Lepechinella schellenbergi Stephensen, 1944

Johansen, Per-Otto & Vader, Wim, 2015, New and little known species of Lepechinella (Crustacea, Amphipoda, Lepechinellidae) and an allied new genus Lepesubchela from the North Atlantic, European Journal of Taxonomy 127, pp. 1-35 : 18-23

Lepechinella schellenbergi Stephensen, 1944

Figs 10–12

Lepechinella schellenbergi Stephensen, 1944: 18–20 , fig 11.

Lepechinella arctica – Barnard 1973: 10. — Barnard & Karaman 1991: 268–270.

Material examined

About 13 specimens of Lepechinella were collected off the west coast of Greenland during the Ingolf Expedition ( Stephensen 1944). The specimens were sampled from station 32 at 599 meters depth, 11 Jul. 1895 and station 35 at 682 meters depth 18 Jul. 1895. The position of station 32 was at 66 o 35’N, 56 o 38’W and station 35 was at 65 o 16’N, 55 o 05’W. The in situ temperatures at the collection sites were 3.6– 3.9 o C.

The type material of Lepechinella from Greenland is deposited in the collections of Zoological Museum in Copenhagen, Denmark. The examined material was prepared on microscope slides from station 35, from one entire female in addition to the front part of one male and female that probably had been cut during sampling.

Lectotype

♀, Ingolf st. 35, on slide (reg.no. ZMUC-CRU-4468) ( Figs 10–11 ).

Paralectotypes

♂, Ingolf st. 35, on slide (reg.no. ZMUC-CRU-4469) ( Fig. 12 ).

♀, Ingolf st. 35, on slide (reg.no. ZMUC-CRU-4470) ( Fig. 12 ).

3 paralectotypes, Ingolf st. 32 (reg.no. ZMUC-CRU-8019).

8– 9 paralectotypes, Ingolf st. 35 (reg.no. ZMUC-CRU-8020).

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 1973; Barnard & Karaman 1991).

Redescription

Lectotype

Female 6 mm.

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

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.

MOUTHPARTS. Mandible incisor stronger than lacinia mobilis, both armed with denticles, molar surface with transverse ribs, 5–6 accessory spines. Maxilla 1, inner plate distally tapering with two apical setae;

outer plate broad with 7 serrate spine teeth; palp distally expanded and obliquely truncated, with 6 blunt spines and one apical long spine. Maxilla 2, inner plate shorter and narrower than outer plate; outer plate with 13 distal setae; inner plate with 5 apical setae. Maxilliped, inner plate reaching to 1/2 of outer plate, apically 3 blunt spines and a few setae; outer plate with 11 broad spine teeth of varying length; palp 4-articulate; outer plate reaches to end of palp article 3.

PERAEON. Proximal part of gills obliquely pleated. Gnathopod 1, subchelate; coxal plate 1 asymmetrically bifid; propodus distally tapering and slightly shorter than carpus; 5 groups of long setae on posterior part of carpus; dactyl curved; dactyl 1/2 the length of propodus; 3–4 groups of setae on anterior and posterior margins of propodus; palm of propodus serrulate. Gnathopod 2 longer and more slender than gnathopod 1; coxal plate 2 tapering to an acute tip; gnathopod 2, basis 1.2x longer than carpus; 6–8 groups of setae along the margins of carpus; carpus longer than propodus; palm of propodus serrulate; dactyl curved. Peraeopod 3 longer than gnathopod 1 and 2; coxal plate 3 asymmetrically bifid and anterior part acute; merus longer than carpus; merus subequal to basis; carpus subequal to propodus and dactyl; dactyl lanceolate. Coxal plate 4 asymmetrically bifid; proximal posterior part of coxal plate 4 produced; peraeopod 4, merus 1.7x longer than carpus; dactyl subequal to propodus; merus 1.3x longer than basis. Coxal plate 5 anterior part acute; peraeopod 5, carpus 1.4x merus; carpus shorter than basis; carpus longer than propodus; dactyl lanceolate and subequal to propodus. Coxal plate 6 twice as broad as high; peraeopod 6, carpus 1.3x longer than merus and propodus; basis 1.2x longer than carpus; dactyl shorter than propodus; dactyl lanceolate. Coxal plate 7 is 2.8x as broad as long; posterodistal part of coxal plate 7 rounded; peraeopod 7, basis 1.2x longer than carpus; carpus 1.7x longer than merus; propodus longer than dactyl, dactyl lanceolate.

PLEON. Segments 1–3 each with one large and one small mid-dorsal process. Posterior angle of epimeral plates 1–3 acute forming a sinus; sinus largest in epimeral plate 3; setae along margin of epimeral plate 1; spines distributed in 2–3 arrays on epimeral plates 1–3. Urosome segment 1 with one tooth; length of urosome segment 1 subequal to 2 and 3 combined; urosome segments 2–3 fused. Uropod 1 peduncle with 2 distal large spines and several smaller marginal ones; peduncle longer than rami; outer ramus 1.1x inner ramus. Uropod 2 peduncle subequal to outer ramus; outer ramus 0.7x inner. Uropod 3 peduncle 1/5 of rami; shorter ramus 0.9x longer. Telson cleft to 50 % of total length and widely gaping; apical setae longer than telson; 2 setae along each lateral margin of telson.

Paralectotype 1

Female, head + peraeon segments 1–4 = 2 mm.

Mandible, incisor longer than lacinia mobilis both with denticles; molar with transverse ribs; 5–6 accessory spines; mandible palp article 1 is1.2x article 3; mandible palp article 2 is 4x article 3.

Paralectotype 2

Male, head + peraeon segments 1–5 = 2 mm.

Mandible, incisor and lacinia mobilis with denticles; molar with transverse ribs; 3–4 accessory spines; upper lip rounded lobes, tapering medially; lower lip bilobate, inner lobes reaching ½ of outer lobes. Antenna 1, margins of peduncle articles 1–2 with dense row of short setae and a few long setae; peduncle article 1 broader than article 2 and 3; peduncle article 2 is 2x article 1; peduncle article 2 tapering medially; peduncle article 3 is 1/5 of article 2; flagellum 23-articulate; flagellum longer than peduncle articles 1–3 combined; accessory flagellum 1-articulate with one apical setae. Antenna 2, peduncle article 4 margins with dense row of small setae, peduncle articles 1–3 broader than article 4–5; article 4 tapering distally; peduncle article 5 is 2.2x article 4; peduncle article 5 shorter than flagellum; flagellum 31-articulate.

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.

Remarks

The dorsal armature of L. schellenbergi is not as heavy as in L. norvegica sp. nov. Stephensen did not dissect the mouthparts of L. schellenbergi from Greenland. The microscope slides of the specimens from

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 .

Figures

Fig. 10. Lepechinella schellenbergi Stephensen, 1944, lectotype, ♀. A. Right Gn1. B. Right Gn2. C. Left P3. D. Gill of P5. E. Right P4. F. Left P5.

Fig. 11. Lepechinella schellenbergi Stephensen, 1944, lectotype, ♀. A. Left U1. B. Right U2. C. Right U3 and telson. D. Right Ep1. E. Right Ep2. F. Right Ep3. G. Female A1. H. Accessory flagellum. I. Female A2. J. Left Mxp. K. Left Mx2. L. Left Mx1. M–N. Left and right mandible.

Fig. 12. Lepechinella schellenbergi Stephensen, 1944. — A–C. Lectotype, ♀. A. Left P7, 1 spine on basis is enlarged. B. Left P6. C. Tooth of peraeon segment 6. — D–J. Paralectotype 1, ♂. D. Left and right male A2. E–F. Male A1 with accessory flagellum. G–H. Right and left mandible. I. Lower lip. J. Upper lip. — K–L. Paralectotype 2, ♀, mandible and mandible palp.