Neastacilla tarni, 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 : 401-404

Neastacilla tarni sp. nov.

Figures 22–24

Material examined. Holotype. Australia: SA, Topgallant I., Investigator Group , 33º43.0’S, 134º36.6’E, 15 m ,, K. Brandon and G.C.B. Poore, 21 Apr 1985, NMV J16579 (1 female, 6.0 mm).

Paratypes. Australia: SA. type locality , NMV J40676 (1 male, 7.0 mm) ; NMV J40677 (6 females, 4.5–5.0 mm; 7 males, 5.0– 6.5 mm; 3 manca 2, 3.0– 3.5 mm; 2 manca 1, 2.5 mm) .

Description of female. Head with dorsal elevation (with 2 apices) posterior to eyes, anterolateral lobes angular, rostral point absent; lateral margin of head and pereonite 1 not incised. Pereonite 1 with posterior dorsal elevation. Pereonites 2 and 3 with dorsal and dorsolateral elevations, lateral margins extended. Pereonite 4 about 6 times as long as pereonite 3; with 2 dorsal elevations at midlength, 2 dorsolateral elevations posterior to them, a posterior dorsal elevation with 2 apices and 2 small dorsal elevations posteriorly; anterolateral margins extended and rounded. Pereonites 5–7 progressively shorter posteriorly, with small posterior dorsolateral and lateral elevations. Pleon longer than combined lengths of pereonites 5–7, with lateral wings, apex blunt.

Eyes small and subtriangular. Antenna 1 reaching to the end of the second peduncular article of antenna 2; aesthetascs present laterally on flagellum. Antenna 2 slender, more than half as long as body; flagellum of 3 articles ending in claw, 2 rows of scales along full length.

Maxilla 1 mesial lobe with 3 terminal setae; lateral lobe with 9 distal robust setae. Maxilla 2 mesial lobe with 13 plumose setae, middle lobe with 4 setae, lateral lobe with 3 setae. Maxillipedal endite with 10 mesial setae; 1 coupling hook; palp article 2 with mesial setal rows, article 3 with mesial and lateral setal rows, article 4 with mesial and lateral setae, article 5 with 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 dactylus denticulate, with unguis 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 and thickened distolateral edges. A pair of fleshy pads are visible on the ventral surface of pereonite 5 that may be vestigial fifth oostegites.

4.5–6 mm.

Male. With less ornamentation than female. Head with 1 dorsal elevation between eyes. Pereonite 1 without dorsal elevations. Pereonites 2 and 3 without dorsal elevations. Pereonite 4 about 8 times as long as pereonite 3, constricted for the first quarter length, with 2 small elevations at quarter length and a posterior elevation. Pereonites 5–7 progressively shorter posteriorly, without dorsal elevations. Pleon longer than combined lengths of pereonites 5–7, with lateral wings, apex blunt.

Antennae, mouthparts, pereopods and uropods as for female.

Pleopod 1 exopod with lateral notch and 2 plumose lateral setae of equal length. Pleopod 2 appendix masculina with ridge on posterior face; curved; extending quarter length past the distal edge of the endopod; apex simple. Penial plate widened proximally, apex simple.

5–7 mm.

Distribution. Australia: South Australia; subtidal.

Etymology. “Tarni ” is an Australian Aboriginal name from the Kaurna language group in South Australia. It means “the sea”.

Remarks. The female of this species resembles Neastacilla tuberculata ( Thomson, 1879) from New Zealand. However the arrangement of the dorsal tubercles on pereonite 4 and the shape of the pleotelson distinguish the two species; in N. tarni the dorsal tubercles are medially and posteriorly placed on pereonite 4 and the pleotelson is narrow and sculpted with a blunt apex, whereas in N. tuberculata the tubercles are in the anterior first half of pereonite 4 and the pleotelson is wide and tapered to an acute apex.

Figures

Figure 22. Neastacilla tarni sp. nov., female holotype (NMV J16579): A, lateral view; B, dorsal view; D, ventral view with oostegites. Male (NMV J40676): C, lateral view; E, dorsal view. Scale = 1.0 mm.

Figure 23. Neastacilla tarni sp. nov., female holotype (NMV J16579): A1, A2, left MXP, MX1, MX2, MD; P1, P3. Scales: a (A1) = 0.25 mm; b (A2) = 0.5 mm; c (MXP, MX1, MX2, MD) = 0.25 mm; d (P1, P3) = 0.5 mm.

Figure 24. Neastacilla tarni sp. nov., female holotype (NMV J16579): P5, U. Male (NMV J40676): PL1, PL2, Pe. Scales: a (PL1, Pl2, Pe) = 0.2 mm; b (P5) = 0.5 mm.