Ascorhynchus quartogibbu

Bamber, Roger N., 2013, Deep-water Pycnogonida from recent cruises to Papua New Guinea and Melanesia, with an appendix of new records from Polynesia and descriptions of five new species, Zoosystema 35 (2), pp. 195-214 : 199-202

Ascorhynchus quartogibbu s n. sp. ( Fig. 1 )

HOLOTYPE. — 1 ♂, MNHN-IU-2008-20493; Stn. CP 2783, New Georgia Sound, Solomon Islands, 08°53’S, 159°23’E, 1501-1545 m, 13.XI.2007, coll. Richer & Boisselier.

PARATYPES. — 2 ♂♂, MNHN-IU-2008-20491 and 20644; Stn. CP 2817, S Malaita, Solomon Islands, 09°55’S, 161°33’E, 1136-1750 m, 18.XI.2007, coll. Richer & Boisselier. — 1♂, MNHN-IU-2011-3331 ; Stn.CP 3731, Vicinity of Mambare Bay , Papua New Guinea, 07°50’S, 148°04’E, 895-1150 m, 08.XI.2010,coll. Samadi & Corbari.

ETYMOLOGY. — From the Latin quartus – fourth, and gibber – a hump on the back, this species being characterized by having a mid-dorsal tubercle on the fourth trunk-segment.

DESCRIPTION OF MALE HOLOTYPE

“Giant” Ascorhynchus , body length 16.5 mm ( Fig.1A, B ).

Trunk glabrous, completely segmented, posterior margins of trunk segments flared. Cephalon 43% of total length, raised anteriorly (but without tubercles) at attachment of chelifores; low boss-like tubercle at anterior of cephalon above attachment of palps; tall, spired ocular tubercle above attachment of ovigers, without eyes. Second and third trunk segments with pointed mid-dorsal tubercle at posterior margin. Fourth trunk segment with low but conspicuous mid-dorsal tubercle at mid-length. Lateral processes longer than trunk diameter, separated by more than their own diameter, without tubercles. Oviger implantation well anterior of first lateral processes. Abdomen articulated at base, slender, clavate, setose dorsodistally, its tip exceeding half the length of second coxa of fourth leg. Proboscis bulbous with proximal and less-pronounced distal constrictions, just longer than half length of trunk.

Chelifore scape of two articles, proximal article 0.8 times as long as distal article; chela atrophied, with short, stubby fingers ( Fig. 1C ).

Palp ( Fig. 1D ) of 10 articles; article 3 longest, 2.7 times as long as article 4; article 6 very short, article 7 twice as long as article 6; article 8 elongate, 1.5 times as long as subequal articles 9 and 10; distal five articles each with dense row of ventral setae.

Oviger ( Fig.1E, F ) proximal three articles glabrous; articles 4 to 6 with ventral and dorsal fine setae; article 4 just longer than article 5, article 6 half as long as article 4; articles 7 to 10 with compound spines in two or three rows, main row comprising 12, 8, 7 and 8 spines respectively; terminal claw curved, simple, 0.4 times as long as article 10.

Third leg ( Fig. 1G ) glabrous, first coxa shorter than lateral process, second coxa 2.6 times as long as first coxa; third coxa less than half length of second coxa; femur longest article, 2.2 times as long as second coxa, with row of cement-gland pores; first tibia 0.8 times as long as femur, also with row of cement-gland pores; second tibia 0.65 times as long as first tibia, tarsus about one quarter length of second tibia, and 0.8 times as long as propodus; main claw one-third length of propodus; no auxiliary claws.

Cement gland pores on holotype:20 on femur, 14 on tibia; one on paratypes: MNHN-IU-2008-20644 (18.5 mm body-length) – 26 and 16; MNHN- IU-2008-20491 (18.2 mm body-length) – 24 and 13; MNHN-IU-2011-3331 (20.6 mm bodylength) – 20 and 14.

Female unknown.

Measurements of holotype (mm): trunk length 16.5; width across second lateral processes 8.6; proboscis length 8.75; abdomen length 3.6. Chelifore scape article-1 1.5; scape article-2 1.9.

Palp article 3 (Pa3) 4.5; Pa4 1.65; Pa5 3.2; Pa6 0.5; Pa7 1.0; Pa8 2.7; Pa9 1.7; Pa10 1.6.

Oviger article 1 (O1) 0.5; O2 2.0; O3 1.65; O4 6.0; O5 5.4; O6 2.9; O7 1.9; O8 1.1; O9 1.1; O10 0.9.

Third leg: coxa-1 2.7, coxa-2 7.0, coxa-3 3.0, femur 15.3, tibia-1 12.3, tibia-2 8.0, tarsus 2.1, propodus 2.7, claw 0.9.

REMARKS

Child (1987) defined a group of “giant” species of Ascorhynchus , being those species having a trunk length of 13 mm of more, and with median dorsal tubercles, long abdomina, two-segmented chelifore scapes, numerous cement-gland pores on multiple leg segments, and a tarsus almost or as long as the propodus. Other species generally have a trunklength of 7 mm or less, although A. colei Hedgpeth, 1943 (vide Hedgpeth, 1948) can be up to 10 mm long.

Of the previous eight recorded “giant” species of Ascorhynchus (see below), none has a median dorsal tubercle on the fourth trunk segment, unlike the present species. Six of those species have eyes, unlike A. quartogibbus n. sp., the other two being A. levissimus Loman, 1908 , from the Flores Sea, Indonesia, and A. glaber Hoek, 1881 , from the Indian Ocean off Africa. A. levissimus differs from A. quartogibbus n. sp. in having the tarsus of the walking legs as long as the propodus (shorter in A. quartogibbus n. sp.), the ocular tubercle a low dome (tall and pointed in A. quartogibbus n. sp.), palp article 8 (Pa8) twice as long as Pa9 (1.6 times as long in A. quartogibbus n. sp.), and Pa3 5.6 times as long as Pa4 (2.7 times in A. quartogibbus n. sp.). A. glaber (a smaller animal, body length <14 mm) differs from A. quartogibbus n. sp. in its conspicuously short third palp article, only 1.5 times as long as Pa4, and in the chelate and functional chelae in the adult.

Ascorhynchus quartogibbus n. sp. was collected off the Solomon Islands and Papua New Guinea at depths from 895 to 1750 m.

Child (1987) produced an identification key to six of the giant Ascorhynchus species known at the time, not including A. levissimus or A. orthorhynchus Hoek, 1881 . Below is an identification key to the nine species now known. Note: A. agassizi Schimkewitsch, 1893 and A. pararmatus Stock, 1975 key out twice, as their dorsodistal lateral-process-tubercles are low swellings which may not be noticed.

IDENTIFICATION KEY TO GIANT ASCORHYNCHUS SPECIES

1 Lateral processes smooth, without any dorsodistal tubercle ......................................... 2

— Lateral processes with dorsodistal tubercles; eyes present ............................................ 7

2 Claws on first walking legs not conspicuously shorter than those on other legs; eyes present; proximal scape article clearly shorter than distal scape article ......................................... ................................................................................... A. agassizi Schimkewitsch, 1893

— Claws on first walking legs conspicuously shorter than those on other legs; eyes present or absent; scape article proportions various ................................................................. 3

3 Mid-dorsal tubercle present on trunk segment 4; eyes absent .........................................

.................................................................................................... A. quartogibbus n. sp. — No mid-dorsal tubercle on trunk segment 4; eyes absent or present ............................ 4

4 Palp article 3 only 1.5 times as long as article 4; tarsus clearly shorter than propodus;

proximal scape article about as long as distal scape article; eyes absent; chelifores chelate

.................................................................................................... A. glaber Hoek, 1881 — Palp article 3 more than four times as long as article 4 ................................................ 5

5 Palp article 3 about 4.5 times as long as article 4; tarsus clearly shorter than propodus; proximal scape article shorter than distal scape article; eyes present; chelae atrophied ..... ............................................................................................ A. pararmatus Stock, 1975

— Palp article 3 over 5 times as long as article 4; tarsus about as long as propodus; eyes present or absent; chelae various ................................................................................. 6

6 Proximal scape article longer than distal scape article; eyes present; palp article 8 only 1.3 times as long as article 9; chelae atrophied ........................... A. japonicus Ives, 1892 — Proximal scape article clearly shorter than distal scape article; eyes absent; palp article 8 twice as long as article 9; chelifores chelate .......................... A. levissimus Loman, 1908

7 Proximal scape article longer than distal scape article; palp article 7 twice as long as article 10 (distal article); chelifores chelate ....................... A. orthorhynchus Hoek, 1881

— Proximal scape article shorter than or equal to distal scape article; palp article 7 about as long as article 10 (distal article); chelae atrophied ....................................................... 8

8 Claws on first walking legs not conspicuously shorter than those on other legs; palp article 3 no more than 3 times as long as article 4 ....... A. agassizi Schimkewitsch, 1893

— Claws on first walking legs conspicuously shorter than those on other legs; palp article 3

at least 3.5 times as long as article 4 ............................................................................ 9

9 Palp article 3 about 3.5 times as long as article 4; tarsus as long as propodus; ocular tubercle not pointed distally ...................................................................... A. cooki Child, 1987

— Palp article 3 about 4.5 times as long as article 4; tarsus shorter than propodus; ocular tubercle various ........................................................................................................ 10

10 Proximal scape article shorter than distal scape article; ocular tubercle not pointed distally; tarsus 0.5 to 0.6 times as long as propodus; lateral process tubercles low and rounded ... ............................................................................................ A. pararmatus Stock, 1975

— Proximal scape article about as long as distal scape article; ocular tubercle pointed distally; tarsus 0.8 to 0.9 times as long as propodus; lateral process tubercles conspicuous and pointed .............................................................................. A. armatus (Wilson, 1881)

Figures

FIG. 1. — Ascorhynchus quartogibbus n. sp., male: A, D–I, holotype (MNHN-IU-2008-20493);B, C, paratype (MNHN-IU-2008-20644). A, habitus, lateral; B, habitus, dorsal; C, left chelifore; D, palp; E, oviger;F, oviger strigilis, with detail of compound spine; G, third leg; H, distal articles of first leg; I, distal articles of third leg. Scale bar: A, B, 5 mm; C, H, I, 2 mm; D, E, 0.3 mm; F, 0.14 mm; G, 10 mm.