Niphargus khwarizmi, Hekmatara & Zakšek & Baladehi & Fišer, 2013

Hekmatara, M., Zakšek, V., Baladehi, M. Heidari & Fišer, C., 2013, Two new species of Niphargus (Crustacea: Amphipoda) from Iran, Journal of Natural History 47 (21 - 22), pp. 1421-1449 : 1434-1442

Niphargus khwarizmi sp. nov.

( Figures 7–11 )

Type locality

Cheshmeh Kahriz (Qanat), Kharvana village, 141 km north of Tabriz, East Azarbaijan Province, Iran. Coordinates: 38 ◦ 41, N, 46 ◦ 10, E ( Figure 1 ).

Material examined

Holotype is 12 mm long, male, partially damaged. Paratypes include a dissected female (11.1 mm) and male (11.1 mm), both partially damaged. Smaller paratypes were left intact (two males and two females).

Etymology

The species is named in honour of Abū ‘Abdallāh Muhammad ibn Mūsā Khwārizm¯ı (c. 780 to c. 850), a Persian mathematician, astronomer and geographer, a scholar in the House of Wisdom in Baghdad. In the twelfth century Latin translations of his work on the Indian numerals, introduced the decimal positional number system to the western world. In Renaissance Europe he was considered the original inventor of algebra. He revised Ptolemy’s Geography and wrote on astronomy and astrology.

Diagnosis

Mid-sized slender niphargids. Pleonites I–III with 5–10 setae along the dorsoposterior margin. Epimeral plates II–III subrounded. Urosomite I postero-dorsolaterally with one slender seta; urosomite II postero-dorsolaterally with two slender or spiniform setae. Each telson lobe with three apical spiniform setae; no mesial spiniform setae; lateral margins with one or two spiniform setae and may be one dorsal spiniform seta. Coxal plates sexually dimorphic, in males longer than deep, in females slightly deeper than long. Mouthparts as in majority of Niphargus species. Gnathopods propodi trapezoidal and small. Dactyli of pereopods III–VII with single spiniform seta at the base of nail. Pleopods with two retinacles. Uropod I and III sexually dimorphic. Endopodite: exopodite lengths is 1: 1.45–1.55 in uropod I in males, in females inner ramus is shorter. Uropod III measures up to 0.40 of body length, endopodite measures 0.65–0.70 of protopodite length, exopodite rod-shaped, distal article 0.65–1.00 of the proximal article length.

Description of holotype and dissected paratypes

Head and trunk ( Figure 7 ). Body length up to 12 mm. Head length up to 10% of body length; rostrum absent. Pereonites I–VI without setae; pereonite VII with two slender posteroventral setae.

Pleonites I–III with 5–10 setae along the dorsoposterior margin. Epimeral plate II roughly perpendicular, posterior and ventral margins distinctly convex; ventroposterodistal corner indicated with seta; along ventral margin four or five spiniform setae; along posterior margin seven to nine thin setae. Epimeral plate III inclined, posterior and ventral margins distinctly convex; ventro-posterodistal corner indicated with seta; along ventral margin two to four spiniform setae; along posterior margin seven or eight thin setae.

Urosomite I postero-dorsolaterally with one slender seta; urosomite II posterodorsolaterally with two slender or spiniform setae; urosomite III without setae. At the base of uropod I one spiniform seta.

Telson length: width ratio is 1: 0.90–1.00; cleft 0.50–0.75 of length. Telson spiniform setae (per lobe): three apical spiniform setae of 0.25–0.33 telson length; mesial margins without spiniform setae; lateral margins with one or two spiniform setae, dorsal surface normally without spiniform setae, rarely one spiniform seta occurs. Pairs of plumose setae inserted mid-laterally.

Antennae ( Figure 8 ). Antenna I 0.35–0.40 of body length. Flagellum with 20–22 articles; each article with one aesthetasc. Peduncle articles in ratio 1: 0.65–0.75: 0.30–0.35. Proximal article of peduncle dorsodistally slightly produced. Accessory flagellum biarticulated; distal article shorter than one half of proximal article length.

Length ratio antenna I: antenna II as 1: 0.45–0.50. Flagellum of antenna II with 9–10 articles; each article with setae and an elongate sensillum of unknown function. Peduncle articles lengths 4: 5 is 1: 0.80–0.90; flagellum 0.75–0.80 of the length of the articles 4+5.

Mouthparts ( Figure 8 ). Labrum typical; inner lobes of labium longer than half of the outer lobes.

Left mandible: incisor with five teeth, lacinia mobilis with four teeth; between lacinia and molar row of thick serrated setae, long seta at the base of molar. Right mandible: incisor processus with four teeth, lacinia mobilis with several small denticles, between lacinia and molar a row of thick serrated setae. Length of mandibular palp article 2 is 0.95–1.00 of the length of article 3 (distal article). Proximal palp article without setae; the second article with 8–14 setae; distal article with four setae in A group; three or four groups of B setae; 20–22 D setae; three or four E setae.

Maxilla I distal palp article with eight or nine apical and subapical setae. Outer lobe of maxilla I with seven uni-, bi- or pluri-toothed stout setae; inner lobe with two setae.

Maxilla II inner lobe slightly shorter than outer lobe; both of them setose apically and subapically.

Maxilliped palp article 2 with eight or nine rows of setae along inner margin; distal article with a dorsal seta and a group of setae at the base of the nail. Maxilliped outer lobe with 10–13 flattened thick setae mesially, and seven or eight serrated setae apically and subapically; inner lobe with four flattened thick setae apically and five to seven apical and subapical serrated setae.

Coxal plates, gills ( Figures 9, 10 ). Coxal plate I of flattened rhomboid shape, anteroventral corner subrounded; anterior and ventral margin of coxa I with 9–11 setae. Coxal plate II width: depth is 1: 1.05–1.10 (males) and 1: 0.90 (female); anterior and ventral margin with 9–13 setae. Coxal plate III width: depth ratio is 1: 1.05–1.10 (males) and 1: 0.90 (female); along anteroventral margin 8–11 setae. Coxal plate IV width: depth ratio is 1: 1: 1.15–1.20 (males) and 1: 1.05 (female); posteriorly slightly concave (0.05–0.10 of coxa width); along anteroventral margin 10–11 setae. Coxal plates V–VI: anteriorly developed lobe; posterior margin with three or four setae. Coxal plate VII shaped like a half-egg, at posterior margin 1 seta. Gills II–VI ovoid and reach up to the mid of basis.

Gnathopod I ( Figure 9). Ischium with six to nine posterodistal setae. Carpus 0.55–0.65 of basis length and 0.80–0.90 of propodus length. Anterior margin of carpus with the distal group of setae accompanied with additional pair of subapical–mesial setae; carpus posteriorly with transverse rows of setae proximally, a row of lateral setae; posteroproximal bulge large (but less than one-third of carpus length), positioned proximally. Propodus trapezoidal, palm convex and slightly inclined. Along posterior margin five or six rows of denticulated setae. Anterior margin with 12–16 setae in three or four groups in addition to 12–15 anterodistal setae. Group of five or six facial setae proximally of palmar spiniform seta; several groups of setae on the inner surface. Palmar corner with strong palmar spiniform seta, single supporting spiniform

seta on inner surface and three denticulated thick spiniform setae on outer side. Nail length 0.30–0.35 of total dactylus length; along anterior margin seven setae in four or five groups; along inner margin a row of short setae.

Gnathopod II ( Figure 9). Basis width: length is 1: 0.30–0.40. Ischium with five posterodistal setae. Carpus 0.55–0.65 of basis length and 0.90–1.05 of propodus length. Anterior margin of carpus with distal row of setae; carpus posteriorly with transverse rows of setae proximally and a row of lateral setae; posteroproximal bulge large (one-third of carpus length), positioned proximally. Propodus small (circumference measures up to 0.15 of body length) and larger than propodus of gnathopod I (1: 0.85–0.90). Propodus trapezoidal, palm convex and more inclined than palm of gnathopod I. Posterior margin with 7–10 rows of denticulated setae. Anterior margin with 7–11 setae in three groups in addition to 11–16 antero-distal setae. Group of three to five facial setae proximally of palmar spiniform setae; several surface setae groups present. Palmar corner with strong palmar spiniform setae, single supporting spiniform seta on inner surface and two denticulated thick spiniform setae on outer side. Nail length 0.30–0.35 of total dactylus length. Along anterior margin 6–10 setae in four to six groups; along inner margin few short setae.

Pereopods III–IV ( Figure 10 ). Lengths of pereopods III: IV equal to ratio 1: 0.90–0.95. Dactylus IV 0.35–0.40 of propodus IV; nail length 0.40–0.45 of total dactylus length. Dactyli III–IV with dorsal plumose seta; at the base only spiniform seta.

Pereopods V –VII ( Figure 10 , 11 ). Lengths of pereopods V: VI is 1: 1.38; distal part of pereopod VII is broken in all individuals.

Bases V–VII length: width is 1: 0.65–0.75; posterior margins straight, with small posterodistal lobes; posteriorly with 14–15, 14 and 14 thin flexible setae respectively; anteriorly five or six, five and five slender spiniform setae respectively. Dactyli V–VI with one or two dorsal plumose seta; at the base of nail a tiny seta and spinform seta.

Pleopods and uropods ( Figure 11 ). Pleopods I–III with two-hooked retinacles. Pleopod II rami of 8–13 articles each.

Uropod I protopodite with five or six dorsolateral spiniform setae and three or four dorsomedial spiniform setae. Endopodite: exopodite lengths is 1: 1.45–1.55 (males) and 1: 1.20 (female); rami curved. Endopodite with up to 11–21 setae in four to seven groups; apically five spiniform setae. Exopodite with 8–11 setae in two or three groups; apically five spiniform setae.

Uropod II endopodite: exopodite lengths is 1: 1.20–1.35.

Uropod III (males only) up to 0.40 of body length. Protopodite with two or three lateral setae and eight apical spiniform and thin setae. Endopodite 0.65–0.70 of protopodite length, apically with three to six spiniform setae; laterally with one seta. Exopodite of uropod III rod-shaped, distal article 0.65–1.00 of the proximal article length. Proximal article with five or six groups of plumose, thin flexible and spiniform setae along inner margin and four to six groups of thin flexible and spiniform setae along outer margin. Distal article with three or four and four or five setae groups along each margin; apically with six setae.

Variability

Spiniform seta dorsally on telson lobe occurs at unknown frequency; we noted it only in paratypes (only on one lobe, not on both). Similarly questionable are frequencies of occurrence of anterosubapical setal group on carpal article of gnathopod I and presence of tiny seta at the base of nail in dactyli of peropods of III – VII. Although this seta regularly occurs in almost all species, we noted it only once in the case of pereopod V. Unfortunately, we have no information about length of pereopod VII and distal ornamentation of this appendage. Sexual dimorphism includes more flattened coxal plates I–IV in males (see above), remarkably more elongated inner ramus of uropod I and most likely also elongated uropod III, especially distal part of exopodite. Although the female paratype had no uropod III, other females have this appendage non-differentiated .

Remarks and affinities

Slender body, subrounded epimeral plates, small gnathopods and sexually dimorphic uropods I and III suggest the inclusion of N. khwarizmi in the N. longicaudatus species group ( Straškraba 1972). Several species of this type have been identified in Europe and first molecular analyses proved that they do not share a common ancestor ( Fišer et al. 2008; Trontelj et al. 2009). We present exhaustive comparison with species sharing these traits in Table 2.

As in the case of N. khayyami , we limit our discussion to two characters; discussion on telson setae is provided above. The most common setal pattern of dactyli of pereopods III–VII consists of tiny seta and spiniform seta at the base of nail. Additional spines may appear, but the pattern of appearance differs from species to species: in some cases these extra spiniform setae are present on all pereopods, or only on dactyls III–IV, sometimes only on dactyls V–VII, VI–VII or exclusively on dactyls VII. In addition, pereopods III–IV are morphologically different from pereopods V–VII. Different setal patterns and overall appendage morphology implies that evolution of seta on pereopods III–IV differs from evolution of pereopods V–VII. This is the reason why we treat the “same” dactylar pattern as two independent characters. On the other hand, lumping different patterns of setal patterns on pereopods V–VII may be an oversimplification; however, the comparative aspect of the study is not weakened.

As in N. khayyami , the distance to the morphologically most similar species is large, over 800 km ( N. turcicus from Turkey; Andreev and Kenderov 2012). Apart from the fact that N. turcicus have two distinct and rather unique traits (setae on proximal article of mandibular palpus, sexually dimorphic uropod III that is unusually short), the large distance itself implies that it is very unlikely that the members of the two populations belong to the same species.

Phylogenetic analysis

The phylogenetic analysis recovered the main relationships identified in a previous analysis (see Fišer et al. 2008). Additional species in analyses do not affect the hypothesis of monophyly of the genus. Unfortunately, specimens of N. khwarizmi were not well-enough preserved to amplify the target fragment successfully and we successfully sequenced only N. khayyami . It is nested within the basal polytomy showing no affiliation with any other species in the analysed data set ( Figure 12 ). Its sister relationship with the rest of the niphargid species is neither supported nor excluded.

Figures

Figure 1. Distribution of Niphargus species in the Middle East and Iran.

Figure 7. Niphargus khwarizmi sp. nov., holotype, lateral view. The appendages indicated with dashed lines are reconstructed from the other side of the animal.

Figure 8. Niphargus khwarizmi sp. nov., holotype: antennae and mouthparts.

Figure 10. Niphargus khwarizmi sp. nov., holotype: pereopods III–VI.

Figure 11. Niphargus khwarizmi sp. nov., holotype: pleopod, uropods, telson and pereopod VII.

Figure 12. Bayesian consensus tree of 88 Niphargus taxa (87 taxa from Fišer et al. 2008), based on the 28S ribosomal RNA sequences. Species are identified and named according to the valid taxonomic description. Posterior probabilities are indicated on main branches.