Cilunculus mergus, Bamber, Roger N., 2004

Bamber, Roger N., 2004, Pycnogonids (Arthropoda: Pycnogonida) from French Cruises to Melanesia, Zootaxa 551, pp. 1-27 : 10-13

Cilunculus mergus sp. nov. ( Figs 5–6 )

Material: Solomon Islands: 1 female, holotype (MNHN­Py 1041), station CP1781, N/ O 'Alis' Campagne SALOMON 1, 08º31.2'S 160º37.7'E, 1036–1138 m, 29/09/2001; coll. Bouchet, Dayat, Warén, Richer­IRD.

Description of female: trunk ( Fig. 5 A, B) completely segmented with raised posterior margins of segments; lateral processes and trunk without tubercles or other setae. Ocular tubercle conspicuous, dome­shaped, with slightly­pigmented eyes (in alcohol); two small anterodorsal cephalon tubercles (horns) above chelifores. Abdomen fusiform, not articulating at base, with pair of mid­dorsal setae longer than abdomen. Proboscis elongate barrel­shaped.

Chelifores of two articles, naked, short, one third length of cephalon; chelae atrophied.

Palp ( Fig. 5 C) of nine articles, second article longest, third article one­third length of fourth; sixth article nearly twice length of fifth and seventh; ninth article almost as long as fourth, more than twice length of eighth article. Distal five articles with rows of short ventral setae, fourth article with dorsal row of short spines.

Oviger ( Fig. 6 A, B) of ten articles, article 2 longest, article 4 three­quarters of article 2 and just shorter than article 5; compound oviger spines on distal four articles numbering 5:3:1:3.

Third leg ( Fig. 6 C, D) first coxa half as long as second coxa and 0.83 times as long as third coxa, all three naked; femur with pair of mid­dorsal sinuous setae twice as long as femur diameter, and longer central and shorter pair of dorsodistal setae. First tibia 1.25 times length of femur, second tibia 1.1 times length of first tibia; first tibia with two dorsal pairs of long setae, paired dorsodistal spines; second tibia dorsodistally with two low swellings each distal of a single spine, ventral margin finely setose. Tarsus compact, with finely setose ventral margin and ventrodistal spine. Propodus without prominent heel, but with four heel spines, one larger subdistal and numerous shorter sole spines; dorsal margin with swelling in proximal third and stout mid­dorsal seta; main claw half length of propodus, auxiliary claw one third length of main claw.

Eggs present in second coxa and femur. Male unknown.

Measurements of female (mm): trunk length (anterior of cephalon to tip of 4th lateral process) 3.04; length of cephalon 0.88; width across 2nd lateral processes 1.85; proboscis length 2.27; abdomen length 1.0; chelifore length 0.38; palp article 2 (P2) 1.04, P3 0.17, P4 0.57, P8 0.21, P9 0.53; third leg, first coxa 0.38, second coxa 0.77, third coxa 0.46, femur 2.42, first tibia 3.08, second tibia 3.4, tarsus 0.15, propodus 1.12, main claw 0.55, auxiliary claw 0.17; oviger article 2 ( O 2) 0.51, O 4 0.37, O 5 0.44.

Etymology: From the Latin merga, a two­pronged fork, referring to the pair of prominent setae on the abdomen, mirrored on the femur and first tibia.

Remarks: The present species most closely resembles Cilunculus scaurus Stock, 1997 , recorded from New Caledonia at a similar depth; that species is named for the conspicuous “hump” proximodorsally on the propodus. Such a swelling is also present in C. mergus sp. nov., as are further swellings distally on tibia 2 which do not occur in Stock’s species. A number of differences between these two includes the spiniferous tubercles on the lateral processes and first coxae of C. scaurus (absent in C. mergus ), and the elongate distal palp article, compound spines on the seventh oviger article, and the long paired setae on abdomen and first tibia in the present species.

Figures

FIGURE 5. Cilunculus mergus sp. nov., female holotype, A, body, lateral; B, body, dorsal; C, left palp. Scale line = 1.5 mm for A and B, 0.55 mm for C.

FIGURE 6. Cilunculus mergus sp. nov., A, oviger; B, detail of oviger strigilis; C, third right leg; D, distal articles of third leg. Scale line = 0.6 mm for A, 0.3 mm for B, 1.5 mm for C, 0.5 mm for D.