Gammarus hegmatanensis, 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 : 40-49

publication ID	https://doi.org/ 10.5281/zenodo.202031
DOI	https://doi.org/10.5281/zenodo.3501095
persistent identifier	https://treatment.plazi.org/id/A17F87A0-FFB4-FFEE-F8B8-F89AFDA6D107
treatment provided by	Plazi
scientific name	Gammarus hegmatanensis
status	sp. nov.

Treatment

Gammarus hegmatanensis View in CoL sp. n.

( Figs. 2–7 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Type locality. Gardaneh Asadabad spring, W of Hamadan city, Hamadan Province, Iran (N 34º 49ʹ, E 48º 0 4ʹ), altitude 1677 m (locality 1).

Material examined. One male (holotype), body length 18 mm, one female (allotype), body length 15.1 mm, few paratypes. ZUTC, Amph. 2249, September 2007, collected by M. Hekmatara. Additional samples: Chavaneh- Lar qanat and spring, Hame-kasi village, 41 Km NW of Hamadan (N 34º 57ʹ, E 48º 0 9ʹ), altitude 2109 m (locality 2, 3). River of Ali-Abad village, Hamadan-Ghorveh road, 30 Km NW of Hamadan, (N 34 º 56ʹ, E 48 º 15ʹ), altitude 1830 (locality 4). 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. 2249).

Diagnosis. A medium–large species; it differs from other similar taxa by following distinct characters: the most remarkable feature of this species is the shape of epimeral plate 3, with a very sharply pointed and extended posterior corner and a distinct lobate anterior corner; no protruding lobe at postero-distal corner of pereopod 7 basis; antenna 2 flagellum armed with numerous long setae, the fifth peduncular article longer than the fourth and highly setose; pereopods 5–7 posterior margin poorly setose; uropod 3 endopodite length about 80% of exopodite.

Etymology. The epithet of hegmatanensis derived from “Hegmataneh”; the ancient city whose old remains are found within Hamadan city. The type locality is in the vicinity of Hamadan city.

Description. Male: Body length 18 mm. Head: Lateral head lobe rounded, anterior lower part of head extended forward; eyes elliptical to slightly reniform, smaller than diameter of first peduncular article of antenna 1 ( Fig. 2 View FIGURE 2 , C).

Antenna 1: Longer than antenna 2, flagellum with 25–27 articles, armed with very short simple setae, peduncular articles 1>2>3, accessory flagellum with four articles ( Fig. 2 View FIGURE 2 , A).

Antenna 2: Fifth peduncular article longer than the fourth, highly setose; flagellum with 8–10 articles, armed with long simple setae. Their size twice or longer than the diameter of the corresponding antennal articles; length of the first flagellar article two times the second; gland cone is pointed, shorter than the third peduncular article; calceoli not present ( Fig.2 View FIGURE 2 , B).

Mandible palp: First article without setae; second segment with ventral setae; 6–7 proximal setae shorter than the width of the segment and 8–10 closely placed distal setae longer than the width of the segment; inferior margin of the third segment armed with a comb-like row of 32–37 D-setae, 5–6 long E-setae, one group of B-setae and one group of A-setae ( Fig. 2 View FIGURE 2 , D).

Maxilla 1: Palps asymmetric; left palp with seven median spines, one subapical spine on its outer margin and three short setae ( Fig. 2 View FIGURE 2 , F); right palp with five robust tooth-like spines, one longer separate subapical spine on its outer margin with one short seta opposed by one smaller spine, anterodistally; lateral margin with two short setae ( Fig. 2 View FIGURE 2 , E).

Gnathopod 1: Coxal plate distally not or slightly wider than proximally, rounded corners with a postero-distal seta and two to three antero-distal setae. Basis with long simple setae on anterior and posterior margins. Ischium with a postero-distal row of setae. Carpus triangular and anterior margin with two groups of simple setae, posteriorly with plumose rows of setae. Propodus poorly setose, armed with one mid-palmar and one palmar angle spine, six spines at posterior palmar margin, several spines on posterior sub-margin, two groups of setae on propodal surface, one group of setae on the propodal anterior margin; dactylus long ( Figs.3 View FIGURE 3 , A & B).

Gnathopod 2: Distal end of coxal plate finely wider than proximal, rounded corners with a seta postero-ventrally and three setae antero-ventrally. Basis with long setae on anterior and posterior margins. Ischium with postero-distal row of setae. Carpus triangular and anterior margin with two groups of setae, posteriorly with plumose rows of setae. Propodus densely setose, palm subrectangular with one mid-palmar spine, 2–3 palmar angle spines, five groups of setae on propodal surface, three groups of setae at the propodal anterior margin ( Figs. 3 View FIGURE 3 , C & D).

Pereopod 3: Coxal plate rectangular and rounded distally; with four very short setae antero-distally and one postero-distally; basis with some long simple setae; basis–carpus bear groups of long setae at posterior margin; posterior margin of merus with several groups of dense setae and anterior margin with two groups of one (or none) short seta and one spine and a group of long setae and a spine antero-distally; carpus with three groups of spines and 5–6 groups of setae on posterior margin and a long spine and a group of longer setae implanted on both its antero and postero-distal; propodus with five groups of spines and some long setae ( Fig. 4 View FIGURE 4 , E).

Pereopod 4: Coxal plate wide and emarginated with three small setae on antero-distal margin and several setae on postero-distal margin; segments similar to pereopod 3, but setae are much shorter and the number of setae and groups is lower; anterior margin of merus with just one spine, one spine implanted antero-distally among a group of simple setae; carpus has four groups of spines among most groups of short setae; propodus with five groups of spines and few short setae ( Fig. 4 View FIGURE 4 , A).

Pereopod 5: Basis subrectangular, postero-distal corner rounded, posterior margin with 11 short setae, anterior margin with 4–5 spines, anterior margin of merus with three groups of short setae (without spine) and posterior margin with one spine; carpus with two groups of anterior spines and 0–3 short setae; propodus bears five groups of spines anteriorly ( Fig. 4 View FIGURE 4 , B).

Pereopod 6: Longer than pereopod 5; basis slender and posterior margin with 10 setae and anterior margin with 2–3 spines; other segments are similar to pereopod 5 ( Fig. 4 View FIGURE 4 , C).

Pereopod 7: Basis wider proximally, no protruding lobe at postero-distal corner of basis, antero-proximal part of basis with three long setae and anterior margin with three spines, posterior margin with 14 short setae; merus anteriorly with 2–3 groups of spines and short setae; anterior margin of carpus and propodus with some groups of spines without simple setae ( Fig. 4 View FIGURE 4 , D).

Epimeral plate 1: Antero-distal margin rounded with some long setae, posterior margin with three short setae ( Fig. 5 View FIGURE 5 , E).

Epimeral plate 2: Antero-distal margin lobate, posterior margin moderately pointed with four short setae ( Fig. 5 View FIGURE 5 , F).

Epimeral plate 3: With very sharply pointed posterior corner and markedly lobate antero-distal margin, some short setae on posterior margin and three spines on lower margin ( Fig. 5 View FIGURE 5 , G).

Urosomites 1–3: With moderate dorsal elevation, urosomite 1 armed with four dorso-medial spines and three setae and two dorso-lateral spines and three setae; urosomite 2 with 2–3 dorso-medial spines and four setae and 1– 2 dorso-lateral spines and two setae; urosomite 3 armed with three dorso-medial spines and 7–8 setae ( Fig. 4 View FIGURE 4 , E).

Uropod 1: Longer than uropod 2, mid-dorsal margin of peduncle with two spines, endopodite and exopodite with two mid-dorsal and some terminal spines ( Fig. 5 View FIGURE 5 , A).

Uropod 2: Exopodite slightly shorter than endopodite, both rami with two mid-dorsal and some terminal spines ( Fig. 5 View FIGURE 5 , B).

Uropod 3: Endopodite length about 80% of exopodite, distal article minute; outer margin of exopodite with simple setae, without any plumose setae; inner margin of endopodite and exopodite and outer margin of endopodite with plumose setae ( Fig. 5 View FIGURE 5 , C).

Telson: Lobes more than twice as long as width with 2–4 subdistal long setae, one distal spine and some long setae ( Fig 5 View FIGURE 5 , D).

Female: Smaller than male (15.1 mm.), antenna 1 and 2 shorter, propodus of gnathopod 1 wider than propodus of gnathopod 2, propodus of gnathopod 1 and 2 smaller than in male, pereopod 3,4 similar to male, pereopod 5 similar to male but with some long setae on antero-inferior margin of basis. In female, compared to male, merus and carpus of pereopod 5–7 with more and longer setae, uropod 3 and telson are smaller than male and less setose. Oostegite 1 (of gnathopod 2) is illustrated ( Figs. 6–7 View FIGURE 6 View FIGURE 7 ).

Discussion. The similarities and differences of Gammarus hegmatanensis with some of the morphologically closest species are discussed below.

The most remarkable feature of Gammarus hegmatanensis is the shape of epimeral plate 3, with a very sharply pointed and an extended posterior corner and distinct lobate anterior corner. The very sharply pointed posterior corner resembles G. syriacus Chevreux, 1895 , which has been reported by Stock et al., 1998, from Kohgiluye-Buier Ahmad Province (South-east of the location, but not bounded). However, Gammarus hegmatanensis can be distinguished from G. syriacus by lateral head lobes that are more rounded, anterior lower part of head more extended, the second and the third peduncular articles of antenna 1 not equal, flagellum with 26 articles; the fourth and fifth peduncular articles of antenna 2 not equal, flagellum has only eight articles, highly setose with long setae; posterior margin of pereopod 4 has much shorter setae and the number of setae and groups is lower; anterior margin of pereopods 5–7 is spinous (only with few short setae) versus long and numerus setae in G. syriacus ; epimeral plate 1 and 2 without extended posterior corner and epimeral plate 2 and 3 with very lobate anterior corner. Moreover, pereopod 6 in G. syriacus has a group of spines and setae at antero-inferior corner of basis; pereopod 5–7 basis with groups of marginal setae anteriorly, and pereopod 7 has a group of several setae at sub-marginal of antero-proximal part.

Gammarus hegmatanensis View in CoL is similar in some characters such as antenna 1 and 2 and gnathopod 1 to G. parthicus Stock et al., 1998 View in CoL reported and described from Markazi Province (the Eastern neighbouring province). However, G. parthicus View in CoL differs from new species markedly with truncate lateral head lobes (versus rounded lateral head lobes in Gammarus hegmatanensis View in CoL ); different shapes of gnathopod 2 and epimeral plate 2; anterior corner of EP3 is not lobate and posteriorly more weakly pointed than the one in new species; basis of pereopod 5–7 anteriorly with some groups of marginal setae; existence of one group of setae and spines at postero-distal corner of basis of pereopod 6 and 7; uropod 3 outer margin of exopodite has plumose setae and telson lobes are very elongate and the length of lobes is longer 2.5 times than its width.

Gammarus zagrosensis Zamanpoore et al, 2009 View in CoL , described firstly in the Southern Zagros Mountains, has similar head lobe and antenna 1 as the new species; in contrast it has longer antenna 2 with 11–17 flagellar articles armed with calceoli, short setae not forming a flag-like brush. Carpus and propodus of pereopod 3 bear some groups of long setae (2–3 times longer than the diameter of the segments). Merus and carpus of pereopod 4 have some groups of long setae. Anterior basis of pereopod 5 and 6 has one to two groups of 3 marginal setae and one seta at sub-margin of antero-proximal part of basis. Pereopod 6 bears 1–3 setae at the inner surface of the posterodistal corner of basis. Pereopod 7 is set with few long setae at postero-inferior corner basis. EP3 moderately pointed in posterior corner with 4–7 long setae on distal sub-marginal area of the second and the third epimeral plate. Dorsal surface of metasomites posteriorly is covered with very short setules.

G. sepidannus Zamanpoore et al, 2009 View in CoL , has been described as a sympatric species with G. zagrosensis View in CoL from southern Zagros Mountains. It differs from the new species in the following ways: Antenna 2 flagellum with 11–14 articles, gland cone is slightly longer than the third peduncle segment and peduncle segments 4 and 5 enjoy the same length. All segments of pereopod 3 and 4 posteriorly with dense groups of setae about 1–2 times the diameter of the segments. Pereopod 5–7 anterior margin of basis with a row of 4–8 setae, 3–4 spines and 1–3 long setae at antero-proximal inner surface. Endopodite of Uropod 3 half the length of the exopodite and plumose setae only on outer margin of exopodite and endopodite. Postero-inferior corner of EP3 is weakly to moderately pointed.

Finally, G. komareki View in CoL shares some features with G. hegmatanensis View in CoL , like small eyes, long setae on antenna 2, more or less the same ratio of U3 endo- and exopodite, but it has some differences with this new species including short gland cone, shape of basis in pereopod 7, shape of EP 2 & 3 and elevation of urosomites.

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