Hemichela nanhaiensis, Wang, Jianjia, Xia, Zhen, Lin, Rongcheng, Liang, Qianyong, Lin, Heshan, Wang, Jianjun & Zheng, Chengxing, 2015

Wang, Jianjia, Xia, Zhen, Lin, Rongcheng, Liang, Qianyong, Lin, Heshan, Wang, Jianjun & Zheng, Chengxing, 2015, A new species of Hemichela Stock, 1954 from the South China Sea (Arthropoda, Pycnogonida, Ammotheidae), ZooKeys 526, pp. 1-8 : 3-6

Taxon classification Animalia Pantopoda Ammotheidae

Hemichela nanhaiensis sp. n. Fig. 1

Material examined.

One male, holotype (DS06-13-01), Station DS06-13, South China Sea, 21.95°N 118.81 °E, 1317.5 m depth, BC, 5 May 2013.

Diagnosis.

Trunk slender, lateral processes with a single distal dorsal tubercle and armed with pedunculate asterisk-shaped setae. Ocular tubercle long with bifurcate tip (Fig. 1A, B). Chela dactylus bearing 12 denticulations on the inner margin (Fig. 1C). Palps seven-articled, second article with a conical outgrowth (Fig. 1A, G). Ovigers ten-articled, fifth article with a reversed spine located on the ventral surface near the proximal end (Fig. 1E arrow b), seventh to tenth articles with compound spines in formula 3: 2: 1: 1 (Fig. 1F). Legs slender, major articles with short lateral spines, main claw approximately 3/5 length of propodus, auxiliary claws absent (Fig. 1D).

Description of the holotype

(male). Size large for genus. Trunk slender, intersegmental lines absent, with many tiny papillae (Fig. 1A, B). Lateral processes very long, widely separated, slightly dilated distally, armed with asterisk-shaped setae on tip of tiny outgrowth. A distal dorsal tubercle is present on each lateral processe. Each tubercle long and slender, length is nearly twice diameter of lateral processes, with several minute setae. Ocular tubercle long, erected obliquely, armed with many tiny papillae, tip bifurcate with two lateral tubercles, without obvious eyes (Fig. 1A, B). Proboscis short, like a circular cone with flat tip. Abdomen very tall, directed upwards (Fig. 1A, B).

Chelifore scape one-segmented, armed distally with long setae. Palm short, with several long setae. Chela with one dactylus only, curved and bearing 12 denticulations on inner margin (Fig. 1C).

Palps seven-articled (Fig. 1G, H). First article short, without spines or setae. Second and third articles with few distal long setae. Second article longest, with a conical outgrowth on the outer surface, located in the first third of the article. Fourth to seventh articles armed with fields of ventral and distal setae mostly little longer than their article diameter (Fig. 1H).

Ovigers ten-articled (Fig. 1E, F). First and second articles stout, without setae and spines. Fourth and fifth articles longest, bearing few short setae and spines. Fifth article with a reversed spine basally. Sixth article with two distal spines and few ventral setae. Seventh to tenth articles with compound spines in formula 3: 2: 1: 1. Each spine bears one to three lateral denticulations. Terminal claw as long as tenth article (Fig. 1F).

Legs slender (Fig. 1D). Major articles with short lateral spines. First coxa short. Second coxa longest, distally swollen, with short ventral and distal seta. Genital pores present on ventral surface of second coxae of the third and fourth legs, borne on a spherical tubercle (Fig. 1D, arrow a). Third coxa short with short setae. Femur and tibiae with short ventral setae, lateral spines and long dorsal setae. Femur and second tibia subequal, longer than first tibia. Cement gland not evident. Tarsus long with short setae and spines. Propodus without heel, with single row of sole spines. Main claw strong, approximately 3/5 length of propodus. Auxiliary claws absent.

Female and juvenile are unknown.

Measurements of holotype in mm: Trunk length (from chelifore insertion to tip of fourth lateral processes) 3.46; width across second lateral processes 3.49; proboscis length 0.63.

Lengths of palp articles 1 to 7 respectively: 0.09; 0.25; 0.14; 0.10; 0.06; 0.05; 0.04.

Lengths of oviger articles 1 to 10 respectively: 0.06; 0.13; 0.16; 0.33; 0.33; 0.15; 0.08; 0.08; 0.06; 0.07; 0.07 (claw).

Third leg, coxa 1, 0.24; coxa 2, 0.51; coxa 3, 0.30; femur, 1.24; tibia 1, 1.13; tibia 2, 1.23; tarsus, 0.53; propodus, 0.65; claw, 0.40.

Etymology.

The species name, nanhaiensis, is derived from the Chinese language, Nanhai meaning South China Sea, referring to the location where the new species was found.

Remarks.

The specimen is identified as belonging to the genus Hemichela by the absence of a movable chela finger. Compared with Hemichela longiunguis and Hemichela micrasterias , the body size of Hemichela nanhaiensis is distinctly larger, length of lateral process tubercles are nearly twice diameter of lateral processes in Hemichela nanhaiensis , and are much taller than those in the other two species, and the Hemichela nanhaiensis palps are armed with more setae. The outgrowths with asterisk-shaped setae of Hemichela micrasterias are branching and large while the ones of Hemichela longiunguis and Hemichela nanhaiensis are simple and not distinct. The length ratio of the terminal claw and propodus, 0.62, lies between that of the previous two species (1.06 in Hemichela longiunguis and 0.46 in Hemichela micrasterias ), and the relative length of the oviger terminal claw is evidently shorter than the other species in the genus (the length ratio of terminal claw and tenth article: 1 in Hemichela nanhaiensis , 2.33 in Hemichela longiunguis and 1.88 in Hemichela micrasterias ). The chelifores are different from those of the other two species, with 12 denticulations on the inner margin of the dactylus compared to six in Hemichela micrasterias and two in Hemichela longiunguis ; the chelifore scape and palm are armed with more seta than those of the other two species of the genus ( Stock 1954, 1985; Staples 1982).

The records of this genus are from Japan to Queensland, Australia (Fig. 2) and the island systems of the western Pacific Ocean, with the deepest record of 657 m in the Flores Sea ( Nakamura and Child 1990; Bamber 1992; Müller 1993). The new species was obtained from 1317.5 m, increasing the depth range of this genus. The occurrence of the new species fills a gap in the distribution ‘corridor’ of this genus, connecting the species in Japan with the Philippines and equatorial and Australian species.

The type habitat was sea floor predominantly composed of soft mud.