Nymphon japonicum Ortmann, 1890

Takahashi, Yoshie, Kajihara, Hiroshi & Mawatari, Shunsuke F., 2012, Sea spiders of the genus Nymphon (Arthropoda: Pycnogonida) from waters around the Nansei Islands, Japan, Journal of Natural History 46 (21 - 22), pp. 1337-1358 : 1344-1346

Nymphon japonicum Ortmann, 1890

( Figure 4 )

Nymphon japonicum Ortmann, 1890, p. 158 , pl. 24, fig. 1.

Nymphon japonicum: Ohshima 1936, p. 862 ; Utinomi 1951, p. 159; 1955, p. 5; 1959, p. 199; 1962, p. 92; Stock 1954, p. 19, fig. 6a–c; Nakamura 1987, p. 30, pls. 27, 38; Nakamura and Child 1983, p. 56.

Material examined

ZIHU 4093–4095 (three males), 26 ◦ 33.00 ′ N, 127 ◦ 32.30 ′ E, east of Aguni Island , Okinawa, 25 May 2003, 223– 237 m depth, beam trawl, Y. Takahashi . ZIHU 4096 (four juveniles), 26 ◦ 49.50 ′ N, 127 ◦ 42.00 ′ E, northeast of Ie Island , Okinawa, 23 May 2003, 199– 202 m depth, beam trawl, Y. Takahashi .

Description

Size very large for genus. Trunk ( Figure 4A,B ) elongate, completely segmented, without setae or dorsal median processes. Lateral processes about 1.5 times as long as wide, separated by their length, with a tiny seta dorsodistally, and without protuberances. Neck fairly long, about 4.5 times as long as proximal width, widest part 2.5 times the narrowest width. Oviger insertion at or slightly anterior to first lateral processes, not touching them. Ocular tubercle in midline between anterior margins of first lateral processes, its height almost equal to basal diameter, dome-shaped, tilted posteriorly, with small distal knob; eyes pigmented and situated on upper part of ocular tubercle. Abdomen about 3.5 times as long as wide, cylindrical proximally, slightly tapering distally, with mid-dorsal pair of setae. Proboscis cylindrical, straight, about four times as long as wide, slightly shorter than neck, without setae, swollen at midpoint; distal end of proboscis with one dorsal and two ventrolateral triangular bulges.

Chelifore scapes more than six times as long as wide, with several short setae dorsally and laterally, and setae of the distal rim. Chelae ( Figure 4C ) slender, curved inward; palm cylindrical, 0.8 times length of movable finger, with many short and longer setae. Movable finger with 50 pointed teeth endally, longer than immovable finger having 36 larger teeth. Fingers not crossed at tips.

Palps ( Figure 4D ) slender, five-segmented; second segment longest, with several sparse short setae; third segment 0.7 times as long as second segment and 1.5 times as long as fourth segment, setae longer than those on second segment; fourth segment equal in length to fifth segment, both with more setae than third segment over entire surface.

Ovigers ( Figure 4E ) 10-segmented; fifth segment longest, more than 1.3 times length of fourth segment, gradually curved inwards, swollen distally, distal width less than twice proximal width, with short setae in a line ectally and several longer setae distally; first and third segments glabrous; second segment with single seta at distal end; fourth segment with line of short setae endally and a row ectodistally; sixth segment relatively straight, 0.4 times as long as fifth segment, with many setae over entire surface; seventh segment 1.5 times as long as terminal two segments; eighth segment 0.8 times as long as seventh segment; distal four segments with many setae over entire surface except endally, and with compound spines having four denticles per side endally; terminal two segments almost equal in length; terminal claw slightly shorter than terminal segment, with nine serrations; compound spine formula 13: 5: 7: 7 :: 9.

Legs ( Figure 4F ) extremely long and slender, with many short and longer setae on all segments, especially on tibiae; each segment except for first, narrower than the next proximal segment (propodus width about 0.2 times that of coxa or femur). Second coxa more than three times as long as first and third coxae, with a few tiny setae; second tibia longest, more than 1.7 times as long as first tibia, more than twice as long as femur. Cement gland pores open on ventral side of both femur and first tibia; 30–43 pores in line on femur and 15–21 pores in mid-ventral line on first tibia. Tarsus ( Figure 4G ) 1.3 times as long as propodus; tarsus and propodus with many small setae dorsally and laterally and with spines ventrally; a few setae are longer than segment width. Main claw slender, less than half as long as propodus; auxiliary claws half as long as main claw.

Remarks

Our specimens generally agree with the figures by Nakamura (1987) and Hong and Kim (1987), but there are some differences. Our specimens have a longer neck, more conspicuous triangular bulges (one dorsal and two ventrolateral) distally, and a much longer second tibia extending to more than twice the length of the femur. Nymphon japonicum can be confused with N. ortmanni Helfer, 1938 , because of their overall similarity. However, the two can be distinguished by auxiliary claws more than half as long as the main claw in N. japonicum , but much shorter in N. ortmanni . In our material, there are numerous cement gland pores on the ventral side of the femur and tibia 1; this is the first report of these structures in N. japonicum . Cement gland pores seem to have been previously overlooked, as they also occur on the first tibiae of N. ortmanni (see also Remarks for that species).

Figures

Figure 4. Nymphon japonicum Ortmann, 1890, ZIHU 4093, non-type, male. (A) Trunk, dorsal view; (B) trunk, lateral view; (C) chelifore; (D) palp; (E) oviger; (F) third leg; (G) enlargement of distal segments of third leg. Scale bars: 1 mm.