Ascorhynchus dietheus Child 2002, new species
Creators: name: Child, C. Allan
Publisher: name: Zenodo
Year: 2002
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Pycnogonida
Pantopoda
Ascorhynchidae
Ascorhynchus
Ascorhynchus dietheus

description: Ascorhynchus dietheus, new species  (gure 2)  
 Types. Saudi Arabia: Sta. 2RS-2, Peninsula S of Al Khobar, 26ss04.5¾N, 50ss08.8¾E, intertidal, 18 November 1985 (one with eggs, holotype, USNM 234726); Sta. 2RIu-2, same locality, 12 June 1985 (one, paratype, USNM 234727).   
 Other material. United Arab Emirates, Abu Dhabi, Ruwais Basin, 2–8 February 1983 (one, one juv.).   
 Saudi Arabia: ARAMCO Tarut Bay stations: Sta. 710813A/ 3, 7–10 m, 13 August 1971 (one); Sta. 730120 A/4, intertidal, 20 January 1973 (one); Sta. 740718A/1, in mud with Halophilia ovalis, 5–6 m, 18 July 1974 (one); Sta. 740719 A/2, 19 July 1974 (one juv.).   
Northern Area Baseline Survey (NABS) stations: Sta. 1G-2, 14 November 1984 (one); Sta. 1G-2, 6 November 1985 (one); 1G-3, 6 November 1985 (two, one juv.); Sta. 2G-2, 5 March 1982 (one); Sta. 4G-3, 20 November 1981 (one); Sta. 5G-1, 8 March 1982 (one); 5 S-1, 8 March 1982 (two with eggs, one); Sta. 5G-3, 20 November 1981 (one); Sta. 6G-1, 18 November 1981 (one juv.); Sta. 7G-1, March 1982 (ve); Sta. 7G-2, March 1982 (one, three juv.); Sta. 7G-3, March 1982 (nine spec.); Sta. 8G-1, 23 November 1981 (one, one juv.); Sta. 8G-1, April 1982 (one with eggs, one); Sta. 8G-2, 23 November 1981 (two juv.); Sta. 8G-3, 23 November 1981 (two); Sta. 6A-3, 30 December 1984 (one); Sta. 8A-1, 30 December 1984 (one); Sta. 8A-2, 30 December 1984 (one); Sta. 8G-3, 30 December 1984 (one).  
Later Tarut Bay stations: Sta. 2TG-2, 3 January 1987 (one juv.); Sta. 4TG-1, 20 November 1984 (one); Sta. 4TG-1, 8 December 1985 (one juv.); Sta. 4TS-1, 20 November 1984 (one juv.); Sta. 4TS-3, 20 November 1984 (one, one juv.); Sta. 4TG-3, 12 January 1985 (one); Sta. 11TG-2, 14 May 1985 (one); Sta. 11TS-2, 14 May 1985 (one juv.); Sta. 11TG-3, 14 May 1985 (one); Sta. 12TG-1, 13 May 1985 (one); Sta. 19TG-3, 15 May 1985 (one); Sta. 20TS-1, 14 May 1985 (two juv.); Sta. 7RG-2, 17 February 86 (one).  
 Distribution. The species is found to be relatively common on the Saudi Arabian northern Gulf (Hasa) coastline from Bandar Mish’ab near the Kuwaiti border south to Tarut Bay and in the United Arab Emirates, in depths from littoral to 10 m. Most collecting stations during annual survey seasons turned up a few specimens of this species. The species was the second most frequently collected pycnogonid (Callipallene pectinata (Calman), being the most commonly collected). The new species types came from shallows on the peninsula just to the south of the town of Al Khobar.   
 Description. Size moderately small for genus, leg span about 13.5 mm. A graceful, slender species of the longitarsal group with a single scape segment. Trunk slender, glabrous, completely segmented. Posterior trunk segment ridges not greatly in ated, but slightly swollen, without tubercles. Lateral processes slender, longest at least three times longer than diameters, separated by their diameters or slightly more, with broad low dorsodistal tubercle, each of which is armed with one or two tiny lateral setae. Neck long, as long as posterior three trunk segments, oviger implants well anterior to rst lateral processes, at about 0.4 of neck length, ocular tubercle anterior to oviger implants, at about 0.6 neck length. Ocular tubercle a low in ated cone no taller than base diameter. Eyes well pigmented, anterior pair larger than posterior pair. Trunk anterior with pair of low inconspicuous bumps dorsal to chelifore insertions. Proboscis short, not quite as long as neck, of typical tripartite shape acutely tapering at each end. Abdomen slender, reaching slightly beyond rst coxae of posterior legs, slightly in ated distally, carried horizontally, glabrous.   
Chelifores with short, club-shaped, one-segmented scapes. Chelae tiny atrophied tubercles with hint of lateral nger base. One nger with tiny curved claw. Palps typical for the genus, third segment longest, slightly longer than fth. Distal ve segments with ventral fringe of setae, most longer than segment diameters. Setae with broad proximal shaft for 0.6 of their length, distal 0.4 of length agellum- or hair-like. Seventh, eighth and tenth segments subequal, sixth and ninth shorter. Oviger conventional, fth segment longest, with few ventral setae in row, fringe of dorsal setae, most shorter than segment diameter. Strigilis segments each shorter than preceding, with denticulate spines in two rows, one spine group smaller than other group, larger spines with three lateral lobes. Spines distributed on the segments in formula 7: 6: 6: 7. Terminal claw moderately curved, slightly longer than terminal segment diameter, without teeth.  
Legs slender, with very few short setae, mostly on distal segments. First tibiae the longest segments, subequal in length to combined length of tarsus, propodus and claw. Second tibiae quite short, only 0.7 length of rst. Tarsus a straight glabrous cylinder about 0.8 length of propodus. Propodus a glabrous slightly curved cylinder, claw of posterior three leg pairs slightly longer than tarsus. Claw of rst leg pair very short, little longer than propodal diameter, tarsus longer, almost propodal length, both with few tiny setae. Cement glands divided on each leg: slightly proximal to midlength of both femora and rst tibiae, with multiple at pores, three on femora, three to ve on rst tibiae. Pores consist of sieve plates with many tiny holes clustered in circles.  
Female characters: size larger in all measurements except oviger which is slightly smaller. Legs with greater number of short setae, oviger fth segment shorter in relation to fourth, strigilis with one or two more denticulate spines per segment.  
 Measurements of holotype in mm. Trunk length (chelifore insertion to tip fourth lateral processes), 2.78; trunk width (across second lateral processes), 1.5; proboscis length, 1.18; abdomen length, 0.64; third leg, coxa 1, 0.41; coxa 2, 0.49; coxa 3, 0.35; femur, 1.09; tibia 1, 1.25; tibia 2, 0.9; tarsus, 0.41; propodus, 0.59; claw, 0.43.   
 Etymology. The speci c epithet (Gr.: dietheo, to strain through, sieve or percolate) refers to the sets of sieve plate outlets for cement glands which are unusual by their placement on both femora and rst tibiae of males.   
 Remarks. This species is very closely related to a group of Indo-West Paci c forms which include A. minutus Hoek, 1881, A. glaberrimus Schimkewitsch, 1913, A. parvituberculatus Stock, 1953, A. ramipes (Böhm, 1879) and A. utinomii Nakamura and Child, 1982. All these are what might be called conservative species with very few conspicuous characters among them with which to highlight their diVerences. They are of the longitarsal group where the elongate cylindrical tarsus measures more than half the propodal length. They also agree with the new species in having one-segmented scapes. The only conspicuous characters which might allow them to stand out from the hordes of Ascorhynchus species (701) are their lateral process or rst coxae tubercles of one kind or another.   
 The closest species is probably A. glaberrimus from Japan, which has the same general non-tuberculate or low tuberculate habitus as this species, although it has slightly taller lateral process tubercles, shorter chelifore scapes, and a diVerent series of nine to ten raised cribriform cement gland cups on each male femur with none on the rst tibiae.   
 Another closely related species from Japan is A. utinomii which has conspicuous dorsolateral rst coxal tubercles unlike those of A. dietheus. The rst leg distal characters are much diVerent, including the tiny terminal claw, than the rst legs of the new species. The two species are otherwise quite close.   
 Ascorhynchus ramipes is very similar in most characters except for having two slender laterodistal tubercles on each rst coxa. It lacks all trace of any claw on its rst leg pair, and has ve or six small at cribellate pores as cement gland openings on each femur but none on the tibiae.   
 A species also having slender rst coxal tubercles is A. minutus. It has rather short slender tubercles on the trunk and lateral processes, but otherwise agrees very well with this new species in the general trunk habitus, legs, chelifores, palps and ovigers. This species also has multiple raised pores on the femoral cement glands but lacks tibial cement glands. The palp setae are somewhat agellate on A. minutus and resemble those of the new species.   
 Ascorhynchus parvituberculatu s has lateral processes generally more crowded than those of the new species, and has low broad dorsal tubercles on trunk and lateral processes. The necks of both species are very similar, as are the palps, ovigers and legs, including the short second tibiae, but Stock’s species lacks the rst tibiae cement glands.   
 One of the few outstanding characters of A. dietheus is that of separated cement glands divided between the femora and rst tibiae; other similar species lack these multiple glands on two leg segments.
description: Published as part of Child, C. Allan, 2002, Some Pycnogonida from the Eastern (Hasa) District of Saudi Arabia, pp. 1805-1821 in Journal of Natural History 36 (15) on pages 1808-1811, DOI: 10.1080/00222930110075189, http://zenodo.org/record/5298866