Epimeria (Drakepimeria) d'Acoz & Verheye 2017, subgen. nov.

Subgenus Drakepimeria subgen. nov.

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Etymology

Combination of the Greek word: δράκων, dragon and Epimeria. The name, which is feminine, alludes to the highly processiform ornamentation in the species of the subgenus, which is reminiscent of mythological dragons.

Type species

Epimeria loerzae sp. nov.

Description

Body opaque, with teguments strongly calcified. Rostrum long. Ventral lobe of head acute. Pleonites 1–3 and at least some pereionites with strong mid-dorsal dentate carina and one pair of dorsolateral much smaller teeth, swelling or carina. On pleonite 2 and 3, a second pair of small dorsolateral teeth is sometimes observed between the main dorsolateral teeth and the mid-dorsal tooth (this accessory pair of small teeth is not positioned anteriorly to the main pair). Pereionites 1–7 without tooth or protrusion just above connection with coxa. Coxae 1–4 often with (but not always) with sharp tip. Coxae 1–3 usually sharply keeled along their axis. Coxa 4 with sharp carina starting at ventral tip of coxa and terminating at posterior tip of coxa; this arching carina sometimes bears a tooth projecting laterally; posteroventral border concave. Coxae 5–6 with strong sharp tooth projecting backwards. Mid of posterior border of epimeral plates 1–3 not produced into a tooth. Posteroventral tooth of epimeral plate 3 strong to very strong. Dorsal process of urosomite 1 produced into a sharp tooth, which can be directed upwards or backwards. Urosomite 2 with or without pair of small teeth pointing upwards. Lateral borders of urosomite 3 posteriorly terminated into a sharp tooth. Telson deeply bilobed. Eyes present, large to very large, not conical. Peduncle of antenna 1 with teeth (dentition sometimes reduced, but never totally absent). Mandible with molar process triturative. Lower lip with narrow (V-shaped) hypopharyngeal gap. Palp of maxilliped with 4 articles. Gnathopods small but not minute, with carpus and propodus of medium slenderness; propodus not strongly expanded distally, subcheliform, with palm obliquely transverse; posterior border of dactylus lined by row of small oblique slender teeth. Basis of pereiopods 5–6 moderately slender to broad, with posteroproximal rounded protrusion (sometimes weak) and posterodistal tooth projecting posteriorly. Posterior border of basis of pereiopod 7 proximally slightly convex and distally slightly concave, terminated into a tooth projecting posteriorly. Dactylus of pereiopods 5–7 short.

Body length

The maximum body length recorded in Drakepimeria species ranges between 19 and 47 mm.

Ecology

Benthic, 33–2190 m.

Distribution

Circum-Antarctic, as far north as the South Orkney Islands.

Remarks

Drakepimeria species are superficially similar to those of the subgenus Epimeria. See e.g., illustrations of its type species, Epimeria (Epimeria) cornigera (Fabricius, 1779), given by G.O. Sars (1893). However several differences can be observed. In the subgenus Epimeria, the ventral lobe of the head is rounded instead of being sharp, the peduncle of antenna 1 is not dentate; the basis of pereiopod 5 is extremely narrow; the basis of pereiopods 5–6 has neither posteroproximal nor posterodistal process pointing backwards; the posterior margins of the epimeral plates have a median tooth, the lobes of the telson are blunt-tipped instead of being acute and the median notch of the telson is much shallower than in Drakepimeria. Molecular data support the idea that the subgenera Drakepimeria and Epimeria are not closely related (Verheye et al. 2016b, 2017).

Drakepimeria species can be subdivided in two phenotypical categories, which are useful for identification. The species of the first category have a pair of denticles pointing upwards on urosomite 2; they are: E. (D.) anguloce subgen. et sp. nov., E. (D.) corbariae subgen. et sp. nov., E. (D.) havermansiana subgen. et sp. nov., E. (D.) loerzae subgen. et sp. nov., E. (D.) macrodonta Walker, 1906, E. (D.) pandora subgen. et sp. nov., E. (D.) pyrodrakon subgen. et sp. nov., E. (D.) schiaparelli Lörz et al., 2007, and E. (D.) reoproi Lörz & Coleman, 2001.

The species of the second category have no pair of denticles pointing upwards on urosomite 2; they are: E. (D.) acanthochelon subgen. et sp. nov., E. (D.) colemani subgen. et sp. nov., E. (D.) cyrano subgen. et sp. nov., E. (D.) leukhoplites subgen. et sp. nov., E. (D.) robertiana subgen. et sp. nov., E. (D.) similis Chevreux, 1912, E. (D.) vaderi Coleman, 1998, and E. (D.) sp. 1.

Key to the species of Drakepimeria

1. Rostrum curving downwards; number of pereionites with mid-dorsal tooth and pair of dorsolateral teeth (or carinae) variable, but if pereionites 1 and/or 2 have a mid-dorsal tooth, it is never long and slender …………………………………………………………………………........................2

– Rostrum straight and anteriorly directed; all pereionites and pleonites with long and slender middorsal tooth and pair of long dorsolateral teeth................................................................................ …............…………… E. (D.) cyrano subgen. et sp. nov. [Eastern Weddell Sea, around 800–1000 m]

2. Dorsal process of urosomite 1 pointing upwards; basis of pereiopod 5 broad ………………………..3

– Dorsal process of urosomite 1 distinctly pointing backwards; basis of pereiopod 5 narrow …………………………… E. (D.) robertiana subgen. et sp. nov. [Weddell Sea, around 2000 m]

3. Lateral tooth of article 2 of peduncle of antenna 1 tiny, reaching basis of article 3 …………………4

– Lateral tooth of article 2 of peduncle of antenna 1 large to very large, reaching or overreching tip of article 3 ……………………………………………………………………………………………..5

4. Dorsal process of urosomite 1 obtusely triangular; coxa 4 with lateral carina forming a deep curve, so that its deepest point is very distant from the posteroventral border, with ventral corner acutely pointed and strongly curving posteriorly; pleonites 1–2 with one pair of dorsolateral teeth …………………………………………………………… E. (D.) reoproi Lörz & Coleman, 2001

– Dorsal process of urosomite 1 acutely triangular; coxa 4 with lateral carina very close to posteroventral border and parallel to it, with ventral corner angular, acute, but not strongly curving posteriorly; pleonites 1–2 with two pairs of dorsolateral teeth…………………………………… …………………………………… E. (D.) vaderi subgen. nov. Coleman, 1998 [Elephant Island]

5. Urosomite 2 without pair of dorsal denticles pointing upwards ……………………………………6

– Urosomite 2 with pair of dorsal denticles pointing upwards ……………………………………10

6. Lateral carina of coxa 4 without lateral tooth or any trace of angularity visible in dorsal view; merus; carpus and propodus of pereiopods 3–7 stout ……………………………………………………7

– Lateral carina of coxa 4 with lateral tooth or a very obtuse lateral angularity visible in dorsal view; merus; carpus and propodus of pereiopods 3–7 slender …………………………………………8

7. Mid-dorsal carina of pereionite 7 and pleonites 1–2 with anterior border exhibiting a strong angular discontinuity; coxa 4 in lateral view with anterodorsal border more than twice longer than anteroventral border …… E. (D.) leukhoplites subgen. et sp. nov. [Elephant Island and tip of Antarctic Peninsula]

– Mid-dorsal carina of pereionite 7 and pleonites 1–2 with anterior border regularly curved; coxa 4 in lateral view with anterodorsal and anteroventral border subequal ………………………………… ………………………………………………………………… E. (D.) sp. 1 subgen. nov. [Ross Sea]

8. Coxa 4 laterally produced into an obtuse angularity visible in dorsal view; dorsolateral teeth of pereionites laterally carinate; lateral tooth of article 2 of peduncle of antenna 1 overreaching article 3 by about 0.6 of its length ………………………………… E. (D.) colemani subgen. et sp. nov. [South Shetland Islands, Antarctic Peninsula, eastern Weddell Sea, eastwards to the Ross Sea]

– Coxa 4 laterally produced into a sharp tooth; dorsolateral teeth of pereionites not laterally carinate; lateral tooth of article 2 of peduncle of antenna 1 reaching about tip of article 3: E. (Drakepimeria) complex similis ……………………………………………………………………………………9

9. Pereionite 1 never with posterodorsal bump or tooth; pereionite 2 with or without small mid-dorsal tooth; mid-dorsal carina of pleonite 3 with weak anterior lobe followed by very shallow notch …… E. (D.) similis subgen. nov. Chevreux, 1912 [Elephant Island to tip of Antarctic Peninsula]

– Pereionite 1 usually with small posterodorsal bump or small posterodorsal tooth; pereionite 2 with well developed mid-dorsal tooth; mid-dorsal carina of pleonite3with strong anterior lobe followed by fairly deep notch … Epimeria (D.) acanthochelon subgen. et sp. nov. [Eastern Weddell Sea to Adélie Coast]

10. Lateral carina of coxa 4 without lateral tooth: E. (Drakepimeria) complex pandora ………………11

– Lateral carina of coxa 4 with strong lateral tooth …………………………………………………..12

11. Pereionite 2 without mid-dorsal tooth; mid-dorsal tooth of pereionite 3 small; ventral tooth of coxa 4 moderately long and fairly broad ………………………………………………………………… ……………… E. (D.) pandora subgen. et sp. nov. [Elephant Island to tip of Antarctic Peninsula]

– Pereionite 2 with small mid-dorsal tooth; mid-dorsal tooth of pereionite 3 medium-sized; ventral tooth of coxa 4 very long and narrow ……………………………………………………………… ………………… E. (D.) havermansiana subgen. et sp. nov. [eastern Weddell Sea to Adélie Coast]

12. Pereionite 3 with well-developed mid-dorsal tooth ………………………………………………13

– Pereionite 3 with posterodorsal bump ……………………………………………………………… …………………………… E. (D.) schiaparelli subgen. nov. Lörz et al., 2007 [western Ross Sea]

13. Mid-dorsal tooth of pereionites 3–7 and pleonites 1–2 narrow to moderately broad, without angular discontinuity on their anterior border or with a very weak angular discontinuity; mid-dorsal tooth of pereionite 1 absent, weak or fairly strong ……………………………………………14

– Mid-dorsal tooth of pereionites 3–7 and pleonites 1–2 broad, the last four of these teeth presenting a strong angular discontinuity on their anterior border; mid-dorsal tooth of pereionite 1 very strong [article 2 of peduncle of antenna 1 with lateral and medial teeth overreaching article 3] …………………………………………………… E. (D.) loerzae subgen. et sp. nov. [South Orkney Islands to tip of Antarctic Peninsula, very rare in the Eastern Weddell Sea]

14. Lateral and medial tooth of article 2 of peduncle of antenna 1 overreaching article 3 [ventral tooth of article 3 excluded]; ventral border of article 2 of antenna 1 at most with tiny denticle ………15

– Lateral and medial tooth of article 2 of peduncle of antenna 1 not reaching tip of article 3 [ventral tooth of article 3 excluded]; ventral border of article 2 of antenna 1 with large tooth ………………………………………………………………………………..... E. (D.) pyrodrakon subgen. et sp. nov. [Antarctic Peninsula, eastern Weddell Sea, Princess Ragnhild Coast]

15. Lateral and medial tooth of article 1 of antenna 1 long and subequal ………………………16

– Lateral tooth of article 1 of antenna 1 long and considerably longer than medial tooth of the same article, which is short …………… E. (D.) macrodonta subgen. nov. Walker, 1906 [western Ross Sea]

16. Pereionite 1 always with small to medium-sized (always very distinct) mid-dorsal tooth and pair of dorsolateral protrusions; mid-dorsal tooth of pereionites 4–7 very narrow.............................................................................................................................…… E. (D.) anguloce subgen. et sp. nov. [Tip of Antarctic Peninsula, eastern Weddell Sea, Princess Ragnhild Coast, Prydz Bay]

– Pereionite 1 usually without mid-dorsal tooth or with a very reduced mid-dorsal tooth, rarely with a well developed mid-dorsal tooth, pair of dorsolateral protrusions rarely present; mid-dorsal tooth of pereionites 4–7 fairly narrow ……… E. (D.) corbariae subgen. et sp. nov. [Adélie Coast]