Neastacilla levis (Thomson and Anderton)

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 : 390-395

Neastacilla levis (Thomson and Anderton)

Figures 14–15

Astacilla levis Thomson and Anderton, 1921: 114–115 , text-fig.—

Hurley, 1957: 13–15, figs 50–66.— Hurley, 1961: 264, 281.

Material examined. New Zealand, off the W coast of South Island , 42º25.0’S, 171º06.0’E, 35 m, 5 Mar 1982, NMV J4736 (1 female, 9.5), NMV J40692 (1 female, 10 mm), NMV J40675 (1 male, 9.5 mm) .

Description of female. Head without dorsal elevations, anterolateral lobes rounded, rostral point present; lateral margin of head and pereonite 1 incised. Pereonite 1 not extended anterolaterally, with small dorsolateral tuberculate elevations. Pereonite 2 and 3 progressively wider, without dorsal elevations, small lateral extensions present. Pereonite 4 about 7 times as long as pereonite 3; dorsally elevated at first third length, anterolateral margins extended and rounded. Pereonites 5–7 progressively smaller, without dorsal elevations. Pleon length greater than combined lengths of pereonites 5–7, without dorsal elevations, with small lateral wings, apex truncated and notched.

Eyes large and triangular. Antenna 1 extending to the distal edge of second peduncular article of antenna 2; aesthetascs present distally and laterally on flagellum. Antenna 2 slender, more than half as long as body; flagellum of 3 articles ending in a claw, 2 rows of scales along full length.

Maxilla 1 mesial lobe with 3 terminal setae; lateral lobe with 11 distal robust setae. Maxilla 2 mesial lobe with 14 plumose setae, middle lobe with 5 setae, lateral lobe with 4 setae. Maxillipedal endite with three coupling hooks present; palp article 2 with mesial setal rows, articles 3 and 4 with mesial and lateral setal rows, article 5 with mesial and distal setae.

Pereopod 1 propodus and carpus similar length; dactylus longer than wide, without unguis. Pereopods 2–4 with dactylus. Pereopods 5–7 dactylus with 3 denticulations (see Remarks) and setae, with unguis and secondary unguis; secondary unguis about third length of primary unguis. Uropodal exopod with 3 setae of equal length. Oostegite 4 with sutured small posterior lobe.

10–12 mm.

Male. Head ornamentation similar to female. Pereonite 4 about 8 times as long as pereonite 3, without dorsal elevations, anterolateral margins not extended. Pereonites 5–7, Pleon similar to female.

Antennae, mouthparts, pereopods and uropods as for female.

Pleopod 1 exopod with lateral notch and 2 plumose lateral setae of unequal lengths. Pleopod 2 appendix masculina with ridge on posterior face, curved, extending third length past the endopod, apex simple. Penial plate simple and straight.

10–13 mm.

Distribution. New Zealand; subtidal.

Remarks. First described by Thomson and Anderton (1921) as Astacilla levis , only a lateral view of the single female specimen taken off Otago Heads was drawn. The description was brief and relatively uninformative. Hurley (1957) provided further description the species from two males and one female taken from Cook Strait, figuring only the male and not describing the male pleopod 1, female oostegites, maxilla 1, maxilla 2 or mandible. The large triangular eye, shape of the head and pereonite 1 and the truncate, notched pleotelson immediately distinguish this species. Hurley (1957) described the denticulation of pereopods 5–7 as “4–5 small corrugations;” three denticulations were found in all specimens examined for this study so this character must be variable.

Figures

Figure 14. Neastacilla levis (Thomson and Anderson, 1921), female (NMV J4736): A, lateral view; B, dorsal view; E, ventral view with oostegites. Male (NMV J40675): C, ventral view; D, dorsal view. Scale: a (A–D) = 1.0 mm; b (E) = 1.0 mm.

Figure 15. Neastacilla levis (Thomson and Anderson, 1921), female (NMV J4736): A1, A2, P1, P3, P5, U. Male (NMV J40675): PL1, PL2, Pe. Scales: a (A2) = 0.5 mm; b (A1) = 0.5 mm; c (P1, P3) = 0.5 mm; d (PL1, PL2) = 0.5 mm; e (P5) = 0.5 mm; f (U) = 0.5 mm.