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

Holotype.

Male, 6.7 mm. The specimen is mounted on two slides and deposited in the collection of the the Musée de Zoologie, Lausanne, Switzerland under voucher numbers GBIFCH00585716 and GBIFCH00585717. Sampled on May 29, 2014 by Verena Lubini . Additional paratypes include 9.15 mm long and partially dissected female deposited under voucher number GBIFCH00587519, a male 6.8 mm long deposited under voucher number GBIFCH00587518 and several un-dissected specimens deposited in vials under GBIFCH00329353 and GBIFCH00329354.

Material examined.

Two males of lengths 6.7 and 6.8 mm and a female 9.15 mm long; specimens are partially dissected and mounted on slides with voucher numbers GBIFCH00585716, GBIFCH00585717, GBIFCH00587518 and GBIFCH00587519; seven other specimens were sequenced.

Type locality.

Marchbachquelle, Wolfenschiessen, Switzerland (CH1903: 672,490/190,300).

Diagnosis.

Mid-sized species, in general appearance similar to N. forelii . Epimeral plates angular. Telson with three long apical spines, one lateral, and one dorsal spine per lobe. Propods of gnathopods I and II of rectangular shape, propodus of gnathopod II large when compared to body length and propodus I. Maxilla outer lobe with seven spiniform setae, the inner four comb-like with long subapical denticles, the remaining three spines with one such denticle. Uropod I inner ramus slightly shorter than outer ramus; uropod II inner ramus slightly longer than outer ramus. Uropod III distal article elongated in males, as long as 0.5 times proximal article.

Description

(based on dissected specimens).Head and trunk (Fig. 3). Body length up to 9.2 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 convex; ventro-postero-distal corner distinct; two spines along ventral margin; three to six setae along posterior margin. Epimeral plate III inclined, posterior and ventral margin concave and convex, respectively; ventro-postero-distal corner distinct but not produced; two to three spiniform setae along ventral margin; four to five thin setae along posterior margin.

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

Telson length: width ratio is 1: 0.81-0.91; cleft is 0.69-0.72 telson length; telson margins straight and narrowing apically. Telson spiniform setae (per lobe, left-right lobe asymmetry commonly observed): three apical, one dorsal and one lateral spiniform; mesial setae were not observed. Apical spiniform setae 0.44-0.5 telson length. Pairs of plumose setae laterally.

Antennae (Fig. 4). Antenna I 0.41-0.56 times body length. Flagellum with 17-20 articles; each article with one aesthetasc. Peduncle articles in ratio 1: 0.79-0.87: 0.37-0.47. 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 is 1: 0.48-0.57. Flagellum of antenna II with nine to ten articles; each article with setae and elongated sensillae of unknown function. Peduncle articles lengths 4: 5 is 1: 0.93-0.95; flagellum 0.69-0.77 of length of peduncle articles 4 and 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 a 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: 1.01-1.11. Proximal palp article without setae; the second article with seven to eleven setae; distal article with a group of two to four A setae; two to three groups of B setae; 15-20 D setae and three E setae.

Maxilla I distal palp article with five to six apical setae. Outer lobe of maxilla I with a row of seven stout setae, inner four comb-like, with many long subapical denticles, the remaining three setae with one denticle; inner lobe with two to three apical setae.

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

Maxilliped palp article 2 with seven 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 nine to eleven stout setae mesially to subapically, and three to five setae apically; inner lobe apically with three to four stout setae and seven serrated setae.

Coxal plates, and gills (Figs 3, 6, 7). Coxal plate I of parallelogram shape, with rounded antero-ventral corner and armed with four to six setae. Coxal plates II-IV width: depth ratios as 0.87-1.07: 1, 1.03-1.12: 1 and 0.96-1.13: 1; anterior and ventral margins with four to seven, five to six and five to seven setae. Coxal plate IV posteriorly distinctly concave. Coxal plates V–VI anteriorly with large lobes; 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 four to six postero-distal setae. Carpus 0.58-0.61 of basis length and 0.84-0.97 of propodus length; broadened distally. Carpus with single distal group of setae anteriorly, rarely accompanied by an additional seta in the mid of article; transverse rows of setae along posterior margin and a row of setae postero-laterally. Propodus rectangular. Along posterior margin, three to five rows of setae. Anterior margin with two to three groups of total four to eleven setae in addition to antero-distal group of eight setae. Several groups of short setae on the inner surface present. Palmar corner armed with a long spiniform palmar seta, two to three serrated spiniform seta, a single supporting spiniform seta on inner surface and three to five long setae below palmar spine. Palm setose. Nail length 0.31-0.32 of total dactylus length; four setae along anterior margin; a row of short setae along inner margin.

Gnathopod II (Figs 6). Basis width: length is 0.28-0.30: 1. Ischium with three to four postero-distal setae. Carpus 0.52-0.57 of basis length and 0.83-0.91 of propodus length, distally broadened. Carpus with distal group of setae anteriorly, rarely accompanied by an additional seta in the middle of the article; few transverse rows of setae along posterior margin and a row of setae postero-laterally. Propodus rectangular, large (circumference measures up to 0.20-0.23 of body length), much larger than propodus of gnathopod I (I: II as 0.75-0.76: 1). Posterior margin with six to eight rows of setae. Anterior margin with two to three groups of total four to six setae in addition to seven to ten antero-distal setae. Individual surface setae present. Palmar corner with one strong palmar spiniform seta, a single supporting spiniform seta on inner surface and two denticulated thick-spiniform setae on outer side. Palm setose, below spiniform palmar seta, a group of three to four long setae. Nail length 0.30-0.32 of total dactylus length; three to six setae along anterior margin; a few short setae along inner margin.

Pereopods III–IV (Fig. 7): Lengths of pereopods III and IV subequal. Dactylus IV 0.46-0.52 of propodus IV; nail length 0.52-0.59 of total dactylus length. Dactyli III-IV with a dorsal plumose seta; one spiniform seta at the base of nail, sometimes accompanied by a tiny seta.

Pereopods V–VII (Fig. 7): Lengths of pereopods V: VI: VII is 1: 1.33-1.34: 1.39-1.42; pereopod VII measures 0.55-0.59 of body length.

Bases V-VII broad, respective length: width ratios as 1: 0.64-0.67, 1: 0.60-0.65 and 1: 0.60-0.63; posterior margins straight to convex; bases V-VII with moderate posterior lobes; posteriorly eight to eleven, nine to twelve and seven to ten setae, respectively; anteriorly six to seven, six and five to seven groups of spines, respectively. Dactyli V–VII with dorsal plumose seta; spiniform seta at the base of nail, in most cases accompanied by one tiny seta.

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

Uropod I protopodite with three to six dorso-lateral spiniform setae and three to four dorso-medial spiniform setae. Exopodite: endopodite lengths is 1: 0.82-0.99; rami straight. Endopodite with two individual spiniform setae laterally and five spiniform setae apically. Exopodite with two to four groups totalling three to eight setae; mesial groups comprise individual spiniform setae, whereas lateral groups comprise spiniform and flexible setae groups; apically five spiniform setae.

Uropod II exopodite: endopodite lengths is 1: 1.02-1.12.

Uropod III rod-shaped, 0.22-0.41 of body length. Protopodite with one to two lateral setae and six to seven apical spiniform setae. Endopodite 0.45-0.50 of protopodite length, laterally with 0-1 seta, apically with two setae, at least one spiniform. Exopodite of uropod III distal article 0.28-0.48 of the proximal article length. Proximal article with four to six groups of thin-flexible, spiniform and plumose setae along inner margin and four groups of thin-flexible and spiniform setae along outer margin. Distal article with one to four groups of thin-flexible setae along each margin, and five to six of setae apically.

Etymology.

The species is named in honour of Hans Lukas “Luc” Hoffmann (1923-2016), naturalist and ecologists, who importantly influenced nature conservation worldwide. Among others, he was the founder of the MAVA foundation and co-founder of the World Wide Fund for Nature (WWF).

Habitat and distribution.

The species has been hitherto reported from springs, and seems to be endemic to central Switzerland (Fig. 1).

Variability.

The variability of the species is poorly understood, as we could analyse relatively little material, with numerous sub-adult and damaged specimens. Males and females differ in length of distal article of uropod III, which is remarkably longer in males. Larger specimens tend to have narrower bases of pereopods V–VII. The pattern of denticulation on spines on outer lobe of maxilla I is, however, stable and the most important diagnostic trait.

Remarks and affiliation.

In a morphological sense, N. luchoffmanni sp. n. shows some similarities to N. forelii Humbert, 1876. We compared N. luchoffmanni sp. n. with neotypes from Bodensee from Berlin Museum and species descriptions ( Karaman and Ruffo 1993, Ginet 1996). Both species have long dactyls, long telson spines, multiple setae along gnathopod dactyls, an elongated distal article of uropod III in males, and the endopodite of uropod I shorter than the exopodite. Yet, there are few distinct traits separating both species. The differences in sizes of propods of gnathopods I and II is more pronounced in N. luchoffmanni sp. n. than in N. forelii . In addition, endopodite of the uropod II is longer and shorter than the exopodite in N. luchoffmanni sp. n. and N. forelii , respectively. Niphargus luchoffmanni sp. n. has one dorsal spine on telson, while N. forelii is lacking dorsal telson spines. Finally, the spines on the outer lobe of maxilla I are different: while N. luchoffmanni sp. n. has at least four spines multidenticulate, N. forelii has, at most, one such spine.