Gammarus topkarai, Özbek, Murat & Balik, Suleyman, 2009

Özbek, Murat & Balik, Suleyman, 2009, A new freshwater amphipod species, Gammarus topkarai sp. nov., from Turkey (Amphipoda: Gammaridae), with a key for Turkish freshwater Gammarus species, Zootaxa 2073, pp. 45-56 : 48-56

Gammarus topkarai sp. nov.

(figs. 2−7)

Material examined. Holotype male, 11.3 mm (ESFM-MALI/06-01); Ivriz Creek, Konya Province, southern Anatolia (fig. 1), 21 June 2006; collected by E. T. Topkara. Allotype female, 7.4 mm (ESFM-MALI/06-2), same data as holotype. Paratypes (many males and females) (ESFM-MALI/06-3), same data as holotype.

Diagnosis. A medium-large species. Similar to Gammarus agrarius G. S. Karaman, 1973 except for the absence of well developed dorsal elevations on the urosome segments (slightly developed dorsal elevations occur in old specimens), smaller body length and relatively shorter endopod of third uropod. Peduncle segments of antenna 2 bear long setae on ventral side. Second and third epimeral plates are less sharply pointed. Few setae exist on antero-ventral margins of epimeral plates.

Description. Head (fig. 6K): inferior antennal sinus deep. Eyes ovoid to reniform, as long as the diameter of first peduncle segment of antenna 1.

Antenna 1 (fig. 2C): shorter than half the body length; setation weak, peduncular segments bear a few distal setae in addition to 1–2 lateral setae groups shorter than the diameter of the segment where they implanted; article 1 stout; primary flagellum with 30–32 articles; accessory flagellum with up to 5 articles.

Antenna 2 (fig. 2B): ventral margins of peduncular segments armed with 4–5 groups of setae as long as or slightly longer than the diameter of the segment on which they insert; setae on dorsal side of the peduncular segments are shorter; flagellum comprises up to 14 segments with flag-like setation; flagellar segments swollen; calceoli on 2–9th segments.

Upper lip (fig. 3C): convex, with minute setae on distal part.

Left mandible (figs. 2F, 3L): incisor with 5 teeth; lacina mobilis with 4 dentitions; molar triturative; second article of palp bears 16 setae; third segment armed with 22 D-setae, 5−6 E-setae; one group of A-setae, and one group of B-setae; C-setae absent.

Right mandible (figs. 3J, K): incisor 5-dentate, lacina mobilis bifurcate.

Lower lip (fig. 3G): inner lobe absent.

Maxilla 1 (figs. 3D, E): inner plate with 15 plumose setae, outer plate with 10 serrated spines, article 2 of palp with 8 sharp spines and 2 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. 3G): inner plate with a diagonal row of 17 plumose setae.

Maxilliped (fig. 3A): inner plate with 3 apical spines and 1 subapical spine, outer plate with a row of 10−12 spines on medial margin and 5–7 pectinate apical setae.

Coxal plate 1 (fig. 2A): slightly dilated on distal margin, with one or three setae on both the anterodistal and posterodistal margins. Coxal plates 2 and 3 subrectangular (figs. 2H, 3H). Coxal plate 2 with 2 short setae on anterodistal corner and 1 seta on posterodistal corner. Coxal plate 3 with 2 short setae on anterodistal corner and 1 seta on posterodistal corner. Ventral margin of coxal plate 4 slightly convex (fig. 3B), with 2 setae on anteriorodistal corner and 6−7 setae on posterior margin. Coxal plates 5−6 (fig. 5C, E) bilobate. Anterior lobe of coxal plate 5 small with 1 seta, posterior lobe with 2 setae on posterodistal corner. Coxal plate 6 with 1 seta on anterodistal and 2 setae on posterodistal corner. Coxal plate 7 (fig. 5G) with 4 setae on both anterior and posterior margins. Coxal gills 2−7 present.

Gnathopod 1 (fig. 2A): basis with long setae (up to 1.5 times longer than the diameter of the segment) on both anterior and posterior margins; carpus and propodus elongate; propodus with three 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 (fig. 2H): basis with long setae (up to 1.8 times longer than the diameter of the segment) on anterior and posterior margins; carpus and propodus elongate; anterior margin of carpus with three groups of long and curled setae; propodus subrectangular, with long setae on both anterior and posterior margins; median spine present, with 4 spines on posterodistal margin; dactylus with 1 seta on outer margin. Inner side of the carpus and propodus bear many groups of long setae.

Pereopod 3 (fig. 3H, I): slender; posterior margins of basis bear many long setae (up to twice longer than the diameter of the segment); merus and carpus densely setose along their posterior margins, the setae on posterior margins are very long (longer than twice of the diameter of the segment where they implanted) and curled; dactylus with 1 plumose seta on outer margin and 2 setae at joint of unguis.

Pereopod 4 (fig. 3B, F): slender; anterior and posterior margins of basis with many long setae (less dense than that of pereopod 3); posterior margins of merus and carpus bear many groups of long curled setae; dactylus with 1 plumose seta on outer margin and 2 setae at joint of unguis.

Pereopods 5–7 (fig. 5C −H): subequal in length; basis of pereopod 5 subrectangular; bases of pereopods 6 and 7 quadrangular and relatively elongated, anterior margins with 3−4 short spines, posterior margins with 10−13 short setae; 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 setae longer than the spines; dactylus with 1 seta on outer margin and 2 setae at joint of unguis.

Epimeral plates 1−3 (fig. 5I): epimeral plate 1 with 8 setae on anterior corner; epimeral plate 2, posterodistal corner rectangular or slightly pointed, with 2 setae on anterior corner and 3 spines on ventral margin; epimeral plate 3, posterodistal corner pointed (never in a form of sharp hook), with 3 setae on anterior corner and 2 spines on ventral margin.

Pleopods 1−3: 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. 5A, B): almost flat (slightly developed dorsal elevations occur in old specimens); each urosomite bears a dorsomedial and two dorsolateral groups of short spines and longer setae on their posterior margins. Each dorsolateral group consisting of a spine and 4−6 longer setae. First and third urosomites bear no spine (6−7 setae only) in their dorsomedian groups while the second urosomite bears two spines and 4−5 slightly longer setae.

Uropod 1 (fig. 2D): peduncle longer than rami, with 1 seta and 2 spines on outer margin; inner margin with 3 marginal and 2 distal spines; outer ramus slightly shorter (about 0.9 times as long as inner ramus) than inner ramus, with 3 spines on inner margin and 2 spines on outer margin; inner ramus with 3 spines on inner margin 1 seta on outer margin.

Uropod 2 (fig. 2E): peduncle with 1 and 2 marginal spines on inner and outer margin, respectively, in addition to 2 distal spines; outer ramus a little shorter than inner ramus (about 0.85 times as long as inner ramus); outer ramus with 2 spines on outer margin and 1 spine on inner margin; inner ramus with 2 spines on both margins.

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

Telson (fig. 3A): deeply cleft; each lobe with 1−2 distal spines together with many longer distal and dorsolateral setae; the length of distal and lateral setae can be about 0.8 and 0.65 times as long as the length of telson, respectively.

Female. Antenna 1 (fig. 6A): peduncle segments with few short setae, setae on ventral margin longer than the others but not longer than diameter of the segment where they implanted; primary flagellum with 27−28 segments; accessory flagellum with 3−4 segments. Antenna 2 (fig. 6B): peduncle segments bear some groups of short setae on dorsal margin; setae on ventral margins almost as long as the diameter of the segment where they implanted; primary flagellum with 10−11 segments; the setation of flagellar segments seems flag-like, each segment is armed with a transverse row of setae on the inner surface, together forming a flag-like brush ( Karaman and Pinkster 1977); calceoli absent. Gnathopod 1 (fig. 6C): basis with 6 and 9 long setae on both anterior and posterior margins, respectively; setae can be up to 2 times longer than the diameter of basal segment; propodus ovate with two groups of setae on anterior margin, palm not as oblique as that of male, with 5 spines on posterior corner, dactylus with 1 seta on outer margin. Gnathopod 2 (fig. 6D): carpus and propodus elongate, propodus subrectangular, medial palmar spine absent, bearing 4−5 spines on posterior corner and some spines on inner margin. Pereopods 3−7 (figs. 6E, G, H, I) sparser than those of male in setation, especially on pereopod 3 less setae occur on the posterior margins of merus and carpus than those in males (fig. 6I). Uropod 3 (fig. 2G), inner ramus shorter than outer ramus; inner ramus with some plumose setae and 2 spines on outer margin; article 2 of outer ramus longer than the spines on distal part of first article; inner margin of outer ramus with a few plumose setae; outer margin of outer ramus with a few plumose setae and 2 groups of spines accompanying some simple setae longer than the spines. Oostegites are broad, ovate and occur on pereopods 2 to 5.

Etymology. The new species is named in honour of Dr. Esat Tarık Topkara (Ege University, Faculty of Fisheries, Bornova, Izmir). The name is a noun in the genitive singular.

Habitat. Specimens were sampled from a pebbly-gravely zone of a fast running stream with poor aquatic vegetation. Some water quality parameters measured on 21.10.2006 were as follows: water temperature 10.0°C, dissolved oxygen 7.1 mg /l, oxygen saturation 67%, pH 7.9–7.8, salinity 0.1 ppt and conductivity 217 µS25°C.

Remarks. At first sight, this species looks very similar to Gammarus agrarius G. Karaman, 1973 , because of having flag-like setation on the flagellar segments of antenna 2 and a rich setation on the posterior margin of pereopods 3 and 4. However, the body length of mature specimens distinctly shorter than that of G. agrarius (fig. 7). Also, in the males of the new species, the length of the setae on ventral margins of peduncular segments of the second antenna are longer; the endopod/exopod ratio of third uropod is low; the urosome segments have no dorsal elevations in most of the specimens; the second and third epimeral plates are never in a form of a sharp hook, epimeral plates have less number of setae on anterior margins.

This species resembles also Gammarus monspeliensis Pinkster, 1972 and Gammarus syriacus Chevreux, 1895 in the setation of pereopod 3 and 4. It differs from G. monspeliensis by the shorter flagellum of antenna 1. In addition, the new species has many longer setae on ventral margins of peduncular segments of antenna 2. G. topkarai n. sp., also differs from G. m o n s p e l i e n s i s in the absence of dorsal elevations on urosome segments and in the shape of second and third epimeral plates. Distribution areas of the new species and G. monspeliensis are quite different. G. monspeliensis is known only from the River Lez, French ( G. Karaman & Pinkster, 1977).

The species also differs from G. syriacus in the shape and setation of flagellar segments of antenna 2, in the absence of dorsal elevations on urosome segments, in the shape of epimeral plates and in the shape and setation of telson lobes.

When G. Karaman (1973) reported G. agrarius as a new subspecies of G. monspeliensis , he presented detailed information and drawings of extremities of the new subspecies. He also reported some variations such as the number of the setae on epimere, telson, and uropod 3. Similarly, G. Karaman & Pinkster (1977) pointed out the variability on the endopod/exopod ratio (0.75 to 0.88) of third uropod. I also measured the endopod/exopod ratio of 10 paratypes of the present species, the ratios were as follows: 0.75, 0.70, 0.71, 0.71, 0.74, 0.70, 0.63, 0.72, 0.70 and 0.65. In general, the endopod of third uropod looks smaller than that of G. agrarius . Maximum ratio value of the paratypes was found as 0.75 which is equal to the minimum ratio value that of G. agrarius .

There is a confusion on the type locality of G. agrarius where is reported as Karakugu near Pınarbası, Dinar, Konya ( G. Karaman, 1973; G. Karaman & Pinkster, 1977). Konya is a city placed in central part of Anatolia but not has a district named as Dinar or Karakugu. In fact, Dinar is a district of Afyon which is a city placed western part of Anatolia. Similarly, Kararakuyu (=Karakugu) is a place in Dinar where rich rheocrene habitats occur (personal observation). In this case, the type locality of G. agrarius is most probably Karakuyu, Dinar, Afyon province.