Pallenella arangoae, Staples, 2025

Staples, David A., 2025, Pycnogonids, ‘ sea-spiders’ (Arthropoda, Pycnogonida) selected from the collections of the South Australian Museum with descriptions of new species and review of the genus Pallenella., Memoirs of Museum Victoria 84, pp. 1-47 : 29-32

Pallenella arangoae sp. nov.

Figure 9a–h. Plate 11a–h u r n:l sid:z o o b a n k.o rg:a c t:61C3E 6 85- 0E B4 - 475 4 -81FA-

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Material examined. Holotype. Ovigerous male ( SAMA E9455 ). S.E. of Esperance , Western Australia, 34° 39´S, 122° 26´E, 190 m, epibenthic sled. O.R.V. Franklin, stn GAB 097, S. Hageman, P. Bock, Y. Bone, 24 Jul 1995.

Diagnosis. A slender, delicate species with well-defined neck. Pre-ocular surface low, without median swelling, cuticular

Figure 9. Pallenella arangoae sp. nov., male, holotype (SAMA E9455). a–c, trunk, dorsal, anterior and lateral views; d, left chela; e, g, leg 3 and propodus; g, h, right oviger and claw (freehand sketch).

longitudinal division absent. Chela palm slender, fingers short. Four eyes, each with two lenses. Coxa 2, long, slender,> 4 times coxa 1. Propodus almost straight, heel inconspicuous, three strong spines, distal-most spine largest, terminal claw broad, outer edge inflated.

Description. Leg span about 54.0 mm. Trunk segments rounded dorsally, lowly inflated, first lateral processes conspicuously arched upwards and forward, Colossendeis -like, (plate 11c, d.), separation of first and second lateral processes slightly less than basal widths, length of second lateral process about 2.2 times basal width, several tiny dorsal and lateral setae. Neck well-defined, length little more than width, bases not in contact with first lateral processes, pre-ocular surface low, without longitudinal cuticular division, or median mound, cephalon with low swellings at bases of scapes, with several inconspicuous spinules.

Eye tubercle anterior surface sloping from a posterior apex (plate 11e), two dorsolateral papillae above posterior eyes, four eyes, each with two indistinct lenses, lightly pigmented.

Proboscis length about 2.2-times maximum width, distal one-third slightly bulbous, before narrowing to short glabrous tip (fig.9b, plate 11c), basal arthrodial membrane wide when extended.

Chelifore scape with hardly discernible spinules on margins, and possibly over entire surface, proximal half of fingers lined with similar spinules along outer edges, chela palm elongate, finger cutting edges smooth, gaping for most of length when finger tips touching; immoveable finger with Plate 11. Pallenella arangoae sp. nov., male, holotype ( SAMA E9455 ): a, whole specimen; b–d, trunk, dorsal, anterior and lateral views; e, ocular tubercle lateral; f, left chela; g, leg 3; h, propodus .

defined proximal indentation at base (fig. 9d, plate 11f), moveable finger slightly shorter, fingers greater than half length of palm, outer margin of moveable finger evenly curved, immoveable finger almost linear with palm.

Oviger (fig. 9g) ten-segmented, segment 5 longest, curved, widest distally, many surface spinules, distal apophysis with few dorsal spinules, segment 4 next longest, segments 7–10 with many strong, simple, short spines on all surfaces, compound spine formula, segments 7–10, 20:9:11:8 (48 spines), proximal and distal spines offset from median row, segment 10 with large spine overreaching base of terminal claw, claw long, slender, and appears to have deep median furrow but difficult to interpret, distally twisted outwards to pointed tip, tiny, sharp teeth on both distal margins (fig. 9h, freehand sketch).

Anal tubercle inclined upwards at low angle (Plate 11d), short, inflated, few minute setae on surface, distal gape conspicuous.

Legs (figs 9f, e) without irregularities, surface with tiny, fine scattered setae. Second coxa 4.3 times length of coxa 1, widening distally, with low dorsodistal papilla, femur and first tibia widened distally, tibia 2 longest segment, tibia 1 longer than femur, tarsus with one strong ventrodistal spine and many much-shorter, more anterior spines, propodus slender, almost straight, heel inconspicuous, three robust heel spines followed by two lesser spines and about six sole spines accompanied by many minor lateral spines, terminal claw wide, not quite reaching to heel when closed, with inflated outer margin, inner margin almost straight, curved at tip only, terminating in a sharp point. Gonopores cones low, present on the ventrodistal surface of coxae 2 of all legs but no openings are apparent.

Measurements of holotype (mm). Trunk length (frontal margin of cephalic segment to tip of fourth lateral processes), 4.83; width across second lateral processes, 2.14; proboscis length (dorsal), 1.45; greatest diameter proboscis, 0.77; scape length; 1.38. Anal tubercle length, 0.49. Oviger (segs 3–10): seg. 3, 0.55; seg. 4, 1.79; seg. 5, 2.83; seg. 6, 0.73; seg. 7, 0.71; seg. 8, 0.40; seg. 9, 0.40; seg. 10, 0.32; claw, 0.28. Leg 3: coxa 1, 0.69; coxa 2, 3.0; coxa 3, 0.65; femur, 5.90; tibia 1, 6.04; tibia 2, 8.61; tarsus, 0.18; propodus, 1.10; claw, 0.59.

Etymology. The proposed specific name recognizes the significant contribution by Claudia Arango to pycnogonid taxonomy generally, and as editor of PycnoBase: the World Pycnogonida Database.

Remarks. Two bracelets of about sixty eggs, are attached to segment 5 of each oviger. The shape of the terminal claw requires confirmation.

The attenuated habitus of this specimen is more like that of a species of Nymphon , and no other species shares such a long second coxa with this species. These characters alone, are sufficient to separate it from its congeners but in some respects, it is like the more-robust P. tasmania ( Arango et al., 2013) with which it shares a very similar proboscis and propodus shape. From P. tasmania , this species otherwise differs notably, in having much longer lateral processes (length 2.3 times basal width versus 1.5 times in P. tasmania ), a much lower oviger spine count, 49 spines compared to 68 spines in P. tasmania and a longer, well-defined neck versus a short, marked constriction in P. tasmania . It appears to share the oviger claw shape with P. flava and has the same number of compound spines (54) but differs conspicuously in general habitus and in almost all other respects.