Niphargus enslini Karaman, 1932

Weber 1, Dieter, Brad 2,3, Traian, Stoch 1, Fabio & Flot 1,4, Jean-Francois, 2021, Rediscovery and redescription of Niphargus enslini Karaman, 1932 (Amphipoda, Niphargidae) in southern Germany, Subterranean Biology 40, pp. 65-89 : 65

Niphargus enslini Karaman, 1932

Figures 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13

Niphargus orcinus enslini syn: Niphargus orcinus enslini Schellenberg (1933a); Niphargus orcinus virei (Schellenberg, 1933b)

Material examined.

Male. Germany, 1 ♂; Blätterteighöhle; 26-27 August 2017; Bernd Hugger, Rafael Grimm, Dieter Weber leg. The specimen was dissected and used for species redescription. The dissected body appendages were transferred to permanent slides and stored in the collection of the Université libre de Bruxelles (ULB) under voucher number: 170827-004 .

Females. Germany, 3 ♀♀; Blätterteighöhle; 26-27 August 2017; Bernd Hugger, Rafael Grimm, Dieter Weber leg. One female (Voucher number: 170827-001) was dissected and used to study the sexual dimorphism. Two females were not dissected and are preserved in 96% ethanol at -20 °C in the collection of the Université libre de Bruxelles (ULB) , Belgium. Voucher numbers: 170827-002 and 170827-003. Germany, 1 ♀, Falkensteiner Höhle, leg. Enslin, partially dissected and mounted on a slide stored in the crustacean collection of the Natural History Museum of Berlin (GBIF Crustacea - ZMB Berlin, No. 24795) .

Juveniles. Germany, 1 juv. (voucher number 170805-029); Schwarzer Brunnen; 5 August 2017; Harald Knupfer leg. The specimen was far too small for morphological determination and was completely used for DNA extraction .

All DNA isolates are stored at -20 °C at the Université libre de Bruxelles (ULB) in the research unit Evolutionary Biology & Ecology. Voucher numbers: 170827-001, 170827-002, 170827-003, 170805-029.

Diagnosis.

Robust, mid-sized Niphargus . Right to acute postero-ventral angle of epimeral plates. Pleon with 3-6 spines on the postero-dorsal side of each segment. Gnathopods coxae trapezoidal with only one thin seta along the outer margin of dactylus. Coxal plate IV sub-rectangular, with no posterior protrusion. Pereopod VI reaching more than half of the total body length. Uropod I rami subequal. Uropod III sexually dimorphic; exopod elongated in males. Telson relatively elongated in males, bearing 4 apical, 4-5 lateral and 3-5 smaller dorsal spines on each lobe.

Description of male.

Habitus as in Fig. 5 . Body length (measured from anterior part of head to telson insertion) of the single male examined 19.6 mm (Fig. 6 ). All detailed measurements on body appendages were performed according to the methods described in Fišer et al. (2009) and are reported in Suppl. material 1: Table S4.

Head (Fig. 6A ) without rostrum representing 7.2% of total body length.

Antenna I (Fig. 7A ), longer than half of total body length (Suppl. material 1: Table S2), with main flagellum formed of 48 articles. All articles in the distal two thirds of flagellum bear one aestethasc (Fig. 7D ) as long as one half of the respective article. Length of antenna I peduncle almost one third of total length of antenna I. Accessory flagellum formed of 2 articles (Figs 7B, C ); proximal article length slightly exceeding the first article of main flagellum; distal article bearing 2 apical setae and 1 aestethasc and represents slightly less than one third of the total length of the accessory flagellum.

Antenna II (Fig. 7E ) with flagellum formed of 18 articles, almost half of total length of antenna I. Antennary peduncle almost twice as long as flagellum.

Labrum of typical, subovoid shape.

Lower lip (Fig. 8A ) with inner lobes slightly shorter than outer lobes. Inner lobes with thin distal setae. Outer lobes with two rows of thin setae subapically on both sides.

Left mandible (Fig. 8B ) with 3 teeth on incisor process and 4 teeth on lacinia mobilis. Ten serrated setae alternated with sensory setae between lacinia mobilis and molar process (pars molaris).

Right mandible (Fig. 8C ) with 4 teeth on incisor process, several small denticles on lacinia mobilis; a row of 9 serrated setae and 5 sensory setae between lacinia mobilis and molar process; a long seta proximal to molar process.

Mandibulary palps (Figs 8B, C ) of both sides subequal. The three articles of mandibulary palp account for 19.8% (article 1), 37.1% (article 2) and 43.1% (article 3) of the total length of the palp (Suppl. material 1: Table S2). Proximal article without setae, article 2 with 18-22 ventral setae and distal article of the palp with one group of 8 A-setae on the outer face, 4 groups of B-setae on the inner face with 4 setae each, 28-34 D-setae and 7-9 E-setae.

Maxilla I (Fig. 8D ) with 6 apical setae on the distal article of the palp. Outer lobe with 6 spines with one tooth each and one spine with several smaller teeth. Inner lobe with 2 apical setae.

Maxilla II (Fig. 8E ) with inner lobe slightly shorter than outer lobe. Each lobe bearing 2 rows of setae, one apical and one subapical. A row of thin setae along the outer margin of outer lobe.

Maxilliped (Fig. 9A ) with palp formed of four articles. Article 1 without setae, article 2 with numerous setae aligned along the inner margin. Article 3 with one group of 12 setae located on the inner margin, one group of 11 apical setae, of which 5 serrated, and two groups of 4 and 7 setae on the outer margin. Article 4 with a row of 6 setae on the inner margin and one seta located on the outer margin. Outer lobe of maxilliped with 5 shorter setae, 14 flattened spiniform setae and 8 longer setae located apically. Inner lobe provided apically with 5 flattened spines, 6 serrated and 4 normal setae.

Gnathopod I (Fig. 9B ) with a rhomboidal coxal plate larger than wide (ratio depth:width 1.0:0.7). Basipod length:carpus length 1.0:0.5. Ischium with one posteroventral group of 15 setae. Carpus with a row of 45 setae of various lengths along ventral margin, and one group of 5 setae located anterodorsally. Propodite approximately as long as wide and with several groups of 4-6 setae on its ventral margin, one antero-dorsal group of 9 setae and one antero-apical group of 9 setae. Six facial groups with 1-4 setae each on outer surface of propodite close to its ventral side and three groups of 4-7 setae close to the dorsal margin. One group of 6 long setae near palmar corner. Strong palmar spine and 2 supporting spines at palmar corner. Dactylus with nail length almost one third of total dactylus length and with one small seta along outer margin.

Gnathopod II (Fig. 9C ) larger than gnathopod I with a rectangular coxal plate (ratio depth:width 1.0:0.8). Ovoid gill, with a length equal to that of the coxal plate. Basis length:width ratio 1.0:0.3. Ischium with one posteroventral group of 6 setae. Basis length:carpus length ratio 1.0:0.5. Carpus with 8 groups of 4-6 setae along its ventral margin, a row of 15 setae on its surface close to ventral margin and a group of 7 setae located anterodorsally. The propodite approximately as long as wide, with several groups of 4--6 setae on its ventral margin, one antero-dorsal group of 5 setae and one antero-apical group of 9 setae. On its outer surface, propodite with 4 groups of 2-3 setae located close to its ventral margin, 3 groups formed of 5-8 setae closer to the dorsal margin, one group of 4 long setae close to the palmar spine and one seta located medially on the anterior side of the propodus. Strong palmar spine and two supporting spines at palmar corner. Dactylus with nail length one third of total dactylus length and with one small seta along outer margin.

Pereopod III (Fig. 10A ) with rectangular coxal plate, ratio depth:width 1.0:0.7. Gill of similar shape and size. Propodite length:dactylus length ratio 1.0:0.5. Dactylus with nail measuring almost half of total length of dactylus, with one dorsal seta with plumose tip and one spine and one tiny seta at nail base. Pereopod III nearly equal in length to pereopod IV (pereopod III length:pereopod IV length ratio 1.0:0.91).

Pereopod IV (Fig. 10B ) with coxal plate sub-rectangular, with a concavity on the posterior margin. Depth:maximum width ratio 1.0:1.0. Robust dactylus, with nail measuring almost half of total dactylus length; with one dorsal seta with plumose tip and one spine accompanied by a tiny seta near nail base. Propodite length:dactylus length ratio 1.0:0.5.

Pereopod V (Fig. 10C ) with coxal plate of irregular shape, with a deep concavity on the ventral side and two anterior setae. Gill ovoid to trapezoidal. Basis ovoid-rectangular with length:width ratio 1.0:0.7 with 20 short and thick setae on posterior margin, and 7 groups of 1-3 similar setae on anterior margin. Dactylus with one plumose seta on outer margin and one spine and one seta at nail base, which represents 40% of the total dactylus length. Propodite length:dactylus length ratio 1.0:0.3.

Pereopod VI (Fig. 11A ) more than 11 mm long, being the longest leg of the inspected male. Coxal plate less robust compared to that of pereopod V, but highly similar in shape, with three posterior setae and two ventral setae. Basipodite with ovoid-trapezoidal shape, 11 small setae on posterior margin and six groups of 1-2 setae on anterior margin; length:width ratio 1.0:0.65. Dactylus with one plumose seta on outer margin and one spine and a tiny seta near nail base. Nail length slightly more than one third of the total dactylus length. Ratio propodite length:dactylus length 1.0:0.3.

Pereopod VII (Fig. 11B ). Coxal plate trapezoidal, with three setae on the posterior margin. Basis ovoid-trapezoidal, with a ratio length:width 1.0:0.7. Basis bearing 19 setae on posterior margin and five groups of 2-3 thick setae on anterior margin. Dactylus with one seta on the outer margin and one seta accompanied by one spine near nail base. Nail length one third of total dactylus length. Ratio propodite length:dactylus length 1.0:0.3.

Pereopods V:VI:VII ratio 1.0:1.32:1.27.

Pleopods similar each other (pleopod I as in Fig. 11C ), with unequal rami and two retinacles on peduncle.

Uropod I (Fig. 12A ) with two dorso-lateral rows of 4 spines on peduncle. Endopodite and exopodite of same length. Exopodite more setose than endopodite. One strong spine near the insertion of uropod I.

Uropod II (Fig. 12B ) with four dorsolateral spines on peduncle. Endopod longer than exopod, endopod length:exopod length ratio 1.0:0.82, both rami with a low number of spines.

Uropod III (Fig. 12C ) 8.6 mm long, which makes it almost as long as half of total body length. Peduncle with two groups of 4 apical spiniform setae each. Endopod short, about half the length of peduncle, with 4 simple setae and one plumose seta apically. Proximal segment of exopod longer than distal segment (ratio 1.0:0.6). Outer margin of the proximal segment of exopod with 7 groups of setae, almost every group containing one plumose seta; inner margin with 4 groups of 5 small setae each. Distal segment of exopod provided with two groups of 4 setae in its second half and one subapical group of 5 setae on the anterior margin, one subapical row of 4 small setae on the posterior side and several setae of different lengths located apically.

Epimeral plates (Fig. 6C ). Epimeral plate I with acute to right postero-ventral angle, relatively straight ventral margin with no spines and concave posterior margin with 7 setae and three postero-dorsal setae. Epimeral plate II with right postero-ventral angle, convex ventral margin with two spines and relatively straight posterior margin with 6 setae and 6 postero-dorsal setae. Epimeral plate III is slightly different compared to epimeral plates I and II, the postero-ventral angle is rather acute, the ventral margin is relatively straight with 3 spiniform setae, the posterior margin is concave to straight, with 6 setae and 5 postero-dorsal setae.

Urosomite I (Fig. 6B ) with 7 dorso-lateral setae on each side of posterior margin, urosomite II with 5 dorso-lateral setae of various lengths on each side of posterior margin. Posterior margin of urosomite III without setation.

Telson (Fig. 12E ) longer than wide (length:width ratio 1.0:0.75), with 4 apical spines of different lengths. Longest spine slightly shorter than one third of telson length. Two thin setae with plumose tips along each side. 4-5 lateral and 3-5 dorsal spines on each lobe.

Sexual dimorphism.

Male and female highly similar except for the presence of oostegites (Fig. 13C ), uropod III and telson. Uropod III of female (Figs 12D , 13E ) shorter compared to that of male; second article of exopod shorter than in male, slightly longer than endopod. Female telson (Fig. 12F ) similar in shape and size to that of male, but with lower number of spines laterally and dorsally. Female telson missing the lateral plumose setae.

Comparison between the female from the Falkensteiner Höhle (type locality) and the female from the Blätterteighöhle could not detect marked differences. The small differences that could be noticed observing Karaman’s (1932) drawings disappeared after a careful examination of the dissected appendages (Fig. 13 ), confirming that they were due to the poor quality of the original description. The shape of the propodite of the second gnathopod (Fig. 13C ) is very similar, and the presence of minute groups of spinules on its outer surface, not reported in Karaman’s (1932) figure 6, was confirmed in the specimen examined (Fig. 13C ). Only a minor difference was observed in the length of the apical spines of the endopod of uropod III (Fig. 13E ), which are slighter shorter in the female from the type locality in comparison to the one of the Blätterteighöhle. However, the very low number of specimens examined did not allow us to ascertain the variability of this character in different populations of the species.

Figures

Figure 5. Niphargus enslini, live male from the Blaetterteighoehle (Photo: Bernd Hugger).

Figures 6. Niphargus enslini, male from the Blaetterteighoehle A habitus B urosomites and uropods C epimeral plates.

Figure 7. Niphargus enslini, male from the Blaetterteighoehle A antenna I B, C accessory flagellum of antenna I D aesthetascs on antennulary segments of flagellum E antenna II.

Figure 8. Niphargus enslini, male from the Blaetterteighoehle A labium B left mandible C right mandible D maxilla I E maxila II.

Figure 9. Niphargus enslini, male from the Blaetterteighoehle A maxilliped B gnathopod I C gnathopod II.

Figure 10. Niphargus enslini, male from the Blaetterteighoehle A pereopod III B pereopod IV C pereopod V (dactlylus twisted).

Figure 11. Niphargus enslini, male from the Blaetterteighoehle A pereopod VI B Pereopod VII C pleopod I (enlarged: retinacula).

Figure 12. Niphargus enslini, male from the Blaetterteighoehle A uropod I B uropod II C uropod III E telson. Female from the Blaetterteighoehle: D uropod III F telson.

Figure 13. Niphargus enslini, topotype female from the Falkensteiner Hoehle (BZM 24795) A pleonites 2 - 3, dorsal margin with spines B epimeral plates 1 - 3 (left side) C gnathopod II with gill and oostegite (enlarged: the palmar corner), outer side D dactylopodite of pereopod 7 E uropod III (left).