Diastylis acanthoelachys, Gerken, Sarah, 2015

Gerken, Sarah, 2015, New Zealand Diastylidae and Gynodiastylidae (Crustacea: Cumacea), Zootaxa 4031 (1), pp. 1-77 : 15-18

Diastylis acanthoelachys n. sp.

( Figs. 6–7 )

Material examined. Holotype: ovigerous female, NIWA 0 93197, TAN0705/49, 44.4862°S, 177.1413°E – 44.4841°S, 177.1416°E, 1235–1239 m, 6 April 2007. Paratype: preparatory female (dissected), NIWA 0 93201, TAN0705/49, 44.4862°S, 177.1413°E – 44.4841°S, 177.1416°E, 1235–1239 m, 6 April 2007. Non-type material: 2 specimens, NIWA 0 94946, TAN0705/178, 43.5212°S, 178.6203°W – 43.5228°S, 178.6315°W, 424 – 425 m, 18 April 2007; 3 specimens, NIWA 0 94947, TAN0705/134; 2 specimens, NIWA 0 94948, TAN0705/41, 43.8363°S, 176.7092°E – 43.8330°S, 176.7127°E, 478 – 479 m, 5 April 2007; 4 specimens, NIWA 0 95949, TAN0705/178, 43.5212°S, 178.6203°W – 43.5228°S, 178.6315°W, 424 – 425 m, 18 April 2007; 7 specimens, NIWA 0 94950, TAN0707/29, 38.6177°S, 168.9428°E – 38.6258°S, 168.9490°E, 480 – 482 m, 29 May 2007; 2 specimens, NIWA 0 94951, TAN0707/139, 39.6373°S, 172.1532°E – 39.6457°S, 172.1522°E, 264 – 266 m, 7 June 2007; 2 specimens, NIWA 0 94952, TAN0705/231; 8 specimens, NIWA 0 94953, TAN0707/139, 39.6373°S, 172.1532°E – 39.6457°S, 172.1522°E, 264–266 m, 7 June 2007; 1 specimen, NIWA 0 94954, TAN0707/29, 38.6177°S, 168.9428°E – 38.6258°S, 168.9490°E, 480 – 482 m, 29 May 2007; 40 specimens, NIWA 0 94955, TAN0705/49, 44.4862°S, 177.1413°E – 44.4841°S, 177.1416°E, 1235–1239 m, 6 April 2007; 1 specimen, NIWA 0 94977, TAN0705/251, 42.9958°S, 178.9957°E – 42.9910°S, 179.0052°E, 520 – 530 m, 24 April 2007.

Diagnosis. Female and subadult male. Carapace globular, covered in scattered small spines, not organized in lines, with few scattered setae; ventral margin serrate; antennal notch absent. Eyelobe without lenses. Pseudorostrum acute, 0.15 times carapace length anterior of eyelobe. Antennule article 2 shorter than article 3. Maxilliped 3 ischium not produced. Pereopod 1 basis ischium merus together shorter than carpus propodus dactylus together, carpus propodus and dactylus subequal. Pereopod 2 carpus 3 times propodus length. Pereopods 3–4 with rudimentary exopods in female. Telson with 11–13 lateral setae, more than 0.5 times length of uropod peduncles.

Adult male. Unknown.

Etymology. The species name acanthoelachys is from the Greek acanthus meaning spine, combined with elachys meaning small, in reference to the multitude of small spines on the carapace.

Description. Ovigerous female holotype 10.0 mm, preparatory female paratype broken. Body ( Figs. 6 A–B). Carapace covered in small spines, of consistent size throughout, with few setae anteriorly, anterior half of ventral margin serrate, serrations equal in size. Pleon unornamented.

Antennule ( Fig. 6 C) article 1 longest and broadest. Flagellae broken off.

Antenna not examined.

Mandibles ( Fig. 6 D) navicular, lacinia mobilis with 3 cusps, with row of 11–15 microserrate setae medially.

Maxillule ( Fig. 6 E) with 2 endites; palp with 2 microserrate setae.

Maxilla ( Fig. 6 F) with 3 endites; broad endite medial row of setae pedunculate; narrow endites with microserrate setae.

Maxilliped 1 ( Fig. 6 G) lateral margin of merus serrate; carpus without beak setae, with many pappose and simple setae.

Maxilliped 2 ( Fig. 6 H) ischium visible.

Maxilliped 3 ( Fig. 6 I)100:8:10:15:11:9; basis nearly twice length of other articles together, slender.

Pereopod 1 ( Fig. 7 A)100:14:15:45:45:45; basis with many plumose setae, medial margin serrate.

Pereopod 2 ( Fig. 7 B)100:5:23:38:13:broken; basis with long spine distally; exopod longer than basis.

Pereopod 3 ( Fig. 7 C)100:8:22:22:8:5; basis and ischium with plumose setae; merus with simple setae; carpus and propodus with annulate setae; dactylus terminal seta simple; rudimentary exopod 0.08 times basis length.

Pereopod 4 ( Fig. 7 D)100:12:32:28:8:8; basis with plumose setae; ischium with simple seta; merus with simple setae; carpus and propodus with annulate setae; dactylus terminal seta simple; rudimentary exopod 0.08 times basis length.

Pereopod 5 ( Fig. 7 E)100:14:38:43:12:7; basis with annulate setae; ischium with simple seta; merus with simple setae; carpus and propodus with annulate setae; dactylus terminal seta simple.

Telson ( Fig. 7 F) 1.8 times length of pleonite 6, with 11–13 simple setae laterally, pair of terminal setae short, simple.

Uropods ( Fig. 7 F) peduncles longer than telson , with simple setae medially; uropod endopod triarticulate, with simple setae medially and terminal seta short, stout, simple; exopod broken.

Distribution. Chatham Rise, Challenger Plateau, New Zealand, 264–1239 m.

Remarks. Diastylis acanthoelachys is most easily confused with D. acuminata and D. adaioacanthus n. sp. in New Zealand waters. Diastylis acanthoelachys can be easily differentiated from D. adaoiacanthus by the carapace, globular with small spines and a pseudorostrum that only extends 0.15 of the total carapace length anterior of the eyelobe in D. acanthoelachys , while in D. adaioacanthus the carapace is elongate, the spines are larger and the pseudorostrum extends 0.3 of the total carapace length anterior of the eyelobe. Diastylis acanthoelachys can be differentiated from D. acuminata by size, antennule and pereopod 2. In D. acuminata the body size is 14 mm, in the antennule article 2 is longer than article 3, and the pereopod 2 carpus is 5 times the length of the propodus. In comparison, in D. acanthoelachys the body size is 10 mm, antennule article 2 is shorter than article 3, and the pereopod 2 carpus is 3 times the length of the propodus.

Figures

FIGURE 6. Diastylis acanthoelachys n. sp. holotype ovigerous female (NIWA 093174). A, side view. Paratype preparatory female (NIWA 093201). B, side view; C, antennule; D, mandibles; E, maxillule; F, maxilla; G, maxilliped 1; H, maxilliped 2; I, maxilliped 3.

FIGURE 7. Diastylis acanthoelachys n. sp. paratype preparatory female (NIWA 093201). A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pleonite 6, telson and uropods.