Diastylis homoacanthus, Gerken, Sarah, 2015

Gerken, Sarah, 2015, New Zealand Diastylidae and Gynodiastylidae (Crustacea: Cumacea), Zootaxa 4031 (1), pp. 1-77 : 30-33

Diastylis homoacanthus n. sp.

( Figs. 16–17 )

Material examined. Holotype: subadult female (dissected), NIWA 0 93177, TAN0705/49, 44.4862°S, 177.1413°E – 44.4841°S, 177.1416°E, 1235–1239 m, 6 April 2007. Paratype: subadult male (dissected), NIWA 0 93185, TAN0705/49, 44.4862°S, 177.1413°E – 44.4841°S, 177.1416°E, 1235–1239 m, 6 April 2007. Non-type material: 1 specimen, poor condition, NIWA 0 94975, TAN0705/49, 44.4862°S, 177.1413°E – 44.4841°S, 177.1416°E, 1235–1239 m, 6 April 2007.

Diagnosis. Female and subadult male. Carapace globular, with 4 equal spines anteriorly, with 1 pair of spines on tips of pseudorostrum; ventral margin weakly serrate; antennal notch present. Eyelobe without lenses. Pseudorostrum acute, 0.15 times carapace length anterior of eyelobe. Pereonites 4–5 and pleonites 1–3 with paired dorsal spines. Antennule article 2 longer than article 3. Maxilliped 3 ischium not produced. Pereopod 1 basis ischium merus together longer than carpus propodus dactylus together, carpus longer than propodus, propodus longer than dactylus. Pereopod 2 carpus unknown. Pereopods 3–4 without exopods. Telson with 4 lateral setae, longer than uropod peduncles.

Adult male. Unknown.

Etymology. The species name is a combination of the Greek homo meaning same, and acanthus meaning spine, in reference to the spines on the carapace which are uniform in size.

Description. Subadult female holotype 7.4 mm, subadult male paratype broken. Body ( Figs. 16 A–B). Carapace very rounded, dorsal depression, anterior half of ventral margin weakly serrate, with 4 strong spines in an arc from mid–lateral anterior dorsally onto pseudorostrum; pseudorostrum with pair of spines at tips. Pereonites 3–5 with strong paired dorsal spines and lateral spines; pereonite 5 with weak ventral spine. Pleon with strong paired spines dorsally on pleonites 1–3.

Subadult male paratype. Broken at pereonite 4 posterior border.

Antennule ( Fig. 16 C) peduncle article 1 longest, with many simple and 1 plumose setae; article 2 with few simple setae; article 3 shortest, with few simple setae. Main flagellum of 4 articles, 2 aesthetascs and short simple setae terminally; accessory flagellum of 3 articles, longer than main flagellum of article 1, with short simple setae.

Antenna not examined.

Mandibles not examined.

Maxillule ( Fig. 16 D) with 2 endites; palp with 2 microserrate setae.

Maxilla ( Fig. 16 E) with 3 endites; broad endite medial row of setae pedunculate; narrow endites long, with microserrate setae.

Maxilliped 1 ( Fig. 16 F) carpus without beak setae, with few simple and pappose setae.

Maxilliped 2 ( Fig. 16 G) ischium not visible.

Maxilliped 3 ( Fig. 16 H) 100:13:10:16:?(broken); basis medial margin with few strong spines, with alternating plumose and small simple setae, produced weakly distolaterally with 3 plumose setae; merus with spine medially.

Pereopod 1 ( Fig. 17 A) 100:8:13:32:27:24; basis medial margin serrate anteriorly, with plumose, pappose and simple setae; ischium to propodus with many simple setae; dactylus with simple setae.

Pereopod 2 ( Fig. 17 B) 100:6:23:?(broken); basis with many strong spines medially and laterally, with simple and plumose setae; ischium produced as large spine; merus produced as spines medially and laterally, with plumose seta; exopod longer than basis, basal article with several simple setae.

Pereopod 3 ( Fig. 17 C) 100:13:26:29:13:13; basis with many plumose and simple setae; ischium with plumose seta; merus with simple setae; carpus with plumose and annulate setae; propodus with annulate seta; dactylus terminal seta simple; exopod not fully developed.

Pereopod 4 ( Fig. 17 D) 100:11:36:36:14:14; basis, ischium and merus with plumose setae; carpus with plumose, simple and annulate setae; propodus with annulate seta; dactylus terminal seta simple; exopod not fully developed.

Pereopod 5 not examined, missing.

Holotype subadult female.

Telson ( Fig. 17 E) 2.1 times length of pleonite 6, with 4 setae with single setule laterally, terminal setae long and microserrate.

Uropods ( Fig. 17 E) peduncles with 4–6 setae with single setule medially; endopod biarticulate, with few setae with single setule medially, terminal seta short and simple; exopod longer than endopod, with simple setae, terminal seta simple, moderate in length.

Distribution. Chatham Rise, New Zealand, 1235–1239 m.

Remarks. The most similar species is Diastylis curtain , with a smooth globular carapace with few large spines anteriorly. However, in D. homoacanthus the spines are homogenous in size, while in D. curtain the spines are a combination of large and small spines.

Figures

FIGURE 16. Diastylis homoacanthus n. sp. holotype subadult female (NIWA 093177). A, side view. Paratype subadult male (NIWA 093185). B, dorsal view; C, antennule; D, maxillule; E, maxilla; F, maxilliped 1; G, maxilliped 2; H, maxilliped 3.

FIGURE 17. Diastylis homoacanthus n. sp. paratype subadult male (NIWA 093185). A, pereopods 1; B, pereopod 2, C, pereopod 3; D, pereopod 4. Holotype subadult female (NIWA 093177). E, pleonite 6, telson and uropods.