Pallenella octolentium, 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 : 27-29

Pallenella octolentium sp. nov.

Figure 8a–h. Plate 10a–f u r n:lsid:z o oba n k.org:a ct:4E8 4 C D07-B52D - 423F-9 070 -

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Material examined. Holotype. Female, gravid ( SAMA E9445 ). Great Australian Bight, (31° 40´S, 130° 00´E), 45–50 m, Pipe Dredge, ORV Franklin, stn GAB009, Y. Bone, P. Bock, S. Hageman, 14 Jul 1995.

Diagnosis. Pre-ocular cephalon surface bulbous, rounded, without cuticular division. Trunk segments not inflated dorsally. Neck defined by a constriction only. Eight eye lenses. Lateral processes separated by about half basal diameter. Oviger claw rounded at tip, scoop shaped. Legs without irregularities, tibia 2 much wider than tarsus. Propodal heel prominent, with a random group of strong, closely spaced spines, clearly delineated from the sole by distinct gap between heel spines and sole spines. Chela palm swollen, fingers robust, cutting edge of moveable finger with conspicuous elevation on cutting edge at mid-length.

Description. Holotype, female. Leg span about 29.0 mm. Trunk glabrous, segments not inflated dorsally. Lateral processes 2 and 3 separated by about half basal width, processes 3 and 4, narrowly separated, processes 1 and 4 shortest, length about equal to basal width, length lateral processes 2 and 3 about 1.25 times basal width. Cephalon bulbous, without cuticular division, individual swellings over bases of chelifores subsumed into the pre-ocular surface, small median secondary protuberance, which may not be a diagnostic character, is present on the dorsoposterior surface (Fig. 8b, plate 10c). In lateral view, the anterior face of eye tubercle slopes downwards at about 45° rising abruptly at the base of the crop (Fig. 8c, plate 10b).

Eye tubercle height less than width, eyes of equal size, eight lenses, two dorsal papillae.

Proboscis length about twice greatest width, inflated in mid-region, narrowing marginally to another very slightly inflated part before tapering to terminal jaws, setiferous fringe present (plate 10c).

Chelifore scape slightly shorter than proboscis length, proximal constriction present. Chela longer than scape, palm bulbous, fingers curved, shorter than palm, moveable finger not quite reaching tip of immoveable finger, crossing at tips with the moveable finger closing to the outer side of immoveable finger, moveable finger with prominent node on cutting edge at about half length, immoveable finger smooth, cutting edges of both fingers heavily sclerotized (plate 10d).

Oviger bases level with anterior margin of first lateral processes, compound spine formula, segments 7–10, 19:15:15:14 (63 spines), spines slender, curved, segment 4 with small cone on posterior surface at about one-third length, claw greater than half length of segment 10, rounded at tip, fringed with blunt teeth on both margins.

Anal tubercle horizontal short, barrel shaped.

Legs without irregularities (plate 10e), spines fine and sparse, only apparent under high magnification. Coxa 2 about 2.5 times length of coxa 1, longer segments smooth, with inflated appearance, tibia 2 longest segment, width greater than twice that of propodus, femur longer than tibia 1, swollen with oocytes, Figure 8 Pallenella octolentium sp. nov., female holotype ( SAMA E9445 ). a–c, trunk, dorsal, anterior and lateral; d, e, right chela, inner and outer views; f, right oviger; g, leg 3, h, tarsus and propodus .

propodus curved, heel defined, prominent, isolated by absence of spines between heel and proximal sole spines (Fig. 8h, plate 10f), heel with random grouping of about twelve strong spines of equal size accompanied by many lesser spines, sole lined with about ten lesser spines in more than one row and many shorter lateral spines, claw strong, outer margin evenly curved, inflated, wide at base, inner margin straight, curved near tip only, length about 3.5 times base width, reaching to mid-point of heel when closed. Gonopores large, ventrodistal, all legs.

Measurements of holotype (mm). Trunk length (frontal margin of cephalic segment to tip of fourth lateral processes), 3.74; width across second lateral processes, 1.87; proboscis length (dorsal), 1.96; greatest diameter proboscis, 0.98; scape length 1.47; anal

Plate 10. Pallenella octolentium sp. nov., female, holotype ( SAMA E9445 ): a–c trunk, dorsal, lateral and anterior views; d, chelae; e, leg 3; f, propodus leg 3 .

tubercle length, 0.36. Oviger (segs 3–4): seg. 3, 0.36; seg. 4, 1.07; seg. 5, 0.94; seg. 6, 0.25; seg. 7, 0.57; seg. 8, 0.45; seg. 9, 0.41; seg. 10, 0.38; claw, 0.22. Leg 3: coxa 1, 0.49; coxa 2, 1.24; coxa 3, 0.77; femur, 3.39; tibia 1, 2.75; tibia 2, 3.75; tarsus, 0.10; propodus, 0.91; claw, 0.53.

Remarks. No other adult in this genus shares such a well-defined heel as this species. Based on the similarity between the propodal heel of this specimen and Clark’s illustration of a “further propodus” in his description of P.dubia Clark, 1963 ( Clark, 1963 Fig. 18B), it is tempting to resurrect P. dubia from its present status of species inquirenda to accommodate this specimen. However, Clark’s material clearly consisted of juvenile forms and there are too many unknowns to make this a practical alternative. Pallenella brenneisi sp. nov. shares the robust chela fingers and the absence of a median division of the pre-ocular surface with this species but it has far fewer oviger spines ( P. octolentium , 63 spines, versus P. brenneisi , 45 spines). Only two other species have>60 oviger spines; these are P. tasmania (68 spines) and P. laevis (66 spines), but both these species have slender and tapered chelae fingers compared to the robust fingers of this species. Additional images of the P. laevis holotype are included here to assist with comparison (plate 18a–d).