Neastacilla tharnardi, 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 : 405-408

Neastacilla tharnardi sp. nov.

Figures 25–27

Material examined. Holotype. Australia: Vic., Portland , Saxon Reef, 38º18.5’S, 141º38.5’E, 11 m, R. Wilson, 5 Mar 1992, NMV J24200 (1 female, 5 mm).

Paratypes. Australia: SA. Tiparra Bay , Tiparra Reef, 34º04.0’S, 137º23.0’E, 10 m, G.C.B. Poore and H.M. Lew Ton, 15 Mar 1985 , NMV J16575 (1 male, 5 mm). Investigator Group , 33º43.0’S, 134º36.6’E, 20 m, K. Brandon and G.C.B. Poore, 21 Apr 1985 , NMV J47326 (manca-2, 3 mm) .

Description of female. Head with 2 dorsal elevations (each with 3 apices) between the eyes, anterolateral lobes angular with small tubercles, small rostral point present; lateral margin of head and pereonite 1 incised. Pereonite 1 with dorsal elevation with 3 apices; with large, laterally curved anterolateral expansion. Pereonite 2 with dorsal elevation with single apex, with narrow lateral extensions. Pereonite 3 with dorsal elevation with 3 apices, with narrow lateral extensions. Pereonite 4 about 4 times as long as pereonite 3, with 4 anterior dorsal elevations, 2 dorsal elevations with many apices at midlength and 2 small dorsal elevations posteriorly, with anterolateral margins extended. Pereonites 5–7 progressively smaller, with small posterior dorsolateral elevations. Pleon longer than combined lengths of pereonites 5–7, with lateral wings, apex acute.

Eyes small and round. Antenna 1 reaching to the end of the third peduncular article of antenna 2; aesthetascs present laterally on flagellum. Antenna 2 slender, more than half as long as body; flagellum of two articles and claw, second article very small, with a row of scales along full length.

Maxilla 1 mesial lobe with 3 terminal setae; lateral lobe with 10 distal robust setae. Maxilla 2 mesial lobe with 14 plumose setae, middle lobe with 4 setae, lateral lobe with 3 setae. Maxillipedal endite with 14 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 mesial and distal setae.

Pereopod 1 propodus as long as carpus; dactylus slightly longer than wide, without unguis. Pereopods 2 and 3 with small dactylus. Pereopod 4 without dactylus. Pereopods 2–4 slightly dorsoventrally flattened, with tuberculate lateral elevations at proximal edges of the merus and carpus. Pereopods 5–7 dactylus not denticulate, with primary and secondary unguis; secondary unguis half length of primary unguis. Uropodal exopod with 2 setae of subequal length. Oostegite 4 without a suture, with ventrally projecting elevation posterior to insertion of pereopod 4.

5 mm.

Male. With less ornamentation than female. Head with 2 dorsal elevations (each with 2 apices) between eyes, anterolateral margins angular with small tubercles. Pereonite 1 with dorsal elevation with a single apex. Pereonite 2 without dorsal elevations, with lateral extensions. Pereonite 3 with dorsal tubercle with single apex, with lateral extensions. Pereonite 4 about 7 times as long as pereonite 3, constricted for the first quarter length; with 2 anterior dorsal elevations at midlength. Pereonites 5–7 progressively smaller, with small posterior dorsolateral elevations. Pleon longer than combined lengths of pereonites 5–7, with lateral wings, apex acute.

Antennae, mouthparts, pereopods and uropods as for female.

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

5 mm.

Distribution. Australia: Victoria, South Australia; subtidal to 20 m depth.

Etymology. “Tharnardi ” is an Australian Aboriginal word in the Yindjibarndi language from north-western Australia. It means “the sea”.

Remarks. This species of Neastacilla superficially most resembles species of Parastacilla Hale, 1946 ( King, 2000). The lateral extension of the head and pereonite 1 as well as the morphology of the anterior pereonites are very similar and no other Neastacilla species. However, in N. tharnardi pereopods 2 and 3 possess dactyli with claws, antenna 2 is elongate and there are no dorsolateral wings on the pleotelson.

Figures

Figure 25. Neastacilla tharnardi sp. nov., female holotype (NMV J24200): A, lateral view; B, dorsal view. Male (NMV J16575): C, ventral view; D, dorsal view. Scale = 1.0 mm.

Figure 26. Neastacilla tharnardi sp. nov., female holotype (NMV J24200): A1, A2, left MXP, MX1, MX2, MD; P1, P3, P4. Male (NMV J16575): A1. Scales: a (A1, A1, A2) = 0.5 mm; b (MXP, MX1, MX2, MD) = 0.2 mm; c (P1, P3, P4) = 0.5 mm.

Figure 27. Neastacilla tharnardi sp. nov., male (NMV J16575): PL1, PL2, Pe. Female holotype (NMV J24200): U; A, ventral view with oostegites. Scales: a (U) = 0.5 mm; b (P5) = 0.5 mm; c (A) = 1.0 mm; d (PL1, PL2, Pe) = 0.5 mm