Atlantapseudes cyanea, Bamber, 2007

Bamber, Roger N., 2007, New apseudomorph tanaidaceans (Crustacea, Peracarida, Tanaidacea) from the bathyal slope off New Caledonia, Zoosystema 29 (1), pp. 51-81 : 62-66

Atlantapseudes cyanea n. sp.

( Figs 6 ; 7 )

TYPE MATERIAL. — Holotype: New Caledonia, CALSUB, stn PL 13 , Cyana dive 1028/34, 21°26’S, 166°22.7’E, 1807- 1567 m depth, 4.III.1989, coll. M. Segonzac, ♀ with oostegites (MNHN-Ta923).

Paratypes: same data as holotype, 1 subadult ♂ (MNHN- Ta924). — New Caledonia, BIOGEOCAL, stn KG 210, N.O. Coriolis, 22°44.00’S, 166°30.97’E, 1190 m depth, 9.IV.1987, 1 ♂, 2 juveniles (MNHN-Ta925).

TYPE LOCALITY. — Off New Caledonia, 21°26’S, 166°22.7’E.

ETYMOLOGY. — Name derived from that of the submersible Cyana which was responsible for its collection (noun in apposition).

DESCRIPTION

Body ( Fig. 6A ), dorsoventrally flattened, holotype 9.3 mm long (tip of rostrum to posterior of pleotelson), 4.9 times as long as wide, tapering towards posterior.Cephalothorax subrectangular,0.9 times as long as wide, with small, pointed rostrum with lateral shoulders; eyelobes with anterior spinous apophysis, ocelli apparently absent; one lateral cephalothorax spine behind each eyelobe preceded by short seta. Six free pereonites; pereonites 1 shortest, about 1/4 as long as cephalothorax, pereonites 2 to 4 each longer than previous pereonite, pereonite 4 about three times as long as pereonite 1, pereonite 5 just shorter than pereonite 4, pereonite 6 just shorter than pereonite 3 (all pereonites respectively 4.5, 2.5, 1.8, 1.2, 1.3 and 1.7 times as wide as long); pereonites 1 and 2 laterally smoothly convex, without spines or apophyses; pereonites 3 to 6 with anterolateral spine-like apophysis, a midlateral indentation, posteriorly smoothly convex. Pleon three times as long as pereonite 6, of five free subequal pleonites, each extended laterally into a spinous apophysis bearing setae; pleonites three times as wide as long; female without pleopods, subadult male with pleopod rudiments on pleonite 1. Pleotelson rectangular,elongate, more than half length of pleon, 1.1 times as long as wide, stepped at insertion of uropods, naked.

Antennule ( Fig. 6B ) proximal peduncle article four times as long as wide, with single inner seta, midlateral outer plumose sensory seta and two simple setae distal of this; second article twice as long as wide, less than half length of first, with outer distal seta exceeding peduncle tip and adjacent plumose sensory seta, inner distal seta as long as article width; third article 0.3 times length of second, wider than long; fourth peduncle article as long as third, wider than long. Main flagellum of seven segments, first segment as long as any two distal segments, distal article with two aesthetascs; accessory flagellum of three segments.

Antenna ( Fig. 6C ) with simple, naked proximal peduncle article. Second article with inner and proximal setae, and with elongate squama, as long as peduncle article 4, bearing two long distal setae. Third peduncle article shorter than wide with single inner distal seta; fourth article longer than second, with inner distal plumose sensory seta as long as article; fifth article longest, 1.25 times as long as fourth, with simple inner, outer and distal setae and three longer distal plumose sensory setae. Flagellum of six segments.

Simply pointed epistome present.Labrum ( Fig. 6D ) square, simple, setose. Left mandible ( Fig. 6E ) with strong, crenulate pars incisiva, stout lacinia mobilis with four denticles, setiferous lobe setulose and with seven simple setae, pars molaris stout, blunt, distally with delicate marginal teeth and plumose setae on posterior edge ( Fig. 6F ); palp of three articles, proximal article with one inner seta; second article 0.6 times the length of the whole palp, with five simple inner distal setae; third article as long as

A B

first, with six inner finely-denticulate setae in the distal half, increasing in length to distal simple seta. Right mandible as left but lacinia mobilis smaller ( Fig. 6G ). Labium ( Fig. 6H ) with setulose outer and inner margins, palp slender with fine lateral setules and three simple distal setae. Maxillule ( Fig. 6I ) inner endite without apophyses, finely setose margins and three plumose distal setae; outer endite with ten distal spines and one subdistal seta, outer margin finely setose; palp of two articles, distally with four long setae, each biserrate in distal third, serrations oriented proximally and distally on opposite sides. Maxilla not recovered. Maxilliped ( Fig. 7A ) basis simple, naked; first palp article with single simple inner and outer distal setae; second palp article with inner margin bearing seven simple setae, upper face with two simple subdistal setae, and simple outer distal seta; third palp article longer than wide with 12 setae along inner margin; fourth palp article with nine longer and one shorter simple distal setae.Endite with two coupling hooks, distally with outer simple tapering setae, two inner distal plumose setae, three marginal plumose setae. Epignath ( Fig. 6J ) large, cup-shaped, with prominent distally-setose spine.

Cheliped similar in conformation to that of Atlantapseudes lindae Meyer & Heard, 1989, basis 2.5 times as long as wide, proximally with blunt apophysis, ventrally with central spine; exopodite absent. Merus subrectangular, naked, mid-ventrally with prominent tubercle; carpus 2.5 times as long as wide, ventrally with blunt proximal tubercle and single central and distal setae, dorsally with small proximal seta only. Chela ( Fig. 7B ) slender, palm (propodus) 0.6 times as long as wide, fingers longer than palm; fixed finger with single ventral seta, small proximal denticulations on cutting edge and slender terminal claw; dactylus just longer than fixed finger, curved, with small proximal denticulations but no apophyses on cutting edge, terminal claw longer; no black pigment apparent (in preserved material).

Pereopod 1 ( Fig. 7C ) bearing slender coxal spinelike apophysis with two distal setae; basis nearly six times as long as wide, sparsely setose as figured, exopodite absent. Ischium with one ventrodistal seta. Merus wider distally, with finely denticulate ventrodistal spine, marginal ventral setae and tuft of five dorsodistal setae. Carpus shorter than merus, nearly twice as long as wide, with two ventral and one dorsodistal finely denticulate spines; dorsal and ventral margins with 11 and four simple setae respectively.Propodus with four ventral spines, distalmost being finely denticulate, and middorsal and dorsodistal finely denticulate spines; single longer seta between these last two, single dorsoproximal seta and paired ventrodistal setae. Dactylus stout, with four ventral denticulations and two fine dorsoproximal setae; unguis distinct.

Pereopod 2 ( Fig. 7D ) basis almost six times as long as wide, with sparse marginal setae and paired longer ventrodistal seta; ischium with single ventrodistal seta; merus longer than carpus, with simple ventral setae and row of four dorsodistal setae; carpus with numerous ventral and dorsal marginal setae, six dorsodistal setae, and single posterodistal short spine; propodus slender, as long as carpus, with row of six ventral setae, six dorsal marginal setae and tuft of six dorsodistal setae, and three small spines along the posterior face; dactylus finely denticulate and with single small dorsal and ventral setae, unguis distinct. Pereopod 3 ( Fig. 7E ) similar to pereopod 2, but basis with single ventrodistal seta, propodus without posterior spines.

Pereopod 4 similar to pereopod 5, basis stouter than anterior pereopods, five times as long as wide, without ventrodistal seta; merus and carpus subequal; dactylus and unguis of right leg of holotype distorted into pseudo-claw (presumed damaged); that of left leg normal. Pereopod 5 ( Fig. 7F ) basis with simple marginal setae in proximal half; merus shorter than carpus and with one ventrodistal seta; carpus with two ventral spines in distal half and three distal setae; propodus with two ventral spines in distal half and tuft of five distal setae; dactylus slender with fine paired dorsal setae, unguis distinct. Pereopod 6 ( Fig. 7G ) as pereopod 5, but carpus without ventrodistal spine, propodus ( Fig. 7H ) with single mid-ventral spine and posterodistal row of ten small spines not extending to distal margin, dorsodistal group of two short and two longer setae, the latter exceeding tip of unguis.

Pleopods absent in female; only rudimentary first pair present in subadult male.

Uropod missing in holotype; that of paratype biramous, basis with one outer distal seta; exopod longer than basis and of one proximal short segment and three further slender segments, distal segment with four terminal setae; endopod elongate, filiform, multisegmented, longer than pleon plus pereonite 6.

Male closely similar to female, but with pronounced penial tubercle mid-ventrally on pereonite 6.

REMARKS

Of the three described species of Atlantapseudes (see Guţu 1996b), A. diversus (Lang, 1968) is distinct in having an exopodite on the cheliped (inter alia); both A. diversus and A. lindae Meyer & Heard, 1989 (q.v.) have an antennal squama shorter than the third antennal peduncle article, and the latter has only small anterolateral tubercles on the pereonites.

In most respects, A. cyanea n. sp. is closest to the type species of the genus, A. nigrichela Băcescu, 1978 , taken off Portugal in 740 to 1250 m depth. Both have an antennal squama as long as the fourth antennal peduncle article (about 3.5 times the length of the third peduncle article). However, the new species has less spination of the carapace, and is without the prominent anterolateral spine-like apophysis on pereonite 2 present in A. nigrichela ( Băcescu [1978] figured and described such an apophysis also on pereonite 1, but this would have been the coxal apophysis of pereopod 1); other distinguishing features include the shorter labial palp, the more numerous chela-fixed-finger ventral setae, and the lack of distal setal row on the pereopod 6 propodus in A. nigrichela .

The unusual proximal blunt apophysis on the cheliped basis of three of these species may be the remains of the exopodite: this apophysis is absent in A. diversus which has an exopodite.

Family PAGURAPSEUDIDAE Lang, 1970 Subfamily HODOMETRICINAE Guţu, 1981

Figures

FIG. 6. — Atlantapseudes cyanea n. sp.: A, holotype ♀, dorsal; B, antennule; C, antenna; D, labrum; E, left mandible; F, detail of margin of molar process of left mandible;G, lacinia mobilis of right mandible; H, labium; I, maxillule; J, epignath. Scale bar: A, 2 mm; B, C, 0.6 mm; D-J, 0.3 mm.

FIG. 7. — Atlantapseudes cyanea n. sp.: A, maxilliped and endite;B, chela; C-G, pereopods 1-3, 5 and 6 respectively;H, distal articles of pereopod 6. Scale bar: A, 0.3 mm; B-G, 0.6 mm; H, 0.15 mm.