Cheilopallene ogasawarensis, Nakamura, Koichiro & Akiyama, Tadashi, 2015

Nakamura, Koichiro & Akiyama, Tadashi, 2015, Cheilopallene ogasawarensis, a New Species of Shallow-Water Pycnogonid (Arthropoda: Pycnogonida) from the Ogasawara (Bonin) Islands, Japan, Northwest Pacific, Zootaxa 3995 (1) : -

Cheilopallene ogasawarensis n. sp.

Fig. 1

Material. Holotype - adult male (NSMT-Py 5), Hitomaru I., between Chichijima I. and Anijima I., 27°06′57″N – 142°11′14″E, 15–27 m, 14 November 2013.

Description. Trunk ( Figs 1 A–B) oval defined by tips of lateral processes, maximum width 0.60 times trunk length, integument smooth, all segmentation lines discernible. Lateral process as long as wide, processes 1–2 with anteriodorsal tubercles on frontal and hind margins, third processes with single tubercle, fourth processes without tubercle. Ocular tubercle hemispherical, dorsal surface with two pigmented, round tubercles; eyes four, large, almost in contact each other. Cephalon with two prominent anterior lobes each with a strong forward-facing tubercle; neck two-thirds width of trunk. Proboscis with three projecting lips, distally acute ( Figs 1 A, C–E), several minute setae on dorsal surface. Abdomen ( Fig. 1 F) reaching median portion of coxa 1 of leg 4; directed dorsoposteriorly, maximum width of abdomen half of its length; dorsal surface with four stiff setae; apex narrow.

Chelifore ( Fig. 1 G) well-developed, as long as proboscis; length of scape and chela subequal, scape with three distal setae; chela palm with many setae on outer margin; immovable finger broad and truncate, with two prominent tubercles at distal corner, inner surface with several minute setae, movable finger curved, without setae.

Oviger ( Figs 1 H–I) slightly longer than trunk, ten-segmented; proximal three segments subequal; segment 5 longest; segment 4 slightly longer than half length of segment 5; segment 5 with six simple setae on outer margin, distal apophysis well-developed: segment 6 shorter than succeeding segments, glabrous. Strigilis with denticulate spines according to the formula 3: 3: 3: 2; terminal claw robust, both margins denticulate, single tooth on inner surface, four blunt denticles on outer surface.

Legs ( Figs 1 J–K) robust. Coxae 1 and 2 subequal in length; coxa 3 slightly shorter than coxae 2 or 3. Coxa 1 with stout spine-tipped tubercles on distolateral margins. Coxa 2 with a simple seta. Coxa 3 with a few short setae. Tibia 1 weakly curved, with long setae on outer margin. Tibia 2 slightly longer than tibia 1. Femur and tibia 1 of equal length. Femur 3.4 times as long as coxa 3, with several short setae. Tarsus small, as long as wide, with one robust seta on inner margin. Propodus ( Fig. 1 K) weakly curved, half length of tibia 2, six strong spines on inner margin and several simple setae on outer margin. Claw half propodus length, broad at base, strongly curved.

Measurements (in mm). Trunk length (chelifore insertion to tip of 4th lateral processes), 0.72; trunk width (across 2nd lateral processes), 0.43; proboscis length, 0.21; abdomen length, 0.14; 2nd leg, coxa 1, 0.089; coxa 2, 0.087; coxa 3, 0.070; femur, 0.24; tibia 1, 0.24; tibia 2, 0.27; tarsus, 0.032; propodus, 0.14; claw, 0.071.

Etymology. The species name refers to the type locality, the Ogasawara Islands.

Remarks. Of the seven known species of the genus Cheilopallene , only C. ogasawarensis n. sp., C. coralliophila Müller, 1992 and C. brevichela Clark, 1961 have strong tubercle over the base of each chelifore scape. Cheilopallene ogasawarensis is distinguished from the latter two species by (1) lateral process with one or two tubercles (vs. no tubercles in C. coralliophila and C. brevichela ), (2) strigilis with two or three denticulate spines according to the formula 3:3:3:2 (1:1:1: 1 in C. coralliophila and 4:4:3: 5 in C. brevichela ), and (3) abdomen with four stiff setae on dorsal surface (two setae in C. coralliophila , no setae in C. brevichela ).

The new species is geographically closest to Cheilopallene nodulosa recorded directly north of the Ogasawara Islands. The two species can most readily be distinguished by the presence of tubercles on the lateral process and anterior lobes of C. ogasawarensis (absent in C. nodulosa ). Differences are also found in the number and shape of spines on the oviger strigilis.

Figures

FIGURE 1. Cheilopallene ogasawarensis n. sp., holotype adult male. A, trunk, dorsal view; B, trunk, lateral view; C, proboscis, ventral view; D, tip of proboscis, dorsal view; E, tip of proboscis, ventral view; F, abdomen, dorsal view; G, chelifores, dorsal view; H – I, oviger; J – K, second leg.