Pseudopallene constricta, 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 : 422-424

Pseudopallene constricta sp. nov.

Figs. 2 B, 3B, 12A–F

Material examined: Holotype (J4519): 1 male (PSE2), Nov-2009, Eaglehawk Neck, Tasmania , 5–20 m depth, on Orthoscuticella spp. Paratypes (S92223): 4 males (including PSE2a), 3 females (including PSE2b), 2 postembryonic stages (PSE10, PSE10a); all from the same location as holotype.

Diagnosis: Medium-sized species; uniformly yellow when live; marked constriction of proboscis at mid-point, chela fingers straight, tips weakly or distinctly crossing when closed, leaving a narrow proximal gap in between, femora curved, legs slender, with no constrictions, with rows of nodulose, short spines giving ‘prickly’ appearance to legs under high magnification; prominent propodal heel with four stout heel spines. Sequence divergence ranges from 10 to 13 % in COI and 6 to 23 % in ITS.

Description of male: Leg span 32 mm, live colouration uniform bright yellow on body and legs. Body ( Fig. 12 A,C) fully segmented; neck about 0.5 mm long, parallel sides in between the ovigers insertion and the constriction between the neck and a laterally expanded cephalon; cephalon without conspicuous pre-ocular middorsal mound, or longitudinal cuticular division line. Ocular tubercle ( Fig. 12 A,C) as wide as tall, with only weakly protruding dorsal papillae; four small, darkly pigmented eyes, all of equal size. Lateral processes ( Fig. 12 C) 1.25 as long as wide, glabrous, separated by about one-quarter of their basal diameter. Abdomen ( Fig. 12 C) straight, overreaching the distal margin of the fourth lateral processes.

Proboscis ( Fig. 12 A,B) directed ventrally, with conspicuous mid-point constriction, somewhat inflated in distal part, tapering to oral tip, mamilliform, no tuft of setae visible.

Cheliphore ( Fig. 12 A,B) scape one-articled, indistinct proximal constriction, as long as proboscis. Chelae robust, outer surface of palm inflated, spare minute spinules; fingers subequal in length, 80 % of palm length, finger tips cross when closed, leaving proximal gap, immovable finger with straight cutting edge, movable finger slightly curved.

Oviger ( Fig. 12 F) fifth article longest, with distinct apophysis distally; strigilis articles subequal, spine formula 12:6:6:6; terminal claw ~70 % of tenth article length, acute, endal margin denticulate, only distal half of ectal margin denticulate.

Legs ( Fig. 12 D,E) 4.3 times as long as body, with minute spines arranged in longitudinal rows. Second coxa 2.5 as long as subequal first and third; femur curved; tibia 1 distally swollen, shorter than femur; tibia 2 straight, longest article; tarsus typical, with one main distal spine, covered in tiny setae; propodus curved, prominent heel with row of four stout spines, two middle ones larger; sole with median row of 14–15 small spines. Main claw long, nearly 70 % of propodus length. Genital pores on second coxae of third and fourth leg pairs.

Measurements of male holotype in mm: body length = 3.32; body width = 1.96; abdomen length = 0.53; ocular tubercle height = 0.32; proboscis length = 1.18; scape = 1.19; chela fingers = 0.57; oviger 5th article = 1.16, 10th article = 0.27, claw = 0.13; 3rd leg coxa 1 = 0.58, coxa 2 = 1.72, coxa 3 = 0.67, femur = 3.13, tibia 1 = 2.73, tibia 2 = 3.42, tarsus = 0.23, propodus = 1.03, claw = 0.68.

Etymology: The species name refers to the characteristic constriction of the proboscis, which serves to readily distinguish this species from similarly coloured, sympatric congeners.

Remarks: Previously, Stevenson (2003) in his MSc thesis investigated specimens of this form, which had been collected at the same sampling site. In accordance with the present study, he found morphological as well as molecular evidence (16S rDNA and COI fragments) in support of its valid species status, without, however, presenting a formal species description. Recent studies (Brenneis et al. 2011a, b) have focussed on the development of the yellow Pseudopallene species from Tasmania . The investigation of post-embryonic development was conducted on the transparent-yellowish post-embryonic stages that have been clearly assigned by the molecular data to P. constricta sp. nov. (see Brenneis et al. 2011b for morphological description of postembryonic stages). During the collection period (second half of November), all yellow Pseudopallene species encountered in the study area did carry eggs. Yet, in P. constricta , they were observed to be generally in later developmental stages, males often bearing already hatched post-embryonic stages 1 and 2. This might be indicative of a slight shift in the reproductive periods of the sympatric Pseudopallene species.

Figures

FIGURE 2. Live colouration of some of the species of Pseudopallene and Stylopallene included in the study. A, fresh live bryozoans Orthoscuticella spp. with many Pseudopallene specimens; B, P. constricta sp. nov., male in ventral view with egg masses attached to the ovigers; C, P. ‘ variabilis’ - complex, frontal-ventral view, note black tips of proboscis and chela fingers; D, P. flava sp. nov. in its natural habitat; E, Close-up of P. brevicephala male characterized by uniform orange-red body and legs, bearing orange eggs and transparent post-embryonic stages; F, P. pachycheira attached to bryozoan, showing banding pattern and constrictions of long leg articles; G, P. h a r r i s i sp. nov. in its natural habitat showing red-and-yellow colouration; H, specimen from the P. ‘ variabilis’ - complex with yellow-and-red colouration attached to live bryozoan; I, Stylopallene cheilorhynchus showing characteristic live black-and-creamy-white banding, photograph taken in captivity. All specimens from Eaglehawk Neck, Tasmania except 2 G and 2 H collected at Bass point, New South Wales.

FIGURE 12. Pseudopallene constricta sp. nov., female paratype (S 92223). A, frontal-lateral view showing diagnostic midpoint constriction of proboscis; B, detail of chelae, ventral view. Note the slight crossing of the chela finger tips; C, body in dorsal view; D, propodus and terminal claw of third walking leg. Propodus with white epibiont; E, third leg; F, oviger. Scale bars on stereomicroscopic images = 1 mm or as shown.