on its inner surface; articles 4–6 slim, with 2–4 groups of spines on anterior and posterior margin of each segment; anterior margin of segments 3 and 4 with a few setae longer than the spines; dactylus with 1 seta on outer margin and 2 setae at joint of unguis.

Epimeral plates 1–3 (fig. 2H): epimeral plate 1 with 7–8 setae on anterior corner, posterodistal corner not rounded; epimeral plate 2, posterodistal corner is rectangular, with 3 setae on anterior corner and 7–8 long setae on ventral margin; epimeral plate 3, posterodistal corner rectangular, with 4–5 setae on anterior corner and 5 spines on ventral margin.

Pleopods 1–3 (figs. 4E, F): subequal; peduncle with some setae, bearing 2 retinacula accompanied by a few setae; rami with about 15 segments, fringed with plumose setae.

Urosomites 1–3 (fig. 3C): almost flat; each urosomite bearing a dorsomedian and 2 dorsolateral groups of short spines and longer setae on posterior margins. Each dorsolateral groups consisting of 1–3 spines and 3–5 longer setae. All urosomites bearing spines in dorsolateral groups.

Uropod 1 (fig. 2I): peduncle longer than rami, with 1 spine on dorsal surface; outer margin with 3 spines; inner margin bare; outer ramus slightly shorter (about 0.9 times as long as inner ramus) than inner ramus, with 3 spines on inner margin and 1 seta on outer margin.

Uropod 2 (fig. 2I): peduncle with 1 and 2 marginal spines on inner and outer margin, respectively; outer ramus a little shorter than inner ramus (about 0.75 times as long as inner ramus); outer ramus with 1 spine on inner margin; inner ramus with 2 spines on inner margin.

Uropod 3 (fig. 4H): peduncle with 4–6 distal spines; inner ramus distinctly shorter than outer ramus (about 0.7 times as long as outer ramus), with 3 groups of lateral spines and few plumose setae on outer margin, many plumose setae on inner margin; article 1 of outer ramus with 3 groups of spines on outer margin together with few plumose and simple setae; inner margin with plumose setae, first segment of outer ramus bearing 3– 4 distal spines, article 2 longer than adjacent spines.

Telson (fig. 2J): deeply cleft; each lobe with 1–2 distal spines together with many longer distal and dorsolateral setae; length of distal and lateral setae about 0.7 and 0.5 times as long as the length of telson, respectively.

Female: Antenna 1 (fig. 6B): peduncle segments with few short setae (not longer than diameter of the segment where they implanted); primary flagellum with 19–21 segments; accessory flagellum with 3–4 segments; Antenna 2 (fig. 6C): peduncle segments bearing some groups of short setae on dorsal margin; setae on ventral margins almost as long as (some longer) diameter of segment where they implanted; primary flagellum with 8–9 segments; setation of flagellar segments weaker than that of male; calceoli absent; gnathopod 1 (fig. 7I): basis with many long setae on both anterior and posterior margins; setae usually more than 2 times longer than diameter of basal segment; propodus ovate with 3 groups of setae on anterior margin, palm not as oblique as that of male, with 4 spines on posterior corner, dactylus with 1 seta on outer margin. Gnathopod 2 (fig. 7A): merus and carpus elongate, propodus subrectangular, medial palmar spine absent, bearing 3–5 spines on posterior corner and spines on inner margin. Pereopods 3–4 (figs. 7C, D, J, K) similar to those of male in setation; pereopod 3 bearing less setae on posterior margins of merus and carpus than those in males (fig. 7J). Pereopods 5–7 (figs. 6D–G, 7B, H) more setose especially along the anterior margins of ischium and merus segments; basal segment of pereopod 7 bearing a few setae on inner surface. Uropod 3 (fig. 6A), inner ramus shorter than outer ramus; inner ramus with plumose setae and 1 spine on outer margin; article 2 of outer ramus as long as spines on distal part of first article; inner margin of outer ramus with a few plumose setae; outer margin of outer ramus with some simple setae and 2 groups of spines (setae longer than the spines). Oostegites broad, ovate, on pereopods 2 to 5.

Etymology. The epithet kesanensis is derived from the name of the type locality, Keşan, Edirne province in northwesternTurkey.

Habitat. Specimens were collected from an active trough which has mud-detritus sediment.

Remarks. At first sight, this species looks very similar to Gammarus pulex polonensis G. K a r a m a n & Pinkster 1977, because of absence of eyes, swollen flagellar segments of antenna 2 and a rich setation on the posterior margin of pereopods 3 and 4. However, the second antenna bears more setae both on pedunclar and flagellar segments than that of G. pulex polonensis . Also, in both of the males and females of the new species, setae occur on the inner surface of basal segment of pereopod 7; pereopods 5 to 7 bear long setae (longer than the spines) along the anterior margins of their third and fourth (ischium and merus) segments; the posteroinferior corner of the first epimeral plate is not rounded as in G. pulex pulex ; and third uropod is less setose, only a few simple and plumose setae occur along the outer margin of its outer lobe

This species also resembles G. albimanus G. Karaman 1968 , G. vignai Pinkster & Karaman 1977, G. s k e t i G. Karaman 1989, G. xianfengensis Hou & Li, 2002 , G. lichuanensis Hou & Li, 2002 , G. a o c u l u s Hou & Li 2003, G. translucidus Hou et al. 2004 , G. c o m o s u s Hou et al. 2005, G. ustaoglui Özbek & Güloglu 2005 , and G. abstrusus Hou et al. 2006 in the absence of eyes. The new species differs from G. albimanus , G. sketi , G. xianfengensis and G. lichuanensis by the presence of rich setation on pereopods 3 and 4. G. kesanensis , sp. nov. differs from G. vignai , by the presence of swollen flagellar segments of antenna 2 (especially in males). The new species differs from G. a o c u l u s by the weaker setation of gnathopods 1 and 2 and uropod 3 and clearly differs from G. ustaoglui by the presence of second segment of the outer lobe of uropod 3.

Figures

FIGURE 1. Lateral view of Gammarus kesanensis sp. nov. Holotype male.

FIGURE 2. Gammarus kesanensis sp. nov. Holotype male. A, left mandible; B, upper lip; C, right mandible; D, right maxilla; E, palp of left maxilla; F, maxilla 2; G, lower lip; H, epimeral plates; I, uropod 1 and 2; J, telson.

FIGURE 3. Gammarus kesanensis sp. nov. Holotype male. A, antenna 2; B, flagellar segments of antenna 2; C, urosome segments; D, antenna 1; E, accessory flagellum.

FIGURE 4. Gammarus kesanensis sp. nov. Holotype male. A, gnathopod 2; B, detail of gnathopod 2; C, gnathopod 1; D, detail of gnathopod 1; E, detail of pleopod 2; F, pleopod 2; G, maxilliped; H, uropod 3; I, pereopod 3; J, dactyl of pereopod 3.

FIGURE 5. Gammarus kesanensis sp. nov. Holotype male. A, pereopod 4; B, dactyl of pereopod 4; C, pereopod 5; D, dactyl of pereopod 5; E, pereopod 6; F, dactyl of pereopod 6; G, pereopod 7; H, dactyl of pereopod 7.

FIGURE 6. Gammarus kesanensis sp. nov. Holotype male (H), Allotype female (A – G). A, uropod 3; B, antenna 1; C, antenna 2; D, pereopod 7; E, pereopod 5; F, dactyl of pereopod 5; G, dactyl of pereopod 7; H, head.

FIGURE 7. Gammarus kesanensis sp. nov. Allotype female. A, gnathopod 2; B, pereopod 6; C, pereopod 4; D, dactyl of pereopod 4; E, uropod 1; F, uropod 2; G, telson; H, dactyl of pereopod 6; I, gnathopod 1; J, pereopod 3; K, dactyl of pereopod 3.