New and little known species of Lepechinella (Crustacea, Amphipoda, Lepechinellidae) and an allied new genus Lepesubchela from the North Atlantic

. New species of Lepechinella , L. norvegica sp. nov. and L. victoriae sp. nov., from the North East Atlantic are described together with the new, closely related genus and species Lepesubchela christinae gen. et sp. nov. Lepechinella arctica Schellenberg, 1926 from north of Spitsbergen and Lepechinella schellenbergi Stephensen, 1944 from Greenland are redescribed. A key to the species of Atlantic and Arctic Lepechinella is provided. Descriptions of taxonomic characters from related species in the Atlantic and Arctic are discussed.


Introduction
named the amphipod genus Lepechinella (after the Russian author Lepechin who described a White Sea amphipod as early as 1780) for a species he collected at a depth of 850-900 meters off the Orkney Islands, Scotland. More than 30 species have so far been described in the genus Lepechinella Barnard & Karaman 1991;Sittrop & Serejo 2009). The genus has a cosmopolitan distribution and contains mainly deepwater species on soft bottoms; some of the species occur in the hadal trenches of the deep sea (Kamenskaya 1995). Lepechinellids are well adapted to a demersal or epibenthic lifestyle on soft substrates in deep water ).

Taxonomic material
The examined material was collected in the North Atlantic and Arctic. Most of the animals were dissected in glycerol and mounted on microscope slides in Faure's fluid. However, the parts of the holotype of L. arctica and also types of L. schellenbergi were dissected in ethanol and mounted on microscope slides using Euparal. Drawings were made using stacks of photos taken from a Bresser biolux NG microscope with an electronic sensor and the drawings were made with an electronic pc-tablet using the techniques described by Coleman (2003Coleman ( , 2006Coleman ( , 2009. The type material of L. arctica was borrowed from the Museum für Naturkunde in Berlin and that of L. schellenbergi from the Zoological Museum in Copenhagen. The rest of the type material is kept at the Bergen and Tromsø Zoological Museums.

Seta
= flexible structures that are articulated Spine = rigid structures that are articulated Tooth = outgrowth that are not articulated
The description of L. arctica is based on new drawings of the peraeon and pleon in addition to the text and the original drawing of the head made by Schellenberg (1925). The urosome was missing in the original sample. Schellenberg (1925) briefly described the mouthparts and made a drawing of the head, but these parts have unfortunately not been found in the collections.

Holotype
Female with fully developed oostegites, length 5.5 mm without urosome.
Body. Two mid-dorsal teeth on peraeon segment 1. Peraeon segments 2-7 with one dorsal tooth each, a few setae and spines, primarily on the dorsal part. Coxal plates with some spines and thin setae. Coxal plate 1-7 decreasing in height posteriorly. Peraeon segments 1-7 with distinctly developed lobes above the coxal plates.
Head (Fig. 2). According to Schellenberg (1925) (translated from German): "Head short, exclusive of the processes not much longer than 1 st thorax segment. Rostrum shaped as a heavy, acute, horizontal spine, a little wavy, half as long as 1 st joint of antenna 1. Lateral lobe of head not projecting, but provided with 2 marginal spines; postantennal corner acute. No eyes". Schellenberg, 1926 (Dorbanella sp.), head redrawn after Schellenberg (1925 MoutHparts. According to Schellenberg 1925 (translated from German): "Oral parts much projecting. Free margin of upper lip rounded, lateral lobes of lower lip distally rounded; mandibular processes very short and blunt; inner lobes well developed. Mandible strong, molar processes broad; incisor and lacinia mobilis strong and of about equal size, with several blunt teeth; spines long and strong; palp slender, 2 nd and 3 rd joints setose, 1 st joint longer than 3 rd , 2 nd joint 4 times as long as 3 rd . Inner plate of maxilla 1 much narrower than outer plate, apically with 2 strong setae; outer plate broad, with 10 dentate spines on the blunt apex; palp strong, apically with short, broad teeth. Maxilla 2 with plates apically densely setose. Inner plate shorter, and only half as broad as outer plate. Maxilliped has inner lobe somewhat oval, apically blunt, beset with setae and a few short heavy denticles; outer lobe oval, reaches to the last third of 2 nd joint of palp; distal part of inner margin beset with short thick teeth apically ending in spines; palp normal, 2 nd joint twice as long as 3 rd joint." peraeon. Gills smooth with distinct distal capillary pattern; Gnathopods with slender setae on both margins. Gnathopod 1 subchelate; coxal plate 1 asymmetrically bifid, anterior process 2x the posterior process; coxal plate 1 medially tapering; propodus subequal to carpus; propodus 0.5x basis; posterior margin of carpus with 5 rows of long setae; medial part of propodus with 3 groups of setae; palm of propodus with serrulations; dactyl curved and 0.5x propodus. Gnathopod 2 subchelate and longer than gnathopod 1; coxal plate 2 tapering to an acute tip; carpus longer than merus and propodus; dactyl curved; palm of propodus serrulate. Anterior part of coxal plate 3 acute, posterior part squarely produced; width of coxal plate 3 is 4x width of basis; peraeopod 3, merus 2x carpus; merus longer than basis; propodus subequal to carpus and dactyl; dactyl lanceolate. Coxal plate 4 pointed anteriorly, posterior part squarely produced; width of coxal plate 4 is 4x width of basis; peraeopod 4, merus is the longest article and 1.3x basis; basis and propodus subequal in length; dactyl and carpus shorter than propodus; dactyl lanceolate. Coxal plate 5 is anteriorly pointed; peraeopod 5, carpus longer than merus and propodus; dactyl is broken. Coxal plate 6 rectangular shaped with an anterior bulge; peraeopod 6, merus shorter than carpus and subequal to propodus; basis longer than carpus; dactyl shorter than propodus; dactyl lanceolate. Coxal plate 7 parallogram-shaped and 2x broader than high; peraeopod 7, merus shorter than carpus and subequal to propodus; basis with a posterior proximal lobe; the tip of the lanceolate dactyl is broken.

Remarks
L. arctica is characterized by few dorsal and lateral setae and spines. Posterior part of coxal plates 3 and 4 are squarely produced and 4x broader than basis. The shape of coxal plate 3 and 4 and relative length of leg articles of peraeopod 3 and 4 are different from L. schellenbergi and L. norvegica sp. nov. (Table 1). Peraeopod 3 merus / carpus ratio is significantly higher in L. arctica than in the two other species. Schellenberg dissected the mouthparts of specimens from Spitzbergen and described them briefly. However, the mouthparts could not be drawn since we were unable to locate them in the collections. Schellenberg wrote that the postantennal corner of L. arctica was acute and mandible palp article 1 longer than article 3, which is different from L. norvegica sp. nov. Antenna 2 peduncle article 5 is 1.5-2x the length of the penultimate peduncle article in L. schellenbergi and L. norvegica sp. nov. Schellenberg wrote that the two last peduncle articles on the antenna 2 are subequal in length and that the flagellum was broken. However, the exact length of antenna 2 peduncle article 5 is uncertain, because the distal part of peduncle article 5 may also have been lost. Peraeopod 7 carpus of L. arctica is 1.6x propodus. Coxal plate 7 has the shape of a parallelogram and the posterior corner of coxal plate 7 is acute. The Peraeopod 7 carpus / propodus ratio is significantly lower in L. schellenbergi and L. norvegica sp. nov. and the posterodistal part of coxal plate 7 is rounded in these two species.

Diagnosis
Eyes absent. Body heavily covered with spines and setae. Rostrum longer than lateral processes. Mandible palp article 1 subequal to article 3. Molar oval with ragged margins. Maxilliped palp 4-articulate.
Posterior legs long and very slender. Coxal plate 4 symmetrically bifid. Posterodistal corner of coxa 7 rounded. Gills smooth. Pleon segments 1-3 each with one small and one large dorsal tooth. Telson deeply cleft.

Material examined
The holotype of Lepechinella norvegica sp. nov. was collected during the Mareano project using RPsledge at station R-578, situated at Teistengrunnen on the Norwegian coast. The sediment at R-578 consisted of sandy mud with gravel. Additional material examined was collected from the Mareano-  Body. Abundantly covered dorsally and laterally with long setae and spines. Spines, which vary in length, are attached to discs. Coxal plates posteriorly decreasing in height. 2 mid-dorsal teeth on peraeon segment 1 and one on each peraeon segments 2-7. One small mid-dorsal wart with 2 setae prior to the tooth on peraeon segment 7. Pleon segments 1-3, each with 1 small and 1 large dorsal tooth. Gnathopods 1-2 shorter than peraeopod 3-7.
MoutHparts. Upper lip oval lobes and medially constricted; lower lip bilobate; inner lobe extending to 1/2 of the outer lobe. Mandible, incisor and lacinia mobilis of subequal length, both with denticles; molar is elliptic, saucer-shaped with ragged margins; 6-7 accessory spines; mandible palp article 1 and 3 subequal; mandible article 2 slightly curved with 12 long setae; mandible article 2 is 4x article 3, mandible article 3 with 4 lateral and 4 long apical setae. Maxilla 1, inner plate narrow with 2 apical plumose setae; outer plate tapering distally, with 10 apical serrate spine teeth; palp 2-articulate obliquely truncated; palp with 6-7 blunt spines and one longer apical spine. Maxilla 2, inner plate shorter and narrower than outer plate; outer plate with about 25 distal long setae; inner plate with 1 strong plumose setae in addition to apical setae; inner margin of inner plate lined with setae. Maxilliped, outer plate 2x inner plate; inner plate slender with 3 blunt apical teeth and setae along the inner margin; outer plate armed with 14 broad spine teeth of decreasing length on distal and medial margin; outer plate reaches article 3 of palp; palp 4-articulate where the second article is subequal to the two last articles combined.
pleon. Segments 1, 2 and 3 each with one large and one small dorsally situated tooth. Posterodistal angle of epimeral plates 1-3 acute, forming a small sinus; epimeral plate 3 sinus largest; setae along margins and 2 arrays of spines on epimeral plates 1-3. Urosome segment 1 subequal to 2 and 3 combined; urosome segment 1 with 1 mid-dorsal tooth; urosome segments 2 and 3 fused. Uropod 1 peduncle has two distal spines and rows of spines along the margins; peduncle longer than both rami; inner ramus 0.9x outer. Uropod 2 peduncle shorter than inner ramus and subequal to outer; outer ramus 0.8x of inner ramus. Uropod 3 peduncle about 1/ 5 of the rami; longer ramus 1.1x shorter; rami densely covered with long setae. Telson parts are gaping, cleft to 80 % of total length; length of apical setae subequal to telson; four setae along the margins of telson, four spines on the dorsal part of the last urosome segment.

Variation
The rostrum is about 30 % of the length of antenna 1 peduncle article 1 in 2 mm long specimens while it is about 50 % in 7 mm long specimens. The dorsal teeth of coxal plate 1 are about 50 % of the body height of peraeon segment 1 in 6-7 mm long specimens, but only 20 % in 2 mm long specimens. Large specimens have one small dorsal wart armed with two setae prior to the large posterior tooth of peraeon segment 7. Males have large teeth that are pointing backwards, while females have more slender and upright teeth on pleon. Female antenna 1 and 2 peduncle margins have scattered long setae, while males have dense rows of small setae. Antenna 2 is longer than antenna 1 in males, while they are subequal in females and antenna 2 peduncle article 5 is 2x the penultimate peduncle article in males, while it is 1.5x in females. Posterodistal angle of epimeral plate 3 is situated more in centre in females than males, which results in a larger sinus in females. The setae on the rami of uropod 3 seem to be denser in males than in females. Sexual dimorphism has also been observed in dorsal armature, posterodistal shape of epimeral plates and setal armature of antennal peduncles of L. helgi, L. grimi and L. skarphedini (Thurston 1980a).

Remarks
L. norvegica sp. nov. from Northern Norway is characterized by a dense cover of long setae and spines. Spines with the longer setae are usually situated dorsally while spines on disc-shaped pegs are mainly situated laterally on the body, on the coxae and on the basis of the posterior legs. However, a lot of JOHANSEN P.-O. & VADER W., Lepechinella and Lepesubchela gen. nov. from the North Atlantic the spines were probably broken, leaving only the disc to which they were attached. Setae attached to cylinder-shaped pegs were observed on the head. The postantennal corner of L. norvegica sp. nov. is rounded while L. arctica has an acute postantennal corner according to Schellenberg (Table 1). Mandible palp article 1 and 3 of L. norvegica sp. nov. are subequal, while article 3 is larger in L. schellenbergi and L. arctica. The molar is elliptic with small marginal ribs in L. norvegica sp. nov. and has a certain similarity to the molar of Lepechinelloides kari Thurston, 1980 and Lepechinella turpis J.L. Barnard, 1967. The width of maxilla 2 inner plate is about 1/3 of the outer in L. norvegica sp. nov., while it is about 1/2 in L. schellenbergi and L. arctica and 2/3 in L. victoriae sp. nov. L. norvegica sp. nov. has a symmetrical  (2015) bilobate coxal plate 4. Coxal plates 3 and 4 are 2x wider than basis of respective legs and thus the legs seems stouter than in the case of L. schellenbergi and L. arctica. Peraeopod 3 merus of L. norvegica sp. nov. is 1.6x carpus and merus subequal to basis. The merus/carpus ratio is higher in L. arctica and lower in L. schellenbergi. The inner edges of gnathopod 1-2 dactyls have notches resembling dactyls of many Liljeborgia species. The position and number of setae on the telson are different in L. norvegica sp. nov. and L. schellenbergi. The telson is more deeply cleft in L. norvegica sp. nov.(about 80 %) than  Stephensen, 1944 Figs 10-12

Material examined
About 13 specimens of Lepechinella were collected off the west coast of Greenland during the Ingolf Expedition (Stephensen 1944  Stephensen (1938) translated Schellenberg's description of Dorbanella sp. as Lepechinella sp. He was then probably unaware that Schellenberg (1926) in a footnote had changed the name from Dorbanella sp. to Lepechinella artica. When describing the specimens from Greenland, Stephensen (1944) assumed that this was the same species as Schellenberg had recorded from Spitzbergen and named it Lepechinella schellenbergi nom. nov. The specimens from Greenland were later assumed to be Lepechinella arctica Barnard & Karaman 1991).
Body. Covered mainly dorsally and laterally with setae and spines. The spines, which varied in length, are attached to disc-shaped pegs and varied in size. Peraeon segment 1 with two dorsal teeth, peraeon segments 2-7 each with one large mid-dorsal tooth. Urosome segment 1 with 1 dorsal tooth.
Head. Larger than the first body segment; two anteriorly pointing lateral eye lobes; rostrum longer than the eye lobes; eyes absent or at least indistinct in alcohol; anterior postantennal corner with rounded European Journal of Taxonomy 127: 1-35 (2015) angle. Rostrum, about half the length of antenna 1 peduncle article 1. Antenna 1 peduncle article 1 broader than article 2 and 3; article 2 is 2x article 1 and distally tapering; peduncle article 2 is 5x the length of article 3; flagellum 20-articulate; flagellum 1.5x longer than peduncle articles 1-3 combined; accessory flagellum 1-articulate with two apical setae. Antenna 2 peduncle articles 1-3 broader than article 4-5; peduncle article 4 is 3x peduncle articles 1-3 combined; peduncle article 4 tapering distally; distal part of peduncle article 5 is lost.

Variation
Rostrum varies in length, from 40-60 % of antenna 1 peduncle article 1 in 5-6 mm long specimens, to about 35 % in 4 mm long specimen. The dorsal teeth on peraeon segment 1 are 35-45 % of the body height in 5-6 mm long specimens. Large specimens have one small dorsal wart with two setae, prior to the large posterior tooth of peraeon segment 7. The teeth on the pleon are stronger in males than in females. The margin of female antennal peduncle has scattered long setae, while that of males has a dense row of small setae. The female epimeral plate 3 sinus is smaller in L. schellenbergi than in L. arctica and L. norvegica sp. nov. Since the shape of epimeral sinus in Lepechinella seems to vary both between gender and species, this character is probably not applicable to distinguish between species. the same Greenland stations show that the length of mandible palp and shape of mandible molar are different from L. norvegica sp. nov. The molar of L. schellenbergi resembles the descriptions of L. helgi, L. skarphedini and L. grimi. The coxae shape and relative size of peraeopod 3 and 4 also separate L. arctica, L. schellenbergi and L. norvegica sp. nov. L. schellenbergi has a triangularly produced posterior proximal part of coxal plates 3 and 4, and width of coxae is 3x the width of basis (Table  1). According to Stephensen (1944) the anterior postantennal corner is acute, but on the examined specimens the angle seems rounded. The drawing of antenna 1 and 2 made by Stephensen (op. cit.) is probably from a male because of the dense short setae groups along the antennal peduncle margins, while the drawing of gnathopod 2 is from a female because it includes an oostegite. The tip of uropod 2 is broken in Stephensen's figure. However, the microscope slides show that the length of outer ramus of uropod 2 is 0.7x inner, in L. schellenbergi as in L. victoriae sp. nov. and L. manco, while it is 0.8x in L. norvegica sp. nov. and subequal in L. helgi.

Etymology
The species is named after POJ's first grandchild.

Material examined
Two specimens of Lepechinella victoriae sp. nov. were collected at station 83.06.5.1, in the North East Atlantic, south of Iceland. The in situ temperature was measured to 2.7 o C. The type material of Lepechinella victoriae sp. nov. is deposited in the collections of Zoological Museum in Bergen.

Paratype
Female, registration no. ZMBN 99135, 4.5 mm, date and position as for holotype.

Remarks
L. victoriae sp. nov. lacks the distinct additional dorsal humps / teeth found in L. schellenbergi, L. norvegica sp. nov. and L. arctica. Peraeopod 4 carpus longer than propodus, while it is the reverse in the three above mentioned species. The anterodistal lobe on coxae 3-5 is strongly elongated. The gills are proximally pleated. As in L. schellenbergi uropod 2 outer ramus is 0.7x inner, while the ratio is 0.8x in L. norvegica sp. nov. The rostrum is subequal in length to eye lobes, innerlobes of lower lip relatively large as in L. grimi and mandible palp article 1 is half the length of article 3.

Etymology
The name is a combination of the genus name Lepechinella and the word subchela as the two last subchelate peraeopods are the main characteristic of this genus.

Etymology
The species is named after POJ's youngest daughter.

Remarks
Lepesubchela christinae gen. et sp. nov. is characterized by setae attached to crown-shaped pegs on the body; Rostrum and dorsal teeth on peraeon segment 1 is absent. The species has an invagination at the basis of antenna 2 and is lacking postantennal corners as in Lepechinelloides karii Thurston, 1980. Coxal plates 1-5 biacuminate. Antenna 2 peduncle article 5 longer than flagellum. Posterodistal angle of epimeral plates 1-3 without sinus and strongly acute. Gnathopods 1 and 2, peraeopods 6 and 7 subchelate and armed with strong teeth. The mandible molar is special and looks like a trapezoid with spine-like margins. Lower lip of L. christinae gen. et sp. nov. resembles the lower lip of L. skarphedini and upper lip, maxilliped, maxilla 1 and 2 are similar to several Lepechinella species.
The family Lepechinellidae consists of a single speciose genus, Lepechinella, and a number of small genera, that in most cases vary in only one or two apomorphies. The new genus Lepesubchela similarly is primarily distinguished by a single strong autapomorphy, the prehensile posterior peraeopods, although also the morphology of the head is deviant. Whether these different autapomorphies really delimit independent evolutionary lines, can only be decided on the base of a cladistic analysis preferably including molecular data.

Discussion
Since most of the Lepechinellidae species are known from single localities and few specimens only, the nature and degree of allometry and intraspecific variation is poorly understood (Thurston 1980a). Most species seem sufficiently distinct to be fairly readily separable. This is not true, however, for the six species in the L. chrysotheras group. All of these are very similar in body morphology and differ only European Journal of Taxonomy 127: 1-35 (2015) in small and rather subtle characters. More material will be required to understand the true nature of the components of this group (op. cit.). As a consequence of the dearth of qualitative characters, many of the specific differences now attributed to species of Lepechinella are for a large part quantitative (J.L. . This author concluded that because of the early stage of exploration of the genus, referral to morphs as distinct species may be justified, until more is learned about morphological variations and geography of speciation in Lepechinella. A change in species composition on each side of the Greenland-Iceland-Faroe Ridge has been observed for hyperbenthic amphipods in the families Eusiridae and Calliopiidae (Weisshappel 2000(Weisshappel , 2001. The thermohaline characteristics of the deep sea water masses on both sides are very different and the ridge acts as a barrier for deep sea species. Most of the Lepechinella species probably have a benthic lifestyle and are thus less mobile than pelagic species and endemic species with restricted distributional range may be expected.
The shape of the coxae and the number and presence of dorsal teeth, among others, are used in the key of Lepechinella from the Atlantic and the Arctic we provide here. L. victoriae sp. nov. lacks accessory dorsal teeth. L. chrysotheras, L. turpis, L. manco and L.helgii have several accessory teeth in front of the main posterior dorsal tooth on pleon segments 1-3, while L. arctica, L. schellenbergi, L. norvegica sp. nov. and L. eupraxiella have one accessory tooth. L. eupraxiella has also a short rostrum, hook-like processes at posterodistal angles of epimeral plates, bifid shape of coxal plate 1 and an anterior directed hook on coxal plate 6.