Pseudopallene gracilis, Arango, Claudia P. & Brenneis, Georg, 2013

Arango, Claudia P. & Brenneis, Georg, 2013, New species of Australian Pseudopallene (Pycnogonida: Callipallenidae) based on live colouration, morphology and DNA, Zootaxa 3616 (5), pp. 401-436 : 420-422

Pseudopallene gracilis sp. nov.

Figs. 3 F, 11A–G

Material examined: Holotype (J4518): 1 male (PSE6), Nov-24 2009, Fog Rock, Eaglehawk Neck, Tasmania , 10–17 m depth, on bryozoans.

Diagnosis: Legs long, slender, spinose, with no constrictions; ocular tubercle tall; proboscis and cheliphores directed slightly anteroventrally, rather than posteroventrally; straight proboscis with distal tuft, narrow tip; chelae fingers straight, without conspicuous proximal gap when closed. Body and legs orange with yellow-tinted bands when alive (no photograph available). Sequence divergence from other Pseudopallene forms is 11 to 14 % in COI and 19 to 24 % in ITS ( Table 2 ).

FIGURE 11. Pseudopallene gracilis sp. nov., male holotype (J4518). A, dorsal view showing proximal leg articles; B, frontal view, note dark tuft surrounding mouth; C, detail of chelae; D, oviger articles, 5th article with prominent distal apophysis; 7th–9th articles with compound spines; E, second leg; F, detail of distal-most oviger articles including terminal claw; G, propodus and terminal claw of third walking leg. Scale bars on stereomicroscopic images = 1 mm or as shown.

Description of male: Leg span 30 mm, slender appearance, orange colouration when alive. Body (Fig. 11A) fully segmented, neck distinct, with ovigers attaching laterally, raised mid-dorsal mound on pre-ocular surface, longitudinal cuticular division line not seen dorsally, only a fine line at mid-point between cheliphore insertions in frontal view. Ocular tubercle (Fig. 11A,B) tall, twice its width at base, slightly inclined backwards, with prominent distal papillae; four darkly pigmented eyes, anterior pair larger. Lateral processes longer than wide, width 83 % of length, smooth; abdomen as long as fourth lateral process, swollen distally, cleft anal opening.

Proboscis (Fig. 11B,C) directed ventrally, slender, straight, without mid-point constriction, distally narrowing to mouth surrounded by dark tuft of setae.

Cheliphore (Fig. 11B,C) scapes as long as proboscis, directed slightly anteroventrally, slender, hint of constriction line near the base; chelae short, 81 % of scape length, glabrous; palm inflated but not globose; fingers as long as half of palm length, with linear cutting edge leaving only a narrow gap when closed.

Oviger fifth article longest, curved, with prominent apophysis distally (Fig. 11D); fourth article with much smaller, rounded distal apophysis; oviger spine formula 13:9:6:7 (Fig. 11D); terminal claw with strong denticulations on both margins in distal half, longer denticulated margin endally (about 31 denticulations) (Fig. 11F).

Legs (Fig. 11E,G) long, about seven times as long as the trunk, slender, with two or three rows of sparse short spinules dorsally and ventrally on major articles; tibia 2 longest article; femur curved, second longest article; tarsus short, typical, with small distal spine in line with heel spines; propodus straight, propodal heel not conspicuous, six heel spines, gradually increasing in size; 12 sole spines; main claw longer than half of propodus length.

Measurements of male holotype in mm: body length = 2.28; body width = 1.45; abdomen length = 0.35; ocular tubercle height = 0.39; proboscis length = 1.06; chela fingers = 0.53; scape = 1.15; oviger 5th article = 1.21, 10th article = 0.23, claw = 0.16; 3rd leg coxa 1 = 0.48, coxa 2 = 1.35, coxa 3 = 0.7, femur = 3.3, tibia 1 = 3.02, tibia 2 = 3.51, tarsus = 0.19, propodus = 0.88, claw = 0.48.

Etymology: The species name relates to the slender, graceful habitus of this long-legged Pseudopallene species.

Remarks: The comparably short and slender chelae and the relatively long and slender leg articles (including coxa 2), and the short spinules on the legs, giving it a spiky appearance, serve to distinguish this medium-sized individual from previously described species. The new species shows a prominent tuft surrounding the mouth. The narrow, folded terminal oviger claw with numerous sharp denticulations all around the ectal and endal margins are characteristic of the species.

Figures

FIGURE 3. Dorsal view of eight morphotypes of Pseudopallene collected at Eaglehawk Neck, Tasmania. A, P. flava sp. nov.; B, P. constricta sp. nov.; C, P. ‘ variabilis’ - complex; D, P. tasmania sp. nov.; E, P. reflexa; F, P. gracilis sp. nov.; G, P. brevicephala; H, P. pachycheira. Scale bars = 1 mm.