Epimeria (Hoplepimeria), d’Acoz & Verheye, 2017

d’Acoz, Cédric d’Udekem & Verheye, Marie L., 2017, Epimeria of the Southern Ocean with notes on their relatives (Crustacea, Amphipoda, Eusiroidea), European Journal of Taxonomy 359, pp. 1-553 : 72-74

Subgenus Hoplepimeria subgen. nov.

urn:lsid:zoobank.org:act:A5102FE5-2D1C-4365-BFE8-D5163A0748D1

Etymology

Combination of the Greek word οπλα, armour and Epimeria . The name, which is feminine, alludes to the thick and heavily calcified teguments of the members of that subgenus.

Type species

Epimeria quasimodo sp. nov.

Description

Body opaque, with teguments very strongly calcified. Rostrum medium-sized to large. Eyes not conical. Pereionites and pleonites with a wide diversity of ornamentation. Most species have a low and broad mid-dorsal crest on their pleonites and often on their anterior pereionites. However all the pereionites and pleonites can have a very long non-flattened mid-dorsal tooth ( E. rubrieques ), or the body can be strongly sculptured ( E. rimicarinata ). Dorsolateral processes are absent except for E. rimicarinata , where they are part of its sculpured pattern. Pereionites 1–7 without ventrolateral tooth or protrusion just above connection with coxa. Coxae 1–4 with sharp or blunt tip. Coxae 1–3 usually weakly keeled along their axis. Coxa 4 with or without groove along the posteroventral border; when present, the anterior border of this groove forms a kind of blunt carina; when present this carina never bears a tooth projecting laterally; posteroventral border straight or concave. Coxa 5 with tooth or blunt protrusion projecting backwards (size and development very variable). Coxa 6 with or without blunt protrusion projecting backwards. Posteroventral tooth of epimeral plate 3 small to medium-sized. Dorsal process of urosomite 1 produced into a blunt tooth or a rounded lobe directed upwards. Urosomite 2 without pair of small teeth pointing upwards. Lateral borders of urosomite 3 posteriorly terminated into an acute angle. Peduncle of antenna 1 with dentition very reduced (a small ventral tooth can be present on article 1). Mandible with molar process triturative. Lower lip with narrow (V-shaped) hypopharyngeal gap. Palp of maxilliped with 4 articles. Gnathopods of normal size, with carpus and propodus very robust, with palm obliquely transverse (gnathopods subcheliform); propodus often expanded distally; posterior border of dactylus lined by row of small oblique slender teeth. Basis of pereiopods 5–6 broad, with posteroproximal process, which can be a (very low) rounded protrusion or a large (sometimes swordlike) tooth orientated in the same direction as the basis, with or without posterodistal tooth projecting posteriorly. Basis of pereiopod 7 narrow on its distal half; posterior border proximally slightly convex and distally either slightly concave, or deeply concave or deeply angularly notched; the posterior border of the basis of pereiopod 7 can be terminated into a small tooth projecting posteriorly or not. Dactylus of pereiopods 5–7 short.

Body length

The maximum body length recorded in Hoplepimeria subgen. nov. species ranges between 35 and 80 mm.

Ecology

Benthic, 33–2154 m.

Distribution

Circum-Antarctic, as far north as the South Georgia.

Remarks

Hoplepimeria subgen. nov. includes species with diverse body shapes. Most species are globular with only low teeth or crests, whilst E. rubrieques is one of the Epimeria with the longest teeth. However, E. rubrieques has the same robust and distally expanded gnathopods as in other Hoplepimeria subgen. nov. and has the same proximally toothed basis of pereiopods 5–6 as in many other Hoplepimeria subgen. nov. The absence of dorsolateral teeth, and the non- or scarcely laterally flattened dorsal processes of E. rubrieques distinguishes it at first glance from the dentate Antarctic Epimeria of the subgenus Drakepimeria subgen. nov. Hoplepimeria subgen. nov. includes the largest known Epimeria species, namely E. gargantua sp. nov., which can reach up to 80 mm.

Key to the species of Hoplepimeria subgen. nov.

1. Proximal part of posterior border of basis of pereiopod 6 with rounded protrusion (which can be very low) ……………………………………………………………………………………………2

– Proximal part of posterior border of basis of pereiopod 6 with triangular or sword-like tooth directed in the axis of the basis ……………………………………………………………………3

2. Coxa 4 without lateral carina, with posteroventral border straight; posterior border of basis of pereiopod 7 weakly excavate; eye medium-sized and broadly elliptic …… Epimeria (Hoplepimeria) inermis subgen. nov. Walker, 1903 [Elephant Island, to Adélie Coast and western Ross Sea]

– Coxa 4 with lateral carina widely separate from posterior border, with posteroventral border deeply concave; posterior border of basis of pereiopod 7 straight; eye large and narrowly elliptic ………………… E. (Hoplepimeria) heldi subgen. nov. Coleman, 1998 [Elephant Island]

3. Pereionites and pleonites naked, or with low mid-dorsal crest or tooth ………………………4

– Pereionites 1–7 and pleonites 1–2 with very large elongate mid-dorsal tooth; pleonite 3 with large triangular tooth …………………………………………………………………… E. (Hoplepimeria) rubrieques subgen. nov. De Broyer & Klages, 1991 [Eastern Weddell Sea to Davis Sea]

4. Mid-dorsal crest of pereionites 3–7 and pleonites 1–3 very slightly notched or not notched; these segments are not laterally sculptured ………………………………………………………5

– Mid-dorsal crest of pereionites 3–7 and pleonites 1–3 deeply notched; these segments are laterally strongly sculptured ..…………………..........…………………………………… E. (Hoplepimeria) rimicarinata subgen. nov. Watling & Holman, 1980 [Prydz Bay, western Ross Sea]

5. Coxa 5 sometimes angular but not with a distinct tooth when seen in dorsal view; ventral part of coxa 4 moderately produced ……………………………………………………………………6

– Coxa 5 with a distinct tooth pointing laterally or obliquely backwards when seen in dorsal view; ventral part of coxa 4 very strongly produced ………………………… E. (Hoplepimeria) larsi subgen. nov. Lörz, 2009 [Adélie Coast and western Ross Sea, 1900–2200 m]

6. Pleonite 3 with small but well defined, narrow, posterodorsal tooth pointing upwards: E. ( Hoplepimeria ) complex robusta ………………………………………………………………7

– Pleonite 3 without small posterodorsal tooth pointing upwards ……………………………9

7. Pleonite 2 with posterodistal tooth (pointing backwards) ………………………………………8

– Pleonite 2 without posterodistal tooth ..………………….………… E. (Hoplepimeria) robusta subgen. nov. K.H. Barnard, 1930 [Western Ross Sea and Adélie Coast]

8. Dorsolateral margins of urosomite 3 deeply concave; posterodistal corner of the basis of pereiopods 5–7 bluntly angular; body either pure white or with coloured motives on a white background ……………………………………………………………………… E. (Hoplepimeria) robustoides subgen. nov. Lörz & Coleman in Lörz et al., 2009 [Eastern Weddell Sea]

– Dorsolateral margins of urosomite 3 weakly concave; posterodistal corner of the basis of pereiopods 5–7 produced into a sharp tooth; body always pure white………………………………………… ………………… E. (Hoplepimeria) gargantua subgen. et sp. nov. [Tip of Antarctic Peninsula]

9. Dorsal keels of body segments not strongly laterally compressed; eyes elliptic; rostrum ventrally straight or weakly concave, usually longer than article 1 of peduncle of antenna 1; coxa 4 with anteroventral border slightly to significantly concave, with ventral tip fairly blunt to sharp, with more or less distinct groove running along posteroventral border; notch of basis of pereiopod 7 forming a squared or acute angle in adults: E. ( Hoplepimeria ) complex georgiana …………10

– Dorsal keels of body segments strongly laterally compressed; eyes distinctly reniform; rostrum ventrally distinctly concave, as long as article 1 of peduncle of antenna 1; coxa 4 with anteroventral border straight and ventral tip very blunt, without any trace of posterior groove running along posteroventral border; notch of basis of pereiopod 7 forming a very obtuse angle in adults ………………………………… E. (Hoplepimeria) angelikae subgen. nov. Lörz & Linse in Lörz et al., 2011 [eastern Weddel Sea, Adélie Coast; lower shelf species]

10. Anterior corner of coxa 4 broadly rounded ………………………………………………………11

– Anterior corner of coxa 4 bluntly angular ……………………………………………………….12

11. Rostrum broad in frontal view; ventral corner of coxa 4 sharply angular; posterior notch of basis of pereiopods 5–7 broad, that of pereiopod 7 forming a squared angle (or nearly so) in adults ……… E. (Hoplepimeria) cyphorachis sp. nov. [South Shetland Islands, mostly lower shelf]

– Rostrum fairly slender in frontal view; ventral corner of coxa 4 bluntly angular; posterior notch of basis of pereiopods 5–7 narrow, that of pereiopod 7 forming an acute angle in adults ………………………………… E. (Hoplepimeria) xesta subgen. et sp. nov. [Eastern Weddell Sea]

12. Rostrum broad in frontal and lateral view, not ventrally concave ………………………………13

– Rostrum fairly slender in frontal and lateral view, ventrally slightly concave … E. (Hoplepimeria) linseae subgen. et sp. nov. [Plateau of the South Orkney Islands, upper shelf]

13. Coxa 4 with anterior corner angular and not so blunt, with ventral corner forming an acute angle, of which the tip is sharp; anteroventral border markedly concave; basis of pereiopod 5 very broad; posterodistal corner of basis of pereiopods 5–7 laterally strongly produced …… E. (Hoplepimeria) georgiana subgen. nov. Schellenberg, 1931 [ South Georgia, upper shelf]

– Coxa 4 with anterior border broadly angular and blunt, with ventral corner forming a squared angle of which the tip is not especially sharp; anteroventral border inconspicuously concave; basis of pereiopod 5 not especially broad; posterodistal corner of basis of pereiopods 5–7 laterally weakly produced ………………………… E. (Hoplepimeria) quadimodo subgen. et sp. nov. [Elephant Island to tip of Antarctic Peninsula, upper shelf]