Agnathia aria, Staples, 2021

Staples, D. A., 2021, Diagnosis ofthe new genusAgnathia (Pycnogonida, Callipallenidae) and description of two new species from southern Australia, Zootaxa 4950 (3), pp. 487-500 : 489-493

Agnathia aria sp. nov.

Figure 1 A–L ; Plate 1 A–H

Material examined. Holotype, gravid female ( NMV J75180 ), Victoria. West Head , Flinders, sieved from algae at the outer edge of the reef at low tide, J. Chuk, 4 January 2010.

Paratypes. Victoria. One male ( NMV J75181 ), Port Phillip, Point Lonsdale , edge of rock platform, R. Wilson & G.C.B Poore, 6 March 1991 . One larvigerous male ( NMV J75182 ), Gabo I. Harbour, 5m, on red alga. VNPMS stn 69-2.1, 25 March 1996 . One larvigerous male ( NMV J75183 ), two miles south of Marengo on fine red algae, LWM, 19 March 1973 . W.F. Seed. One male, ovigerous ( NMV J75184 ), Aireys Inlet, W.F. Seed , 28 January 1968 . One male ( NMV J75185 ), Bunurong, stn Bun 2.5a, T. O’Hara, 1 April 1997 . One male ( NMV J73291 ), Point Lonsdale kelp beds, 20 m, amongst sorting’s, Port Phillip , D.A. Staples, January 1982 .

Other material. Victoria. One juvenile ( NMV J62428 ), Beware Reef (37º 49.336’S, 148º 47.393’E), 5 to 6m, airlift, T. O’Hara, 15 April 1998 . One juvenile ( NMV J62429 ), Portsea Ocean Beach, sieved from Amphibolis antarctica and brown algae at the edge of large rock pool at low tide, J. Chuk, 8 December 2009 .

Description. (In some cases images of male paratypes have been used to illustrate characters common to both sexes).

Female holotype. Trunk ( Fig. 1A , Plate 1B ) moderately elongate, gently arched, midline smooth, fully segmented in dorsal view, ventral and dorsal surface segments 1 to 3 lowly inflated distally, ventral segmentation line between segments three and four not evident ( Fig. 1D ; Plate 1C , male), lateral processes a little longer than basal width, processes 1, 2 and 3 separated by 60–70% of basal widths, processes 3 and 4 touching or almost touching ( Plate 1H , male), all lateral processes separated from trunk by faint suture line, suture line also straddling trunk behind ocular tubercle, spines on lateral processes inconspicuous, in order 1:2:2:1, those on legs 1 and 4 restricted to inner margins. Neck region of cephalon short, width at narrowest point wider than trunk width, strongly swollen lobes over bases of chelifore implants interspaced by low prominence, each lobe with few random spinules. Ocular tubercle height about two-thirds width at base, dorsal surface with two apical papillae, four eyes ( Plate 1F , male) pigmented.

Proboscis and chelifores directed downward ( Fig. 1B ), in some specimens not visible in dorsal view, basal part narrowing in mid-region, widest proximally, ventral surface vaguely uneven; distal part of proboscis tubiform, representing about 40% of total proboscis length, distally hirsute, setae simple, three petal-shaped lips, flared when open ( Fig. 1L ; Plate 1C, D , male).

Anal tubercle short, inflated, not reaching end of fourth lateral processes, anal slit gaping.

Chelifore scape reaching about level with the merging of the proximal inflated part and tapered distal part of proboscis ( Plate 1E, F , male), one strong dorsodistal and one stronger dorsolateral spine, deep ventral recess near base; chela anaxial, inner surface of palm with single, strong, slender spine originating near base of immovable finger ( Figs 1I, L ; Plate 1C, D male), palm and fingers approximately of equal length, fixed finger oval in cross section, tip rounded, outer-face with scattered, tiny, blunt, tooth-like projections, single, stout tooth on proximal margin ( Fig.1I ), moveable finger more slender, with short upturn at tip.

Oviger ( Fig. 1G ) ten-segmented, bases touching anterior margin of first lateral processes, segment 4 longest, with prominent swelling presumably site of gland, terminal claw about 1.5 times length segment 10, claw with five short teeth on distal inner margin ( Fig. 1H ), spine formula (segments 7–10) difficult to determine but probably 3:2:3:2, spines simple, strongly curved, segments 8 and 9 with tiny dorsodistal spine, segment 10 with multiple dorsodistal spines.

Leg surface irregular, spinous, ( Fig. 1E ) thickened cuticular line extends laterally from coxa 1 to base of tarsus; coxa 2 about 1.5 times length of coxa 3, with strong, slightly offset, dorsal spine-tipped tubercle at about one-third length and a single, similar strong tubercle on posterior lateral surface, coxae 2 and 3 with several short ventral spines; femur longest segment, two prominent spine-tipped ventral peaks, on irregular shape bases each with lesser spine-tipped lateral tubercles and few tiny spines, several spines line otherwise smooth dorsal surface; second tibia longer than first tibia and a little shorter than femur, both tibiae with three pairs of conical dorsolateral peaks, each with one or two apical spines and several much smaller lateral spines, third swelling on tibia 1 placed on distal margin, third swelling on tibia 2 sub-terminal; tarsus short, several ventral spines and single short dorsal spine; propodus gently curved, heel mostly with six spines but one leg with five spines and another with an additional two finer distal spines, distal three longest; sole spination variable between legs, up to twenty spines and many lateral spines, dorsal surface with two to six spines ( Fig. 1F ) all larger spines sit on a basal tubercle or socle, terminal claw strong, reaching to base of heel when folded, auxiliary claws absent. Gut caeca predominantly follow the irregular shape of the leg. Genital pores large, distoventral surface second coxae all legs.

Males (Plate, 1 C–H) slightly smaller but more spinous than the female holotype ( Plate 1C ). Scape with shallow ventral depression near base. Trunk and leg spines on robust basal tubercle or socle. Peaks and swellings on legs large, well defined ( Fig. 1K , Plate 1G ); coxa 2 proportionately longer and more slender than female, about twice length of coxa 3, single, large spine-tipped tubercle at about one-third length of dorsal surface, two (or three) similar protuberances on the distal posterior margin, three ventrodistal spines present; femur widening distally, dorsodistal margin with corona-like fringe of strong, pointed, spine-tipped projections ( Plate 1H ), ventral surface with two evenly-spaced swellings, peaks with a strong spinous tubercle and several lesser spines on swollen lateral margins, dorsal surface with mixture of strong and lesser spines along the margin, tarsus and propodal sole with dense field of fine spines, heel with six or seven robust spines. Oviger six-segmented ( Fig. 1J , Plate 1C ), segment 5 with welldefined distal apophysis, segment 6 reduced. Cement gland ducts not evident. Genital pore tiny, coxa 2 legs 3 and 4, located proximal to middle spine on ventrodistal surface.

Measurements of holotype (mm): Trunk length (frontal margin of cephalic segment to tip of 4 th lateral processes), 1.50; width (across 2 nd lateral processes), 0.90; cephalon length, 0.55; proboscis length (dorsal), 0.78; proboscis diameter, 0.25; third leg; coxa 1, 0.32, coxa 2, 0.48, coxa 3, 0.29; femur, 1.30; tibia 1, 0.98; tibia 2, 1.20; tarsus, 0.08; propodus, 0.56; claw, 0.31. Oviger, seg. 2, 0.14; seg. 3, 0.12; seg. 4, 0.24; seg. 5, 0.18; seg 6, 0.11; seg. 7, 0.16; seg. 8, 0.12; seg. 9, 0.12; seg. 10, 0.12; claw 0.18.

Etymology. Named for my granddaughter Aria Hope.

Distribution. Western, central (including Port Phillip) and eastern Victorian coastline. Depth low-water to 20 m.

Remarks. This species is readily distinguished from A. chuki sp. nov. by distinct characters: its smaller overall size, the chela palm bears a strong inner spine, the absence of separation between segments 3 and 4 and the lack of ventral segmentation between those segments, and the puzzling occurrence of six-segmented male ovigers. Sixsegmented ovigers are recorded in male Cheilopallene clavigera Stock, 1955 and C. nodulosa Hong & Kim, 1987 and in both of these species the fifth oviger is distally clavate or club-shaped rather than having a distinct apophysis. The only other example of similar oviger dimorphism appears to be in Pallenopsis spicata Hodgson, 1915 where the male has seven oviger segments and the female ten segments. The ovigers in all other species of Pallenopsis are ten-segmented in both sexes. The propodus of A. aria is more gently curved than that of A. chuki and the sole of A. aria has far fewer spines. There is general variability in spination between and within specimens. The number of propodal heel spines is most commonly six, but sometimes with seven spines. The development of the dorsal protuberances on tibia 2 show the most variation where, in extreme cases, they are low and rounded as opposed to being conical. In some specimens two spines are present on the fourth lateral processes as opposed to the more common single spine. There is considerable variation in overall size amongst ovigerous specimens suggesting perhaps, that moulting extends beyond reaching maturity.

The presence of eggs and protonymphon attached to oviger segment five confirms the viability of the species, in particular, their presence establishes that the absence of segments 7 to 10 does not adversely affect the male’s ability to successfully harvest and carry eggs ( Plate 1E, F ). Similarly, the body is free of epizoites and the absence of a male strigilis appears to have not effected the ability to maintain a body surface free of encrusting organisms.

Both Labrumoides and Agnathia share similar proboscis shapes and their hirsute brush-like lips suggesting a common feeding strategy. Staples (2020) speculated that a possible food source of Labrumoides may be epiphytes such as diatoms and foraminifera, but the abundant presence of undetermined cnidarians found in association with the holotype of A. aria , may indicate alternative food sources ( Plate 1A ).

Figures

FIGURE 1. Agnathia aria sp. nov., holotype, female. A, trunk, dorsal view; B, trunk lateral view; C, trunk anterior view; D, trunk ventral view; E, third leg; F, propodus; G, oviger; H, oviger claw; I. right chela, proximal view. Paratype, male (NMV J75181). J, oviger; K, leg 3. Paratype, male (NMV J75185). L, proboscis and chelae, lateral view.

PLATE 1. Agnathia aria sp. nov., holotype, female. A, in situ; B, on neutral background. Paratype male, (NMV 75185). C, trunk, ventral view; D, chelae and lips, ventral view. Paratype, male (NMV J75182). E, trunk anterior view; F, anterior view showing attached larvae; G, leg 3, tibia 2, spine broken off. Paratype, male (NMV J75181). H, trunk dorsal.