Paranarthrura sundanensis, Chim & Tong, 2021

Chim, C. K. & Tong, Samantha J. W., 2021, Three new species of agathotanaids (Tanaidacea: Paratanaoidea: Tanaidomorpha) from the lower bathyal zone off southwestern Java, Indonesia, Indian Ocean with notes on the global distribution and diversity of Agathotanaidae, Zootaxa 5004 (1), pp. 67-106 : 83-89

Paranarthrura sundanensis n. sp.

( Figs 5C , 14–17 )

Paranarthrura sp. SJ#1: Chim & Bird (in press)

Material examined. Holotype, non-ovigerous female (1.9 mm), dissected and mounted on 19 slides ( ZRC 2020.0317 ), south of Panaitan Island , Java, Indonesia, Sunda Strait, Indian Ocean, station CR21 (6°44.791’S, 105°06.422’E), 836 m, box corer, layer 0–2 cm, sieve mesh size 300 μm, SJADES cruise, 27 March 2018 . Allotype, juvenile male (1.6 mm), 1 vial ( ZRC 2020.0318 ), same collection data as holotype .

Paratypes: four non-ovigerous females (1.8–2.0 mm) in four vials ( ZRC 2020.0319 – 0322 ), three mancae III (1.2 mm) in one vial ( ZRC 2020.0323 ) and three mancae II (0.9 mm) in one vial ( ZRC 2020.0324 ), layer 0–2 cm, sieve mesh size 300 μm; manca III (1.2 mm) in one vial ( ZRC 2020.0325 ), layer 2–5 cm, sieve mesh size 300 μm; manca II (0.9 mm) in one vial ( ZRC 2020.0326 ), layer 2–5 cm, sieve mesh size 250 μm; other collection data same as holotype .

Diagnosis. Body stout, with pereonites either wider than long or as long as wide. Pereonites 1–4 each with one large anteriorly-directed hyposphenium. Labium with two pairs of lobes; inner lobe pointed with one spiniform seta distally; outer lobe membranous bearing one spiniform projection laterally. Maxilliped basis with one seta distally; endite with two setae and one round process distally; palp article-4 with two spines on inner margin. Chela with heavily chitinised keel ventrally and four spiniform setae on inner margin. Pereopods 1–3 propodus each with four or five stout spiniform setae ventroproximally; unguis with abrupt decrease in width at midlength. Pereopods 2 and 3 dactylus each with one long seta proximally. Pereopod 6 propodus with three short and four long spiniform setae distally. Uropod short; endopod biarticulate, article-2 shorter than article-1.

Description. Non-ovigerous female holotype ZRC 2020.0317

Body ( Figs 5C , 14B ) stout, subcylindrical, tapers posteriorly, about five times longer than wide. Cephalothorax about 19% of body length, 1.1 times longer than wide, lateral margins convex medially, subcircular in dorsal view; rostrum short and subtriangular; eye lobes absent.

Pereon about 66% of body length; pereonite-1 widest, trapezoidal, wider than long; pereonites 2 and 3 of subequal length, subrectangular, wider than long; pereonites 4 and 5 longest, as long as wide; pereonite-6 shortest, subrectangular, wider than long; pereonites 1 to 4 each with one large anteriorly-directed hyposphenia, from smallest to largest; lateral shoulders weakly defined.

Pleon about 15% of body length, narrower than pereon; all five pleonites of subequal length, each 0.2 times as long as wide, pleonite-5 with two pairs of simple setae; pleotelson ( Fig. 14D ) about 42% of pleon length, wider than pleonites, posterior margin with pointed apex bearing one pair of simple setae distally.

Antennule ( Fig. 15A ) about 0.9 times as long as cephalothorax, with four articles; article-1 longest, about 47% of total length, with six simple setae proximally ( Figs 17A–B ) and seven simple setae distally; article-2 about 23% of total length, with five simple and one plumose (lost in left antennule but observed in right antennule) distally; article-3 shortest, about 10% of total length, with two simple setae distally; article-4 about 20% of total length, with five simple setae, one plumose seta and one aesthetasc distally.

Antenna ( Fig. 15B ) about 0.6 times as long as antennule, with six articles; article-1 short and not examined; article-2 about 24% of total length, with one simple seta distally; article-3 about 12% of total length, with one simple seta distally; article-4 longest, about 41% of total length, with two simple setae distally; article-5 about 17% of total length, naked; article-6 about 6% of total length, with five simple setae distally.

Labrum ( Fig. 15C ) hood-shaped, covered with many setules distally. Left mandible ( Fig. 15D ) small; incisor with several blunt teeth; lacinia mobilis long and spiniform. Right mandible lost during dissection. Labium ( Fig. 15E ) with two pairs of lobes; inner lobe pointed, with numerous setules and one spiniform seta distally; outer lobe membranous bearing one spiniform projection laterally. Epignath and maxilla lost during dissection. Maxillule ( Fig. 15F ) long and slender; endite with 11 spiniform setae; palp with one apparent terminal seta, setulose distally. Maxilliped ( Fig. 15G ) bases not fused distally, each with one simple seta distally; endite with one round process and two simple setae distally; palp article-1 naked; palp article-2 with three simple setae distally; article-3 with three simple setae; article-4 with one simple seta subdistally, one simple and four setulose spiniform setae distally and two spines on inner margin.

Cheliped ( Fig. 16A ) pseudocoxa large, about 3.3 times longer than basis, fused ventromedially ( Fig. 14C ); basis trapezoidal, about 0.8 times as long as wide, with one simple seta dorsally; merus triangular, short, about 0.8 times as long as basis, with one simple seta ventrodisally; carpus subrectangular, about 1.6 times longer than basis, with one simple seta dorsomedially, one simple seta dorsodistally and one short ventromedial process bearing two simple setae; propodus about 1.9 times longer than carpus, ventral margin sinuous and with heavily chitinised ‘three-lobed’ process ( Fig. 17C ), palm with four spiniform setae on inner margin distally, fixed finger with one simple seta ventrally, two large teeth dorsodistally and three simple setae on outer margin near cutting edge, terminal spine acute distally; dactylus and unguis together as wide as and about 1.4 times longer than fixed finger; dactylus with one spiniform seta on inner margin dorsoproximally, two small spiniform setae on outer margin near cutting edge and two small teeth ventrodistally; unguis acute distally.

Pereopod-1 ( Fig. 16B ) coxa with one simple seta; basis about 4.8 times longer than wide, lateral margins slightly wider distally, with one plumose seta dorsoproximally; ischium short, less than 0.1 times as long as basis, with one simple seta ventrodistally; merus about 0.4 times as long as basis, with one short simple and one setulose bayonet setae ventrodistally; carpus about 1.2 times longer than merus, with one setulose bayonet seta dorsodistally and one short spiniform and one setulose bayonet setae ventrodistally; propodus about 1.1 times longer than carpus, with five stout spiniform setae ventroproximally, two spiniform setae ventrodistally, one simple seta on inner margin dorsodistally and numerous setules along distal margin; dactylus and unguis naked, slender and curved inwards, together as long as propodus; unguis as long as dactylus, with abrupt decrease in width at midlength and with blunt tip.

Pereopod-2 ( Fig. 16C ) similar to pereopod-1, but merus without short simple seta ventrodistally; propodus with only four stout spiniform setae ventroproximally and one spiniform seta ventrodistally; dactylus and unguis together about 1.4 times longer than propodus; dactylus with one long simple seta proximally.

Pereopod-3 ( Fig. 16D ) similar to pereopod-2, but basis with one additional plumose seta; dactylus and unguis together as long as propodus.

Pereopod-4 ( Fig. 16E ) coxa with one simple seta; basis about 4.3 times longer than wide, with two plumose setae medially; ischium short, less than 0.1 times as long as basis, with two simple setae ventrally; merus about 0.3 times as long as basis, with two setulose spiniform setae ventrodistally; carpus about 1.1 times longer than merus, with one simple and three spiniform setae distally; propodus about 0.8 times as long as carpus, with two short and three spiniform setae distally; dactylus and unguis, slender and straight, combined length about 2.0 times longer than propodus; dactylus with one minute seta distally; unguis slightly shorter than dactylus, with sharp tip.

Pereopod-5 ( Figs 16F & 17D ) similar to pereopod-4.

Pereopod-6 ( Fig. 16G ) similar to pereopod-4 but propodus with three short and four long spiniform setae distally and dactylus lacking minute seta.

Pleopods absent.

Uropod ( Fig. 14D ) short—barely extends beyond pleotelson and thus not clearly visible from dorsal view; basal article naked; endopod biarticulate and about 1.3 times longer than basal article, article-1 with two plumose setae distally, article-2 about 0.5 times as long as article-1 and with one simple seta medially and six (five simple and one plumose) setae distally; exopod fused with basal article forming a long acute spur bearing three simple setae distally.

Juvenile male allotype ZRC 2020.0318 ( Fig. 14A ): Similar to female holotype but with pleopods. Pleopods 1–5 ( Figs 16H–I ) similar; both rami short and naked but endopod slightly longer than exopod; pleonite-5 basal article with one simple seta.

Etymology. The specific epithet is an adjective referring to the type locality Sunda Strait. It agrees with the feminine gender of the genus Paranarthrura (see Larsen 2005).

Distribution and habitat. Only from the type locality, at depth of 836 m, 0–5 cm top layer of soft sediment.

Remarks. Paranarthrura sundanensis n. sp. is among the shortest and stoutest members of the genus. This species is most similar to Paranarthrura crassa Bird & Holdich, 1989 —both species share many characteristics and these include (1) subcircular cephalothorax; (2) wider than long pereonites 1, 2 and 6; (3) pereonites with hyposphenia; (4) chela with ventral process; (5) pereopod-1 propodus with two spiniform setae ventrodistally; (6) pereopods 2 and 3 merus each with one long simple spiniform seta; (7) pereopods 2 and 3 dactylus each with one long simple seta proximally; (8) pereopods 4 and 5 propodus each with two short and three long setae distally; (9) uropod with endopod that is biarticulate and less than 1.5 times longer than basal article. Paranarthrura sundanensis differs from P. crassa by having (1) rounded process on maxilliped endite distally; (2) spines on maxilliped palp article-4 inner margin instead of setules in P. crassa ; (3) plumose setae on pereopods 1–3 bases; (4) large spiniform setae on pereopods 2 and 3 propodus as compared to the small spiniform setae and setules in P. crassa ; (5) three short spiniform setae on pereopod 6 propodus dorsodistally instead of one short spine in P. crassa ; (6) uropod exopod shorter than endopod article-1. Other than these morphological differences, the type localities of both species are also from two distant biogeographical regions— P. sundanensis is from the “Indian” lower bathyal province (836 m depth, Sunda Strait) and P. crassa is from the “North Atlantic” lower bathyal province (1319–1325 m depth, Porcupine Seabight).

The only other Paranarthrura species occurring in the Indian Ocean is Paranarthrura bacescui Kudinova- Pasternak, 1986 from 2280 m depth, south of Madagascar. Paranarthrura bacescui can be distinguished from P. sundanensis by (1) the longer than wide pereonites 4 and 5; (2) having antennule article-4 longer than article-2; (3) lacking spiniform processes on labium inner and outer lobes; (4) having long uropods and endopod article-2 longer than article-1.

Figures

FIGURE 5. Agathotanaids of Southwest Java, Indonesia: (A) Agathotanais cilacapicus n. sp.; (B) Bunburia javanica n. sp.; (C) Paranarthrura sundanensis n. sp..

FIGURE 14. Paranarthrura sundanensis n. sp. Southwest Java, Indonesia. (A) Juvenile male allotype (ZRC 2020.0318) and (B–D) non-ovigerous female holotype (ZRC 2020.0317): habitus, (A) lateral (after right pereopods removed) and (B) dorsal views; (C) cephalothorax, ventral view; (D) pleotelson and uropods, ventral view. Asterisk indicates missing part. Scale bars: 0.5 mm (A–B); 100 µm (C–D).

FIGURE 15. Paranarthrura sundanensis n. sp. Holotype female: (A) antennule, left; (B) antenna, left; (C) labrum; (D) mandible, left; (E) labium; (F) maxillule; (G) maxillipeds. Asterisk indicates missing part. Scale bars: 100 µm.

FIGURE 16. Paranarthrura sundanensis n. sp. (A–G) Holotype female and (H–H`) allotype male: (A) cheliped, right; (B–G) pereopods 1–6, right; pleopods, (H) lateral and (H`) ventral views. Scale bar: 100 µm.

FIGURE 17. Paranarthrura sundanensis n. sp. Holotype female: setae at the base of (A) left and (B) right antennule; (C) heavily chitinised ‘three-lobed’ ventral process (in darker colouration) on chela; (D) dorsodistal spiniform setae on pereopod-5 propodus. Scale bars: 50 µm.