Epimeria (Subepimeria) iota, 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 : 146-148

Epimeria (Subepimeria) iota sp. nov.

urn:lsid:zoobank.org:act:7A557F8F-058F-413B-998C-AED9C9D23EE6

Figs 299–306

Epimeria puncticulata – Watling & Holman 1981: 213, in part, fig. 21.

Epimeria aff. puncticulata –? Rauschert & Arntz 2015: 61, pl. 54, unnumbered photograph.

‘ Clade B puncticulata complex - PUN1’ – Verheye et al. 2016a, supplement: 3 (online).

non Epimeria puncticulata K.H. Barnard, 1930: 377 , fig. 42.

Etymology

Iota is the smallest letter of the Greek alphabet. The name, which is a noun in apposition, alludes to the small size of the species.

Type material

Holotype

RV Polarstern cruises:

SOUTHERN OCEAN: sex undetermined, cruise PS81, ANT-XXIX/3, stn 197-6, Bransfield Strait , 62°45.05ʹ S, 57°26.68ʹ W to 62°45.09ʹ S, 57°26.47ʹ W, 210–222 m, black gravel mixed with sand and a little bit of mud, Rauschert dredge, 25 Feb. 2013, coll. C. d’Udekem d’Acoz and M. Verheye ( RBINS, INV. 122947 ) [extraction ANT 48 ; Genbank nr, 28S: KU759607 ].

Paratypes

RV Polarstern cruises:

SOUTHERN OCEAN: 1 spec., cruise PS69, ANT-XXIII/8, stn 605-3, Elephant Island, 61°20.33ʹ S, 55°31.53ʹ W to 61°20.35ʹ S, 55°30.18ʹ W, 148–154 m, Agassiz trawl, 20 Dec. 2006, coll. C. d’Udekem d’Acoz and H. Robert ( RBINS, INV. 122519); 2 specs, cruise PS69, ANT-XXIII/8, stn 614-3/4/5, Elephant Island, 60°52.37ʹ S, 55°29.80ʹ W to 60°52.71ʹ S, 55°27.83ʹ W, 248–265 m, a lot of epifauna, Rauschert dredge and Agassiz trawl, 22 Dec. 2006, coll. C. d’Udekem d’Acoz and H. Robert ( RBINS, INV. 122525); 1 spec., sex undetermined, cruise PS81, ANT-XXIX/3, stn 164-5, south of Dundee Island, 63°36.84ʹ S, 56°10.28ʹ W to 63°36.72ʹ S, 56°10.46ʹ W, 121–122 m, Rauschert dredge, 11 Feb. 2013, coll. C. d’Udekem d’Acoz and M. Verheye ( RBINS, INV. 122934) [extraction K42; Genbank nr, 28S: KU759655 ].

Description

Basis of description. Description based on holotype.

ROSTRUM. In lateral view fairly short and fairly narrow; distinctly curved, posterior border straight, tip acute; in frontal view narrowly triangular, fairly narrow and with almost straight converging borders, with tip blunt; not reaching tip of article 1 of peduncle of antenna 1.

EYES. Very large, nearly circular (very broadly elliptic).

PEREION–PLEOSOME TOOTH PATTERN. Pereionites 1–7 and pleonite 1 totally smooth; pleonite 2 with small, posterodorsal tooth; pleonite 3 carinate, with posterodorsal tip forming a small, low, rounded lobe very weakly projecting backwards.

COXAE 1–3. Tip blunt.

COXA 4. Narrow; anterodorsal border nearly straight, curving ventrally and followed by weakly curved anteroventral border; anterior corner very rounded but distinct, projecting forward; ventral corner forming a broadly rounded squared angle; posteroventral border distinctly concave; ratio length of posterodorsal border / length of posteroventral border: 0.7.

COXA 5. Very broad, posteroventral corner with broadly rounded angular discontinuity.

COXA 6. Posterior border rounded.

EPIMERAL PLATES 1–3. Posteroventral angle rounded in plate 1, produced into a small tooth in plate 2; produced into a medium-sized tooth in plate 3.

UROSOME TOOTH PATTERN. Urosomite 1 with medium-sized blunt triangular dorsal process; urosomite 3 with dorsolateral borders straight, with tip bluntly angulate.

TELSON. Broad, with lateral border strongly converging, with lobes distally broad, slit narrowly U-shaped, cleft on 0.3.

GNATHOPODS 1–2. Carpus and propodus of normal slenderness; propodus not narrowing distally, and palm weak but distinct.

PEREIOPOD 5. Basis of normal width, with posteroproximal process indistinct (reduced to very low proximal dilatation in continuity with the more distal part of the posterior border), with posterodistal corner forming a blunt-tipped broadly triangular process (squared angle), not projecting backwards; merus, carpus and propodus stout.

PEREIOPOD 6. Basis of normal width, with posteroproximal process indistinct (reduced to very low proximal dilatation in continuity with the more distal part of the posterior border), with posterior border parallel to anterior border, with posterodistal corner forming a rounded triangular process (very rounded squared angle) not projecting backwards; merus, carpus and propodus stout.

PEREIOPOD 7. Basis broad; posterior border nearly straight, with trace of concavity in distal 0.8, terminated into an obtuse rounded lobe.

Variations

The sequenced holotype is obviously immature. Adult specimens preserved in formalin interpreted as adult Epimeria iota sp. nov. have broader coxa 4, a stronger posterodistal tooth on the basis of pereiopods 5 and 6, sometimes a trace of a posterodorsal tooth or bump on pleonite 1 and a more obtuse dorsal process on urosomite 1.

Colour pattern

Holotype: background whitish (some areas very pale pinkish or very pale yellowish); head, pereionites 3–5, lower part of epimeral plates, posterior border of pleonite 3 and urosomites 1–2 suffused with orange-red; two red dots on the anterior part of coxa 4; a large red dot on first epimeral plate; eyes reddish.

Body length

The holotype is 9.5 mm. Non sequenced specimens interpreted as adult E. iota sp. nov. reach 16 mm.

Distribution

Tip of Antarctic Peninsula and Elephant Island, 121– 265 m.

Remarks

The specimens from the stations 605-3 and 614-3/4/5 of ANT-XXIII/8 are interpreted as adult Epimeria (Subepimeria) iota sp. nov. They possess the following character states of E. iota sp. nov.: (1) the anterior margin of their coxa 4 has an angular discontinuity (forming a regular curve in E. teres sp. nov.), and (2) the margins of the basis of pereiopod 6 are parallel (diverging in E. teres sp. nov.). The ‘ Epimeria puncticulata ’ illustrated by Watling & Holman (1981) and the ‘ Epimeria aff. puncticulata ’ illustrated by Rauschert & Arntz (2015: 61, pl. 54) presumably belong to the same morphospecies as well. The collection details are not given by Rauschert & Arntz (2015), but are indicated in an early draft of their book made available to the authors: ANT-XXI/2 stn 276 [i.e., 276-1], 71°06.44ʹ S, 11°27.76ʹ W to 71°06.64ʹ S, 11°27.28ʹ W, 268–277 m, eastern shelf of the Weddell Sea.

Figures

Fig. 299. Epimeria (Subepimeria) iota sp. nov., sex undetermined, holotype, Bransfield Strait, ANT- XXIX/3, stn 197-6, RBINS, INV. 122947. A. Colour in life. B. Lateral habitus. C. Dorsal habitus.

Fig. 300. Epimeria (Subepimeria) iota sp. nov., sex undetermined, holotype, Bransfield Strait, ANT- XXIX/3, stn 197-6, RBINS, INV. 122947. A. Anterior half. B. Posterior half.

Fig. 301. Epimeria (Subepimeria) iota sp. nov., sex undetermined, holotype, Bransfield Strait, ANT- XXIX/3, stn 197-6, RBINS, INV. 122947. A. Frontal view. B. Urosome in dorsal view. C. Telson.

Fig. 302. Epimeria (Subepimeria) iota sp. nov., sex undetermined, holotype, Bransfield Strait, ANT-XXIX/3, stn 197-6, RBINS, INV. 122947. A. Gnathopod 1. B. Gnathopod 2. C. Pereiopod 4. D. Pereiopod 5. E. Pereiopod 6. F. Pereiopod 7.

Fig. 303. Epimeria (Subepimeria) iota sp. nov., sex undetermined, paratype, Elephant Island, ANT- XXIII/8, stn 605-3, RBINS, INV. 122519. A. Lateral habitus. B. Head in facial view.

Fig. 304. Epimeria (Subepimeria) iota sp. nov., sex undetermined, paratype, Elephant Island, ANT- XXIII/8, stn 605-3, RBINS, INV. 122519. A. Coxae 1–7. B. Posterior part of body.

Fig. 305. Epimeria (Subepimeria) iota sp. nov., sex undetermined, paratype, Elephant Island, ANT- XXIII/8, stn 614-3/4/5, RBINS, INV. 122525. A. Lateral habitus. B. Head an body segments 1–3 in lateral view.

Fig. 306. Epimeria (Subepimeria) iota sp. nov., sex undetermined, paratype, Elephant Island, ANT- XXIII/8, stn 614-3/4/5, RBINS, INV. 122525. A. Coxae 1–7. B. Basis of pereiopods 5–7.