Family Maeridae Krapp-Schickel, 2008
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Maera loveni (Bruzelius, 1859) (Figs. 1, 2)
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Gammarus loveni Bruzelius 1859: 59
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Maera loveni Bate 1862: 193; Norman 1869: 416; Sars 1895: 519, pl. 182; Stebbing 1906: 438; Shoemaker 1930: 116; Schellenberg 1942: 44; Gurjanova 1951: 757–758, fig. 526; Lincoln 1979: 286, fig. 133; Krapp-Schickel and Jarrett, 2000: 34, fig. 4.
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Maera tenera G.O. Sars, 1885 (cf. also Stephensen 1940: 311 who already proposed this synonymy)
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Maera prionochira von der Brüggen 1907: 230, Figs. 5, 6, 7 (figure captions are most probably switched: what is labelled as Gn 1 is the normal Gn 2, and what is labelled as Gn 2 must be an anomaly. But Ep 3 and T shape are matching).
Type locality
Bohuslän, Koster Islands, Gullmarfjord, “locis profundioribus”.
Material examined
1 male 34 mm, 83.06.03.2, 1.220 m depth, 60°12,1′N, 06° 37,5′W 1983 3/VI.
Diagnosis
Largest member of the Maera sensu stricto—group; diagnostic differences are the very little visible ommatidia of the small eyes, long flagellum in A 1, the anteriorly acutely lengthened Cx 1, the long spine on the palmar corner of Gn 2, the posterodistal corner of Ep 1–3 with upturned acute tooth, and the asymmetrically incised lobes in the telson with one spine inserted on the inside.
Redescription (using the original one by Bruzelius, completed by the allometric differences of the present specimen):
Body
Uncommonly elongate and narrow, back completely smooth. [Length of type material 20 mm, up to 37 mm after Shoemaker 1930: 334; in the present specimen 34 mm].
Head
Lateral cephalic lobe regularly rounded, anterodistal corner acute. Eyes small [with scattered ommatidia, which are pale and scarcely visible in alcohol].
A1 reaching segment 4 of the abdomen, about twice as long as A 2, regularly beset with short setae; peduncle art 1 long and narrow, but thicker and shorter than art 2; [art 3 about 1/3 length of art 2]; flagellum with about 30 arts, acc. flag. with 7–8 arts.
A 2 ped art 3 much shorter and somewhat thicker than art 4, art 4 subequal art 5 [here art 4 > art 5], art 4 longer than end of A 1 peduncle art 1; art 5 does not reach the end of A1 ped art 2 [does reach it here]; flagellum somewhat shorter than peduncle art 5 [here subequal], consists of 10–12 arts [here 13].
Mouthparts
Mandibles strong, with high molar; palp with 3 arts, the second the longest, art 1 the shortest and with tooth-shaped prolongation. Mx1 IP narrow, distally with 3–4 plumose setae; [OP with bifurcate robust spines]; Mx 2 lobes elongate, densely beset with long marginal setae [partly plumose; on IP also facial setae]. Mxp IP reaches about half of palp art 2, distally with dense setae; OP (=ischium) reaches about 1/3 of palp art 2 (=carpus), along inner margin strong spines which are toothed on one side, distally with setae; art 2 of the palp is the longest and is also densely beset with spines and setae. UL rounded, LL divided into large rounded lobes with short processes anterodistally.
Peraeon
Coxal plates short, Cx 1, 2 smaller than Cx 3, 4 [here clearly the opposite]. Cx 1 anterodistal corner acutely produced, all other coxae rounded.
Gn 1 much smaller than Gn 2
Carpus subequal to propodus [here longer], anterodistal corner acute, posterior margin rounded; anterior margin almost without setae, a number of oblique rows of densely long setae along the posterior margin; [propodus distally widening, posterior margin regularly rounded]; also facial setae on both sides. Dactylus strong, outer margin with long and fine setae, but no spines.
Gn 2 carpus [triangular]
Much smaller than propodus, on posterior margin very dense setae; propodus almost rectangular, proximal part somewhat narrower than distal one. Palm slightly convex, with 7–8 small acute humps beset with shorter spines and longer setae; palmar corner with a strong, straight and acute spine, posterior margin with dense short setae.
P 3 somewhat longer than P 4
Subsimilar: basis long and narrow, ischium short, merus, carpus and propodus gradually shorter; dactylus short [robust].
P 5–7 uncommonly narrow bases (in the type material of 20 mm)
Distally narrowing [in our specimen of 34 mm bases not so narrow], [anterior margin beset with short setae, posterior margin finely serrated; in P 5 basis proximally rounded, in P 6, 7 basis with posteroproximal lobe]; dactyli strong, convex and acute.
Pleon
Ep 1, 2, 3 all with small upturned sharp tooth on posterodistal corner.
U 1 peduncle longer than subequal rami and reaching somewhat further than U 2, with one strong spine along half of anterior margin and two spines distally; rami beset with short spines along the margins and distally; U 2 peduncle shorter than subequal rami, U 3 reaching much further than U 1, 2, rami flattened, subequal in length, margins with shorter, distal end with longer setae and fine spines.
Telson deeply cleft, but not quite to the basis, lobes diverging, distally narrowing and with short V-shaped incision [inner arm of this “V” much shorter], beset with one strong spine [which is subequal or somewhat longer than outer arm of incision].
No sexual differences observed; the female has only slightly shorter appendages.
Colour
Pale.
Distribution
North Atlantic, American and European coasts; Arctic Ocean; Greenland; Iceland; European coasts from northern Norway to British Isles. Depth range as yet only known from 6 to 400 m. Now down to 1,220 m.
For a key to all 12 Maera species worldwide (M. anoculata, M. danae, M. edwardsi, M. fusca, M. grossimana, M. hirondellei, M. loveni, M. pachytelson, M. schieckei, M. similis, M. sodalis, M. tinkerensis) see Krapp-Schickel and Jarrett 2000: 29.
Leucothoidae Dana, 1852
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Leucothoe aff. spinicarpa (Abildgaard, 1789) (Figs. 3, 4)
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Krapp-Schickel 1989; Krapp-Schickel and Menioui 2005, 64–66; Crowe 2006: 57–68.
Material examined
1 ? fem. 6 mm, 4 immatures 4–5 mm, 1,542–1,560 m depth, 62°28.1′N, 14° 13.4′W, Stn 83.06.06.1, 1983 6/VI.
Diagnosis
Eyes oval. Mandibular palp long and narrow, art 3 half length of art 2. Cx 1 inferior margin smooth, about as long as wide. Gn 1 carpus distal part about 6× longer than wide, dactylus reaching about 0,3× of propodus length. P 3, 4 with very narrow basis, P 5–7 basis ovally broadened, with regularly rounded hind margin, ratio length to width 2.5: 4 or 3.5: 5. Ep 2 posterodistally with upturned tip, Ep 3 distoposterior corner with right angle, blunt, anterior corner lacking setae.
Description
Length 4–6 mm.
Head
Anterior margin rounded, anterodistal margin rectangular with rounded corner. Mid-cephalic keel with acute projection. Rostrum small.
Eyes oval
Antenna 1 one-third of body length, flagellum 11- articulate, peduncle art 1 width proximally less than twice article 2, disto-inferiorly with acute tooth, length art 1 subequal art 2, art 3 about 1/3 of art 2, acc. flagellum not seen.
Antenna 2 one-third of body length, subequal in length to antenna 1, peduncle art 4 > art 5, flagellum 6 arts.
Mouthparts
Mandibles lacking molars, palp 3–articulate, ratio of articles 1–3 is about 1: 2,8: 1.4, art 2 with 8–9 long lateral and 1 distal setae, art 3 with 1 distal seta, incisors strongly dentate.
Peraeon
Cx 1–4 relative widths 1.0: 1.2: 0.8: 1.
Cx 1 smooth, length and width subequal; anterior margin smooth, excavate, anterodistal margin produced, anterodistal corner about 120°, distal margin regularly rounded, smooth, posterior margin excavate, facial setae absent.
Gn 1 basis not inflated, with small tiny setae on anterior margin; ischium smooth; carpus distal part linear, length about 6× width; propodus straight, palm dentate with 9 short spines; dactylus smooth, reaching about 0.3× propodus length.
Cx 2 about as long as wide, subquadrangular, much wider than Cx 3, distally smooth; anterior margin straight, anterodistal corner rectangular, inferior margin rounded, posterior margin straight, facial setae absent.
Gn 2 basis slightly inflated, on anterior margin 10 setae of different length; carpus nearly reaching half propodus length, curved, distally truncate, densely setose; propodus distally with tooth-shaped prolongation, palm convex with many low humps, with ?2 mediofacial setal rows, with a few submarginal setae, proximally near dactylus end widening with clear corner of about 120°; dactylus curved, both margins smooth, bare, reaching somewhat more than half of propodus length.
Cx 3 length > width, smooth, bare, anterior and posterior margin straight, distally rounded, facial setae absent.
Cx 4 wider than long, smooth, bare, anterior margin somewhat convex, distal margin scarcely rounded, posterior margin shorter than anterior one, excavate, facial setae absent.
P 3, 4 basis very narrow, about the width of merus and up to 6–7× the width of basis; dactylus reaching nearly half length of propodus, posterior margins with short and thin spines.
Cx 5–7 facial setae absent.
P 5–7 similar, bases length: width ratio about 1.4–1.6, anterior margins with slight serrations and small weak spines, posterior margins strongly serrate.
Pleon
Ep 1 posteroventral corner rounded. Ep 2 with spines on distal margin, posteroventral corner acutely produced. Ep 3 posteroventral corner blunt and rectangular, distally bare, but some short spines on posterior margin.
U 1–3 relative lengths 1.0: 0.8: 1.1.
Telson
Ratio length: width about 3, tip tridentate because of two indentations near distal end, with a short seta inserted in each one.
Remarks
These specimens undoubtedly belong to the “spinicarpa”-group.
We started out with the supposition that material of more than 1,500 m depth cannot be L. spinicarpa which primarily is a shallow water species. Sars (1891) writes “30–150 fathoms”, while Lincoln (1979) records the species as “occasionally intertidally, down to 600 m”. Our material contains no specimens with signs of sexual maturity, and we know extremely little about the life span, variability or allometry in L. spinicarpa. The species has been redescribed by Krapp and Menioui (Krapp-Schickel and Menioui 2005) and by Crowe (2006) on the basis of topotypical material; Crowe also designed a male neotype of 13 mm, deposited in the Zoological Museum of Oslo.
L. spinicarpa (Abildgaard, 1789) is one of the earliest amphipods to be formally described, and the description is correspondingly vague. Shortly after also the species L. articulosa Montagu, L. denticulata A. Costa and L. antarctica Pfeffer were described, all morphologically quite similar to L. spinicarpa and all for a long time synonymized with that species. L. denticulata was re-established and fully described by Krapp-Schickel and Menioui (2005), and the redescription of L. antarctica is in preparation, but a modern redescription of L. articulosa, also revived by Krapp-Schickel and Menioui (loc. cit.), is still lacking.
Sars (1890–1895) revised the species and described L. spinicarpa from Norway, synonymizing L. articulosa (type locality S-Devonshire, type material also lost) with it. But in his illustration on pl. 101 (sub male L. articulosa of 16 mm), Ep 3 has a small but well-defined posterodistal tooth-shaped tip, which is still more acutely illustrated in the drawing of L. articulosa by Bate and Westwood 1863 Fig. 3, while Lincoln 1979 describes Ep 3 in his material (sub L. spinicarpa) as “quadrate OR with minute blunt tooth”; in the illustration of the neotype, Ep 3 is posterodistally rectangular.
Crowe (2006) specified several characters useful for comparison within the “spinicarpa-group”: the number of flagellum articles on the antenna 1 and 2; the anterior setation of the basis and the mediofacial setae on the propodus of gnathopod 2; the propodus and dactylus length of pereopods 3–7; the shape and setation of epimera 3 and the telson.
Our material (4–6 mm) is not fully mature, and therefore a number of these characters cannot be applied here, for example the antennar articles. The deepwater specimens deviate in a few points from Crowe’s redescription of L. spinicarpa: Gn 2 carpus is distally rounded (as in females and juveniles of L. spinicarpa, but differing from adult males). Ep 1 lacks anterodistal setae in our material, and the mediofacial row (or 2 shorter rows?) of setae on the propodus of Gn 2 has a quite different shape than in Crowe‘s material.
As our material does not contain obvious males and none of the specimens seems to be fully adult, we refrain from describing a new species and design our material as L. aff. spinicarpa.
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Leucothoe ushakovi Gurjanova, 1951 (Figs. 5, 6, 7)
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Gurjanova 1951: 487–488, fig. 320 A, B
Material examined
10 specimens of 8–27 mm length, 3,892 m depth, 65° 39,9′N, 04° 35,8′W, Stn 83.06.09.1, 1983 9/VI.
Type locality
Greenland Sea.
Diagnosis
Eyes apparently absent in fixed material. Mandibular palp long and narrow, art 3 up to 2.5× shorter than art 2. Cx 1 inferior margin weakly serrate, ratio length: width in large animals up to 2. Gn 1 carpus distal part about 10× longer than wide, dactylus reaching 0.25× of propodus length. P 3–7 with very narrow and similar basis, ratio length to width up to 4 in P 5–7, up to 7–8 in P 3, 4. Ep 2, 3 posterodistally with upturned tooth. U 1–3 peduncle always longer than rami.
Redescription
Length up to 34 mm.
Head
Anterior margin rounded, anterodistal margin rectangular with rounded corner. Ventral cephalic keel anteroventral margin without projection. Rostrum acute, small.
Eyes apparently absent in fixed material.
Antenna 1 one-third of body length, flag 6–15 articulate, ped art 1 width proximally about twice art 2, length art 1< art 2, art 3 half length art 2, acc. flag with 1 small art.
Antenna 2 one-third of body length, subequal in length with A 1, ped art 4> art 5, flag 6–10 arts.
Mouthparts
Mandibles lacking molars, palp 3–articulate, ratio of articles 1–3 is about 2: 6.5: 2.7 or 1.8: 6.2: 3, art 2 with 8–9 long lateral and 3 distal setae, art 3 with 2–3 distal setae, incisors strongly dentate; left mandible lacinia mobilis large, strongly toothed, with 16 raker spines; right mandible lacinia mobilis small, with 16 raker spines.
Lower lip inner lobes fused, bare; outer lobes with small gap.
Mx 1 palp with 2 arts, with 2 distal setae; outer plate with distal spines and setae, inner plate naked. Mx 2 inner plate with many thin marginal and a few facial setae; outer plate with few distal setae. Mxp inner plates fused, distal margin with a v-shaped indentation; outer plate triangular, reaching 0.3× palp art 1, with one subdistal spine; palp with 4 arts, art 2 and art 3 with marginal and facial setae, dactylus <art 3.
Peraeon
Cx 1–4 relative widths 1.0: 1.3: 1.3: 1.5.
Cx 1 smooth, in smaller specimens ratio length to width about 11: 8, in larger ones up to 2: 1; anterior margin smooth, anterodistal margin produced, rounded, distal margin straight, with some dentations, posterior margin excavate, facial setae absent.
Gn 1 basis scarcely inflated, naked; ischium with posterior setae; carpus distal part linear, length about 10× width, proximal margin finely serrated; propodus straight, palm dentate with 10 short setae; dactylus smooth, reaching 0.25× propodus length.
Cx 2 about as long as wide, subquadrangular, wider than Cx 3, distally weakly dentate; anterior margin straight, anterodistally rectangular, inferior margin straight, posterior margin straight, facial setae absent.
Gn 2 basis slightly inflated, naked; carpus 0.3× propodus length, curved, distally truncate, densely setose; propodus distally with tooth-shaped prolongation, posterior margin smooth, with 1 mediofacial setal row, with a few submarginal setae, palm convex and dentate, proximally near dactylus end widening with angle of about 120°; dactylus curved, outer margin smooth, bare, inner margin with rounded humps, reaching 0.75× propodus length.
Cx 3 length subequal width, anterodistal corner overriding distal face of Cx 2, smooth, bare, anterior margin straight, anterodistal corner rounded, facial setae absent.
Cx 4 wider than long, smooth, bare, anterior margin somewhat convex, distal margin evenly rounded, posterior margin excavate, facial setae absent.
P 3, 4 basis very narrow, about the width of merus and up to 7–8× the width of basis; dactylus reaching 1/3 of propodus, posterior margins with short and thin spines.
Cx 5–7 facial setae absent.
P 5–7 very similar, bases length: width ratio about 4, anterior margins with very slight serrations and small weak spines, posterior margins smooth.
Pleon
Ep 1 with 1 spine on inferior margin, Ep 2, 3 bare. Ep 1 posteroventral corner rounded, Ep 2, 3 posteroventral corner acutely produced.
U 1–3 relative lengths 1.0: 0.8: 1.1. U 1 peduncle nearly twice the outer ramus which is about 0.9× of inner ramus length. U 2 peduncle > inner ramus length, outer ramus length 0.8× inner ramus length. U 3 peduncle about twice inner ramus length, outer and inner ramus length subequal. U 1–3 margins of peduncle, inner and outer rami all with short spines.
Telson
Twice as long as wide, apex with very small V-shaped excavation in the acute tip, with submarginal short spines.
No sexual differences observed.
Colour
In alcohol somewhat yellowish, body semi-transparent.
Distribution
Greenland Sea at the depth of 3,000 m (2 specimens, types). Norwegian Sea at 65°N and 04° W, 3,892 m depth (presently studied material)
Remarks
Gurjanova (1951) reports about the type material that “Gn1 propodus is longer than basal article”, which is not the case in our material, obviously due to the propodus growing allometrically. About the telson, she described that the lateral margins are “completely smooth”, which was the case in some of the presently studied specimens, while others had some submarginal small spines.