Niphargus tonywhitteni, Fiser, Cene, Alther, Roman, Zaksek, Valerija, Borko, Spela, Fuchs, Andreas & Altermatt, Florian, 2018

Fiser, Cene, Alther, Roman, Zaksek, Valerija, Borko, Spela, Fuchs, Andreas & Altermatt, Florian, 2018, Translating Niphargus barcodes from Switzerland into taxonomy with a description of two new species (Amphipoda, Niphargidae), ZooKeys 760, pp. 113-141 : 113

Niphargus tonywhitteni sp. n. Figs 3, 4, 5, 6, 7, 8

Holotype.

Male, 9.1 mm. The specimen is mounted on two slides and deposited in the collection of the Musée de Zoologie, Lausanne, Switzerland under voucher number GBIFCH00585714 and GBIFCH00585715. Sampled on 17 October 2014 by Tom Gonser. Paratypes represent one male of length 7.5 mm with voucher numbers GBIFCH00587517.

Material examined.

Three males of lengths 9.1, 7.5 and 9.1 mm; specimens are partially dissected and mounted on slides with voucher numbers GBIFCH00585714, GBIFCH00585715, and GBIFCH00587517; three other specimens were sequenced.

Type locality.

Gravel bed of Töss River near Winterthur, Switzerland (CH1903: 697,715/257,410)

Diagnosis.

Small Niphargus , of mid-slender appearance closely resembling N. fontanus . Telson narrow, with long apical and lateral spines; dorsal spines lacking. Propodus of gnathopod I of rectangular shape, propodus of gnathopod II almond (hoof) shape. Uropods I with equal rami; uropod III rod shaped, likely sexually dimorphic, with elongated distal article.

Description

(based on dissected specimens).Head and trunk (Figs 3, 8). Body length up to 9.1 mm. Head length approximately 10% of body length; rostrum absent. Pereonites I–VI without setae, pereonite VII with one seta ventro-posteriorly.

Pleonites I–III with up to four setae along the entire respective dorso-posterior margins. Epimeral plate II only slightly inclined, posterior and ventral margins slightly sinusoid and convex, respectively; ventro-postero-distal corner distinct; two spines along ventral margin; four setae along posterior margin. Epimeral plate III inclined, posterior and ventral margin sinusoid and convex, respectively; ventro-postero-distal corner distinct but not produced; two spiniform setae along ventral margin; four thin setae along posterior margin.

Urosomite I postero-dorso-laterally with one strong spiniform seta sometimes accompanied with one slender and flexible seta; urosomite II postero-dorso-laterally with two to three strong spiniform setae; urosomite III without setae. At the base of uropod I a single strong spiniform seta.

Telson length: width ratio is 1: 0.85-0.90; cleft is 0.6-0.65 telson length; telson margins straight and narrowing apically. Telson spiniform setae (per lobe, left-right lobe asymmetry commonly observed): three to five apical, and none to two lateral spiniform setae; dorsal and mesial setae were not observed. Apical spiniform setae up to 0.5 telson length. Pairs of plumose setae laterally.

Antennae (Fig. 4). Antenna I 0.45-0.55 of body length. Flagellum with 21 articles; each article with one aesthetasc. Peduncle articles in ratio 1: 0.85-0.90: 0.41-0.45. Proximal article of peduncle dorso-distally slightly produced. Accessory flagellum biarticulated; distal article shorter than one quarter of proximal article length.

Length ratio antenna I: antenna II as 1: 0.46-0.47. Flagellum of antenna II with seven to eight articles; each article with setae and elongated sensillae of unknown function. Peduncle articles lengths 4: 5 is 1: 0.93-0.98; flagellum 0.55-0.58 times length of peduncle articles 4+5.

Mouthparts (Fig. 5). Labrum typical; inner lobes of labium hardly visible.

Left mandible: incisor with five teeth, lacinia mobilis with four teeth; between lacinia and molar a row of serrated setae, few spatulate setae and one long seta at the base of molar. Right mandible: incisor processus with four teeth, lacinia mobilis with several small teeth, between lacinia and molar a row of thick serrated setae. Ratio of mandibular palp article 2: article 3 (distal) is 1: 1.12-1.22. Proximal palp article without setae; second article with seven to nine setae; distal article with a group of four A setae; three groups of B setae; 18-19 D setae and five E setae.

Maxilla I distal palp article with seven to eight apical setae. Outer lobe of maxilla I with a row of seven stout setae, inner with many subapical denticles, the remaining setae with one denticle; inner lobe with two apical setae.

Maxilla II inner lobe slightly smaller than outer lobe; both lobes setose apically.

Maxilliped palp article 2 with five to eight rows of setae along inner margin; distal article with a dorsal seta, and setae at the base of nail. Maxilliped outer lobe with seven to eight stout setae mesially to subapically, and three setae apically; inner lobe apically with two stout setae and six serrated setae.

Coxal plates, and gills (Figs 3, 6, 7). Coxal plate I of parallelogram shape, with rounded antero-ventral corner and armed with three to four setae. Coxal plates II–IV width: depth ratios are 1.09-1.16: 1, 0.87-0.89: 1 and 0.85-0.92: 1 respectively; anterior and ventral margins with five to six, four and four to five setae respectively. Coxal plate IV posteriorly distinctly concave. Coxal plates V–VI anteriorly with large lobe; posterior margins with one seta. Coxal plate VII half-rounded shaped with one posterior seta. Gills II–VI ovoid.

Gnathopod I (Fig. 6). Ischium with one group of two to six postero-distal setae. Carpus 0.58-0.61 of basis length and 0.77-0.80 of propodus length; broadened distally. Carpus with single distal group of setae anteriorly; transverse rows of setae along posterior margin and a row of setae postero-laterally. Propodus rectangular. Along posterior margin five to six rows of setae. Anterior margin with two to three groups of total 11-12 setae in addition to antero-distal group of seven to eight setae. Several groups of short setae on the inner surface present. Palmar corner armed with a long spiniform palmar seta, three serrated spiniform setae, a single supporting spiniform seta on inner surface and three to four long setae below palmar spine. Palm setose. Nail length 0.31-0.32 of total dactylus length; four to six setae along anterior margin; a row of short setae along inner margin.

Gnathopod II (Fig. 6). Basis width: length is 0.31-0.32: 1. Ischium with four postero-distal setae. Carpus 0.56-0.58 of basis length and 0.75-0.85 of propodus length, distally broadened. Carpus with distal group of setae anteriorly; few transverse rows of setae along posterior margin and a row of setae postero-laterally. Propodus of hoof or almond shape, large (circumference measures up to 0.19-0.20 of body length), larger than propodus of gnathopod I (I: II as 0.79-0.81: 1). Posterior margin with eight to nine rows of setae. Anterior margin with a pair of individual setae in addition to eight to nine antero-distal setae. Individual surface setae present. Palmar corner with one strong palmar spiniform seta, single supporting spiniform seta on inner surface and one to two denticulated thick spiniform setae on outer side. Palm setose, below spiniform palmar seta a group of three long setae. Nail length 0.29-0.36 of total dactylus length; four setae along anterior margin; few short setae along inner margin.

Pereopods III-IV (Fig. 7). Lengths of pereopods III and IV subequal. Dactylus IV 0.34-0.43 of propodus IV; nail length 0.47-0.50 of total dactylus length. Dactyli III–IV with dorsal plumose seta; two tiny setae at the base of nail.

Pereopods V–VII (Fig. 7). Lengths of pereopods V: VI: VII is 1: 1.30-1.33: 1.30-1.41; pereopod VII measures 0.44-0.48 of body length.

Bases V–VII broad, respective length: width ratios as 1: 0.60-0.65, 1: 0.55-0.62 and 1: 0.57-0.62; posterior margins straight to convex; bases V–VII with moderate large posterior lobes; posteriorly eight to nine, eight to ten and seven to nine setae, respectively; anteriorly seven to eight, eight and seven to eight groups of spines, respectively. Dactyli V–VII with dorsal plumose seta, with two tiny setae at the base of the nail.

Pleopods and uropods (Fig. 8). Pleopods I–III with two hooked retinacles. Pleopod II rami with seven to eight and nine to ten articles.

Uropod I protopodite with six dorso-lateral spiniform setae and three dorso-medial spiniform setae. Exopodite: endopodite lengths is 1: 1.0-1.03; rami straight. Endopodite with three individual spiniform setae laterally and five spiniform setae apically. Exopodite with five groups of totally nine setae; mesially with individual spiniform setae and laterally with spiniform and flexible setae; five spiniform setae apically.

Uropod II exopodite: endopodite lengths is 1: 1.09.

Uropod III rod-shaped, 0.25-0.30 of body length. Protopodite with none to one lateral setae and seven to nine apical spiniform setae. Endopodite 0.54-0.61 of protopodite length, laterally without setae, apically with two setae, at least one spiniform. Exopodite of uropod III distal article 0.35-0.41 of the proximal article length. Proximal article with four to six groups of thin-flexible, spiniform and plumose setae along inner margin and four to five groups of thin-flexible and spiniform setae along outer margin. Distal article with two to three groups of thin-flexible setae along each margin, and a pair of setae apically.

Etymology.

The species is named in honour of Tony Whitten (1953-2017), who devoted his life to nature conservation including conserving life in caves. He was a co-chair of the Cave Invertebrate Specialist Group at IUCN.

Habitat and distribution.

The species is known only from interstitial or related habitats. The species was found along the northern margin of the Alpine arch, between Achensee in Austria, Southern Germany and the type locality in Switzerland.

Variability.

Only a small sample was available, not all individuals were adult, and many specimens were damaged. The extent of sexual dimorphism in uropod III is unknown; the terminal article of exopodite indicates elongation, as in N. fontanus from Great Britain, and our observations suggest that this article is longer in males and shorter in females. Most variation noticed can be likely attributed to different sizes of the specimens.

Remarks and affiliation.

The species is closely related to N. thienemanni , from which it clearly differs by the almond-hoof shape of propodus of gnathopod II (rectangular in N. thienemanni ). However, the newly described species is strikingly similar to N. fontanus Bate, 1859 from Great Britain, Belgium and France. The latter comprises a complex of cryptic species, distributed between Great Britain and Alps ( McInerney et al. 2014), whereas the newly described N. tonywhitteni sp. n. belongs to a completely different phylogenetic lineage (Fig. 2), ruling out a possible conspecificity. The morphological differences between the two complexes are difficult to evaluate, mainly because we have only limited insights into variation of N. tonywhitteni sp. n. as well as the species complex containing the nominal species. We compared the newly described species with the lectotype and information available in various descriptions ( Ginet 1996, Hartke et al. 2011). The only observed difference is in the shape of propodus of gnathopod I, which tends to be more rectangular in the newly described species in contrast to more almond shaped propodus of the nominal lineage. Additional identification traits depend on non-morphological information, i.e., geographic origin of the species, and especially on diagnostic COI sequences. While the description of N. tonywhitteni sp. n. substantially improved the knowledge of Niphargus in Switzerland, it is clear that the polyphyletic complex N. fontanus - N. tonywhitteni sp. n. is awaiting revision, which is beyond the scope of the present paper.