Diastylopsis incompta, 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 : 20-23

Diastylopsis incompta n. sp.

Figs 12–13

Type material. Holotype subadult male, dissected, NMV J62370 , Conception Bay , 1 mile S of Clapper, Newfoundland, Canada, 47°29'N 52°58'W, 16 May 1978.

Other material examined. None.

Diagnosis. Female and subadult male. Carapace with weakly serrate ridge on frontal lobe, anterior half of ventral margin weakly serrate, antennal notch present. Pereonite 5 produced acutely posteriorly. Telson longer than uropod peduncles, with at least 10 pairs lateral setae. Adult male. With 2 pairs of pleopods. Otherwise unknown.

Description

Juvenile male. Holotype juvenile male, NMV J62370 , 11.7 mm. —Carapace longer than deep, with weakly serrate ridge on frontal lobe, ending posterior of eye lobe, antennal notch present, anterior half of ventral margin serrate to within antennal notch; pseudorostral lobes 0.4 × carapace length; eye lobe 0.04 × carapace length, without lenses; carapace 1.7 × length of pereonites together. Pereonite 5 strongly produced posteriorly ( Fig. 12A ). —Antennule peduncle article 1 1.3 × articles 2 and 3 together, with simple seta, produced as 2 teeth on distal margin; article 2 0.3 × article 1 length, with 4 simple setae; article 3 1.3 × article 2 length, with 2 simple and 3 pedunculate setae; main flagellum of 4 articles, with 2 aesthetascs and 4 simple setae; accessory flagellum of 2 articles, with 2 simple and 1 pedunculate setae ( Fig. 12B ). —Maxilla with 3 endites; broad endite distal corner with pappose seta, distal margin lined with simple setae with pappose seta at medial corner, medial margin lined with plumose setae and 2 pappose setae; medial narrow endite with 4 microserrate setae terminally; distal narrow endite with 5 microserrate setae terminally; both narrow endites extending past distal margin of broad endite ( Fig. 12C ). —Maxilliped 1 basis produced as lobe, with 2 simple, 2 hook, 7 pappose and 1 very stout microserrate setae; ischium absent; merus with 2 simple setae laterally; carpus 1.8 × merus length, with 7 beak, 2 pappose and many simple setae medially, 4 simple and 1 plumose setae laterally; propodus 0.6 × carpus length, with 2 simple and 2 plumose setae; dactylus 0.6 × propodus length, with 2 simple setae terminally ( Fig. 12D ). —Maxilliped 2 basis 1.3 × length of all other articles together, with 4 simple and 3 plumose setae; ischium 0.03 × basis length, unarmed; merus 4.5 × ischium length, with 2 plumose setae; carpus 2.4 × merus length, with 12 plumose setae medially, plumose seta laterally; propodus 0.5 × carpus length, with 10 plumose setae medially, plumose seta laterally; dactylus 0.4 × propodus length, with 4 simple setae terminally ( Fig. 12E ). —Maxilliped 3 basis 2.3 × length of all other articles together, with 20 pappose setae medially, 4 plumose setae at distal corner; ischium 0.06 × basis length, with 2 pappose setae; merus 1.2 × ischium length, with 2 pappose setae medially, plumose seta laterally; carpus 1.0 × merus length, with 1 plumose and 2 pappose setae medially, plumose seta laterally; propodus 1.9 × carpus length, with 6 plumose setae medially, plumose seta laterally; dactylus 0.6 × propodus length, with 5 simple setae terminally; exopod 0.7 × basis length, basal article unarmed, flagellum with plumo-annulate setae ( Figs 12F–G ). —Pereopod 1 basis 1.0 × length of all other articles together, with plumose setae on margins, distal margin produced as 2 strong teeth; ischium 0.07 × basis length, unarmed; merus 1.7 × ischium length, with plumose seta; carpus 2.5 × merus length, with 2 simple and 3 plumose setae; propodus 1.0 × carpus length, with 8 simple setae; dactylus 0.8 × propodus length, with 3 simple setae and 5 simple setae terminally; exopod 0.8 × basis length, basal article with 7 plumose setae, flagellum with plumo-annulate setae ( Fig. 13A ). —Pereopod 2 basis 1.0 × length of all other articles together, with plumose setae, margin produced as strong teeth, corner produced as strong tooth; ischium 0.05 × basis length, with plumose seta, margin produced as strong tooth; merus 4.3 × ischium length, with 2 plumose setae, margin produced as 3 teeth; carpus 1.9 × merus length, with 3 simple setae; propodus 0.2 × carpus length, unarmed; dactylus 1.7 × propodus length, with 8 simple setae terminally; exopod 1.1 × basis length, basal article with plumose seta, produced as tooth proximally, flagellum with plumo-annulate setae ( Fig. 13B ). —Pereopod 3 basis 1.1 × length of all other articles together, with plumose setae; ischium 0.1 × basis length, with 5 simple setae; merus 5.0 × ischium length, with 7 plumose setae; carpus 0.4 × merus length, with 4 plumose and 4 annulate setae; propodus 0.8 × carpus length, with annulate seta; dactylus 0.7 × propodus length, with simple seta terminally; exopod 0.6 × basis length, of 2 articles, with plumose seta ( Fig. 13C ). —Pereopod 4 basis 0.7 × length of all other articles together, with plumose setae; ischium 0.1 × basis length, with plumose setae; merus 5.5 × ischium length, with simple setae; carpus 0.4 × merus length, with 7 simple and 6 annulate setae; propodus 0.6 × carpus length, with annulate seta; dactylus 0.7 × propodus length, with 2 simple setae terminally; exopod 0.7 basis length, of 2 articles, without setae ( Fig. 13D ). —Pereopod 5 basis 0.7 × length of all other articles together, with plumose setae; ischium 0.1 × basis length, with plumose setae; merus 5.0 × ischium length, with plumose setae; carpus 0.7 × merus length, with 4 plumose and 5 annulate setae; propodus 0.3 × carpus length, with annulate seta; dactylus 0.7 × propodus length, with 2 simple setae terminally ( Fig. 13E ). —Pleopods present on pleonites 1–2, small buds ( Fig. 12A ). —Telson 1.4 × length of pleonite 6, with 10–11 simple lateral setae with single subterminal setule, 2 terminal simple setae ( Fig. 13F ). —Uropod peduncles 1.5 × pleonite 6 length, 1.1 × telson length; medial margin with 15–16 simple setae with single subterminal setule, lateral margin with 1 or 3 simple setae. Uropod endopod of 3 articles, 0.5 × peduncle length; article 1 longer than articles 2 and 3 together, with 6–7 simple setae with single subterminal setule medially; article 2 0.4 × article 1 length, with 3 simple setae with single subterminal setule medially, pedunculate seta laterally; article 3 1.0 × article 2 length, with 2–3 simple setae with single subterminal setule medially, 1 pedunculate and 0–1 simple setae laterally, terminal seta simple. Uropod exopod 1.4 × length of endopod; article 1 0.3 × article 3 length, unarmed; article 2 with many simple and 2 plumose setae, terminal seta plumose ( Fig. 13F ).

Etymology. The species is named incompta from the Latin incomptus meaning unadorned, in reference to the carapace being smooth except for the ridge on the pseudorostral lobes. Within the genus, all other species have much more ornamentation on the carapace.

Remarks. The sole specimen of this species, despite being 11.7 mm long, is clearly a male several moults from becoming an adult, based on the minimal development of the pleopods and the exopods on pereopods 3–4. The adults of this species are expected to be quite a bit larger than this specimen, perhaps as much as 20 mm. It is possible that this species may not belong in Diastylopsis ; however, without the adults in hand, Diastylopsis is the only plausible generic placement at this time.

Figures

Figure 12. Diastylopsis incompta n. sp.male.Holotype subadult male, 11.7 mm, NMV J62370:(A), side view; (B), antennule; (C), maxilla; (D), maxilliped 1; (E), maxilliped 2; (F), maxilliped 3; (G), maxilliped 3. Scale bars A, F = 1.0 mm, B–E, G = 0.5 mm.

Figure 13. Diastylopsis incompta n. sp. male. Holotype subadult male, 11.7 mm, NMV J62370: (A), pereopod 1; (B), pereopod 2; (C), pereopod 3; (D), pereopod 4; (E), pereopod 5; (F), pleonite 6, telson and uropods. Scale bar = 1.0 mm.