Neastacilla yuriel, King, 2003

King, R. A., 2003, Neastacilla Tattersall, 1921 redefined, with eight new species from Australia (Crustacea: Isopoda: Arcturidae), Memoirs of Museum Victoria 60 (2), pp. 371-416 : 409-414

Neastacilla yuriel sp. nov.

Figures 30–32

Material examined. Holotype. Australia: SA, Flinders I., Hotspot Reef , 33º40.5'S, 134º22.0'E, 17 m, G.C.B. Poore, SCUBA, 19 Apr 1985, NMV J16553 (1 female, 3.5 mm).

Paratypes. Australia: SA, collected with holotype , NMV J40678 (1 female, 3 mm) , NMV J40693 (1 male, 3.5 mm) , NMV J40694 (1 male, 4 mm) , NMV J16554 (4 females, 3.5–4 mm) , NMV J16549 (1 male, 3.5 mm). Flinders I., Hotspot Reef, 33º40.8'S, 134º22.5'E, 21 m, 20 Apr 1985 , NMV J16547 (manca 2, 3 mm). Topgallant I., 33º43.0'S, 134º36.6'E, 25 m, 21 Apr 1985 , NMV J16546 (1 male, 3 mm); 33º43.0'S, 134º36.6'E, 12 m, 21 Apr 1985 , NMV J16548 (2 females, 3–3.5 mm; 2 males, 4 mm; manca 2, 2.5 mm). Vic. Central Bass Strait , 38º33.4'S, 144º54.9'E, 55 m, 12 Nov 1981 , NMV J8853 (1 male, 4 mm). Tas. Spiky Bridge coastal reserve, 42º08.0'S, 148º08.0'E, 4 m, 21 Mar 1988 , NMV J40648 (1 female, 3.5 mm; 2 manca 2, 2.5 mm). Bicheno, 41º53.0'S, 147º18.0'E, 7 m, 23 Mar 1988 , NMV J40645 (1 female, 4 mm). WA. Breaksea I., 35º03.9'S, 118º02.9'E, 15 m, 7 Apr 1984 , NMV J16632 (2 females, 3 mm; 1 male, 3.5 mm). King George Sound, 35º00.7'S, 118º10.1'E, 27 m, 15 Apr 1984 , NMV J16630 (1 female, 3 mm) .

Description of female. Head with dorsal elevations slightly posterior to the eyes, anterolateral margins angular, small rostral point present; lateral margin of head and pereonite 1 not incised. Pereonite 1 with 2 indistinct dorsolateral elevations. Pereonites 2 and 3 with indistinct dorsal elevations, with lateral margins extended. Pereonite 4 about 7 times as long as pereonite 3, with large dorsal elevation at midlength, anterolateral margins rounded and extended. Pereonites 5–7 progressively smaller, without distinct elevations. Pleon longer than combined lengths of pereonites 5–7, with 2 sets of lateral wings, without dorsal elevations, tapering to subacute apex.

Antenna 1 reaching to end of third peduncular article of antenna 2; aesthetascs present laterally and distally on flagellum. Antenna 2 slender, more than half as long as body; flagellum of 3 articles and claw; with row of scales along full length.

Maxilla 1 inner lobe with 3 terminal setae; outer lobe with 10 distal robust setae. Maxilla 2 inner lobe with 18 plumose setae, middle lobe with three setae, outer lobe with three setae. Maxillipedal endite with 14 mesial setae; one coupling hook; palp article 2 with mesial setal rows, article 3 with mesial and lateral setal rows, article 4 with mesial setae, article 5 with mesial and distal setae.

Pereopod 1 propodus as long as carpus; dactylus slightly longer than wide, without unguis. Pereopods 2–4 with small dactylus. Pereopods 5–7 progressively smaller, dactylus denticulate; with primary and secondary unguis; secondary unguis half length of primary unguis. Uropodal exopod with 2 setae of subequal length. Oostegite 4 with sutured small posterior lobe.

3–4 mm.

Male. With less ornamentation than female. Head with indistinct dorsal elevation between eyes, anterolateral margins angular, very small rostral point present; lateral margin of head and pereonite 1 not incised. Pereonite 1 with indistinct dorsal and dorsolateral elevations. Pereonite 2 and 3 with indistinct dorsal elevations, lateral margins not extended. Pereonite 4 about 6 times as long as pereonite 3; constricted in dorsal view for first fifth of length, with 2 small posterior dorsal elevations at midlength. Pereonites 5–7 progressively smaller, without dorsal elevations. Pereonites 6 and 7 without dorsal elevations. Pleon longer than combined lengths of pereonites 5–7, with 2 sets of lateral wings, with small dorsal elevations, tapering to a subacute apex.

Antennae, mouthparts, pereopods and uropods as for female.

Pleopod 1 exopod with lateral notch and 2 plumose setae of equal length. Pleopod 2 appendix masculina with ridge on posterior face; curved; extending third length past endopod; apex simple. Penial plate unknown.

Distribution. Australia: Victoria, Tasmania, South Australia, Western Australia; subtidal to 55 m depth.

Etymology. "Yuriel " is an Australian Aboriginal word for "coastal bay" in reference to the area specimens were first taken from.

Remarks. This species is the smallest of the Australian arcturids (2.5–4 mm) making the species instantly recognisable. The ornamentation of females has been seen to differ slightly within populations. In a few specimens the dorsal elevation on pereonite 4 possessed two apices and the small elevations on the head and pereonites 1–4 were more enlarged.

Figures

Figure 30. Neastacilla yuriel sp. nov., female holotype (NMV J16553): A, lateral view; B, dorsal view. Male (NMV J40693): C, lateral view; D, dorsal view. Scale = 1.0 mm.

Figure 31. Neastacilla yuriel sp. nov., female holotype (NMV J16553): A1, A2, left MXP, MX1, MX2, MD; P1, P3. Scales: a (A2) = 0.5 mm; b (A2) = 0.5 mm; c (MXP, MX1, MX2, MD) = 0.5 mm; d (P1, P3) = 0.5 mm.

Figure 32. Neastacilla yuriel sp. nov., male (NMV J40693): PL1, PL2, pleopod 2. Female holotype (NMV J16553): U; A, ventral view with oostegites; P5. Scales: a (A) = 1.0 mm; b (P5) = 0.5 mm; c (PL1, PL2, Pe, U) = 0.2 mm.