Apseudes coriolis, 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 : 58-62

Apseudes coriolis n. sp.

( Figs 4 ; 5 )

TYPE MATERIAL. — Holotype: New Caledonia, BIO- GEOCAL, N.O. Coriolis, 21°29.15’S, 166°26.59’E, 1520 m depth, stn KG 240, 14.IV.1987, 1 ♂ (MNHN- Ta921).

Paratype: New Caledonia, CALSUB, stn PL 13, Cyana dive 1028/34, 21°26’S, 166°22.7’E, 1807- 1587 m depth, 4.III.1989, coll. M. Segonzac, 1 juvenile (MNHN- Ta922).

TYPE LOCALITY. — Off New Caledonia, 21°29.15’S, 166°26.59’E.

ETYMOLOGY. — Named after the cruise ship N.O. Coriolis which collected the holotype (noun in apposition).

DESCRIPTION

Body slender ( Fig. 4A ), 6.8 mm long, 7 times as long as wide, cephalothorax subtriangular, without preorbital spines, ocular lobes present, without spinous apophyses, no pigmented eyes in preserved material, conspicuous sharp rostrum. Six free pereonites; pereonite 1 shortest, with convex anterolateral margins, without apophyses; pereonites 2 to 5 gradually increasing in length, pereonite 6 shorter than pereonite 3; these five pereonites with anterolateral spine-like apophysis and convex posterior corner at attachment of pereopod coxae. Five free subequal pereonites, each with lateral setose, spine-like apophyses, each bearing pair of pleopods; elongate pleotelson 1.5 times as long as wide, stepped slightly at insertion of uropods, and with paired distal setae. Hyposphenia present as pointed, posteriorly directed processes ventrally on pereonites 3 and 5 and pleonites 1, 2 (smaller), 4 and 5; penial tubercle present mid-ventrally on pereonite 6.

Antennule ( Fig. 4B ) proximal peduncle article slender, 7.6 times as long as wide, with sparse, simple setae; second article 1/4 as long as first with five simple distal setae; third article as long as second; fourth as long as wide; main flagellum of 11 segments, with single aesthetasc present on each of segments 1 to 6 and 8; accessory flagellum of two segments.

Antenna ( Fig. 4C ) proximal peduncle article short, simple; second article four times as long as wide, with tiny distal squama (shorter than third article) bearing single distal seta; third article 1/4 length of second, fourth and fifth articles subequal, 1.3 times as long as second; flagellum of five segments.

Simply pointed epistome present; labrum lost in preparation. Right mandible ( Fig. 4D ) with crenulate pars incisiva, slender lacinia mobilis similar to compound setae on setiferous lobe; pars molaris robust, blunt; palp of three articles, first article with simple inner seta, second article longest with paired simple setae along distal half of inner margin, distal article with seven short and two longer distal setae. Left mandible similar to right mandible, but lacinia mobilis larger with crenulate distal margin ( Fig. 4E ). Maxillule ( Fig. 4G ) outer endite with ten distal spines and two subdistal setae, inner endite without apophyses, with four simple distal setae; palp of two articles with five simple, distal setae. Maxilla ( Fig. 4F ) generally with simple distal setae and spines, fixed endite with bifurcate distal spines, rostral row of 24 simple setae sheltering two longer, bilaterally denticulate setae. Labium ( Fig. 4H ) with denticulate outer margin, palp finely setose with two larger distal setae. Maxilliped ( Fig. 5A ) basis

A B

simple with inner distal seta; proximal palp article with short outer distal seta and longer inner distal seta exceeding tip of second article; second article with single outer distal seta and two rows of simple inner setae; third article with five simple setae in distal half on inner apophysis; fourth article with seven simple distal setae. Endite with three coupling hooks, inner caudodistal seta simple, slender; inner distal setae short, square, outer distal setae slender. Epignath ( Fig. 4I ) large, typical of the genus, with slender distal spine bearing some corrugations in proximal half.

Cheliped ( Fig. 5B ) basis with small proximal ventral seta, conspicuous mid-ventral spine-like apophysis and elongate subdistal simple seta; merus subrectangular with ventrodistal pair of simple setae; carpus longer than basis, three times as long as wide, with three longer and one distal shorter ventral setae, and single mesiodistal seta. Chela fingers longer than palm, propodus fixed finger with three ventral setae forming a “crown” with paired distal and three inner setae, cutting edge with fine denticulation distally, and large tooth-like apophysis proximally; dactylus longer than fixed-finger, with distal crenulations on cutting edge and larger toothlike apophysis proximally. Exopodite present with three distal setae.

Pereopod 1 ( Fig.5C ) coxa with prominent,pointed spine-like apophysis; basis 3.4 times as long as wide, with stout ventrodistal spine and with small threearticled exopodite bearing four plumose distal setae; ischium with single ventrodistal seta; merus longer than carpus, with outer midlateral group of three longer setae, three ventral and two small dorsodistal setae, and robust ventrodistal spine; carpus with two spines mid-ventrally and one ventrodistally interspersed with simple setae as figured, dorsodistal spine with three adjacent setae; propodus with three ventral and two dorsal spines, single simple seta adjacent to each of latter pair and one adjacent to dactylus, and compound, bilaterally denticulate seta at base of dactylus; dactylus with two large, ventral denticulations, unguis distinct.

Pereopod 2 ( Fig. 5D ) basis slender, 6.5 times as long as wide, naked; ischium naked; merus nearly three times as long as ischium, with single ventrodistal seta; carpus slender, twice as long as merus, with two ventral and four distal simple setae; propodus shorter than carpus, with paired ventroproximal setae, and single mid-ventral and ventrodistal setae, and three dorsodistal setae; dactylus longer than unguis, both slender, together longer than propodus. Pereopod 3 as pereopod 2.

Pereopod 4 ( Fig. 5E ) similar to pereopod 2, but basis with two small, simple ventroproximal setae, merus just more than twice as long as ischium and with two distal setae, propodus with middorsal plumose sensory seta and distal crown of five longer outer and three shorter inner simple setae. Pereopod 5 as pereopod 4 but basis naked, propodus with only four distal setae. Pereopod 6 ( Fig. 5F ) similar to pereopod 4, but basis with single dorsoproximal plumose sensory seta, merus expanding distally, with two distal setae, carpus sparsely setose, propodus distally with row of 12 fine leaf-like spines and three simple distal setae.

Pleopods ( Fig. 5G ) all similar, highly reduced; basis slender, naked; rami slender, as long as basis, almost naked, bearing only a single distal plumose seta three times length of ramus. Uropods missing, detached.

REMARKS

With a conspicuous spine-like apophysis on the first coxa and a “normal” caudo-distal spine on the maxilliped endite, Apseudes coriolis n. sp. accords comfortably with the characters of the genus Apseudes . It also has a number of features unusual for the genus, particularly the highly reduced antennal squama and pleopods, and also the generally simple setation throughout. Reduced pleopods are a feature of Langapseudes tuberculatus (Lang, 1968) , removed from Apseudes by Băcescu (1987): in that species the pleopod rami are much shorter than the basis (1/4 or less as long); in addition, there are multiple aesthetascs on the antennule segments, and there are differences in the pereonite and pleonite conformation (inter alia); L. tuberculatus has a “normally-developed” antennal squama.

Despite the lack of leaf-like inner caudodistal seta on the maxilliped endite, the present species has the appearance of a Leviapseudes , with gross similarity to, for example, L. gracillimus (Hansen, 1913) . In this vicinity, only Nierstrasz (1913) described Leviapseudes species (as Apseudes ), viz. L. sibogae and L. weberi , both from Indonesia at> 1500 m depth; the present specimen shows some affinities to these. The only other Pacific record is of L. zenkevitchi (Kudinova-Pasternak, 1966) , from the North Pacific at 1067-6065 m depth. None of these species have the pleopod, squama, or reduced setation characters of A. coriolis n. sp.

While in some ways the present species could be associated with any of these three genera, it has a number of clear distinctions from them all, which even in combination are not considered sufficient to warrant erection of a new genus.

Figures

FIG. 4. — Apseudes coriolis n. sp., ♂: A, body, dorsal; B, antennule; C, antenna; D, right mandible (lacinia mobilis arrowed); E, distal detail of incisor of left mandible; F, maxilla; G, maxillule; H, labium; I, epignath. (E and I from paratype). Scale bar: A, 1.0 mm; B, C, 0.3 mm; D-I, 0.1 mm.

FIG. 5. — Apseudes coriolis n. sp.: A, maxilliped; B, right cheliped; C-F, pereopods 1, 2, 4 and 6 respectively; G, third pleopod. Scale bar: A, 0.1 mm; B-F, 0.3 mm; G, 0.15 mm.