Sericosura hedgpethi, Bamber, Roger N., 2009

Bamber, Roger N., 2009, Two new species of Sericosura Fry & Hedgpeth, 1969 (Arthropoda: Pycnogonida: Ammotheidae), and a reassessment of the genus, Zootaxa 2140, pp. 56-68 : 59-63

Sericosura hedgpethi sp. nov.

( Figs. 2–3 )

Material examined: ovigerous male holotype ( NIWA 31959), 1 ovigerous male paratype (NHM 2008.3456), 1 female paratype ( NIWA 31947): Station SO191-3/238, “Rock Garden”, on the Hikurangi Margin, 39º58.64–58.63’S, 178º14.14–14.17’E, 907–908 m depth, 0 6 March 2007, coll. IFM GEOMAR from the FS Sonne.

Description of male: generally typical of Sericosura ; trunk ( Fig. 2 A) compact, fully segmented, segments slightly raised (flared) at segment articulations. Cephalon expanded anteriorly, constricted anterior to first lateral processes, 0.47 times total trunk length; anterior margin with dorsolateral angular corners furnished with four slender spines; ocular tubercle near anterior margin, tall, slender, distally bifurcate, without eyes; palp and proboscis attachment on anterior face of cephalon. Lateral processes without tubercles, with fine spines on dorsodistal margins, processes separated by about 0.2 times their own width, processes 3 and 4 separated least; first lateral process curved anteriorly. Abdomen 0.4 times as long as trunk, elongate, distally swollen, downcurved, reaching to distal edge of coxa 1 of leg 4, with distinct basal articulation, bearing laterodistal slender spines.

Proboscis stout, parallel-sided, naked, held below cephalon, 0.6 times as long as trunk.

Chelifore absent.

Palp ( Fig. 2 B) of seven articles. First article (P1) short, wide, compact; P2 elongate, slightly downcurved, 3.6 times as long as P1, with mid-outer spine, dorsal and lateral distal spines, and sparse ventral setae; P3 half as long as P1 with single dorsal and outer setae; P4 0.9 times as long as P2, with convoluted ventral margin, with sparse dorsal and ventral setae and row of outer spines; P5 as long as P3, ventrally densely setose as figured; P6 just shorter than P5, with dense ventral and sparse outer setae; P7 twice as long as P5, densely setose all round.

Oviger ( Fig. 2 C; 3A) of ten articles; article 1 ( O 1) stout, naked; O 2 longest, three times as long as O 1, with fine ventral setae; O 3 articulating anaxially on O 2, as long as O 1, with fine ventral setae and distal spines directed proximally; O 4 twice as long as O 3, with fine setae along dorsal margin, inner proximally-directed spines in proximal two-thirds and distally, fine ventrodistal setae; O 5 as long as O 4, with ventrodistal tuft of setae, dorsal margin beset with small, proximally oriented spines ( Fig. 3 A), Distal articles forming a strigilis ( Fig. 3 A). O 6 almost globular, as long as O 3, beset with numerous setae, those on dorsal margin stout and spine-like; O 7articulating anaxially on O 6, with ventral tuft of longer setae; O 8 articulating anaxially on O 7, half as long as O 6, with strong outer-distal seta and paired stout inner-distal compound spines, each with inner margin crenulated; O 9 1.25 times as long as O 8, with single ventrodistal stout compound spine with crenulated margin, laying in opposition to spines on O 10; O 10 shortest, half length of O 7, with paired distal stout compound spines with crenulated inner margin. Compound spines distally rounded.

Third leg ( Fig. 2 E) elongate, not slender. Coxa 1 compact, with anterodistal, posterodistal and dorsodistal slender straight spines; coxa 2 twice length of coxa 1, ventrally with single subdistal gonopore in tuft of short spines, and with row of median posterior slender spines; coxa 3 as long as coxa 1, not wider distally, with sparse ventral setae, and paired dorsal and posterodistal small spines; femur twice as long as coxa 2, setose proximoventrally and dorsodistally, median row and dorsodistal tuft of fine spines; cement gland in dorsoproximal half of femur with blunt proximal tube almost half as long as femur width. Tibia 1 as long as femur, dorsally and ventrally setose, with median row and distal group of fine spines. proximally angled to articulation with femur; tibia 2 as long as tibia 1, more slender, with similar spination. Tarsus small, subtriangular, with slender ventral spines and dorsal seta. Propodus without heel, sole with numerous slender spines, dorsal setation as figured; main claw half length of propodus, auxiliary claws conspicuous, slender, 0.7 times as long as main claw. Other legs identical.

Distinctions of female: female generally similar to male, but without femoral cement gland. Sexual dimorphism shown in oviger ( Fig. 2 D, 3B): O 1 to O 5 proportions as in male, but naked other than ventrodistal seta on O 5; O 6 not globular, as long as O 3, with sparse inner, outer and ventral setae oriented distally; O 7 articulating axially with O 6, twice as long as wide, 1.4 times as long as O 6, with two inner-distal bilaterallycrenulate compound spines; O 8 half length of O 7, with three inner-distal bilaterally-crenulate compound spines; O 9 1.8 times as long as O 8, with single inner-distal bilaterally-crenulate compound spine; O 10 shortest, half length of O 8, with paired distal bilaterally-crenulate compound spines. Compound spines distally pointed (not rounded as in the male).

Walking legs show no sexual dimorphism of proportion or setation.

Measurements of holotype (mm): Trunk length (anterior of cephalon to posterior tip of fourth lateral process): 2.64; cephalon: 1.3; trunk segment 2: 0.38; trunk segment 3: 0.42; width across 2nd lateral processes: 1.85; abdomen length: 1.0; proboscis length (lateral): 1.54.

Lengths of palp articles 1 to 7 respectively: 0.28; 1.01; 0.14; 0.9; 0.14; 0.13; 0.31.

Lengths of oviger articles 1 to 10 respectively: 0.2; 0.59; 0.2; 0.42; 0.42; 0.18; 0.25; 0.13; 0.24; 0.06.

Third leg, coxa 1: 0.51; coxa 2: 1.01; coxa 3: 0.51; femur: 2.0; tibia 1: 2.08; tibia 2: 1.97; tarsus: 0.16; propodus: 1.04; main claw: 0.48; auxiliary claw: 0.33.

Paratype male, trunk length, 2.84; width across 2nd lateral processes: 1.93. Paratype female, trunk length 2.63; width across 2nd lateral processes: 1.66.

Etymology: named in memoriam to Joel Hedgpeth, who sadly died in 2006.

Remarks: In the morphology of the ovigers, the trunk, the legs and the conformation of the palp, S. hedgpethi sp. nov. is typical of the genus. It is immediately distinct from all other species in its complete absence of chelifores (in the adult). Amongst the species with only 7 articles in the palp, it is distinct in having the second palp article longer than the fourth (subequal or shorter in the other four species). The female of this species does not show the long tibial setae found in many other species.

The sample site was in very close proximity to a cold seep.

Figures

FIGURE 2. Sericosura hedgpethi sp. nov., A, body dorsal; B, left palp; C, right oviger, male; D, right oviger, female; E, third left leg. Scale line = 2 mm for A, 1.5 mm for B to E.

FIGURE 3. Sericosura hedgpethi sp. nov., distal oviger articles of A, male; B, female. Scale line = 0.3 mm.