Niphargus arolaensis, Alther 1 & Bongni 1 & Borko 3 & Fišer 3 & Altermatt 1, 2021
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https://dx.doi.org/10.3897/subtbiol.39.66755 |
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https://treatment.plazi.org/id/F8FE1485-6A9E-5DDE-BCF1-7A3F8958C599 |
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scientific name |
Niphargus arolaensis |
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sp. nov. |
Niphargus arolaensis sp. nov.
Type material.
Holotype (Figs 5 View Figure 5 - 9 View Figure 9 ): Female, 7.8 mm (tip of rostrum to tip of third urosomite). The sample is deposited in the collection of the Musée de Zoologie, Lausanne, Switzerland under voucher number GBIFCH00602901 and GBIFCH00602902 . GoogleMaps
Paratypes: One male and three females of respective lengths 7.7, 7.8, 8.7 and 9.5 mm; specimens are partially dissected and mounted on slides with voucher numbers GBIFCH00602903 , GBIFCH00602904 , GBIFCH00602905 , GBIFCH00602906 , GBIFCH00602907 .
Type locality.
Stedliquelle GoogleMaps (left inflow), Aarberg, Switzerland. CH1903: 588'518, 209'959 (WGS84: 47.04056°N, 7.28756°E), 478 m a.s.l.
Habitat and distribution.
Only known from three drinking water wells: Stedtliquelle close to Aarberg, Stöckhof close to Egliswil and Lätzloch close to Kölliken, all in Switzerland.
Etymology.
The name " Niphargus arolaensis " is derived from the Latin name of the river Aare (Arola), since all findings were located in the drainage basin of the river Aare.
Diagnosis.
Small and slender Niphargus , defined by combination of two traits. Two spiniform setae are located on the lower distal part of the first urosomite near the insertion of uropod I (Fig. 5 View Figure 5 ). The outer lobe of maxilla I is armed with seven comb-like spiniform setae (Fig. 5 View Figure 5 ).
Description.
Head and trunk (Fig. 5 View Figure 5 ): Body length up to 9.5 mm. Head length 6.6-7.4% of body length; rostrum absent. Pereonites I-VI without setae, pereonite VII with tiny seta close to ventro-posterior corner.
Pleonites I-III with up to three setae along the entire dorso-posterior margins. Epimeral plate II roughly perpendicular, posterior and ventral margins convex; ventro-postero-distal corner distinct; along ventral and posterior margins three spiniform and four to five thin setae, respectively. Epimeral plate III inclined, posterior and ventral margin slightly-distinctly concave and slightly convex, respectively; ventro-postero-distal corner distinct but not produced. Along ventral and posterior margin 3-4 spiniform seta; along posterior margin five thin setae.
Urosomite I postero-dorso-laterally with one slender, flexible seta; urosomite II postero-dorso-laterally with 2-3 strong setae among which at least one is strong and stout; urosomite III without seta. Ventrally on urosomite I, at the base of uropod I, are two strong spiniform setae in a row.
Telson (Fig. 9E View Figure 9 ) length : width ratio is 1 : [0.81-0.85]; cleft measures 0.61-0.75 of telson length; telson lobes margins straight and narrowing apically. Telson armature (per lobe, left-right lobe asymmetry commonly observed): 2-4 apical, 0-1 mesial, 1-2 lateral and no dorsal spiniform setae. Apical spiniform setae as long as 0.50-0.63 of telson length. Pairs of plumose setae inserted medially, along lateral margins.
Antennae (Fig. 6 View Figure 6 ): Antenna I (A) measures 0.40-0.45 of body length. Flagellum with 18-22 articles; each article with one aesthetasc. Peduncle articles in ratio 1 : [0.70-0.82] : [0.35-0.40]. Accessory flagellum biarticulated, proximal : distal article in ratio 1 : [0.25-0.33].
Ratio of lengths antenna I : antenna II as 1 : [0.48-0.52]. Flagellum of antenna II (B) with 7-8 articles; each article with setae and elongated, thick sensilla of unknown function. Peduncle articles lengths 4 : 5 in ratio 1 : [0.89-0.95]; flagellum 0.57-0.66 of length of peduncle articles 4+5.
Mouthparts (Fig. 7 View Figure 7 ): Labrum (A) and labium (B) typical of the genus; inner lobes of labium well visible.
Left mandible (C and D): incisor with five teeth, lacinia mobilis with four teeth; between lacinia and molar a row of serrated setae, molar triturative, at the base of molar long seta. Right mandible (E and F): incisor processus with four teeth, lacinia mobilis with several small teeth, between lacinia and molar a row of thick serrated setae, molar triturative. Mandibular palp article 3 articulated. Ratio of mandibular palp article 2 (middle) : article 3 (distal) is 1 : [1.2-1.37]. Proximal palp article without setae; the middle article with 7-8 setae; distal article with 3-5 A setae in a row; 3-4 B setae; 15-18 D setae and four E setae.
Maxilla I (G and H), distal palp article with 6-7 apical setae. Outer lobe of maxilla I with a row of 7 stout spiniform setae, each with many (>4) denticles (comb-like); inner lobe with two setae along medial and apical margin.
Maxilla II (I and K) inner lobe slightly smaller than outer lobe; both lobes setose apically and medially.
Maxilliped (L) inner lobe with three stout flattened and tooth-like setae apically and 6-11 setae along latero-apical margins; outer lobe with 7-11 stout and flattened, tooth-like setae mesially-subapically and 5-7 thick rounded and hairy setae apically. Maxilliped palp article 2 with 8-10 rows of setae along inner margin; dactylus with a dorsal seta, and few tiny setae at the socket.
Coxal plates, and gills (Figs 6 View Figure 6 and 8 View Figure 8 ): Coxal plate I in shape of flattened parallelogram; anterior and ventral margin of coxa I with 5-6 setae. Coxal plates II-IV width : depth ratios as [0.90-1.10] : 1, [0.85-0.94] : 1 and [1.00-1.13]: 1, respectively; anterior and ventral margins with 8-9, 6-11 and 6-7 setae. Coxal plate IV posteriorly shallowly concave. Coxal plates V-VI with well-developed anterior lobe, posterior coxal margin with one seta. Coxal plate VII half-circular with one posterior seta. Gills II-VI narrowly ovoid.
Gnathopod I (Fig. 6C View Figure 6 ): Ischium with up to 5 postero-distal setae in a single row. Carpus 0.70-0.73 of propodus length; broadened proximally. Carpus with only one distal group anteriorly, transverse rows of setae on a posterior bulk and a row of setae postero-laterally. Propodus quadratic with moderately inclined palm. Along posterior margin 4-5 rows of setae. Anterior margin with antero-distal group counting 5-10 setae and additional 8-10 setae in three groups. On the inner surface are several pairs of short setae. Palmar corner armed with one strong and stout palmar spine, a group of three long thin and simple setae anteriorly to palmar spine, one strong short and smooth “supporting” spine on the inner surface and three serrated spines behind the palmar spine. Palm with a row of short setae. Nail length 0.30-0.34 of total dactylus length; along anterior margin 2-4 single seta; along inner margin a row of short setae.
Gnathopod II (Fig. 6D View Figure 6 ): Ischium with 1-3 postero-distal setae in a single row. Carpus 0.66-0.84 of propodus length, proximally broadened. Carpus with a single groups of distal setae anteriorly; some transverse rows of setae on a posterior bulk and a row of setae postero-laterally. Propodus hoof-shaped with strongly inclined palm and large. Circumference measures up to 0.19-0.23 of body length; ratio between propodus I and II lenghts is [0.74-0.95] : 1. Along posterior margin six rows of setae. Anterior margin with antero-distal group counting 6-8 setae and additional 4-5 setae in 2-3 groups. On the inner surface are several pairs of short setae. Palmar corner armed with one strong and stout palmar spine, a group of 2-3 long thin and simple setae anteriorly to palmar spine, one strong short and smooth spine on the inner surface and 1-2 serrated spines behind the palmar spine. Palm with a row of short setae. Nail length 0.30-0.34 of total dactylus length; along anterior margin 2-4 single seta; along inner margin a row of short setae.
Pereopods III-IV (Fig. 8A View Figure 8 and 8B View Figure 8 ): Lengths of pereopods III : IV as [0.90-0.97] : 1. Dactyli III-IV long and slender, dactylus IV measures 0.42-0.46 of propodus IV; nail length 0.56-0.65 of total dactylus length. Dactyli III-IV with 1 dorsal plumose seta; at the base of nail 1 tiny seta and one tiny spiniform seta.
Pereopods V-VII (Fig. 8C-8E View Figure 8 ): Lengths of pereopods V : VI : VII is 1 : [1.34-1.41] : [1.31-1.41]; pereopod VII measures 0.46-0.47 of body length.
Bases V-VII slender, respective length : width ratios as 1 : [0.57-0.64], 1 : [0.57-0.64] and 1 : [0.58-0.64]; posterior margins straight or slightly convex, distally ending with small to moderate-sized lobes; posterior margins armed with 8-10, 9-10 and 8-10 setae, respectively; anterior margins armed with 6-7, 6-7 and 5-6 groups of stouter setae, respectively. Dactyli V-VII with one dorsal plumose seta; at the base of nail one tiny setae and one spiniform seta. Dactylus VII long and slender, its length measures 0.28-0.32 of propodus length; nail long, measuring 0.34-0.38 of total dactylus length.
Pleopods and uropods (Fig. 9 View Figure 9 ): Pleopods I-III (A) with two hooked retinacles. Pleopod II inner and outer rami with 6-7 and 8-9 articles, respectively.
Uropod I (B) protopodite with six dorso-lateral spiniform setae and 2-3 dorso-medial spiniform setae. The ratio exopodite : endopodite lengths is 1 : [0.98-1.06]; rami straight. Endopodite with four individual spiniform setae laterally, rarely accompanied with a slender and flexible seta, and four spiniform setae apically. Exopodite with 2-6 spiniform setae alone or in groups; apically 4-6 spiniform setae.
Uropod II (C) exopodite : endopodite lengths ratio is 1 : [1.00-1.05].
Uropod III (D) rod-shaped, measuring 0.20-0.22 of body length. Protopodite elongated, sometimes with a single weak lateral seta and with 5-7 apical spiniform setae. Endopodite short, measures approximately 0.56-0.63 of protopodite length; laterally armed with 0-1 spiniform setae, apically armed with 3-4 spiniform setae, of which 1-2 are strong and spiniform. Exopodite of uropod III rod-shaped, distal article 0.16-0.22 of the proximal article length. Proximal article with five groups of spiniform and plumose setae along inner margin and 4-5 groups of spiniform setae along outer margin. Distal article with 0-2 setae laterally and 1-4 setae apically.
Variability.
We found no sexual dimorphism in proportions, females had oostegites on pereopods II-IV. Number of setae vary, smaller specimens had fewer setae.
Remarks and affiliation.
The diagnosis is a combination two unambiguous traits. Two strong spiniform setae at the base of uropod I is a rare character, hitherto found only in Niphargus bodoni G. Karaman, 1985 (Italy, Karaman 1985), Niphargus lindbergi S. Karaman, 1956 ( Borko et al. 2019; Greece, Karaman 2018), Niphargus sertaci Fišer, Çamur-Elipek & Özbek, 2009 (Western Turkey, Fišer et al. 2009), Niphargus turcicus Andreev & Kenderov, 2012 (Eastern Turkey, Andreev Kenderov 2012) and Niphargus borisi Esmaeili-Rineh, Sari & Fišer, 2015 (Iran, Esmaeili-Rineh et al. 2015). However, all these species have a different spiniform setae on outer lobe of maxilla I, i.e., the inner seta is multidenticulate and the remaining six setae have 1-3 denticles. By contrast, the herein described N. arolaensis sp. nov. has all these spiniform setae on outer lobe of maxilla I multidentate. To ease its identification in Europe, it is noteworthy that the species remarkably differs from N. bodoni in shape of its gnathopods. The Italian species has much smaller and more quadratic propods of gnathopods I-II, while the herein described species from Switzerland has relatively large propodi with a strongly inclined palm. Finally, it is worthy to warn that the newly described N. arolaensis sp. nov. superficially resembles Niphargus forelii Humbert, 1876 from the Alpine region. It is small, of relatively slender body, with large gnathopods, long and slender dactyli, a telson with no dorsal spiniform setae, but very long apical and marginal spiniform setae. Besides the diagnostic combination, the newly described species differs from N. forelii as its males apparently do not have an elongated uropod III ( Karaman and Ruffo 1990).
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