Halirages cainae, dAcoz, 2012

D'Acoz, Cédric D'Udekem, 2012, On the genus Halirages (Crustacea, Amphipoda), with the description of two new species from Scandinavia and Arctic Europe, European Journal of Taxonomy 7, pp. 1-32 : 5-16

Halirages cainae sp. nov.

Figs 1-7

? Halirages elegans – Oldevig 1959: 65 (pro parte).

Etymology

Caina (Divine Comedy, Canto XXXII, verse 58): first round of the ninth circle of Dante's Inferno, which the poet describes as a frozen lake. The name alludes to the deep basin of the Norwegian Sea, which is the habitat of the species. With its negative temperatures, this body of icy abyssal water, trapped under a layer of warmer Atlantic waters is not unlike the frozen lake of Dante's Inferno. The vernacular noun in medieval Italian is Latinized as caina, -ae and is a genitive.

Type material

MAREANO 2009-111 cruise, RV G.O. Sars, R-station 487, sample 157, 69°04'N 012°28'E, 2589- 2615 m, RP-sledge, mud, 8 Oct. 2009: 5 specimens [holotype subadult ♂ mounted on 26 slides in Euparal ( ZMBN 87795) and 4 paratypes ( ZMBN 87796) of which one is a 40 mm long ovigerous ♀, coll. C. d'Udekem d'Acoz]; MAREANO 2009-111 cruise, RV G.O. Sars, R-station 488, sample 379, 69°44'N 015°11'E, 2241-2245 m, mud, beam trawl, 10 Oct. 2009: 2 adult paratypes, RBINS, I.G. 31227, INV. 100853, coll. C. d'Udekem d'Acoz.

Description

HEAD. ( Figs 1 , 2 , 3A ) Rostrum feeble; anterior lobe of head very bluntly subquadrate (almost rounded), posteriorly followed by narrow sinus; ventral lobe of head acute, pointing forward, not denticulate; eye present, rather small, subreniform, without defined ommatidia, unpigmented in alcohol.

ANTENNAE. ( Figs 1 , 2 , 3 A-B) Typical for the genus Halirages ; article 1 of peduncle with 2 normally developed ventrolateral distal teeth.

UPPER LIP. ( Fig. 3C ) Apically rounded.

LOWER LIP. ( Fig. 3D ) With narrow mandibular processes and broad outer lobes.

MANDIBLE. ( Fig. 3 E-F) Incisor process with 4 very blunt teeth; left lacinia mobilis with 4 blunt teeth (left one well developed, right one reduced); molar ridged, lateral margin, with a row of narrow spines, left molar with 2 anterolateral longer setae; palp article 1 short, with 1 D1-seta and 3 short F1-setae; article 2 and 3 equal in length; article 2 stout (3.2 x as long as wide), with row of D2-setae and row of A2-setae

becoming strong and narrowly spaced near tip; article 3 falciform, with row of D3-setae on distal 0.8 of posterior border, with apical tuft of E3-setae.

MAXILLA 1. ( Fig. 3 G-L) Inner plate with 9 plumose setae, of which the length significantly increases towards tip; outer plate with 10 spines on left side and 8 on right side (they include deeply bifurcate spines and spines with 1-3 strong denticles on posterior border); palp well developed, with broad article 2; left article 2 with row of long styliform marginal spines and margino-facial setae (most of them forming a row); right article 2 with row of stout conical marginal spines (partly fused with article 2), with 2 longer anterodistal spines (most upper one arising medially), with margino-facial row of setae.

MAXILLA 2. ( Fig. 3M ) Basal part with 2 short anterior setae (one is lost on illustrated Maxilla 2); plates rather narrow; inner plate with marginal and margino-facial row of setae respectively on distal 0.7 and 0.6 of posterior border, with microtrichs on proximal 0.3 of posterior border; outer plate with upper border straight, with one tiny anteroproximal medial seta, with microtrichs on upper subdistal border, with about 6 short anterodistal setae (2 are lost on illustrated Maxilla 2), with double row of strong distal setae.

MAXILLIPED. ( Fig. 4A ) Typical for the genus Halirages .

GNATHOPOD 1. ( Fig. 4 B-C) Coxa with anteroventral corner forming a square angle (not produced into a tooth pointing forwards), with 10 weak crenulations along ventral margin; carpus 3.8 x as long as wide, as long as basis, anterior border not setose (except for distal tuft of seta); propodus 2.3 x as long as wide, 0.71 x as long as carpus; palm sharply denticulate, with marginolateral row of thin setae; palmar part of propodus 0.31 x as long as propodus; dactylus dentate all along its posterior border.

GNATHOPOD 2. ( Fig. 4D ) Coxa square, with 10 weak crenulations along ventral margin; carpus 5.0 x as long as wide, as long as basis, with anterior border scarcely setose to glabrous (except for distal tuft of seta); propodus 2.5 x as long as wide, 0.63 x as long as carpus; palm sharply denticulate, with marginolateral row of thin setae; palmar part of propodus 0.25 x as long as propodus; dactylus dentate all along its posterior border.

PEREIOPOD 3. ( Fig. 5A ) Coxa square with about 10 weak and in some cases indistinct crenulations; leg weakly spinose/setose; basis anteriorly distinctly concave and posteriorly distinctly convex, with setae on its two borders; carpus 8.9 x as long as wide, 1.8 x as long as merus; propodus 12.6 x as long as wide, 2.1 x as long as merus; dactylus 0.41 x as long as propodus, 0.88 x as long as merus.

PEREIOPOD 4. ( Fig. 5 B-C) Coxa broad and posteriorly produced into a bluntly triangular protrusion, with ventral margin with 10 weak crenulations; leg weakly spinose/setose, slightly longer than pereiopod 3; basis anteriorly concave and posteriorly convex, with setae on its two borders; carpus 9.0 x as long as wide, 1.8 x as long as merus; propodus 13.5 x as long as wide, 2.2 x as long as merus, 1.2 x as long as propodus of pereiopod 3; dactylus 0.39 x as long as propodus, 0.87 x as long as merus.

PEREIOPOD 5. ( Fig. 6 A-B) Pereiopod 5 <pereiopod 6 <pereiopod 7; posterior lobe of coxa distinctly longer than anterior lobe; leg weakly spinose/setose; basis elliptic, 1.3 x as long as wide, anterior border with 8 styliform spines and sparse thin setae, distally without tooth, posterior border with 9 very low crenulations, posterodistal border rounded and smooth, with 2 long styliform posterodistal medial spines; ischium without anterodistal tooth; carpus 11.6 x as long as wide, 1.7 x as long as merus; propodus 19 x as long as wide, 1.9 x as long as merus; dactylus 11 x as long as wide, 0.33 x as long as propodus, 0.63 x as long as merus.

PEREIOPOD 6. ( Fig. 6 C-D) Posterior lobe of coxa considerably longer than anterior lobe; leg weakly spinose/setose; basis elliptic, 1.3 x as long as wide, anterior border with 9 styliform spines (one rubbed off on illustrated basis) and sparse thin setae, distally without tooth, posterior border with 14 very low crenulations, posterodistal border rounded and smooth, with 2 long styliform posterodistal medial spines; ischium without anterodistal tooth, with anterodistal spine; carpus 11.5 x as long as wide, 1.6 x as long as merus; propodus 19 x as long as wide, 1.7 x as long as merus; dactylus 13 x as long as wide, 0.29 x as long as propodus, 0.51 x as long as merus.

PEREIOPOD 7. ( Fig. 6 D-E) Coxa small and elliptic; large coxal gill present; leg weakly spinose/setose; basis with anterior and posterior border straight and converging towards tip, 1.2 x as long as wide, anterior border with 5 styliform spines and a few thin setae, distally without tooth, posterior border with 18 serrations, posterodistal border with 3 serrations; junction between posterior and posterodistal border bluntly angular; ischium without anterodistal tooth; carpus 11.2 x as long as wide, 1.6 x as long as merus; propodus 18.4 x as long as wide, 1.8 x as long as merus, 1.02 x as long as propodus of P6, 1.30 x as long as propodus of P5; dactylus 12 x as long as wide, 0.28 x as long as propodus, 0.49 x as long as merus.

DORSAL ORNAMENTATION. ( FigS 1-2 ) Pereionite 7 and pleonites 1-2 with strong posterodorsal tooth; pereionite 6 without posterodorsal tooth.

EPIMERON 1. ( Fig. 7A ) With facial carina, with 2 isolate margino-facial spines, with very weak posteroventral tooth, with posterior border rounded and smooth.

EPIMERON 2. ( Fig. 7B ) With facial carina, with 4 isolate margino-facial spines, with very weak but acute posteroventral tooth, with posterior border straight and smooth.

EPIMERON 3. ( Fig. 7C )Without facial carina, with 7 isolate margino-facial spines, with weak posteroventral tooth, with posterior border weakly rounded and weakly serrate.

UROSOMITE 1. ( Fig. 7D ) With 4 ventrolateral spines and 1 posteroventral spine.

UROPOD 1. ( Fig. 7D ) Peduncle with 24 dorsolateral slender irregular-sized spines, with 22 dorsomedial slender irregular-sized spines; outer ramus 0.72 x as long as inner ramus, with 15 dorsolateral irregularsized spines, with at least 8 dorsomedial spines, with 4 apical spines; inner ramus as long as peduncle, with 25 dorsolateral spines (5 lost on illustrated uropod), with 41 dorsomedial slender irregular-sized spines; medial border of inner ramus minutely serrate.

UROPOD 2. ( Fig. 7E ) Peduncle with 12 dorsolateral slender irregular-sized spines, with 13 dorsomedial slender irregular-sized spines; outer ramus 0.53 x as long as inner ramus, with 8 dorsolateral irregularsized spines, with at least 3 dorsomedial spines, with 4 apical spines, border of ramus minutely serrate; inner ramus 1.2 x as long as peduncle with 19 dorsolateral spines (2 lost on illustrated uropod), with 21 dorsomedial slender irregular-sized spines, with 4 apical spines; medial border of inner ramus minutely serrate.

UROPOD 3. ( Fig. 7F ) Peduncle with 4 distolateral dorsal spines, with dorsomedial and ventromedial border spinose; outer ramus 0.93 x as long as inner ramus, with about 47 lateral irregular-sized (most small and slender) spines (several lost on illustrated uropod), with at least 46 medial irregular-sized (most small and slender) spines; inner ramus 2.1 x as long as peduncle, without distinct medio-proximal bulging, with 49 lateral spines (most small and slender; some lost on illustrated uropod) and at least 15 plumose setae, with 49 medial slender irregular-sized spines (most small and slender; some lost on illustrated uropod) and at least 9 plumose setae.

TELSON. ( Fig. 4E ) Triangular, with border convex, distally produced into a single tooth, without setules.

COLOUR PATTERN. ( Fig. 1 ) Uniformly crimson, eyes dull reddish pink. In alcohol, the red pigment persists longer on the oral field and the gnathopods.

BODY LENGTH. 40 mm.

Distribution

Norwegian Sea, west of Norway, 2589-2615 m. Besides the type series listed above, several other specimens of H. cainae sp. nov. from the Norwegian deep Sea were found during the workshop 'Deepwater amphipods of the Norwegian Sea, Skibotn Feltstasjon, August 2nd-9th, 2009', and were at that time provisionally identified as H. caecus Kamenskaya, 1980 . These specimens, which were not re-examined in this study, should have been deposited in the Zoological Museum of Bergen. In addition to the collected specimens, large red Halirages , which were presumably also H. cainae sp. nov., were observed on muddy bottoms with the video platform Campod (see e.g. Anonym 2006; Buhl-Mortensen et al. 2009 for description) during the MAREANO 2009-111 cruise. H. cainae sp. nov. is a species associated with the deep-sea Arctic water mass with negative temperature of the Norwegian Sea ( Tomczak & Godfrey 2003). Like almost all other organisms collected in that sea during the second leg of the MAREANO 2009-111 cruise, they were already dead when arriving on deck, after crossing the warmer upper water mass of Atlantic origin.

Remarks

Halirages cainae sp. nov. belongs to the Halirages species of the group qvadridentatus , together with H. qvadridentatus G.O. Sars, 1877 , H. gorbunovi Gurjanova, 1946 and H. caecus Kamenskaya, 1979 . The accounts given by G.O. Sars (1885) and Stephensen (1931) provide a clear picture of the diagnostic characters of the North-European species H. qvadridentatus , while the descriptions of the two other species (from the Arctic Ocean) are very deficient. The differences between the four species are described in the next section and are summarized in table 1.

H. cainae sp. nov. can be separated from H. qvadridentatus by the following characters. The eye is small, reniform to subreniform in H. cainae sp. nov., whilst it is large and quadrato-elliptic in H. qvadridentatus (see G.O. Sars 1885, plate 14 fig. 4). In H. cainae sp. nov., the junction between the anterior and ventral borders of coxa 1 forms a square angle, while in H. qvadridentatus it forms a tooth pointing forwards. The ventral border of coxa 1 and 2 bears about 10 weak crenulations in H. cainae sp. nov. vs. about 20 pronounced serrations in H. qvadridentatus . H. cainae sp. nov. has a posterodorsal tooth on the seventh pereionite and the first and second pleonite, never on the sixth pereionite (the dorsal dentition was also checked in the specimens seen during the workshop 'Deepwater amphipods of the Norwegian Sea'). In adult and subadult H. qvadridentatus , there is always a tooth on the seventh pleonite, and usually also a tooth on the sixth pereionite. On the posterior margin of the basis of pereiopods 5-7, the number of crenulations or serrations is lower in H. cainae sp. nov. (9, 14, 18) than in H. qvadridentatus (17,>22, 22-37). The posteroventral angle of the basis of pereiopod 7 is less angular in H. cainae sp. nov. than in H. qvadridentatus . The carpus and merus of pereiopod 7 are longer and more slender in H. cainae sp. nov. than in H. qvadridentatus . The carpus is 11.5 x as long as wide and 1.6 x as long as posterior border of basis in H. cainae sp. nov., whilst these ratios are 8.8 and 1.3 in H. qvadridentatus , respectively. The propodus is 18.4 x as long as wide and 1.8 x as long as posterior border of basis in H. cainae sp. nov., whilst these ratios are 13.0 and 1.4 in H. qvadridentatus , respectively. Finally, the tip of the telson has a single tooth in H. cainae sp. nov., whilst it is tridentate in H. qvadridentatus .

H. gorbunovi is very inadequately described but exhibits the following differences with the present species. In H. cainae sp. nov. the crenulations of the ventral border of coxa 1 and coxa 2 are weaker than in H. gorbunovi . In H. cainae sp. nov. the posteroventral angle of the basis of pereiopod 6 is rounded, whilst it is distinctly angular in H. gorbunovi (see Gurjanova 1946: 288 fig. 21.4). In H. cainae sp. nov.. the posterior border of the basis of pereiopod 6 has about 9 crenulations vs. about 5 scarcely distinct crenulations in H. gorbunovi . The Russian text also indicates that the basis of pereiopods 5 and 7 have an almost smooth posterior border, while H. cainae sp. nov. has small, but distinct serrations on the posterior border of the basis of pereiopod 7. Finally, H. cainae sp. nov. has eyes (which disappear only after a long preservation period), whilst H. gorbunovi is said to have none. This absence of eye will have to be confirmed when fresh specimens of H. gorbunovi will be available to study. It must be noted that the pleon of the two syntypes of H. gorbunovi is missing and that they are small juveniles: 6.5 mm from the tip of the rostrum to the end of the pereion (the largest H. cainae sp. nov. is 40 mm long). An adequate characterization of H. gorbunovi would only be possible when topotypical specimens from a wide size range will be available for study.

The description of H. caecus is also very deficient but includes the following differences with the new species. In H. cainae sp. nov., article 2 of mandibular palp is stout and is densely setose, all along its medial margin, whilst it is slender and sparsely setose in H. caecus . In H. cainae sp. nov., article 3 of mandibular palp is apically broader than in H. caecus . In H. cainae sp. nov., the anteroventral corner of coxa 1 forms a square angle, whilst in H. caecus it forms a tooth pointing forward. It must be pointed out that pereiopods 5-7 of the types of H. caecus were neither illustrated nor described and were possibly missing in all specimens. Finally, H. caecus is said to be eyeless whilst H. cainae sp. nov. does have eyes (which can become indistinguishable after a long preservation period). As for H. gorbunovi , the absence of eyes needs confirmation.

Figures

Fig. 1. Halirages cainae sp. nov., paratype, sex unknown, about 40 mm, MAREANO 2009-111, R-station 488, sample 379, habitus.

Fig. 2. Halirages cainae sp. nov., holotype ♂, 40 mm, Norwegian Sea, MAREANO 2009-111, R-station 487, sample 157, habitus, left side; pereiopods illustrated in leveled position; gnathopods (except coxae) illustrated after right legs.

Fig. 3. Halirages cainae sp. nov., holotype ♂, 40 mm, Norwegian Sea, MAREANO 2009-111, R-station 487, sample 157. A. head and remaining parts of left antennae. B. right A2. C. upper lip and epistome. D. lower lip. E. left Md. F. right Md. G. left Mx1. H. tip of palp of left Mx1. I. article 2 of palp of right Mx1. J. tip of palp of left Mx1. K. tip of upper plate of left Mx1 (spines for next intermoult inside old cast). L. tip of upper plate of right Mx1 (spines for the next intermoult inside old cast).

Fig. 4. Halirages cainae sp. nov., holotype ♂, 40 mm, Norwegian Sea, MAREANO 2009-111, R-station 487, sample 157. A. Mxp. B. right Gn1. C. tip of chela of right Gn1. D. right Gn2. E. telson.

Fig. 5. Halirages cainae sp. nov., holotype ♂, 40 mm, Norwegian Sea, MAREANO 2009-111, R-station 487, sample 157. A. left P3. B. left P4. C. propodus and dactylus of left P4. D. left pleopod 1. E. coupling hooks of left pleopod 1.

Fig. 6. Halirages cainae sp. nov., holotype ♂, 40 mm, Norwegian Sea, MAREANO 2009-111, R-station 487, sample 157. A. left P5 (basis drawn after right leg). B. basis and ischium of right P5 (inverted). C. left P6 (basis drawn after right leg). D. basis and ischium of right P6 (inverted). E. left P7. F. basis and ischium of left P7.

Fig. 7. Halirages cainae sp. nov., holotype ♂, 40 mm, Norwegian Sea, MAREANO 2009-111, R-station 487, sample 157. A. pleonite 1. B. pleonite 2. C. pleonite 3. D. ventrolateral part of urosomite 1 and right U1 (apical cluster of spines of outer ramus drawn after left U1). E. left U2. F. right U3.