Metepimeria Schellenberg, 1931

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 : 116-117

Subgenus Metepimeria Schellenberg, 1931

Metepimeria Schellenberg, 1931: 162 .

Metepimeria – Gurjanova 1955: 189, 209. — J.L. Barnard 1961: 102; 1969: 396. — Watling & Holman 1981: 215. — J.L. Barnard & Karaman 1991: 380, 397. — Coleman 1998b: 215; 2007: 61. — Lörz & Brandt 2004: 184, 188.

Type species

Metepimeria acanthurus Schellenberg, 1931 .

Description

Body opaque, with teguments strongly calcified. Rostrum medium-sized. Eyes not conical. Pleonites and at least posterior pereionites with low mid-dorsal carina, which is sometimes posteriorly produced into a tooth pointing backwards; some carinae with slight or strong median concavity. Dorsolateral processes (small teeth or low carinae) always present on pleosomites and posterior pereionite(s); some body segments have 2 or more dorsolateral processes, some in longitudinal arrangement. Pereionites 1–7 without tooth or protrusion just above connection with coxa. Coxae 1–4 with sharp to fairly sharp tip. Coxae 1–3 distinctly keeled along their axis. Coxa 4 with groove along the posteroventral border; this groove might be limited by a distinct carina; when present this carina never bears a tooth projecting laterally; posteroventral border concave. Coxae 5–6 without tooth or distinct protrusion. Mid of posterior border of epimeral plates 1–3 not produced into a tooth. Posteroventral tooth of epimeral plate 3 small to medium-sized. Dorsal process of urosomite 1 produced into a sharp tooth 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 without teeth. Mandible with molar process triturative. Lower lip with narrow (V-shaped) hypopharyngeal gap. Palp of maxilliped with 3 or 4 articles. Gnathopods of normal size, with carpus and propodus elongate, with palm very reduced, forming a weak oblique convexity in continuity with the axis of the propodus (gnathopods nearly achelate); propodus not expanded distally; ornamentation of posterior border of dactylus weak. Basis of pereiopods 5–6 broad, with posteroproximal process present, of variable development (strong nearly dentiform lobe at the base of basis; weak lobe at the base of basis; or a low lobe occupying half of posterior border), with or without posterodistal tooth or lobe (if present not distinctly projecting posteriorly). Posterior border of basis of pereiopod 7 with distinct median blunt angle; the distal half is slightly to distinctly concave; distal corner rounded. Dactylus of pereiopods 5–7 short.

Body length

The body length recorded in Metepimeria species ranges between 15 and 22.6 mm.

Ecology.

Benthic, 27–1025 m.

Distribution

Sub-Antarctic and low Antarctic seas: Patagonia; Falkland Islands; Shag Rocks; South Georgia; Macquarie Ridge.

Remarks

Metepimeria was initially erected as a monotypic genus for the Magellanic species Epimeria acanthurus , based on a single character state: the absence of dactylus on the palp of the maxilliped. This character state is most likely autapomorphic, and the recognition of a separate genus for E. acanthurus is not supported here. Epimeria acanthurus is morphologically similar to Epimeria intermedia ( South Georgia endemic) and E. ashleyi from Macquarie Ridge. In the present paper, Metepimeria is redefined, as a subgenus for these three species only. However, the New Zealand species, E. sophie Lörz & Coleman, 2014 (see Lörz & Coleman 2014) exhibits morphological similarities with them and a future transfer of E. sophie to Metepimeria seems possible.

Key to the species and “forms” of Metepimeria

1. Palp of maxilliped with 4 articles; posterior border of basis of pereiopods 5–6 with a weak or a strong lobe occupying no more than 0.3 of the border …………………………………………2

– Palp of maxilliped with 3 articles; posterior border of basis of pereiopods 5–6 with a proximal very low expansion occupying half of posterior border …………………………… E. (Metepimeria) acanthurus ( Schellenberg, 1931) [ Falkland Islands and Patagonia]

2. Posterior border of basis of pereiopods 5–6 with very strong (nearly dentiform) posteroproximal process ………………………………………………………………………………………………3

– Posterior border of basis of pereiopods 5–6 with low rounded posteroproximal process………… …………………………… E. (Metepimeria) ashleyi Lörz, 2012 [Macquarie Ridge:Hjort Seamount]

3. Dorsal carina starting at pereionite 3; pleonite 3 posterodorsally terminated in a trapezoidal process ………………………… E. (Metepimeria) intermedia Schellenberg, 1931 forma A [ South Georgia]

– Dorsal carina starting at pereionite 1; pleonite 3 posterodorsally terminated in a triangular process ……… E. (Metepimeria) intermedia Schellenberg, 1931 forma B [ South Georgia, Shag Rocks]