Nymphon ortmanni Helfer, 1938

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 : 1349-1352

Nymphon ortmanni Helfer, 1938

( Figure 6 )

Nymphon ortmanni Helfer, 1938, p. 164 , fig. 1.

Nymphon ortmanni: Stock 1953, p. 34 , fig. 1; 1954, p. 20, fig. 6d–e; Utinomi 1955, p. 10, fig. 5; 1962, p. 92; 1971, p. 320; Nakamura and Child 1983, p. 56; Nakamura 1987, p. 6, pls. 4, 35.

Material examined

Paratypes. ZMA 1072 (three males), Sagami Bay , Japan, 7 July 1904, K.A. Haberer .

Non-types. ZIHU 4097 (one female) , ZIHU 4098 (one female) , 26 ◦ 32.18 ′ N, 127 ◦ 43.96 ′ E, off Nago Bay , Okinawa, 26 May 2002, 394– 404 m depth, beam trawl, Y. Takahashi ; ZIHU 4099 (one male with eggs) , ZIHU 4100 (one female) , ZIHU 4101 (three juveniles) , 26 ◦ 48.23 ′ N, 127 ◦ 52.18 ′ E, off Nago Bay , Okinawa, 26 May 2002, 337– 340 m depth, beam trawl, Y. Takahashi ; ZIHU 4102 (one juvenile) , 26 ◦ 19.10 ′ N, 127 ◦ 25.56 ′ E, off north of Kuro Island , Okinawa, 24 May 2003, 596– 606 m depth, beam trawl, Y. Takahashi ; ZIHU 4103 (one male with eggs), 26 ◦ 14.75 ′ N, 127 ◦ 31.90 ′ E, south of Nagannu Island , Okinawa, 25 May 2003, 51– 53 m depth, dredge, Y. Takahashi ; ZIHU 4104 , (one juvenile) , 28 ◦ 09.20 ′ N, 129 ◦ 31.50 ′ E, southeast of Amami Islands , Kagoshima, 25 May 2004, 332– 334 m depth, beam trawl, Y. Takahashi ; ZIHU 4105 (one male with eggs) , ZIHU 4106 (one juvenile) , 26 ◦ 32.90 ′ N, 127 ◦ 43.94 ′ E, west of Nago , Okinawa, 22 May 2005, 386– 402 m depth, beam trawl, Y. Takahashi .

Description

Trunk ( Figure 6A ) slender, completely segmented. Lateral processes twice as long as their diameters, separated by their lengths, each with single tiny distal seta without protuberance; some lateral processes lack setae. Neck more than three times as long as wide. Ocular tubercle in midline between anterior margins of first lateral processes, shorter than its basal diameter, dome-shaped, tilted toward posterior, with small distal knob; eyes pigmented and situated halfway up ocular tubercle. Abdomen height about three times basal diameter, cylindrical proximally, slightly tapering and blunt distally, without setae. Proboscis long, straight, cylindrical, almost as long as neck, less than three times as long as wide, swollen distally and centrally, without setae; lips flat.

Chelifore scapes ( Figure 6A ) about seven times as long as wide, with several dorsal setae, with rows of setae dorsodistally and laterodistally. Chelae ( Figure 6B ) slightly curved inwards; palms cylindrical, equal to finger length, with many short setae; movable finger with 39 pointed teeth endally; immovable finger same length as movable finger, with 34 teeth; fingers crossed at tips.

Palps ( Figure 6C ) slender, five-segmented; second segment longest; third segment 0.7 times length of second segment and 1.2 times length of fifth segment; fifth segment 1.5 times length of fourth segment; all segments except for first have setae over entire surface, each segment more setose than next proximal segment.

Ovigers ( Figure 6D ) 10-segmented; fifth segment longest, 1.3 times length of fourth, gently curved, swollen distally, distal width 1.5 times basal width, with moderately long setae dorsally, smaller setae ventrally, and several distal setae longer than dorsal setae; first segment glabrous; second and third segments with a few setae; fourth segment with setae ventrally and dorsodistally; sixth segment less than half length of fifth, with many setae over entire surface except ventrally; distal four segments ( Figure 6E ) with several setae ectally and laterally, and with compound spines having three denticles per side; eighth and ninth segments equal in length, 0.6 times as long as seventh segment; terminal segment slightly shorter than eighth and ninth segments; terminal claw equal to or slightly shorter than terminal segment, with seven tooth serrations; spine formula 10: 6: 6: 6 :: 7.

Legs ( Figure 6F ) long, slender, with many small setae and a few longer distal setae on every segment, each segment after second coxa narrower and more setose than preceding segment, propodus about one-third the width of coxa and of femur. Second coxa slightly longer than first and third coxae combined; femur 0.7 times length of first tibia; second tibia longest, less than 1.5 times length of first tibia. Cement gland pores open on ventral side of femur and first tibia, numbering six to 41 in a line on femur and seven to 31 on first tibia. Tarsus and propodus length ( Figure 6G ) subequal. Main claw slender, longer than half propodus length; auxiliary claws short, about a quarter as long as main claw.

Remarks

Our specimens correspond well with the original description of N. ortmanni by Helfer (1938) and the re-description by Nakamura (1987) in the morphology of chelifores, ovigers and palps, and in the length ratios of tarsus to propodus and of auxiliary claws to main claw. Our specimens, however, have a more elongate trunk than that described by these two authors.

Nymphon ortmanni is most similar to N. japonicum in the structures of chelifores, palps, and ovigers, shape of the trunk and body size. However, the two species can be easily distinguished by the proportions of the claws. Nymphon ortmanni has a main claw that is over half the length of the propodus, and relatively small auxiliary claws that are a quarter the length of main claw, whereas N. japonicum has a smaller main claw that is less than half the length of the propodus, and longer auxiliary claws that are nearly or over half the length of the main claw.

Careful re-examination of the paratype specimens of N. ortmanni revealed that this species has multi-pored cement glands on both the femur and first tibia. The number of pores, which seems to depend on segment length, is 24–41 on the femur and 22–31 on the first tibia of paratype males, compared with six to 26 on the femur and seven to 11 on the first tibia in our specimens.

Nymphon ortmanni was originally described from Sagami Bay, central Japan ( Helfer 1938), and was subsequently found at various sites from Sagami Bay to Tsugaru Strait, northern Japan. Hedgpeth (1949) noted concerning the geographical distribution of pycnogonids that “a few endemic species are found along the shore both north and south of 35 ◦ N, however, on the whole species do not cross this boundary”. Since his study, three species of Nymphon ( N. gunteri Hedgpeth, 1949 , N. japonicum and N. kodanii Hedgpeth, 1949 ) have been found to occur across the 35 ◦ N parallel; our study adds N. ortmanni as the fourth.

This species is endemic to Japan. It was previously known from Tsugaru Strait to Suruga Bay at depths of 75–450 m, ( Utinomi 1971; Nakamura and Child 1983, 1991); our study extends its known distribution southward to Okinawa and its minimum known depth to 51 m. Our specimens represent the first record from subtropical waters.

Figures

Figure 6. Nymphon ortmanni Helfer, 1938, ZIHU 4103, non-type, male. (A) Trunk, dorsal view; (B) chelifore; (C) palp; (D) oviger; (E) enlargement of distal segments of oviger; (F) third leg; (G) enlargement of distal segments of third leg. Scale bars: A, C, F, G, 1 mm; B, D, 0.5 mm; E, 0.25 mm.