Gammarus sirvannus, Hekmatara, Maryam, Sari, Alireza & Baladehi, Mohammad-Hadi Heidary, 2011

Hekmatara, Maryam, Sari, Alireza & Baladehi, Mohammad-Hadi Heidary, 2011, Two new Gammarus species (Crustacea: Amphipoda: Gammaridae) from Zagros Mountains, Iran, Zootaxa 2894, pp. 39-57 : 49-56

Gammarus sirvannus sp. n.

( Figs. 8–13 )

Type locality. Sirvan river (Paveh branch), 25 Km west of Paveh city, Kermanshah province, Iran (N 35º 0 7ʹ, E 46º 15ʹ), altitude 694 m (locality 5).

Material examined. One male (holotype), body length 15.9 mm, one female (allotype), body length 12.4 mm, few paratypes. ZUTC, Amph. 2262, September 2007, collected by M. Hekmatara. Descriptions were based on the holotype and were compared to some paratypes for variations.

All specimens including holotype are deposited in the Zoological Museum of the University of Tehran ( ZUTC, Amph. 2262).

Diagnosis. A medium sized species; it differs from other similar taxa in the following distinct characters: eyes longer than the diameter of the first peduncular article of antenna 1; the first article of mandible palp with one long seta; gnathopod 1 Coxal plate wide and dilated distally, partially covering the head; pereopod 6 and 7 basis with projecting and overhanging postero-distal corner; poorly setose pereopods 5–7 posterior margin.

Etymology. The name sirvannus refers to the type locality.

Description. Male: Body length 16.2 mm. Head: Lateral head lobe truncate, anterior lower part of the head not extended; eyes reniform and longer than the diameter of the first peduncular article of antenna 1 ( Fig. 8 , C).

Antenna 1: Longer than antenna 2, flagellum with 26 articles, armed with very short setae, peduncular articles 1>2>3, accessory flagellum with four articles ( Fig. 8 , A).

Antenna 2: The fourth and the fifth peduncular articles almost equal, highly setose, flagellum with 11 articles, armed with long simple setae; gland cone pointed, rather slender, half length of the third peduncular article, no calceoli ( Fig. 8 , B).

Mandible Palp: The first article with one long setae, 10 long setae on the second article, the third article with a comb-like row of 30–33 D-setae, 5–7 long E-setae, two groups of A-setae, no B group ( Fig. 8 , D).

Maxilla 1: Palps asymmetric; left palp with two median spines and two short setae, one subapical spine on its outer margin ( Fig. 8 , F); right palp with two robust tooth-like spines, one longer separate subapical spine on its outer margin with one subapical short setae opposed by one smaller spine, anterodistally ( Fig. 8 , E).

Gnathopod 1: Coxal plate wide and dilated distally, partially covering the head, antero-distal corner with 2–3 and postero-distal corner with one short seta; basis with long setae on anterior and posterior margins; ischium with a postero-distal row of setae; carpus triangular, anterior margin with two groups of setae, carpus posteriorly with rows of plumose setae; propodus poorly setose armed with a large and 1–2 smaller medial palmar and a palmar angle spine, posterior margin with a row of two groups of small spines (each having 1–2 spine(s), a row of spines on the posterior sub-margin; three groups of setae at propodus anterior margin; a group of three setae very close to medial palmar spines; two groups of short setae on palmar surface ( Figs. 9 , A & B).

Gnathopod 2: Coxal plate distally narrower than proximal part, two short setae on antero-distal corner and one on the postero-distal; basis with long setae on anterior and posterior margins; ischium with a postero-distal row of setae; carpus triangular-shaped, anterior margin with two groups of setae and posteriorly with rows of plumose setae; palm subrectangular armed with a medial palmar and three palmar angle spines, three spines behind them; 4– 5 groups of setae on palmar surface, four groups of setae at propodus anterior margin ( Figs. 9 , C & D).

Pereopod 3: Coxal plate rectangular and rounded distally, with 2–3 very short setae at the antero-distal and one at the postero-distal margins; basis with some long setae; merus and carpus posteriorly with dense groups of setae 2–3 times longer than the diameter of the segments and at the anterior margin with two groups of one spine and 1–2 longer setae and a group of long setae and a spine antero-distally; carpus with three groups of spines and 3–4 groups of setae on posterior margin and a long spine and a group of longer setae implanted both antero and postero-distally; propodus with five groups of spines and 2–3 short setae distally ( Fig. 9 , E).

Pereopod 4: Coxal plate wide and emarginated with 2–3 small setae on antero-distal margin and 5–6 on postero-distal margin; segments similar to pereopod 3, but with rather shorter setae and less numerus, Anterior margin of merus with just one spine and two short setae, one long spine implanted antero-distally among a group of simple setae; carpus has three groups of spines among most groups of short setae; propodus with four groups of spines and few short setae ( Fig. 10 , A).

Pereopod 5: Basis subrectangular, postero-distal corner rounded, posterior margin with 12 short setae, anterior margin with 4–6 spines, anterior margin of merus with two groups of spines among few short setae and one group of two short setae, posterior margin with two groups of spines; carpus anteriorly with two groups of spines and 0–2 short setae; propodus having 4–5 groups of spines ( Fig. 10 , B).

Pereopod 6: Basis with projecting and overhanging postero-distal corner, posterior margin of basis with 13 setae and anterior margin with 4–5 spines; other segments are similar to pereopod 5 ( Fig. 10 , C).

Pereopod 7: Basis with projecting and overhanging postero-distal corner, antero proximal part of basis with two long setae and anterior margin with 5–6 spines, posterior margin with 14 short setae; anterior margin of meruspropodus with some groups of spines and short setae ( Fig. 10 , D).

Epimeral plate 1: Antero-distal margin rounded with few long setae, posterior corner not pointed, posterior margin with five short setae ( Fig. 11 , E).

Epimeral plate 2: Antero-distal margin slightly lobate, posterior corner slightly pointed with five short setae and three spines on lower margin ( Fig. 11 , F).

Epimeral plate 3: Anterior corner slightly lobate, posterior corner more pointed than epimeral plate 2, four short setae, and three spines on lower margin ( Fig. 11 , G).

Urosomites 1–3: with slight dorsal humps, urosomite 1 armed with two mid-dorsal spines and five setae, three dorso-lateral spines and four setae; urosomite 2 armed with two mid-dorsal spines and three setae, three dorso-lateral spines and 3–4 setae; urosomite 3 with two mid-dorsal spines and three setae ( Fig. 10 , E).

Uropod 1: Longer than uropod 2, mid-dorsal margin of peduncle with two spines, endopodite and exopodite with some mid-dorsal and three terminal spines ( Fig. 11 , A).

Uropod 2: Exopodite slightly shorter than endopodite, both rami with some mid-dorsal and terminal spines, mid-dorsal margin of peduncle with one spine ( Fig. 11 , B).

Uropod 3: Densely setose, endopodite about two-third of exopodite, peduncle shorter than rami, distal exopodite article minute, inner margin of both endo and exopodite and outer margin of endopodite with plumose setae, but outer margin of exopodite with simple setae, without any plumose setae ( Fig. 11 , C).

Telson: Lobes almost twice as long as width, right lobe armed with three distal spines and three setae and three subdistal setae, left lobe armed with two distal spines and five setae and two subdistal spines and two setae ( Fig. 11 , D).

Female: Smaller than male (12.4 mm.), antenna 1 and 2 rather shorter and poorly setose, pereopod 3 and 4 with fewer setae, pereopod 5 and 6 with some long setae on posterior margin of basis. Pereopod 7 with one long setae on upper corner of anterior margin of basis and three groups of setae on posterior margin of propodus. Dorsal surface of peleon articles 2 and 3 with many short setae and long setae on distal part of articles. Uropod 3 shorter and less setose than male. Oostegite 1 (of gnathopod 2) is illustrated. ( Figs. 12–13 ).

Discussion. Similarities and differences of Gammarus sirvannus with some of the morphologically closest species are discussed below.

Three distinctive characters for Gammarus duebeni- group reported by Stock et al 1998 are: large, elongated eyes (versus small, rounded to reniform in members of the G. p u l e x -group), the presence of a protruding posteroventral lobe on the basis of pereopods 5 to 7, endopodite of uropod 3 half or less than the length of exopodite. However, according to Pinkster et al. (1970) and Khalaji-Pirbalouty & Sari, 2006 the endopodite length is not consistent.

Nevertheless, Gammarus sirvannus shows similarities with Gammarus duebeni Liljeborg, 1852 by having large, elongated eyes (compared to small, rounded to reniform eyes in members of G. pulex -group); protruding postero-ventral lobe on the basis of pereopods 5 to 7 and outer margin of the exopodite armed with simple setae. In contrast, Gammarus duebeni has longer and more numerous setae on pereopods 5 to 7 and on the posterior margin of the epimeral plates. The endopodite of uropod 3 is half or nearly more than half the length of the exopodite; antenna 2 bears calceoli.

Gammarus sirvannus with elongated eyes and wide gnathopod 1 coxal plate partially covering the head is similar to Gammarus lobifer Stock et al., 1998 inhabiting Kohgiluye-Buier Ahmad Province (South-east to the type location). However, Gammarus sirvannus is distinguished from G. lobifer with the following features: different shape of head, shorter gland cone than the peduncular article of antenna 2, propodus of gnathopod 2 almost rectangular (versus ovoid in G. lobifer ), propodus of pereopod 3 without many long setae (only with few short setae), pereopod 4 with less and shorter setae in comparison with pereopod 3, endopodite of uropod 3 longer than the half length of exopodite, outer margin of exopodite lacking plumose setae, dorsal surface of urosomite armed with short setae.

Some characters of Gammarus sirvannus are shared with Gammarus balutchi Khalaji-Pirbalouty & Sari, 2006 reported and described from Chaharmahal-va-bakhtyari Province (South-east to the type location): eyes are longer than the diameter of the first peduncular article of antenna 1 and shape of epimeral plates. But G. balutchi markedly differs by having rounded head lobe; coxal plate of gnathopod 1 is not wide unlike wide and distally dilated coxal plate partially covering the head in the new species; without projecting postero-distal corner on the basis of pereopod 6 and 7; uropod 3 exopodite more than twice as long as endopodite and outer margin of exopodite with plumose and simple setae.

G. k o m a re k i has similarities with G. sirvannus , including long setae on antenna 2, short gland cone, ratio of length /width in telson and setation of merus and carpus in pereopod 3, but the different features are following: the small eyes, as long as or shorter than the diameter of the first peduncle of segment of antenna 1, rounded lateral head lobes, anterior lower part of head extended forward, mandible palp first article without seta, coxal plate in gnathopod 1 are not dilated distally, no distinct projecting and overhanging postero-distal corner in basis of pereopod 6 and 7 and setation of pereopod 5–7.

Gammarus proiectus Stock et al., 1998 which was firstly reported and described from Markazi province (South-east to the type location) resembles Gammarus sirvannus with the overhanging postero-distal lobe on the basis of pereopods 6 and 7 and has a slightly similar shape of epimeral plates, but it differs in reniform, small eyes (smaller than the diameter of first peduncular article of antenna 1), rounded lateral head lobes, anterior lower part of head extended, antenna 2 densely covered with long, curved setae, telson lobes less than twice as long as wide, and uropod 3 endopodite only slightly shorter than exopodite.

This species looks like Gammarus loeffleri Zamanpoore et al., 2010 , because of having eyes elongated (longer than the diameter of the antenna 1); similar antenna 1 and slightly similar setation of antenna 2; telson lobes about twice as long as width; uropod 3 endopodite length less than 2/3 of the exopodite. On the other hand, G. loeffleri has lateral head lobes more or less rounded, anterior lower extension of the head weakly developed; antenna 2 bears calceoli on its flagellum; mandible palp first article without seta, while G. sirvannus has one long seta; pereopod 3 propodus with 5 groups of one small spine and some longer setae; pereopod 4 all segments bear groups of setae at posterior margin, about 1–2 times as long as the diameter of the segments; postero-distal protruding lobe of pereopod 6–7 poorly developed, merus and carpus anterior margin of pereopods 5–7 with some groups of long spines and longer setae, about 1–2 times than the segment’s width, with less dense setae at posterior; epimeral plate 2 and 3 more sharply pointed and posterior dorsal of urosomites do not have clear elevations, but each epimere is placed in a lower level than its anterior segment and dorsal armature consists of some 5–6 long setae sometimes mixed with a spine on laterals and mid-dorsal surface.

G. parthicus can be distinguished by having: the small eyes, as long as or shorter than the diameter of the first peduncle of segment of antenna 1, anterior lower part of head extended forward, mandible palp first article without seta, coxal plate in gnathopod 1 are not dilated distally, no distinct projecting and overhanging postero-distal corner in basis of pereopod 6 and 7 and spines and setae on postero-distal corner of basis in pereopod 6 and 7.

Variability. The examined paratypes show variations in some characters such as: the number of terminal spines in uropod 1 and 2, number of setae and spines on distal and subdistal position of telson and the number of setae and spines in palp of right and left maxilla.

Figures

FIGURE 8. Gammarus sirvannus sp. n., holotype, 3, 15.9 mm., from Sirvan River, W of Paveh. A (A 1), B (A 2) and C (H) on scale i; D (MNDP) on scale ii; E (PRMX) and F (PLMX) on scale iii.

FIGURE 9. Gammarus sirvannus sp. n., holotype, 3, 15.9 mm., from Sirvan River, W of Paveh. A (GN 1) and C (GN 2) on scale i; B (PGN 1) and D (PGN 1) on scale ii; E (P 3) on scale iii; F (dactyl of P 3) on scale iv.

FIGURE 10. Gammarus sirvannus sp. n., holotype, 3, 15.9 mm., from Sirvan River, W of Paveh. A (P 4), B (P 5), C (P 6) and D (P 7) on scale i; E (US) on scale ii; F (dactyl of P 4), G (dactyl of P 5), H (dactyl of P 6) and I (dactyl of P 7) on scale iii.

FIGURE 11. Gammarus sirvannus sp. n., holotype, 3, 15.9 mm., from Sirvan River, W of Paveh. A (U 1) and B (U 2) on scale i; C (U 3) on scale ii; D (T) on scale iii; E (EP 1), F (EP 2) and G (EP 3) on scale iv.

FIGURE 12. Gammarus sirvannus sp. n., Allotype, Ƥ, 12.4 mm., from Sirvan River, W of Paveh. A (A 1) and B (A 2) on scale i; C (P 3), D (P 4), E (Basis of P 5) and F (Basis of P 6) on scale ii; G (dactyl of P 3) and H (dactyl of P 4) on scale iii.

FIGURE 13. Gammarus sirvannus sp. n., Allotype, Ƥ, 12.4 mm., from Sirvan River, W of Paveh. A (Pleon) on scale i; B (O 1), C P 7) D P 7) on E (U 3) on