Neastacilla inaequispinosa (Guiler)

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 : 384

Neastacilla inaequispinosa (Guiler)

Figures 7–8

Astacilla inaequispinos a Guiler, 1949: 49–53, figs 3, 4.— Guiler, 1952: 24.— Monod, 1970: 1139.

Astacilla unicornis Guiler, 1949: 53–55 , fig. 5.— Guiler, 1952: 24.— Monod, 1970: 1139–1140.

Astacilla derwenti Guiler, 1949: 56–57 , fig. 6.— Guiler, 1952: 24.— Monod, 1970: 1139–1140.

Astacilla oculata Guiler, 1949: 59–61 , fig. 7.— Guiler, 1952: 24.— Monod, 1970: 1139–1140.

Neastacilla inaequispinosa .— Poore et al., 2002: 259.

Material examined. Syntypes of Astacilla inaequispinosa Guiler, 1949 . Tas., N end of D´Entrecasteaux Channel, TMG76a (male), TMG76b (1 specimen).

Holotype of Astacilla derwenti Guiler, 1949 . Tas., N end of D´Entrecasteaux Channel, TM (not registered).

Holotype of Astacilla oculata Guiler, 1949 . Tas., N end of D´Entrecasteaux Channel, TM (not registered).

Holotype of Astacilla unicornis Guiler, 1949 . Tas., N end of D´Entrecasteaux Channel, TM (not registered).

Australia: Vic. Port Phillip Bay , 38º17.6’S, 144º42.3’E, 17 m, 4 Mar 1991, NMV J39217 (1 female, 6.4 mm), NMV J40691 (male, 8 mm) NMV J40695 (1 male, 6 mm). Western Bass Strait , 39º26.3’S, 143º06.8’E, 115 m, 21 Nov 1981, NMV J8843 (1 female, 7.0 mm; 2 males, 7 mm); 39º21.0’S, 143º06.0’E, 101 m, 10 Oct 1980, NMV J8844 (1 female, 6.5 mm); 39º06.0’S, 143º21.0’E, 59 m, 8 Oct 1980, NMV J8837 (1 immature male, 5.5 mm); 39º20.0’S, 143º34.0’E, 95 m, 10 Oct 1980, NMV J8842 (1 male, 10 mm). Western Port, 38º26.48’S, 145º13.03’E, 23 m, 25 Nov 1973, NMV J1014 (1 female, 10.5 mm; 1 immature male, 8 mm); 38º21.39’S, 145º14.03’E, 16 m, 25 Mar 1965, NMV J1011 (1 male, 8.5 mm; 1 immature male, 7 mm). 9.5 km SW of Port Albert, 38º44.0’S, 146º37.0’E, 9 m, 22 Nov 1983, NMV J12580 (1 female, 10.5 mm). Tas. Central Bass Strait, 40º31.1’S, 145º04.0’E, 29 m, 3 Nov 1980, NMV J8841 (2 females, 10–11 mm; 1 immature male, 8 mm) .

Description of female. Head with a dorsal elevation between the eyes; anterolateral margins angular; rostral point present; lateral margin of head and pereonite 1 not incised. Pereonite 1 with small dorsal elevation. Pereonites 2 and 3 progressively wider, with small dorsal elevations, with small anterolateral extensions present. Pereonite 4 about 6 times as long as pereonite 3; with a dorsal elevation at third length and an elevation on the posterior dorsal margin, anterior anterolateral margins rounded and extended, widest anteriorly. Pereonites 5–7 progressively shorter posteriorly, without dorsal elevations. Pleon length greater than combined lengths of pereonites 5–7; without dorsal elevations, with small lateral wings, tapered to a narrow rounded apex.

Eyes large and round. Antenna 1 reaching to the end of the 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 with claw, with 2 rows of scales along full length.

Maxilla 1 mesial lobe with 3 terminal setae; lateral lobe with 12 distal robust setae. Maxilla 2 mesial lobe with 20 plumose setae, middle lobe with 4 setae, lateral lobe with 3 setae. Maxillipedal endite with 8 mesial setae; 1 coupling hook; 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 as long as carpus; dactylus slightly longer than wide, without unguis. Pereopods 2–4 with small dactylus. Pereopods 5–7 dactylus not denticulate, with unguis and secondary unguis; secondary unguis half length of primary unguis. Uropodal exopod with 2 setae of unequal length. Oostegite 4 with sutured small posterior lobe.

6.5–11 mm.

Male. Head and pereonite 1 similar to female. Pereonites 2 and 3 without dorsal elevations. Pereonite 4 about 11 times as long as pereonite 3, constricted for the first quarter length, with a posterodorsal curved elevation. Pereonites 5–7 progressively shorter posteriorly, without dorsal elevations. Pleon length greater than combined lengths of pereonite 5–7, with a pair of small dorsal elevations, with lateral wings, tapering to a narrow rounded apex.

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, with tufts of fine setae at three-quarters length, curved, extending quarter length past endopod, apex simple. Penial plate proximally widened, straight, apex simple.

6.0– 10.5 mm.

Distribution. Australia: Victoria, Tasmania; subtidal to 115 m depth.

Remarks. This species was briefly described by Guiler (1949) along with three others from the same locality that are synonymous. The similarity between Guiler’s specimens, two of A. inaequispinosa and one of each of the others, was first correctly noted by Lew Ton (unpublished) who attributed the alleged specific differences to uneven mounting and illustrations of the material, and incorrect differentiation of males, females and juveniles. The large dorsal elevation between the eyes and the lack of an incision in the groove between the head and pereonite 1 most easily distinguishes N. inaequispinosa from other species of Neastacilla . Also, the shape of the pleotelson, the dorsal elevations on pereonites 1–4 of the female and the posterior dorsal elevation on pereonite 4 of both males and females are key characteristics.

Figures

Figure 7. Neastacilla inaequispinosa (Guiler, 1949), female (NMV J39217): A, lateral view; B dorsal view; C, ventral view with oostegites; A1, A2. Male (NMV J40691): D, lateral view; E, ventral view. Scales: a (A, B) = 1 mm; b (C) = 1.0 mm; c (A2) = 1.0 mm; d (A1) = 0.5 mm.

Figure 8. Neastacilla inaequispinosa (Guiler, 1949), female (NMV J39217): P1, P3, P5, U. Male (NMV J40691): PL1, PL2, Pe. Scales: a (P1, P3) = 0.5 mm; b (PL1, PL2, Pe) = 0.5 mm; c (U) = 0.5 mm.