Dimorphostylis nordaustraliana, Gerken, 2014

Gerken, Sarah, 2014, Eleven New Species and a New Genus of Diastylidae (Crustacea: Cumacea) from Australia and One New Species from Canada, Records of the Australian Museum 66 (1), pp. 1-62 : 32-37

Dimorphostylis nordaustraliana n. sp.

Figs 20–23

Type material. Holotype preparatory female, AM P85775; paratype ovigerous female, dissected, AM P85776; paratype adult male, dissected, AM P85777; paratypes 1 adult male, 1 subadult male, AM P85778; 10°54'S 133°02'E, 6 m, J. K. Lowry, 13 Oct. 1982.

Other material examined. AM P84313, 11°34'16"S 129°50'14"E, 49 m, Geoscience Australia, 28 Aug. 2009 . AM P84761, 22°06'12"S 113°52'06"E, 38.7 m, Geoscience Australia, 16 Aug. 2008 . 11 adult males, 4 subadult males, 6 ovigerous females, 4 subadult females AM P85779; 2 ovigerous females, 4 subadult females, 15 subadult males, 8 juveniles, 16 mancae AM P85780; 10°54'S 133°02'E, 6 m, J. K. Lowry, 13 Oct. 1982 . 1 adult male, 1 subadult male, 2 ovigerous females, 4 subadult females, AM P85781, 10°54'S 133°02'E, 10 m, J. K. Lowry and G. C. B. Poore, 14 Oct. 1982 . 8 adult males, 3 subadult males, 2 mancae AM P85782; 2 ovigerous females, 1 subadult female , AM P85783; 11°00'S 132°49'E, 5 m, J. K. Lowry, 20 Oct. 1982 . 4 individuals, AM P85784, 20°29'46"S 116°47'29"E, 10 m, P.A Hutchings and L. Avery, 4 Aug. 2000 .

Diagnosis. Female and subadult male. Carapace with oblique lateral ridge, strongly serrate, continuing onto pseudorostral lobe, with narrow depression parallel to lateral portion of ridge. Telson shorter than pleonite 6, with distinct post-anal portion, without lateral setae. Adult male. Carapace without ridges. Pereonite 5-pleonite 4 with ventrolateral stout setae to entrain antennal flagellum. Antennule with brush of setae on peduncle article 3. Antennae extending past posterior border of telson. Pleopods small. Telson with distinct post-anal portion, 2 pairs of lateral setae, 2 terminal setae.

Description

Ovigerous and preparatory females. Holotype preparatory female, AM P85775, 3.2 mm; paratype ovigerous female, AM P85776, 2.9 mm. —Carapace with dentate ridge starting near posterior border, sweeping dorsally to a point, then sweeping ventrally onto pseudorostral lobe, not meeting anterior margin, with narrow depression parallel to longer part of ridge, antennal notch oblique, anteroventral corner of carapace with several teeth; pseudorostral lobes 0.5 × carapace length, with 2–3 separated teeth on dorsal midline, 2 teeth at tip of pseudorostral lobe; eye lobe 0.1 × carapace length, at least twice as broad as long, with lenses, distinct tooth at dorsal midline; carapace 2.3 × length of pereonites together ( Figs 20A–C ).

Paratype ovigerous female, AM P85776, 2.9 mm. — Antennule peduncle article 1 1.0 × articles 2 and 3 together, with 2 plumose setae and margin lined with fine hair-like setae; article 2 0.4 × article 1 length, with plumose seta; article 3 1.8 × article 2 length, with 2 simple and 1 pedunculate setae; main flagellum of 3 articles, with 2 aesthetascs and simple seta; accessory flagellum of 1 article, 0.5 × length of main flagellum, with 3 simple setae ( Fig. 20D ). —Antenna of 2 subequal articles; article 1 with pappose seta; article 2 with 3 pappose setae ( Fig. 20E ). —Mandible navicular, with 9–10 microserrate setae medially, lacinia mobilis with 3 cusps ( Fig. 20F ). —Maxillule with 2 endites; outer endite with double row of stout simple setae, margins lined with fine hair-like setae, with pappose seta; inner endite with 3 simple, 1 microserrate and 1 tricuspid setae, margins lined with fine hair-like setae; palp with 2 simple setae ( Fig. 20G ). —Maxilla with 3 endites; broad endite distal margin lined with simple setae and 4 pappose setae, medial margin with row of pedunculate setae and 2 pappose setae; medial narrow endite with 4 microserrate setae terminally; distal narrow endite with 5 microserrate setae terminally; both narrow endites relatively broad, barely reaching past distal margin of broad endite ( Fig. 20H ). —Maxilliped 1 basis produced as lobe with 3 simple, 6 pappose, 2 hook and 1 very stout simple setae; ischium absent; merus unarmed; carpus 2.2 × merus length, with field of simple setae and 6 beak setae medially, plumose seta laterally; propodus 0.5 × carpus length, with 2 pappose, 2 comb-like, and 3 plumose setae; dactylus 0.5 × propodus length, with 3 simple setae terminally ( Fig. 20I ). —Maxilliped 2 basis 0.4 × length of all other articles together, with 4 plumose setae distally; ischium 0.08 × basis length, unarmed; merus 8.0 × ischium length, with plumose seta laterally; carpus 1.6 × merus length, with 5 pappose setae medially, plumose seta laterally; propodus 0.8 × carpus length, with 3 pappose and 3 plumo-dentate setae medially, plumose seta laterally; dactylus 0.5 × propodus length, with 4 simple setae ( Fig. 20J ). —Maxilliped 3 basis 1.2 × length of all other articles together, with 8 pappose setae medially, distomedial corner produced as tooth, distolateral corner expanded, with 5 plumose setae, width of article double distally; ischium 0.1 × basis length, produced as 2 teeth medially; merus 0.8 × ischium length, with 2 pappose setae medially, plumose seta laterally; carpus 2.0 × merus length, with 4 plumose setae medially, plumose seta laterally; propodus 0.8 × carpus length, with 3 plumose setae medially, plumose seta laterally; dactylus 1.0 × propodus length, with 2 simple and 1 pappose setae, 2 simple setae terminally; exopod 0.6 × basis length, basal article unarmed, flagellum with plumo-annulate setae ( Fig. 21A ). —Pereopod 1 basis 0.5 × length of all other articles together, with 7 plumose setae; ischium 0.05 × basis length, with plumose seta; merus 4.3 × ischium length, with 1 simple and 2 plumose setae; carpus 3.0 × merus length, unarmed; propodus 1.4 × carpus length, with 6 simple setae; dactylus 0.3 × propodus length, with 4 simple and 6 simple setae terminally; exopod 0.7 × basis length, basal article unarmed, flagellum with plumoannulate setae ( Fig. 21B ). —Pereopod 2 basis expanded, 0.8 × length of all other articles together, with 1 simple and 4 plumose setae; ischium 0.03 × basis length, unarmed; merus 9.0 × ischium length, with plumose seta; carpus 1.7 × merus length, with 2 simple setae; propodus 0.5 × carpus length, with plumose seta; dactylus 1.9 × propodus length, with 3 simple setae and 4 simple setae terminally; exopod 1.3 × basis length, basal article with simple seta, flagellum with plumo-annulate setae ( Fig. 21C ). —Pereopod 3 basis 1.0 × length of all other articles together, with simple seta; ischium 0.08 × basis length, with simple seta; merus 5.7 × ischium length, with 5 simple and 2 annulate setae; carpus 0.5 × merus length, with 4 simple and 2 annulate setae; propodus 0.9 × carpus length, with annulate seta; dactylus 0.7 × propodus length, with 1 simple seta and simple seta terminally ( Fig. 21D ). —Pereopod 4 basis 0.9 × length of all other articles together, with 5 simple and 2 pedunculate setae; ischium 0.1 × basis length, with 2 simple setae; merus 2.8 × ischium length, with 3 simple setae; carpus 0.6 × merus length, with setae; article 2 0.3 × article 1 length, unarmed; article 3 2.0 × article 2 length, with 2 simple setae and brush of simple setae on margin; main flagellum of 5 articles, with 2 aesthetascs and 3 simple setae; accessory flagellum of 3 articles, 0.6 × main flagellum length, with simple seta terminally ( Figs 22D–E ). —Antenna extending past uropod rami; peduncle of 4 articles, article 1 with pappose seta; article 4 with ranks of setae, incompletely circling article; flagellum with long articles ( Figs 22B, F ). —Maxilliped 3 basis 1.1 × length of all other articles together, with 1 simple and 6 pappose setae medially, lateral corner with 5 plumose setae; ischium 0.1 × basis length, with pappose seta; merus 2.3 × ischium length, with pappose seta medially, plumose seta laterally; carpus 0.6 × merus length, with 3 pappose setae medially, plumose seta laterally; propodus 1.1 × carpus length, with 2 pappose setae medially, plumose seta laterally; dactylus 0.5 × propodus length, with 6 simple setae terminally; exopod 0.8 × basis length, basal article with plumose seta, flagellum with plumo- annulate setae ( Fig. 23A ). —Pereopod 1 basis 0.6 × length of all other articles together, with 5 plumose setae; ischium 0.1 × basis length, unarmed; merus 1.4 × ischium length, with simple seta; carpus 3.0 × merus length, with 3 simple setae; propodus 1.3 × carpus length, with 9 simple setae; dactylus 0.3 × propodus length, with 3 simple setae and 3 simple setae terminally; exopod 0.8 × basis length, not broadened, basal article unarmed, flagellum with plumo-annulate setae ( Fig. 23B ). —Pereopod 2 basis 1.2 × length of all other articles together, with 4 simple, 1 pappose and 2 pedunculate setae; ischium 0.04 × basis length, unarmed; merus 4.0 × ischium length, with pappose seta; carpus 2.0 × merus length, with 2 simple and 1 pappose setae; propodus 0.3 × carpus length, with 4 simple setae; dactylus 1.8 × propodus length, with 3 simple setae and 7 simple setae terminally; exopod 0.8 × basis length, basal article with 2 pappose setae, flagellum with plumo-annulate setae ( Fig. 23C ). —Pereopod 3 basis 0.9 × length of all other articles together, broadened, with 2 simple setae; ischium 0.1 × basis length, with 2 simple setae; merus 3.5 × ischium length, with simple seta; carpus 0.6 × merus length, with 2 simple and 2 annulate setae; propodus 0.6 × carpus length, with annulate seta; dactylus 0.8 × propodus length, with simple seta and simple seta terminally; exopod 1.0 × basis length, basal article broad, unarmed, flagellum with plumo-annulate setae ( Fig. 23D ). —Pereopod 4 not illustrated. —Pereopod 5 basis 0.8 × length of all other articles together, with 5 plumose setae; ischium 0.08 × basis length, with 2 simple setae; merus 5.5 × ischium length, with 7 simple setae; carpus 0.8 × merus length, with 2 simple and 3 annulate setae; propodus 0.6 × carpus length, with 1 simple and 1 annulate setae; dactylus 0.8 × propodus length, with 2 simple setae and simple seta terminally ( Fig. 23E ). —Pleopod 1 peduncle with 6 simple and 3 plumose setae; endopod uniarticulate, without process, with 4 plumose setae; exopod biarticulate, with 5 plumose setae ( Fig. 23F ). —Pleopod 2 peduncle with 4 simple setae; endopod uniarticulate, with 4 plumose setae; exopod biarticulate, with 3 plumose setae ( Fig. 23G ). —Telson 1.0 × length of pleonite 6, with 2 pairs lateral simple setae with single subterminal setule, 2 simple terminal setae ( Fig. 23H ). —Uropod peduncles 2.5 × pleonite 6 length, 2.5 × telson length, medial margin lined with fine hair-like setae and with 14 microserrate setae with single subterminal setule. Uropod endopod of 3 articles, 0.5 × peduncle length; article 1 longer than articles 2 and 3 together, with 4–5 microserrate setae with single subterminal setule medially; article 2 0.4–0.5 × article 1 length, with 2 microserrate setae with single subterminal setule medially; article 3 1.0 × article 2 length, with 2 microserrate setae with single subterminal setule medially, simple seta laterally, terminal seta simple. Uropod exopod 0.8 × length of endopod; article 1 0.3 × article 2 length; article 2 with 3 simple setae, simple terminal seta longer than exopod ( Fig. 23H ).

Etymology. The species is named nordaustraliana because the specimens were collected in the Northern Territory of Australia.

Remarks. The new species Dimorphostylis roccatagliatai is quite similar to the new species D. nordaustraliana . In the females, the carapace and antenna are different, and in both males and females the proportions of the pereopods are different. The females of both species share a similarly shaped dentate ridge in the same position on the carapace; however, in D. roccatagliatai there are a strong and a weak ridge ventral and parallel to the anterior part of the dentate ridge, while in D. nordaustraliana there is only a narrow depression parallel to dentate ridge. The female antenna in D. nordaustraliana is bi-articulate with pappose setae, while in D. roccatagliatai the antenna is tri-articulate, with a mix of simple and plumose setae. The propodus of pereopod 1 is no more than 1.2 × as long as the merus in both sexes in D. roccatagliatai , while it is at least 1.3 × or more as long as the merus in both sexes in D. nordaustraliana . In females of D. nordaustraliana the bases of maxilliped 3 and pereopod 2 are much wider than in females of D. roccatagliatai .

Figures

Figure 20. Dimorphostylis nordaustraliana n. sp. female. Holotype preparatory female, 3.2 mm, AM P85775: (A), dorsal view; (B), side view carapace. Paratype ovigerous female, 2.9 mm, AM P85776: (C), side view; (D), antennule; (E), antenna; (F), mandibles; (G), maxillule; (H), maxilla; (I), maxilliped 1; (J), maxilliped 2. Scale bars A–C = 1.0 mm, D–J = 0.5 mm.

Figure 21. Dimorphostylis nordaustraliana n. sp.

Figure 22. Dimorphostylis nordaustraliana n. sp. male. Paratype adult male, 3.6 mm, AM P85777: (A), side view; (B), dorsal view; (C), pleonites 1–4; (D), antennule; (E), antennule without setae on article 3; (F), antenna. Scale bars A–B = 1.0 mm, C–F = 0.1 mm.

Figure 23. Dimorphostylis nordaustraliana n. sp. male.Paratype adult male, 3.6 mm,AM P85777:(A), maxilliped 3; (B), pereopod 1; (C), pereopod 3; (D), pereopod 4; (E), pereopod 5; (F), pleopod 1; (G), pleopod 2; (H), pleonite 6, telson and uropods. Scale bar = 0.5 mm.