Neastacilla monoseta (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 : 396-401

Neastacilla monoseta (Guiler)

Figures 18–20

Astacilla monoseta Guiler, 1949: 47–49 , figs 1, 2.— Guiler, 1952: 24.— Monod, 1970: 1139–1140.

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

Material examined. Australia: Vic. Western Port , 38º21.48’S, 145º13.85’E, 15 m, 30 Mar 1965, NMV J1022 (1 female, 10 mm); 38º22.0’S, 145º32.0’E, NMV J1027 (1 female, 15.5 mm; 7 manca 1 individuals), NMV J1028 (1 female, 15 mm); 38º20.67’S, 145º14.74’E, 9 m, 4 Mar 1965, NMV J1018 (immature male, 8 mm); 38º21.0’S, 145º14.0’E, 8 m, 12 Oct 1964, NMV J1017 (1 male, 15 mm; 1 immature male 9 mm); 38º21.39’S, 145º14.03’E, 16 m, 25 Mar 1965, NMV J1023 (1 male, 15.5 mm); 38º21.17’S, 145º14.0’E, 18 m, 29 Mar 1965, NMV J1024 (immature female, 11 mm). Portsea, 38º19.0’S, 144º43.0’E, NMV J1029 (1 female, 17 mm). Bass Strait, 39º01.0’S, 143º22.1’E, 84 m, 31 Jan 1981, NMV J40641 (1 male, 8.5 mm). Eastern Bass Strait, 38º18.0’S, 147º37.0’E, 55 m, 31 Jul 1983, NMV J8818 (immature male, 8 mm). Bennison Channel, 38º49.0’S, 146º23.0’E, 6 m, 23 Nov 1983, NMV J12579 (manca 2, 6.5 mm). Tas. Central Bass Strait, 39º32.8’S, 144º16.0’E, 18 m, 1 Nov 1980, NMV J8830 (1 female, 13 mm) .

Description of female. Head without dorsal elevations, anterolateral lobes rounded, rostral point present; lateral margin of head and pereonite 1 incised. Pereonite 1 anterolaterally extended. Pereonites 2 and 3 without dorsal elevations. Pereonite 4 about 11 times length of pereonite 3, wider than pereonites 2 and 3, anterolateral margins extended and angular. Pereonites 5–7 progressively shorter posteriorly, lateral margins not expanded. Pleon length greater than combined lengths of pereonites 5–7, with 2 sets of lateral wings, apex acute.

Eyes small and round. Antenna 1 reaching just past the distal edge of the second peduncular article of antenna 2; aesthetascs present distally and laterally on flagellum. Antenna 2 slender, more than half length of the body; flagellum of 2 articles ending with claw, row of scales along full length.

Maxilla 1 mesial lobe with 3 terminal setae; outer lobe with 10 robust setae. Maxilla 2 mesial lobe with 20 setae; middle lobe with 3 setae; lateral lobe with 3 setae. Maxillipedal endite with 12 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 setal rows; article 5 with mesial and distal setae.

Pereopod 1 propodus and carpus similar length; dactylus almost twice as long as wide, without unguis. Pereopods 2–4 slender, with dactylus. Pereopods 5–7 dactylus not denticulate, posteriorly; unguis and secondary unguis present; secondary unguis less than half length of primary unguis. Uropod exopod with 2 setae distally. Oostegite 4 with suture at midlength.

11–17 mm.

Male. Pereonites, mouthparts, pereopods as for female.

Pleopod 1 exopod with lateral notch and 2 plumose setae of unequal lengths. Pleopod 2 with appendix masculina with ridge on posterior face, apex simple, curved, not extending past the endopod. Penial plate widened proximally, apex simple.

8–15.5 mm

Distribution. Australia: Victoria, Tasmania; subtidal to 84 m depth.

Discussion. Guiler (1949) called the species ‘ monoseta ’ because he found only one seta on the uropod exopod. This has subsequently been found to have been erroneous and every specimen examined for this redescription had two setae on the uropodal exopod. The best distinguishing characteristic for this species is its possession of an elongate distally acute pleotelson that flares out laterally into two acute wings.

Figures

Figure 18. Neastacilla monoseta (Guiler, 1949), female (NMV J1022): A, lateral view; B, dorsal view; C, ventral view with oostegites. Male (NMV J40641): D, ventral view; E, dorsal view. Scale: a (A, B, D, E) = 1.0 mm; b (C) = 1.0 mm.

Figure 19. Neastacilla monoseta (Guiler, 1949), female (NMV J1022): A1, A2, P1, P3, P5, U. Male (NMV J40641): PL1, PL2, Pe. Scales: a (A1) = 0.5 mm; b (A2) = 1.0 mm; c (P1, P2) = 1.0 mm; d (P5) = 0.5 mm; e (PL1, PL2, Pe, U) = 0.5 mm.

Figure 20. Neastacilla soelae sp. nov., female holotype (NMV J16652): A, lateral view; B, dorsal view; C, ventral view with oostegites; A1, A2, left MXP, MX1, MX2, MD. Scale: a (A, C) = 1.0 mm; b (B) = 1.0 mm; c (A2) = 0.5 mm; d (A1) = 1.0 mm; e (MXP, MX1, MX2, MD) = 0.5 mm.