Nymphon nagannuense, Takahashi & Kajihara & Mawatari, 2012

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 : 1346-1349

Nymphon nagannuense sp. nov.

( Figure 5 )

Material examined

Holotype. ZIHU 3329 , male, 26 ◦ 14.64 ′ N, 127 ◦ 31.01 ′ E, Nagannu Island , Okinawa, 22 May 2005, 57 m depth, dredge, Y. Takahashi.

Paratype. ZIHU 3330 , male, 27 ◦ 58.83 ′ N, 129 ◦ 16.80 ′ E, southwest of Uke Island , 11 November 1994, 128 m depth, sledge net, S. Ohtsuka .

Measurements of holotype (millimetres)

Trunk length, 2.3; body width, 1.13; proboscis length, 0.60; length of abdomen, 0.25; third leg (L3) coxa 1, 0.20; L3 coxa 2, 1.04; L3 coxa 3, 0.25; L3 femur, 2.04; L3 tibia 1, 2.60; L3 tibia 2, 3.16; L3 tarsus, 0.82; L3 propodus, 0.77; L3 main claw, 0.19; L3 auxiliary claws, 0.19; oviger first article (O1), 0.15; O2, 0.23; O3, 0.23; O4, 0.82; O5, 1.07; O6, 0.35; O7, 0.21; O8, 0.19; O9, 0.16; O10, 0.15; oviger terminal claw, 0.11.

Etymology

The specific epithet, an adjective, refers to the type locality, Nagannu Island .

Description

Trunk ( Figure 5A,B ) elongate, completely segmented. Lateral processes slightly more than twice as long as their diameter and separated by twice their diameter, without tubercles or setae. Neck moderately long, at least half as narrow as trunk diameter, widening distally; crop 3.6 times as wide as the minimum width of neck. Ocular tubercle in midline at level of anterior extent of first lateral processes, almost as tall as its basal diameter, rounded, with two small lateral projections. Eyes large, lightly pigmented. Proboscis cylindrical, rounded distally, slightly constricted laterally at onequarter the length from the tip, 2.6 times as long as basal diameter. Abdomen robust, twice as long as basal diameter, slightly tapering distally, with several short setae dorsolaterally.

Chelifores ( Figure 5A,B ) very slender; scapes slightly curved endally, six times as long as its diameter, with many tiny setae laterally and some longer setae dorsally and dorsodistally. Chela palms ( Figure 5C ) almost twice as long as wide, with several dorsal setae. Fingers very long; movable finger straight, with 16 sharp teeth endally, without setae; immovable finger slightly curved endally, with 18 sharp teeth endally and with slight inflation bearing several long setae at base.

Palp ( Figure 5D ) first segment as long as wide; second segment longest, 1.2 times as long as third segment, armed with low dorsal tubercle distally; third segment 1.5 times as long as fifth segment, with several ventral setae; fourth segment two-thirds length of fifth segment, with a few lateral setae and many ventral setae; fifth segment with many lateral and ventral setae and longer distal setae. Second and third segments each with several short setae ventrodistally (not visible in Figure 5D ).

Ovigers ( Figure 5E,F ) long, 10-segmented; first segment very short, as long as wide; second segment equal in length to third segment; fourth segment about 0.8 times as long as fifth; sixth segment 0.3 times as long as fifth segment; fifth and sixth segments each with ectal row of short setae. Strigilis with several ectal setae, with endal compound spines in the formula 7: 6: 5: 6 :: 6. Spines with three denticles per side. Terminal claw 0.7 times the length of terminal segment, slightly curved, with six sharp endal teeth.

Legs ( Figure 5G,H ) slender, with many minute and some longer setae. Coxae with several tiny setae ventrally and laterally; first coxa short, 1.5 times as long as wide; second coxa long, more than five times as long as first coxa; third coxa 0.4 times length of second coxa. Femur sparsely setose; first tibia 1.3 times as long as femur, with some sparse short setae on ventral side; second tibia 1.5 times as long as femur, setose on ventral side especially, half the thickness of femur; tarsus ( Figure 5H ) slightly longer than propodus, both without heel or large heel spines, sole with row of very short spines over entire length; claw slightly curved, about one-quarter as long as propodus; auxiliary claws same length as main claw. Cement gland not visible.

Remarks

This species is similar to Nymphon improcerum Nakamura and Child, 1991 in the trunk configuration, the moderately long neck, the short chela palm and long chela fingers with many endal teeth, and the short main claw, which is almost the same length as the auxiliary claws. However, it differs from N. improcerum in having no tubercles on the lateral processes or anterodistally on the cephalic segment, and in having the third segment of the palp short, almost the same length as the fifth segment. In Japan, another short-palmed Nymphon species is N. akanei Nakamura and Child, 1983 . Nymphon nagannuense differs from N. akanei in having slender trunk and neck; short and robust claws; more chela teeth (12–14 in N. akanei ; 16–18 in N. nagannuense ); and different ratios of leg-segment lengths. Nymphon nagannuense is unique in having some pigmented spots (reddish-brown in ethanol-preserved material) at the base of each chelifore scape and each first coxa, and on the anterior two trunk segments.

Figures

Figure 5. Nymphon nagannuense sp. nov., ZIHU 3329, holotype, male. (A) Trunk, dorsal view; (B) trunk, lateral view; (C) chelifore; (D) palp; (E) oviger; (E) third leg; (F) enlargement of distal segments of oviger; (G) third leg; (H) enlargement of distal segments of third leg. Scale bars: G, 1 mm; A, B, E, H, 0.5 mm; D, F, 0.25 mm; C, 0.1 mm.