Diastylopsis trisetosa, 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 : 26-31

Diastylopsis trisetosa n. sp.

Figs 16–19

Type material. Holotype preparatory female, NMV J62361 ; paratype preparatory female, dissected, NMV J46867 ; paratype ovigerous female, dissected, NMV J46868 ; 66°03'00"S – 66°02'54"S 49°50'00"E – 49°47'54"E, 690–911 m, M. D. Norman, 29–30 Nov. 1985.

Other material examined. 1 ovigerous female, 21 preparatory females, 3 subadult females, 9 subadult males, 5 mancae, NMV J46869 , 66°03'00"S – 66°02'54"S 49°50'00"E – 49°47'54"E, 690–911 m, M. D. Norman, 29–30 Nov. 1985 .

Diagnosis. Female and subadult male. Carapace with 2 oblique serrate parallel ridges, strongly serrate short ridges anterior of the oblique ridges, carapace covered in small ridges posterior of the oblique ridges, producing a rugose appearance, dorsal margin strongly serrate. Pereonites 3–4 not fused. Pereopods 3–4 with rudimentary exopods in female. Telson 3–4 pairs of lateral setae and with 3 terminal setae. Adult male. Unknown.

Description

Ovigerous and preparatory female. Holotype preparatory female, NMV J62361 , 9.7 mm; paratype preparatory female, NMV J46867 , 10.0 mm; paratype ovigerous female, NMV J46868 , 9.9 mm. —Carapace with 2 strongly serrate parallel ridges curving from mid-dorsum anteroventrally, not reaching anterior margin, posterior to ridges carapace covered in small ridges, creating strongly rugose appearance, anterior of ridges with groups of strong teeth on frontal lobe and pseudorostral lobes; pseudorostral lobes 0.4 × carapace length; eye lobe 0.06 × carapace length, without lenses; carapace 1.9 × length of pereonites together. Pereonite 3 expanded anteriorly laterally, overriding pereonite 2 laterally ( Figs 16A–C ).

Paratype preparatory female NMV J46867 . —Pereopod 1 basis 0.6 × length of all other articles together, with plumose setae, produced as strong teeth; ischium 0.2 × basis length, unarmed; merus 0.9 × ischium length, with 2 simple setae, produced as 2 teeth distally; carpus 2.4 × merus length, with 1 simple and 1 plumose setae; propodus 1.3 × carpus length, with 3 simple setae; dactylus 1.0 × propodus length, with simple setae; exopod 0.7 × basis length, basal article with plumose seta, flagellum with plumo-annulate setae ( Fig. 17A ). —Pereopod 2 basis 0.8 × length of all other articles together, with plumose setae; ischium 0.06 × basis length, unarmed; merus 5.0 × ischium length, with 2 plumose setae; carpus 1.5 × merus length, with 3 stout simple setae distally; propodus 0.3 × carpus length, with simple seta; dactylus 1.7 × propodus length, with 4 simple setae and 5 simple setae terminally; exopod 1.1 × basis length, basal article with 4 plumose setae, flagellum with plumo-annulate setae ( Fig. 17B ). —Telson 1.7 × length of pleonite 6, with 3–4 simple setae with single subterminal setule laterally, 3 simple terminal setae; pre-anal portion margins produced as teeth ( Fig. 17C ). —Uropod peduncles 1.4 × pleonite 6 length, 0.8 × telson length, with 11–12 simple setae medially. Uropod endopod of 3 articles, 0.6 × peduncle length; article 1 longest, with 4 simple setae medially; article 2 0.6 × article 1 length, with 4 simple setae medially; article 3 0.8 × article 2 length, with 2 with plumose setae ( Fig. 19B ). —Pereopod 4 basis 0.6 × length of all other articles together, with plumose setae; ischium 0.1 × basis length, with plumose setae; merus 6.2 × ischium length, with plumose and annulate setae; carpus 0.4 × merus length, with annulate setae; propodus 0.8 × carpus length, with 1 simple and 1 annulate setae; dactylus 0.8 × propodus length, with simple seta terminally; exopod rudimentary, 0.4 × basis length, of 2 articles with plumose setae ( Fig. 19C ). —Pereopod 5 basis 0.4 × length of all other articles together, with plumose setae; ischium 0.2 × basis length, with plumose setae; merus 4.5 × ischium length, with plumose and annulate setae; carpus 0.7 × merus length, with 2 plumose and 3 annulate setae; propodus 0.6 × carpus length, with annulate seta; dactylus 0.8 × propodus length, with simple seta and simple seta terminally ( Fig. 19D ). —Telson 1.9 × length of pleonite 6, with 4 pairs of simple setae with single subterminal setule laterally, 3 simple terminal setae, central terminal seta small; pre-anal margins produced as teeth ( Fig. 19E ). —Uropod peduncles 1.4 × pleonite 6 length, 0.8 × telson length, with 9 simple setae with single subterminal setule medially. Uropod endopod of 3 articles, 0.6 × peduncle length; article 1 1.0 × articles 2 and 3 together, with 6 simple setae with single subterminal setule medially; article 2 0.5 × article 1 length, with 4 simple setae with single subterminal setule medially; article 3 1.0 × article 2 length, with 4 simple setae with single subterminal setule medially, terminal seta simple. Uropod exopod of 2 articles, 0.9 × length of endopod; article 1 0.2 × article 2 length, with simple seta; article 2 with 8 simple setae laterally, simple seta medially, terminal seta simple ( Fig. 19E ).

Etymology. The species is named trisetosa in reference to the three terminal setae present on the telson, a unique characteristic within the genus.

Remarks. Without males, it is impossible to be certain that this species does not belong in the family Lampropidae . However, the antennules and antennae are short in the female, which is characteristic of the Diastylidae , rather than long as is characteristic of the Lampropidae . The structure and ornamentation of the carapace are typical for Diastylopsis and would be unique within the Lampropidae . In the Lampropidae the telson is typically not divided between pre-anal and post-anal, with a narrowing at the anus, while this is quite common in the Diastylidae and is apparent in this species. In the diastylid genus Dimorphostylis , the adult males of several species have three terminal setae on the telson, while the females and subadult males have two terminal setae. This is the first record of a diastylid species in which the females have three terminal setae on the telson.

Figures

Figure 16.Diastylopsis trisetosa n. sp. female.Holotype preparatory female, 9.7 mm,NMV J62361: (A), side view. Paratype preparatory female, 10.0 mm, NMV J46867: (B), side view. Paratype ovigerous female, 9.9 mm, NMV J46868: (C), side/dorsal view. Scale bar = 5.0 mm.

Figure 17. Diastylopsis trisetosa n. sp. female. Paratype preparatory female,10.0 mm, NMV J46867: (A), pereopod 1; (B), pereopod 2; (C), pleonite 6, telson and uropods. Scale bar = 1.0 mm.

Figure 18. Diastylopsis trisetosa n. sp. female. Paratype ovigerous female, 9.9 mm, NMV J46868: (A), antennules and antennae; (B), mandibles; (C), maxillule; (D), maxilla; (E), maxilla narrow endites; (F), maxilliped 1; (G), maxilliped 2; (H), maxilliped 3. Scale bars A–D, F–G = 0.5 mm, E = 0.25 mm, H = 1.0 mm.

Figure 19. Diastylopsis trisetosa n. sp. female. Paratype