Niphargus dancaui, Traian BRAD, Cene FIŠER, Jean-François FLOT, Serban M. SARBU & Emil Racoviţă, 2015

Traian BRAD, Cene FIŠER, Jean-François FLOT, Serban M. SARBU & Emil Racoviţă, 2015, Niphargus dancaui sp. nov. (Amphipoda, Niphargidae) - a new species thriving in sulfidic groundwaters in southeastern Romania, European Journal of Taxonomy 164, pp. 1-28 : 4-25

Niphargus dancaui sp. nov.

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Figs 1–15

Niphargus cf. stygius – Sarbu & Popa 1992: 651.

Diagnosis

Mid to large-sized Niphargus of robust appearance, with acute to right postero-ventral angle of epimeral plates. Pleon with at most 4 setae along the posterior margin of each segment and a single tiny seta in postero-lateral position on urosomite I. Antenna I shorter than half of the total body length. The outer lobe of maxilla I has 7 spines with 1–3 teeth. The inner lobe of maxilliped has 9 spines. The propodus of both gnathopods are almost square-shaped, with 5 setae along the outer margins of the dactyli. The pereopods are shorter than half of the total body length, with one spine at the nail base. The uropods III are sexually dimorphic and elongated in males. The male telson bears 3 apical spines, 1 lateral and 1 dorsal spine on each lobe, plus 1 subapical spine per lobe for the female telson.

Etymology

The specific name is derived from the name of the late Dan Dancău (1933–1994), who first studied the amphipod fauna in the Dobrogea region and described some of its species, notably Pontoniphargus racovitzai from Doi Mai and Mangalia (Dancău 1970) and Niphargus dobrogicus from Doi Mai, Schitu and Vama Veche (Dancău 1964).

Material examined

Holotype

ROMANIA: ♂, Movile Cave, Mangalia ( Fig. 1, Table 2). The holotype specimen collected from location 1 in Fig. 1 was not dissected, but was deposited intact in 75 % ethanol.

Paratypes

ROMANIA: Mangalia, 1 ♂, 3 ♀♀, well 12, Aleea Cetăţii 1; 1 ♂, well 7, str. Avram Iancu 26; 1 ♀, well 10, str. Crinului 34; 1 ♀, well 3, str. General Dragalina; 1 ♂, 1 ♀, well 8, str. Horia, Cloşca şi Crişan 13.

Remark

The description was performed and species variability was examined on the basis of several paratypes collected from various hand-dug wells in the town of Mangalia ( SE Romania) ( Fig. 1, Table 2). The male and female described here were sampled from a well on Aleea Cetăţii 1. The other specimens were included in order to examine the variability.

Description (male)

The total male body length is 17.4 mm ( Fig. 2 A). A detailed chart containing the measurements of all diagnosis-relevant body appendages for both male and female is presented in Table 1.

Head

The head ( Fig. 3 A) represents 8.5 % of total body length, no rostrum was observed.

Antennae

Antenna I ( Fig. 3 B) almost half of total body length ( Table 1), with a flagellum formed of 32 articles. Most flagellum articles bear one short aesthetasc ( Fig. 3 C). Length of peduncle slightly more than one third of the total length of antenna I. Accessory flagellum ( Fig. 3 D) biarticulated, the proximal article exceeds half of second article of main flagellum, distal article is approximately one fifth of total length of accessory flagellum. Antenna II ( Fig. 3 E) with flagellum formed of 13 articles, half as long as antenna I. Peduncle almost twice as long as flagellum.

Mouthparts

Labium ( Fig. 4 A) bilobate; length of inner lobes half length of outer lobes. Both inner and outer lobes with distally fine setae. Labium displayed in Fig. 4 A from female sampled from str. Horia, Cloşca şi Crişan 13; identical to all inspected labia from other specimens, males and females.

Left mandible ( Fig. 4 B) with five teeth on incisor process, four teeth on lacinia mobilis and a row of eight serrate spines between lacinia mobilis and molar process ( Fig. 4 C).

Right mandible ( Fig. 4 D) with four teeth on incisor process, several small denticles on lacinia mobilis and a row of five denticulate setae between lacinia mobilis and molar process ( Fig. 4 E).

Two mandibular palps ( Fig. 4 B and Fig. 4 D), highly similar and of same length. The three articles represent 21 % (article 1), 37 % (article 2) and 42 % (article 3) of total palp length ( Table 1). Proximal article without setae, article 2 with 8–11 ventral setae and article 3 with one group of 5–6 A setae, three groups of 3–4 B setae, approximately 36 D setae and 5 E setae (Fišer et al. 2009).

Latitude Longitude EC H 2 S

Nr. Location pH T˚C

N E μS cm- 1 mg /l

1 Movile Cave 43 ° 49 ’ 36 ” 28 ° 33 ’ 43 ” 7.4 21.2 1071 8.3

2 Mangalia, str. Dumitru Ana 13 43 ° 49 ’ 23 ” 28 ° 34 ’01” 7.3 19.1 1052 3.4

3 Mangalia, str. General Dragalina 10 43 ° 49 ’ 15 ” 28 ° 34 ’08” 0 4 Mangalia, str. Matei Basarab 74 43 ° 49 ’ 10 ” 28 ° 34 ’06” 7.4 19.5 1550 12.2

5 Mangalia, str. Gheorghe Netoi 1 43 ° 49 ’ 10 ” 28 ° 34 ’ 12 ” 7.4 18.6 1078 4.5

6 Mangalia, str. Matei Basarab 62 43 ° 49 ’09” 28 ° 34 ’ 15 ” 0

7 Mangalia, str. Avram Iancu 26 43 ° 49 ’ 14 ” 28 ° 34 ’ 22 ” 7.5 19.6 1540 6.4

8 Mangalia, str. Horia, Cloşca şi Crişan 13 43 ° 49 ’ 18 ” 28 ° 34 ’ 23 ” 7.7 18.7 1870 0

9 Mangalia, str. Ion Mecu 51 43 ° 49 ’ 25 ” 28 ° 34 ’ 29 ” 7.68 19.9 1135 2.2

10 Mangalia, str. Crinului 34 43 ° 49 ’ 13 ” 28 ° 34 ’ 41 ” 7.43 20.2 1490 0

11 Mangalia, str. Pictor Tonitza 1 43 ° 49 ’09” 28 ° 35 ’03” 7.27 19.0 1242 0

12 Mangalia, Aleea Cetăţii 1 43 ° 48 ’ 53 ” 28 ° 35 ’01” 7.42 19.3 1650 0

13 Mangalia, str. Mihai Viteazul 20 43 ° 48 ’ 49 ” 28 ° 34 ’ 50 ” 7.3 19.5 1770 0

14 Hagieni Spring 43 ° 48 ’08” 28 ° 28 ’ 29 ” 7.6 10.5 905 5.2 Maxilla I ( Fig. 4 F) with 7 apical setae on distal palp article. Outer lobe with 7 spines with 1–3 teeth, inner lobe with 3 apical setae.

Maxilla II ( Fig. 4 G) with inner lobe slightly shorter than outer lobe; both lobes with numerous apical setae.

Maxilliped ( Fig. 4 H) with palp formed of four articles. Article 2 with numerous setae in approximately 10 groups aligned along inner margin. Article 3 with three groups of 4–5 setae on inner margin, one group of 3 setae on dorsal margin and one apical group with 5 setae. Article 4 without setae. Outer lobe of maxilliped with 6 shorter, flattened spines and 7 longer, slightly hairy, apical spines. Inner lobe with 9 setae-like spines.

Gnathopod I

Gnathopod I ( Fig. 5 A) with relatively ovoid coxal plate with depth greater than its width (ratio depth:width 1.0: 0.6). Basis length:width ratio 1.0: 0.4. Ischium with one posteroventral group of 4 setae. Basis length:carpus length 1.0: 0.6. Carpus with two groups of 8–10 setae on ventral margin, and one group of 4 setae located anterodorsally. Length:width ratio of propodus 1.0: 0.8. Propodus with 7 groups of 3–4 setae on ventral margin, one anterodorsal group with 6 setae and one antero-apical group of 4 setae. Two groups with 2–3 setae on lateral surface of propodus close to its ventral side,and two groups of 4–5 setae closer to propodus dorsal margin. One group of 3 long setae present close to palmar spine. Strong palmar spine and 4 outer denticulate spines in palmar corner. Dactylus ( Fig. 5 B) strong, with claw representing one quarter of total dactylus length and with five setae along outer margin.

Gnathopod II

Coxal plate ( Fig. 5 C) with rectangular shape, deeper than wide (ratio depth:width 1.0: 0.8). Basis length:width ratio 1.0: 0.3. Ischium with one anteroventral group of 2 setae. Basis length:carpus length 1.0: 0.6. Carpus has with two groups of 8–10 setae on ventral margin and one group of 2 setae located anterodorsally. Propodus almost square-shaped, with length:width ratio of 1.0: 0.96. Propodus with 7 groups of 2–4 setae on ventral margin, one anterodorsal group of 2 setae, and one apical group of 4 setae. Lateral surface of gnathopod II propodus without setae, with only two long setae close to palmar spine.

One strong spine and one outer, smaller spine on palmar corner. Dactylus ( Fig. 5 D) strong, with claw representing one quarter of total dactylus length and with five setae along outer margin.

Pereopod III

Coxal plate of pereopod III ( Fig. 6 A) with rectangular shape, with depth:width ratio of 1.0: 0.7. Posterior margin concave, with three setae. Gill irregularly ovoid. Dactylus ( Fig. 6 B) robust, with a nail measuring half of total dactylus length; with one dorsal seta with plumose tip and one spine at nail base. Propodus length:dactylus length ratio 1.0: 0.34. Pereopod III nearly equal in length to pereopod IV (pereopod III length:pereopod IV length ratio 1.0: 0.95).

Pereopod IV

Coxal plate of pereopod IV ( Fig. 6 C) almost square-like, depth:width ratio 1.0: 0.96. Posterior margin concave, with four setae. Gill irregularly ovoid. Dactylus ( Fig. 6 D) robust, with nail slightly longer than half of total dactylus length; with one dorsal seta with plumose tip, one spine and one seta with plumose tip at nail base. Propodus length:dactylus length ratio 1.0: 0.35.

Pereopod V

Coxal plate of pereopod V ( Fig. 6 E) shape of heart, with one small seta on anterior lobe. Basis with ovoid-trapezoidal shape, with length:width ratio of 1.0: 0.68. Basis with 9 spine-like setae on anterior margin and 9 small setae on posterior margin. Dactylus ( Fig. 6 F) with one seta with plumose end on outer margin and one spine and one smaller seta with plumose end at base of nail. Nail represents 41 % of total dactylus length.

Pereopod VI

Coxal plate of pereopod VI ( Fig. 7 A) highly similar to that of pereopod V. Basis with ovoid-trapezoidal shape, with length:width ratio of 1.0: 0.68. Basis with 9 spine-like setae on anterior margin and 9 small setae on posterior margin. Dactylus ( Fig. 7 B) with one seta with plumose end on outer margin and one spine and one smaller seta with plumose end at base of nail. Nail represents 34 % of total dactylus length.

Pereopod VII

The pereopod VII ( Fig. 7 C) is almost half of the total body length. The coxal plate pereopod VII is halfovoid, with one small seta on its posterior margin. The basis has a ovoid-trapezoidal shape, with a ratio length:width of 1.0: 0.66. The basis presents 6 spine-like setae on the anterior margin and 11 small setae on the posterior margin. The dactylus ( Fig. 7 D) has one seta with a plumose end on the outer margin, one spine and one smaller seta with a plumose end at the base of the nail. The nail represents 33 % of the total dactylus length.

Pereopods V:VI:VII equal 1.0: 1.35: 1.40.

Pleopods

Pleopods I–III ( Fig. 8 A, Fig. 8 B and Fig. 8 C) highly similar, with rami of unequal length and 2 retinacles each.

Uropod I ( Fig. 8 D) with two dorsolateral spines onto peduncle. Length of endopodite equal to that of exopodite, segments with a low number of spines. One strong spine at base of uropod I.

Uropod II ( Fig. 8 E) with three dorsolateral spines onto peduncle. Exopodite slightly longer than endopodite, exopodite length:endopodite length ratio 1.0: 0.88, both rami with a low number of spines.

Uropod III ( Fig. 8 F) long (43 % of body length) and sexually differentiated. Protopodite with 4–5 small apical spines. Endopodite as long as protopodite with two apical setae. Proximal segment of exopodite almost equal to distal segment (ratio 1.0: 0.94). Proximal segment with seven groups of 1–3 spines on inner margin, and six groups with 1–3 spines on outer margin. Distal segment of exopodite with 8 spines on inner margin, 6 spines on outer margin and 5 apical setae.

Epimeral plates

Epimeral plate I ( Fig. 8 G) with acute postero-ventral angle, convex ventral margin with no spines and straight posterior margin with five setae.

Epimeral plate II ( Fig. 8 G) with right postero-ventral angle, straight posterior margin and convex ventral margin. Two spines present along ventral margin, one strong spine in postero-ventral angle and two shorter setae along posterior margin.

Epimeral plate III ( Fig. 8 G) slightly different compared to epimeral plate II; postero-ventral angle rather acute, posterior margin slightly concave, ventral margin convex. Three spines present along ventral margin and nine setae along posterior margin.

Urosomite I with two dorsolateral spines, whereas urosomite II with four dorsolateral spines of various lengths. Dorsal margin of urosomite III spineless ( Fig. 8 H). Urosome on Fig. 8 H belonged to ♂ analyzed from str. Horia, Cloşca şi Crişan 13. Number of setae on urosomites identical on all inspected specimens.

Telson

Telson ( Fig. 8 I) slightly longer than wide (width:length ratio 1.0: 1.2). Three apical spines relatively short, approximately one fifth of telson length. Telson with two fragile, plumose-ended setae along each side, as well as one lateral spine and one dorsal spine per lobe.

Sexual dimorphism

The female ( Fig. 1 B) is smaller (body length 14.3 mm) compared to the male. The female appendages ( Figs 9–14) are highly similar to those of males, with a few exceptions. Antenna I, with 22 articles, reaches only one third of the total body length ( Fig. 9 B). Antenna II has just 9 articles ( Fig. 9 E). The female gnathopods I and II ( Fig. 11) are similar to those of the male, except that the female propodus has a more inclined palmar margin, conferring it a rather trapezoidal shape in comparison to the more rectangular shape of the male propodus ( Fig. 5). The female telson ( Fig. 14 H) is slightly different from the male one, with one sub-apical spine on each lobe. The uropod III ( Fig. 14 F) presents a distal segment of the exopodite shorter than that of the male. For the female, the proximal segment:distal segment ratio of the exopodite is 1.0: 0.17, vs. 1.0: 0.94 for the male.

Intraspecific variability

The intraspecific variability of Niphargus dancaui sp. nov. appears to be relatively low. The individuals sampled from various locations differed mainly in age-related size. The male and female described here were fully grown adults. These two specimens sampled from the well on Aleea Cetăţii 1 were larger and probably older than the other inspected specimens. However, their appendages, including their mouth parts, gnathopods, pereopods, pleopods and uropods, were largely similar with a few exceptions. The number of articles in the flagellum of antennae I and II appears variable, with numbers of articles ranging from 17 to 24 and from 9 to 11, respectively. Although the telson has always three apical spines and a pair of lateral spines its number of subapical and dorsal spines is variable ( Fig. 14 I – J). The shape of the epimeral plates is largely similar but the number of spines along their ventral margins ranges from 1 to 2 and from 1 to 3 in epimeral plates II and III, respectively.

Discussion

Morphological affinities of Niphargus dancaui sp. nov.

Niphargus dancaui sp. nov. shares several similarities with N. stygius (Sket 1974; personal observations). Both species are mid- to large-sized, robust and have similar lengths of appendages (e.g., pereopods, antennae) compared to their body lengths. Moreover, both species present similar mouthparts, gnathopods (notably the shape of the propods), spine patterns on pereopod dactyli, sexually non-dimorphic rami of uropod I, as well as similar sexually dimorphic traits such as elongated uropod III in males.

Yet, several details help distinguish N. dancaui sp. nov. from N. stygius. As pointed out by S. Karaman (1952), N. stygius and some related species (N. novomestanus Karaman, 1952, N. likanus Karaman, 1952, N. podpecanus Karaman, 1952, N. kenki Karaman, 1952, N. karamani Schellenberg, 1935) share four main traits: the outer margins of the dactyls of both gnathopods are armed with groups of setae, at most 4 setae are present along the posterior margin of the pleon segments, the first urosomite segment has a single tiny seta in a postero-lateral position, and the uropod III is sexually dimorphic. Some of these characters are also present in N. dancaui sp. nov. (namely, its sexually dimorphic uropod III and the fact that the dorso-posterior margin of its pleonites presents less than 4 setae). However, the setae along the gnathopod dactyls of N. dancaui sp. nov. are not in groups, and the urosomite I of this species has more than one seta, which sets N. dancaui sp. nov. apart from N. stygius and related species.

In this aspect, N. dancaui sp. nov. resembles some other species from the N. costozzae group living in northern Italy (N. costozzae Stoch, 1998, N. lessiniensis Stoch, 1998, N. montellianus and N. tridentinus; see Stoch 1998 for a revision) or the N. sphagnicolus-N. plurispinosus group from Slovenia and Slovakia (Rejic 1956; Hudec & Mock 2014). The latter group differs from N. dancaui sp. nov. by having more than three dorsal spines per telson lobe. Niphargus costozzae and N. montellianus differ from N. dancaui sp. nov. by having their setae along the gnathopod dactyli arranged in groups and by having more than one dorsal spine per telson lobe. Niphargus lessiniensis and N. tridentinus, however, show striking similarities to N. dancaui sp. nov. as described here. The only difference we found is the number of setal groups along the proximal exopodite article of uropod III in males: in both Italian species up to five setal groups can be found along the inner or outer margin of this article, whereas this number is slightly higher in N. dancaui sp. nov. (up to seven groups of setae).

Position of N. dancaui sp. nov. in the niphargid tree of life

The updated 28 S rRNA phylogeny of Niphargidae presented here ( Fig. 15) is consistent with the ones in Flot et al. (2014) and McInerney et al. (2014): notably, the position of the two species Niphargus glenniei and N. irlandicus as a sister group to the rest of the genus is confirmed with a very strong bootstrap support. This phylogeny shows that N. dancaui sp. nov. (black arrow) is genetically very distinct from all the species to which it is morphologically similar (white arrows): instead, it may be related to Niphargus montanarius and Niphargus sp. 4 from the Frasassi Cave system (Flot et al. 2010), a relationship that only receives low bootstrap support.

Ecological data

Individuals of N. dancaui sp. nov. collected from various wells in the town of Mangalia, in Hagieni Spring and in Movile Cave were largely similar regardless of the concentration of hydrogen sulfide in the waters where they were collected ( Table 2). These niphargids seem to be highly tolerant of the presence of hydrogen sulfide in water, but are not dependent on it for their survival.

Niphargus dancaui sp. nov. is probably more widely distributed in the area than our 14 sampled locations since it was found to occur in Hagieni Spring ( Fig. 1), which is located at an aerial distance of 8 km from the town of Mangalia. However, N. dancaui sp. nov. is probably endemic to the area of Mangalia, given that it was never found in the wells sampled in the neighboring villages (i.e., Limanu, Vama Veche, Doi Mai, Arsa, Albeşti, Vânători, Coroana, Pecineaga, Dulceşti, 23 August - data not shown).

Groundwater crustaceans are in general stenobiontic: they do not tolerate large fluctuations of the abiotic conditions in their environment (Gibert 2001). In places inhabited by humans, groundwater ecosystems are in general polluted with various anthropogenic wastes produced by industries, agricultural practices or household activities. Niphargus dancaui sp. nov. therefore appears vulnerable to extinction according to IUCN Red List categories and criteria.Apart from the occurrence of this species in Hagieni Spring, all other recorded sampling locations (Movile Cave and in 12 old hand-dug wells in the town of Mangalia) are spread over approximately 2 km 2. The wells were used in the past as drinking water sources but have now been replaced with a modern water supply system.As a result, most of these wells are abandoned or are even being used for dumping various wastes, with potentially severe consequences for groundwater crustaceans inhabiting the aquifer. It is our hope that the description of N. dancaui sp. nov. and its recognition as a species endemic to Mangalia and its vicinity will lead to conservation measures to protect the fauna of this unique sulfidic ecosystem.

Tables

Table 1. Measurements in mm of the various appendages of male and female Niphargus dancaui sp. nov. sampled from a well located on Aleea Cetăţii 1 in the town of Mangalia (SE Romania).

Appendage	Male	Female		Appendage	Male	Female
Body length	17.4	14.3		Coxal plate depth	1.4	1.3
Head length Peduncle length	1.5 3.1	1.4 2.3		Coxal plate width Basis	1.0 2.0	1.0 1.7
Antenna I Flagellum length	5.2	3.4		Ischium	0.3	0.2
Art 1 Fl. acc.	0.2	0.2	PIII	Merus	1.2	1.0
Peduncle length Antenna II Flagellum length	2.6 1.3	2.0 1.1		Carpus Propodus	0.7 1.0	0.6 0.7
Art 1	0.3	0.2		Dactylus 1	0.2	0.2
Mandible palp Art 2	0.5	0.4		Dactylus 2	0.2	0.1
Art 3	0.6	0.4		Coxal plate depth	1.4	1.3
Propodus length	1.2	0.9		Coxal plate width	1.4	1.0
Propodus width	1.0	0.8		Basis	2.0	1.7
Propodus depth	0.9	0.8		Ischium	0.3	0.3
Dactylus 1	0.9	0.6	PIV	Merus	1.0	0.8
Dactylus 2 Gnathopod I Carpus length	0.3 0.8	0.3 0.5		Carpus Propodus	0.8 0.9	0.6 0.7
Basis width	0.6	0.5		Dactylus 1	0.2	0.2
Basis length	1.4	1.1		Dactylus 2	0.2	0.1
Coxal plate depth	1.3	1.1		Basis length	1.7	1.5
Coxal plate width Propodus length	0.8 1.6	0.7 1.2		Basis width Ischium	1. 3 0.3	1.0 0.3
Propodus width Propodus depth	1.5 1.2	1.2 1.0	PV	Merus Carpus	1.0 1.2	0.9 1.0
Dactylus 1	1.3	1.0		Propodus	1.3	1.0
Dactylus 2 Gnathopod II Carpus length	0.4 1.0	0.3 0.8		Dactylus 1 Dactylus 2	0.2 0.1	0.1 0.1
Basis width	0.6	0.5		Basis length	1.9	1.7
Basis length	1.9	1.7		Basis width	1.3	1.1
Coxal plate depth	1.3	1.0		Ischium	0.3	0.3
Coxal plate width Basis length	1.1 1.4	0.9 1.3	PVI	Merus Carpus	1.3 1.7	1.1 1.5
Uropod I Endopodite length	1.1	1.0		Propodus	2.1	1.8
Exopodite length	1.1	1.0		Dactylus 1	0.3	0.2
Basis length	0.8	0.6		Dactylus 2	0.2	0.1
Uropod II Endopodite length	0.7	0.7		Basis length	2.0	1.6
Exopodite length	0.8	0.6		Basis width	1.3	1.1
Basis length	0.9	0.5		Ischium	0.3	0.4
Endopodite length Uropod III Exopodite art 1	0.5 3.4	0.3 2.1	PVII	Merus Carpus	1.2 1.7	1.0 1.4
Exopodite art 2	3.2	0.3		Propodus	2.4	2.0
Cleft length	0.5	0.4		Dactylus 1	0.4	0.2
Telson width Telson Telson length Longest spine length	0.6 0.8 0.2	0.5 0.7 0.2		Dactylus 2	0.2	0.1