Pseudopallene difficile, Arango, Claudia P., 2009

Arango, Claudia P., 2009, New species and new records of sea spiders (Arthropoda: Pycnogonida) from deep waters in Western Australia, Zootaxa 1977, pp. 1-20 : 9-11

Pseudopallene difficile n.sp.

( Figures 4 & 5 )

Holotype: WAM T92361, 1 ovigerous male. 3 December 2005, Houtman Abrolhos, Western Australia, CSIRO station 092-29, collected by Sherman sled from 28.9714°S 113.8320°E to 28.9744°S 113.8350°E, hard bottom, 86 m.

Diagnosis: Small size; trunk smooth, rounded cephalon with no longitudinal mark. Proboscis ventrally positioned, narrowing distally. Moveable finger with lobe; immovable finger smooth. Oviger terminal claw serrated on both sides. Leg segments smooth; propodus heel not prominent, with four strong spines; main claw 0.6 times length of propodus.

Description: Leg span 20 mm, body size small for the genus, trunk completely segmented, smooth, neck short, no longitudinal mark on cephalon in frontal view; lateral processes smooth, slightly longer than wide, separated by about half their own diameter or less. Abdomen smooth, short, horizontal, reaching to margin of fourth lateral processes. Ocular tubercle low, with four darkly pigmented eyes. Proboscis directed ventrally, almost cylindrical in the first half, then narrowing sharply ending in a tube-shaped section. Chelifore scape one-segmented, slightly constricted on first half; fingers half the length of palm, immovable finger straight, longer than moveable finger, moveable finger curved, with lobe at inner edge, all glabrous. Oviger 10-segmented, fifth segment longest, curved, with distal apophysis, spine formula 13:8:9:7; terminal claw elongate, triangular in shape, margin denticulate. Legs smooth, margins regular, first coxa shortest, second coxa twice length of third, femur longest segment, tarsus very short, propodus with small heel bearing four heel spines, 5–6 sole spines; main claw 0.6 times length of propodus. Genital pores on second coxa of third and fourth legs.

Measurements of holotype (in mm): Trunk length = 2.2, trunk width (across second pair of lateral processes) = 1.27, proboscis = 1.28, abdomen = 0.26; oviger segment 1 (o1) = 0.22, o2 = 0.27, o3 = 0.35, o4 = 1.75, o5 = 1.26, o6 = 0.35, o7 = 0.36, o8 = 0.26, o9 = 0.24, o10 = 0.17, terminal claw = 0.12; coxa 1 = 0.29, coxa 2 = 1.17, coxa 3 = 0.58, femur = 2.20, tibia 1 = 1.91, tibia 2 = 2.11, tarsus = 0.12, propodus = 1.17, claw = 0.73.

Etymology: The species name difficile (Latin) alludes to the difficulty in assigning this specimen to this species of Pseudopallene . Difficulties are associated to the intraspecific variation and the overlapping of diagnostic characters in closely related species.

Remarks: This is a mature male specimen that cannot be assigned to any of the existing species. It shares many diagnostic characters of adults of Pseudopallene reflexa Staples 2005 including the configuration of trunk, abdomen, cephalon and ovigers, but main differences are in a smaller size, [mature male in Staples (2005) is 3.55 mm long] and in the legs, which are regular and smooth in the Abrolhos specimen rather than spiny and irregular as in material from South Australia and Victoria. In particular, the propodus differs in lacking the distinctive V-shaped arrangement of heel spines ( Staples 2005). The moveable fingers of the chelae have a lobe on the edge while those of P. re f l e x a are smooth ( Bamber 2005; Staples 2005; 2007).

Figures

FIGURE 4. Pseudopallene difficile n. sp., holotype male. A. Frontal view of chelifores, proboscis and anterior of cephalon and ocular tubercle. B. Lateral view. C. Dorsal view. D. Oviger segments 3 – 10. E. Third leg. Scale bars = 1 mm.

FIGURE 5. Pseudopallene difficile n. sp. A. Frontal view of chelifores, eggs attached to ovigers seen below. B. Tarsus, propodus and claw. C. Strigilis, segments 7 to 10 of the oviger with compound spines and denticulate main claw distally. Scale bars = 125 μm.