Akanthophoreus vikingra, Błażewicz-Paszkowycz, Magdalena & Bamber, Roger N., 2011

Błażewicz-Paszkowycz, Magdalena & Bamber, Roger N., 2011, Tanaidomorph Tanaidacea (Crustacea: Peracarida) from Mud-Volcano and Seep Sites on the Norwegian Margin, Zootaxa 3061, pp. 1-35 : 26-31

Akanthophoreus vikingra sp. nov.

( Figs 15–17)

Material examined. Holotype, Ƥ (MNHN-IU- 2010-2858), Vicking, PL277-7, ASPI 6, PP-V14 HMMV, 72°00.335ʹN 14°42.746ʹE, 1263 m, 06/06/2006. Paratypes: 1 neuter (MNHN-IU- 2010-2859), Vicking, PL277-7, ASPI 6, PP-V14 HMMV, 72°00.335ʹN 14°42.746ʹE, 1263 m, 06/06/2006; 1Ƥ (MNHN-IU-2010-2860), Vicking, PL272-2, ASPI 3, G12 Nyegga, 64°39.790ʹN 05°17.313ʹE, 734 m, 25/05/2006; 2ƤƤ (MNHN-IU- 2010-2861), Vicking, PL272-2, ASPI 8, G11 Nyegga, 64°39.980ʹN 05°17.351ʹE, 733 m, 26/05/2006; 1 mancae (MNHN-IU- 2010-2862), Vicking, PL272-2, ASPI 8, G11 Nyegga, 64°39.980ʹN 05°17.351ʹE, 733 m, 26/05/2006; 3ƤƤ, 63 (MNHN-IU- 2010-2863), Vicking, PL272-2, GCL 1, G11 Nyegga, 64°39.996ʹN 05°17.346ʹE, 736 m, 25/05/2006; 3ƤƤ, 9 mancae (MNHN-IU- 2010-2864), Vicking, PL277-7, ASPI 2, PP-V16 HMMV, 72°00.336ʹN 14°42.741ʹE, 1264 m, 06/06/2006; 7ƤƤ (1 partly dissected in slides, see IU- 2010-2871), 2 preparatory 33 (one dissected in slides, see IU-2010-2870), 14 neuters, 2 mancae (1 dissected in slides, see IU- 2010-2872) (MNHN-IU- 2010-2865), Vicking, PL277-7, ASPI 3, PP-V16 HMMV, 72°00.335ʹN 14°42.732ʹE, 1264 m, 06/06/2006; 2ƤƤ, 6 neuters, 3 mancae, (MNHN-IU- 2010-2866), Vicking, PL277-7, ASPI 4, PP-V16 HMMV, 72°00.336ʹN 14°42.723ʹE, 1263 m, 06/06/2006; 3 specimens (MNHN-IU- 2010-2867), Vicking, PL277-7, ASPI 7, PP-V16 HMMV, 72°00.336ʹN 14°42.749ʹE, 1263 m, 06/06/2006; 3ƤƤ, 2 neuters, 3 mancae (MNHN-IU- 2010-2868), Vicking, PL277-7, ASPI 8, PP-V16 HMMV, 72°00.336ʹN 14°42.746ʹE, 1263 m, 06/06/2006; 1Ƥ (MNHN-IU- 2010-2869), Vicking, MTB-5, HMMV, 72°00.177ʹN 14°43.958ʹE, 1272 m, 07/06/2006; 13 (dissected on 3 slides, see IU- 2010-2865), (MNHN- IU-2010-2870), Vicking, PL277-7, ASPI 3, PP-V16 HMMV, 72°00.335ʹN 14°42.732ʹE, 1264 m, 06/06/2006; 1Ƥ (dissected on 1 slide, see IU- 2010-2865) (MNHN-IU- 2010-2871), Vicking, PL277-7, ASPI 3, PP-V16 HMMV, 72°00.335ʹN 14°42.732ʹE, 1264 m, 06/06/2006; 1 juvenile Ƥ, 1 manca (1 slide, see IU- 2010-2865) (MNHN-IU- 2010-2872), Vicking, PL277-7, ASPI 3, PP-V16 HMMV, 72°00.335ʹN 14°42.732ʹE, 1264 m, 06/06/2006.

Description of female with oostegites. Body ( Fig. 15 B) slender, holotype 3.4 mm long, 8.4 times as long as wide. Cephalothorax subrectangular, tapering towards anterior, 1.5 times as long as wide, with slight triangular rostrum, single seta at each anterolateral corner, eyes and eyelobes absent. Six free pereonites; pereonite 1 rectangular, shortest, 0.45 times as long as cephalothorax, 1.5 times as long as wide; pereonites 2, 3 and 4 subequal in length, 1.5 times as long as pereonite 1, as long as wide, with convex lateral margins; pereonite 5 just shorter, 1.3 times as long as pereonite 1, as wide as long; pereonite 6 just longer than pereonite 1 and 1.2 times as wide as long. Five free subequal pleonites bearing pleopods; each pleonite 4.6 times as wide as long, with one stout dorsolateral seta on each side and slight, rounded sternal process. Pleotelson semicircular, 1.7 times as wide as long, 2.5 times as long as last pleonite, without ventrolateral spurs, and bearing two setae mid-posteriorly ( Fig. 17 I).

Antennule ( Fig. 15 C) proximal article 3.25 times as long as wide, as long as distal three articles together, with outer distal group of two penicillate and two simple setae, longest simple seta longer than second article; second article 1.5 times as long as wide, 0.4 times as long as first article, with outer pair of penicillate setae and single inner and outer simple distal setae, outer simple seta exceeding tip of antennule; third article 1.75 times as long as wide, 0.7 times as long as second article, with inner distal seta; fourth article tapering, just longer than second article, with six distal setae and one aesthetasc.

Antenna ( Fig. 16 B) of six articles,; second article (partially demaged during dissection) with stout single dorsodistal and ventrodistal setae; third article as long as wide, with stout dorsodistal seta; fourth article longest, curved, over four times as long as third article, five times as long as wide, with incipient articulation at about mid-length, distally with two penicillate and four simple setae; fifth article half as long as fourth with one distal seta; sixth article minute with four distal setae.

Labrum ( Fig. 16 C) rounded, distally flattened and densely setulose. Left mandible ( Fig. 16 D) with three rounded teeth on pars incisiva, narrow, crenulate lacinia mobilis, pars molaris slender, tapering with numerous distal spinules. Right mandible ( Fig. 16 E) as left but without lacinia mobilis. Labium ( Fig. 16 H) simple, outer distal margins with microtrichia, without palp. Maxillule ( Fig. 16 F) with eight distal spines, some spines with two inner rows of fine denticulation; palp and maxilla not recovered. Maxilliped ( Fig. 16 I) palp first article naked, second article with one fine outer distal and three stouter inner distal setae, third article with one longer and two smaller inner distal setae, longest seta exceeding tip of fourth article, fourth article with five longer setae along inner and distal margins and one smaller outer subdistal seta; basis with single, long seta not reaching margin of endites; endites distally with two small setae and two oval tubercles. Epignath ( Fig. 16 G) ribbon-like, tapering to naked distal seta.

Cheliped as that of preparatory male (see below).

Pereopods as those of male ( Fig. 17 ). Pereopod 1 ( Fig. 17 B) coxa with simple seta; basis 3.2 times as long as wide, with two dorsal penicillate setae; ischium with one ventral seta; merus one-third as long as basis, with one ventrodistal seta and one finely-denticulate ventrodistal spine; carpus 1.25 times as long as merus, with single dorsodistal and ventrodistal finely-denticulate spines and fine distal setulation; propodus 1.4 times as long as carpus, with single ventrodistal seta and dorsodistal spine-like apophysis, and fine distal setulation; dactylus 0.6 times as long as slender unguis, both curved, together 0.9 times as long as propodus. Pereopod 2 ( Fig. 17 C), coxa similar to pereopod 1, basis 3.3 times as long as wide, dorsally with simple seta in proximal half and penicillate seta in distal half; ischium with one ventral seta; merus 0.7 times as long as carpus, with one ventrodistal seta and one finelydenticulate ventrodistal spine; carpus with single dorsodistal and ventrodistal finely-denticulate spines and one shorter ventrodistal simple spine; propodus 1.5 times as long as carpus, with smaller dorsodistal and longer ventrodistal setae, and slight dorsodistal pointed apophysis and adjacent microtrichia; dactylus with longer unguis as long as propodus. Pereopod 3 ( Fig. 17 D) similar to pereopod 2, but with microtrichia distally on merus, and distally and ventrally on carpus.

Pereopod 4 ( Fig. 17 E) coxa distinct with one seta; basis 3.3 times as long as wide, with dorsoproximal pair of penicillate setae, mid-ventrally with one simple and one penicillate setae; ischium with one ventral seta; merus two-thirds as long as carpus, with two finely-denticulate ventrodistal spines; carpus with three finely-denticulate distal spines and fine dorsodistal seta, ventral margin with microtrichia; propodus as long as carpus, with two finely-denticulate ventrodistal spines, one finely-denticulate dorsodistal spine and distal microtrichia; dactylus and shorter unguis not fused, straight, together 1.2 times as long as propodus; dactylus with ventral rows of fine denticulation. Pereopod 5 ( Fig. 17 F) similar to pereopod 4, but basis with one dorsal and two ventral penicillate setae, ischium with two ventral setae. Pereopod 6 ( Fig. 17 G) as pereopod 5, but basis with one ventral penicillate seta, propodus with three dorsodistal setae.

Pleopods ( Fig. 17 H) all alike, with naked basis, endopod as long as exopod, endopod and exopod without setae on inner margin; endopod with subdistal inner seta and 13 setae around distal-outer margins in distal half only; exopod with 19 setae along outer margin, proximal seta separated from others.

Uropod ( Fig. 17 I) biramous, basis naked; exopod short, half as long as proximal endopod segment, of two segments; first segment with one distal seta, second segment with one longer and one shorter distal setae; endopod of two segments, first segment distally with two penicillate and one simple setae, second segment with two penicillate and four subequal simple setae distally.

Female without oostegites ( Fig. 15 A): similar to female with oostegites but pereonites 2 to 5 subequal, as long as wide.

Distinctions of preparatory male. Body as female without oostegites; dimorphism shown in antennule. Antennule ( Fig. 16 A) of five articles; proximal article stout, 1.6 times as long as wide, with outer distal group of three penicillate and one simple setae, simple seta not as long as second article; second article as long as wide, 0.4 times as long as first article, with outer tuft of four penicillate setae and single inner and outer simple distal setae, outer simple seta exceeding tip of fourth article; third article shorter than wide, half as long as second article, with inner distal seta; fourth article 0.8 times as long as third article, naked; fifth article tapering, 1.5 times as long as third article, with five distal setae and one aesthetasc.

Cheliped ( Fig. 17 A) with elongate basis 1.7 times as long as wide with one dorsal seta; merus subtriangular with single ventral seta; carpus with slight rounded dorsoproximal extension, 1.5 times as long as wide, with one mid-ventral seta and single dorsoproximal and dorsodistal setae, ventral margin expanded as a flange over distal two-thirds; propodus large, palm just longer than wide with coarse dorsodistal denticulations, comb-row of four spines; fixed finger just shorter than palm with three ventral setae, three setae adjacent to cutting edge which bears rounded cusps in distal half; dactylus with raised, crenulated dorsal margin, stout spinules on cutting edge.

Etymology. Euphonius formation from the Old Norse vikingr, a Scandinavian pirate (hence “Viking”); noun in apposition.

Remarks. Confusion has long reigned over the related genera Akanthophoreus , Paraleptognathia Kudinova- Pasternak, 1981 and Scoloura Sieg & Dojiri, 1991 (the monophyly of some of which are yet to be established), and was most recently and competently discussed by Bird (2007), who relegated Scoloura to a junior synonym of Akanthophoreus (see Bird 2007, for discussion on the historical confusion with “ Leptognathia ” gracilis /sarsi/longiremis). The present species is without the very large ventrodistal carpal shield, extensive surface setation of the cheliped, and proximal incisive margin dentition shown by the poorly-described Paraleptognathia sensu Kudinova-Pasternak (1981 ; 1985), and is thus not easily attributable to that genus.

Bird (2007) listed ten species of Akanthophoreus , to which some of the new species attributed to Paraleptognathia by Guerrero-Kommritz (2004) could be added on reanalysis. Since then, the only other species to be added to the genus is A. nanopsenos Bamber & Bird, 2009 from the eastern Mediterranean (see Bamber et al. 2009). Akanthophoreus vikingra sp. nov., with its cheliped bearing a row of rounded crenulations along the dorsal margin of the dactylus but not laterally on the propodus nor ventrally on the carpus, with a single ventrodistal spine on the merus of pereopod 1, together with the proportions of the antennule and uropods, shows closest affinity to Akanthophoreus gracilis (Krøyer, 1842) , and indeed keys out to that taxon in the Appendix of Guerrero-Kommritz (2004). However, A. gracilis is without the proximoventral carpus flange on the cheliped, and does not have the group of small denticles dorsodistally on the cheliped propodus, both evident in the present species.

Akanthophoreus vikingra was taken at both the HMMV and the Nyegga seep sitee, in depths from 733 to 1272 m.

Figures

FIGURE 16. Akanthophoreus vikingra sp. nov., male, A, antennule; B, antenna; C, labrum; D, left mandible; E, right mandible; F, maxillule endite; G, epignath; H, labium; I, maxilliped. Scale lines = 0.1 mm for A to E, G to I, 0.1 mm for F.

FIGURE 17. Akanthophoreus vikingra sp. nov., A, cheliped, with A’, detail of chela; B to G, pereopods 1 to 6 respectively; H, pleopod; I, uropod. Scale lines = 0.1 mm.