Pallenella nuyts, 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 : 34-36

Pallenella nuyts sp. nov.

Figure 11a–h. Plate 13a–f u r n:lsid:zo oba n k.org:act:0E E2C6F1-F5C8- 4194 -A E2D -

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Material examined. Holotype. Male ( SAMA E9446 ). Nuyts Archipelago, two nm South of Carnan reefs, 20–30 m, 32° 41´S, 133° 16´E, rocky reef, L. Hobbs, 22 Jan 1991.

Diagnosis. Trunk segments inflated dorsodistally. Pre-ocular surface of cephalon with an acute median mound divided by cuticular line that extends beyond apex of crop, neck short. Four eyes, each with single lens. Chela fingers moderately robust, moveable finger evenly curved. Leg segments slender, heel low, merging into sole, five linear spines. Oviger claw pointed. Anal tubercle inclined, only a little taller than basal width, cleft at tip.

Description. Holotype, leg span about 23.0 mm. Trunk smooth, dorsoposterior surface of trunk segments inflated (plate 13b). Lateral processes 3 and 4 separated by little less than half width, length of each process about 1.5 times base width. Pre-ocular surface of cephalon with acute median mound divided by cuticular line (fig. 11b), neck sloping downwards from base of eye tubercle, rising sharply to inflated crop.

Eye tubercle height about equal to width, the number of eye lenses is unclear, but eight indistinct lenses appear to be present, two dorsal papillae.

Proboscis dilated at about one third and two thirds overall length, distal-most inflated part covered in microscopic setae and with rather inconspicuous blister-like, dorsomedian swelling, oral surface surrounded by dense setiferous fringe (plate13c).

Chelifore fingers of equal length, both fingers slightly compressed towards tips, proximal half of immoveable finger with swollen outer surface, moveable finger mostly evenly curved, cutting edges of both fingers heavily chitinized, immoveable finger with low proximal protuberance, moveable finger with strong indentation in mid-region creating a conspicuous gap, tiny setae extend along the dorsal margin of the palm and proximal half of both fingers (fig. 13f, plate 13f).

Ovigers typical of males, bases originating immediately in front of first lateral processes but not in contact, directed ventrally, segment 5 longest with tall distal apophysis, compound spine formula, segments 7–10, 14:11:9:9 (43 spines). Claw about half-length segment 10, narrow, lateral teeth blunt at tips.

Anal tubercle inclined upwards at about 45 degrees, short, inflated, only a little taller than basal width, strongly cleft at tip.

Legs spinous, spines mostly tiny but robust, with few longer spines, spines placed on small papillae resulting in slightly roughened appearance under magnification. Coxa 1 with several tiny dorsodistal spinules, second coxa little more than three times length of coxa 1, coxa 3 with small dorsal swelling and many short ventral spines, tibia 2 longest, femur marginally longer than tibia 1, widest distally, gently bowed upwards, tarsus with two strong ventrodistal spines of similar size, propodal heel low, merging into sole, five primary spines, linear, increasing in height distally, followed by two, lesser side-by-side spines, sole almost straight, about eleven sole spines accompanied by many small lateral spines, claw reaching to base of heel when closed, outer margin of claw only slightly swollen than inner margin. Gonopores ventrodistal, legs 3 and 4.

Measurements of holotype (mm). Trunk length (frontal margin of cephalic segment to tip of fourth lateral processes), 3.12; width across second lateral processes, 1.43; proboscis length (ventral), 1.02; greatest diameter proboscis, 0.22; scape length; 0.96; anal tubercle length, 0.16. Oviger (segs 2–10): seg 2. 0.34; seg. 3, 0.22; seg. 4, 1.02; seg. 5, 1.18; seg. 6, 0.26; seg. 7, 0.32; seg. 8, 0.28; seg. 9, 0.24; seg. 10, 0.22; claw, 0.12. Leg 3: coxa 1, 0.36; coxa 2, 1.16; coxa 3, 0.47; femur, 2.49; tibia 1, 2.43; tibia 2, 3.10; tarsus, 0.14; propodus, 0.69; claw, 0.55.

Etymology. Named after the type locality, Nuyts Archipelago, South Australia.

Remarks. The remains of egg bracelets are still attached to the ovigers. This specimen can best be compared with three other very similar species; P. inflata , P. karenae and P. gracilis . These species share an inclined anal tubercle, chela fingers that narrow conspicuously towards the pointed tips and legs with a roughened surface due the many tiny spines being placed on small papillae or sockets, and a weakly defined propodal heel. Whilst these species appear to share an acute conical pre-ocular surface, the shape of the pre-ocular surface of P. gracilis is rather ambiguous. Arango and Brenneis (2013) described the adult male P. gracilis holotype with a raised mid-dorsal mound and a fine longitudinal line limited to the anterior margin, but in the same paper (Table 3.) the authors state that pre-ocular mid-dorsal mound is absent. Subsequently, Brenneis et al. (2020) state that P. gracilis shares an acute pre-ocular mid-dorsal mound with P. karenae . Both the P. karenae holotype and the specimen discussed in the 2020 paper were sub-adult, Figure 11. Pallenella nuyts sp. nov., male, holotype (SAMA E9446). a, b trunk, dorsal and lateral views: c anterior view; d, right chela; e, left oviger; f. strigilis segments 7–10; g, leg 3; h, propodus.

raising the possibility that development of the pre-ocular mound is age-related. For this analysis, the tip of the pre-ocular mid-dorsal mound in P. gracilis is regarded as being acute and the longitudinal cuticular line is only seen in anterior view. The absence of an extended longitudinal division line on the pre-ocular surface of the adult P. gracilis distinguishes that species, inter alia, from P. inflata and P. karenae . With a leg span of about 23mm this specimen is much smaller than P. gracilis (leg span about 30mm) but larger than either P. inflata or P. karenae which have leg spans of 16–17 mm. Pallenella nuyts is the only species amongst this group where the cutting edges of the chela fingers are conspicuously uneven.

Plate 13. Pallenella nuyts sp. nov. male, holotype ( SAMA E9446 ): a–c, trunk, dorsal, lateral and anterior views; d, leg 3; e, propodus; f. right chela .