Hedgpethia elongata, Takahashi & Dick & Mawatari, 2007

Takahashi, Yoshie, Dick, Matthew H. & Mawatari, Shunsuke F., 2007, Sea spiders (Arthropoda: Pycnogonida) from waters adjacent to the Nansei Islands of Japan, Journal of Natural History 41 (1 - 4), pp. 61-79 : 70-72

Hedgpethia elongata sp. nov.

( Figure 4 )

Material examined. Holotype: male ZIHU 03171 , 26 ° 49.50 9 N, 127 ° 42.00 9 E, northeast of Ie Island , Okinawa, 23 May 2003, 199– 202 m depth; collected by beam trawl, Y. Takahashi collector.

Measurements of holotype (mm). Trunk length, 2.92; body width, 1.12; length of abdomen, 0.12; length of palp, 6.37; first article (P1), 0.21; P2, 0.06; P3, 2.59; P4, 0.28; P5, 1.44; P6, 0.28; P7, 0.42; P8, 0.49; P9, 0.47; P10, 0.39; length of proboscis, 4.31; third leg, coxa 1, 0.32; coxa 2, 0.45; coxa 3, 0.37; femur, 5.06; tibia 1, 6.58; tibia 2, 4.84; tarsus, 1.13; propodus, 1.03; claw, 0.39; oviger, first article (O1), 0.04; O2, 0.11; O3, 0.11; O4, 1.20; O5, 0.21; O6, 1.18; O7, 0.21; O8, 0.19; O9, 0.19; O10, 0.14.

Etymology. The species name refers to the long trunk and proboscis.

Description. Moderately large in size for the genus, slender, leg span 20.2 mm. Trunk ( Figure 4A, B ) relatively elongate for the genus, completely segmented, posterior rims inflated, lateral processes almost as long as their basal width, separated from one another by roughly twice their basal width, glabrous. Ocular tubercle relatively tall, less than twice as high as its basal width, with pointed apex projecting forward. Four eyes of equal size, pigmented, each eye consisting of two bulges, situated at top of column of ocular tubercle. Proboscis ( Figure 4A, B ) 1.35 times as long as trunk, curved downward; proximal narrow stalk about one-quarter of length; remainder swollen, four times as wide as stalk; spindle-shaped distal part constricted a little less than one-third of total length from proximal expansion, tapering distally; lips rounded. Abdomen very small, located on ventral side, hidden from dorsal view.

Palps ( Figure 4C ) longer than proboscis, very slender; 10-segmented, with two short basal segments; first segment about twice as wide as other segments; second segment shortest; third segment longest, straight, with sparse short setae, with a few longer setae distally; fourth segment the same length as sixth segment; fifth segment slightly longer than half the length of third segment, with many setae over entire surface, slightly swollen in middle; seventh, eighth, and ninth segments subequal in length; terminal segment slightly longer than sixth segment; distal five segments fairly setose ventrally, setae as long as segment widths.

Oviger ( Figure 4D ) very slender, long, 10-segmented; fourth and sixth segments longest, with very tiny setae ectally and endally; fifth segment almost as long as second and third combined; strigilis ( Figure 4E ) curved endally, armed with scattered short, sparse setae ectally, with rows of slender endal spines lacking denticles; seventh segment equal to fifth segment in length; terminal segment less than two-thirds the length and width of seventh segment; terminal claw short, about one-fifth as long as terminal segment.

Legs ( Figure 4F ) slender, with many tiny setae over entire surface; first and third coxae subequal and shorter than second coxa; femur almost equal to second tibia in length, curved ventrally, thickened in distal half, with several longer setae on distal end; tibiae straight, with a single long seta on distal end; first tibia 1.3 times as long as femur and second tibia; tarsus slightly longer than propodus, both segments with dense, short setae ventrally and sparse, short setae dorsally; main claw about two-thirds as long as propodus.

Remarks. We have assigned this species to Hedgpethia because of its expanded posterior segment ridges and the massive, spindle-shaped, distally tapered proboscis without a tooth. Three species of Hedgpethia have been previously recorded from Japan: H. brevitarse ( Losina-Losinsky & Turpaeva, 1958) , H. chitinosa ( Hilton, 1943) , and H. dofleini ( Loman, 1911) . The latter two are very similar to one another, both in morphology and distribution (from the Aleutian Islands to west of Kyushu). Although various authors (e.g., Stock 1958; Utinomi 1955; Nakamura & Child 1983) have discussed their close similarity, Nakamura and Child (1991), referring to Hedgpeth (1949), concluded that these two nominal species are valid. Compared to H. dofleini , H. chitinosa has (1) a body three times as large, (2) a larger ratio of claw to terminal segment of oviger, (3) no spine in opposition to terminal claw of oviger, and (4) a shorter ratio of main claw to propodus. Hedgpethia elongata sp. nov. shares characters (1) (3) and (4) with H. dofleini , but like H. chitinosa it has a much smaller terminal claw (2) on the ovigers. Hedgpethia elongata resembles species of Rhopalorhynchus in having an elongate trunk and a long proboscis stalk.

Distribution. Known only from Ie Island, Okinawa, 199–202 m depth.

Figures

Figure 4. Hedgpethia elongata sp. nov., holotype, male: (A) trunk, dorsal view; (B) trunk, lateral view; (C) palp; (D) oviger; (E) strigilis; (F) third leg; (G) enlargement of distal segments of third leg. Scale bars: 1 mm (A–D, F, G); 0.2 mm (E).