Paranarthrura coimbrai, Larsen, Kim, Bird, Graham & Ota, Mayumi, 2013

Larsen, Kim, Bird, Graham & Ota, Mayumi, 2013, The ANDEEP Tanaidacea (Crustacea: Peracarida) revisited I: the family Agathotanaidae Lang, with description of four new species, Zootaxa 3630 (3), pp. 424-444 : 439-442

Paranarthrura coimbrai n. sp. Larsen & Bird

Figs 9–10

Material examined. Holotype: non-ovigerous female (Reg. # ZMH K-43318). ANDEEP II, sample # DZMB-HH 10432, station 141, 58°25.08'S, 25°00.77'W, 2313 m, 23 March 2002, EBS-epi. Paratypes (Reg. # ZMH K-43319): one non-ovigerous female (dissected), two juveniles. ANDEEP II, sample # DZMB-HH 10431, same locality and data as holotype, EBS-supra.

Diagnosis female. Cephalothorax in dorsal view with smooth lateral margins, longer than wide, shorter than pereonites 1 and 2 combined. Pereonites 1, 2 and 6 wider than long. Pleotelson shorter than three last pleonites combined. Antennule article-1 as long as rest of antennule. Cheliped fixed finger and apex of dactylus heavily chitinised. Pereopods 4–6 propodus with two distal spines; unguis with small dorsal accessory spine at midlenght. Pleon as wide as pereon. Uropods as long as pleotelson; endopod longer than basal article, biarticulate; exopodal process shorter than first endopod article.

Etymology. Named after the recently retired director of CIIMAR Professor João José Oliveira Dias Coimbra, in appreciation of his many years of hard labour to keep the institution in survival mode.

Description. Adult female.

Body ( Fig. 9 A, B) 6.7 times as long as wide. Carapace with smooth lateral edges in dorsal view, longer than wide, shorter than combined length of pereonites 1 and 2. Pereonites. Lateral shoulders undefined. Pereonites 1, 2, and 6 wider than long. Pereonites 3–5 as long as wide. Pleon short, including pleotelson, only 0.15 times total body length. All pleonites subequal. Pleotelson shorter than three pleonites combined, acorn-shaped, apex blunt and covered by dorsal plate with one pair of setae.

Antennule ( Fig. 9 C) as long as carapace. Article-1 as long as rest of antennule, with two setulated setae medially, and distally with three setulated setae and one simple seta. Article-2 twice as long as article-3, with subdistal process, with one setulated and three simple distal setae. Article-3 shorter than other articles, with one simple long and two short distal setae. Article-4 longer than article-2, with one tiny, three long simple distal setae and two aesthetascs. Terminal cap-like article absent.

Antenna ( Fig. 9 D) with five apparent articles, 0.8 times as long as antennule. Article-2 longer than article-3, with one simple dorsodistal seta. Article-3 is 0.5 times as long as article-5, with one simple dorsodistal seta. Article-4 longer than other articles, with two setulated and two simple distal setae. Article-5 shorter than article-2, with one long simple distal seta. Article-6 minute, with three long simple distal setae.

Mouthparts. Labrum ( Fig. 9 E) hood-shaped with dorsal process (in lateral view), apparently naked. Mandibles with indistinct molar, without chitinised crushing surface. Left mandible ( Fig. 9 F) lacinia mobilis as long as incisor; incisor broad with two denticles. Right mandible ( Fig. 9 G) incisor blunt with three denticles. Labium ( Fig. 9 H) lobes pointed. Maxillule ( Fig. 9 I) endite with ten spiniform distal setae, palp with two long distal setae. Maxilla ( Fig. 9 J) fairly large with broad basis. Maxilliped ( Fig. 9 K) endites without medial process but with one distal seta on each margin of each endite; palp article-1 naked, articles 2 and 3 with three setae on inner margin, article-4 only half as wide as article-3, with four inner and one smaller outer setae. Epignath ( Fig. 9 L) as long as maxillule palp, with apparently bifurcated apex although this may be an artefact.

Cheliped ( Fig. 10 A) sclerite about twice as long as long as basis, protruding below cephalothorax ventrum. Basis longer than merus, with one small dorsal seta. Merus with small ventral seta. Carpus 0.7 times as long as propodus including fixed finger, with one dorsomedial seta and two simple ventromedial setae. Propodus not including fixed finger, apparently naked. Fixed finger with one ventral seta and three on inner margin, with strong unguis twice as long as that of dactylus. Dactylus robust, as long as fixed finger, naked and blunt.

Pereopod - 1 ( Fig. 10 B) coxa lost. Basis as long as the three succeeding articles combined, smooth. Ischium with two setae. Merus more than half as long as carpus, widening distally, with two ventrodistal bayonet setae. Carpus half as long as basis, with three serrated distal bayonet setae. Propodus with two stout spiniform ventrodistal setae and row of six small spines. Dactylus with one small dorsal seta. Unguis lost.

Pereopods 2–3 ( Fig. 10 C, D) as pereopod-1 except: coxa with seta. Propodus with only one stout spiniform seta. Dactylus naked.

Pereopod-4 ( Fig. 10 E) coxa apparently naked. Basis longer than the three succeeding articles combined, naked. Ischium with two setae. Merus more than half as long as carpus, widening distally, with two distal bayonet setae. Carpus shorter than half as long as basis, with one bone-shaped and three distal bayonet setae. Propodus longer than carpus, with three distal bayonet setae and two dorsodistal spines. Dactylus and unguis combined longer than propodus. Unguis with small dorsodistal spine.

Pereopod-5 ( Fig. 10 F) as pereopod-4 except coxa with seta.

Pereopod-6 ( Fig. 10 G) as pereopod-5 except basis with ventromedial setulated setae.

Uropod ( Fig. 10 H) as long as pleotelson. Endopod longer than basal article, biarticulate; article-1 with long distal seta; article-2 with at least two (broken) distal setae. Exopodal process shorter than first endopod article, with medial seta.

Remarks. If the bifurcate epignath is real this would be unique within the Tanaidacea , but we do not presume to use such an uncertain character. Otherwise, this species is morphologically very similar to P. bispinosa Larsen (from the Gulf of Mexico) but can be distinguished by the maxilliped endites being without a medial process and having distal setae. From P. arctowskii , a species from the same area, the new species can be separated by: 1) an elongated carapace; 2) the cheliped fixed finger unguis blunt and only twice as long as that of the dactylus; 3) the less acute cheliped dactylus; 4) the pereopods 4–6 unguis accessory spine. From most other species with biarticulate uropod endopods it can be separated by the uropod exopodal process being shorter than the first endopod article. From P. angolensis Guerrero-Kommritz , which also has a short exopodal process, it can be distinguished by the presence of the pereopods 1–3 propodal spines and the pereopods 4–6 double dorsodistal spines.

Figures

FIGURE 9. Paranarthrura coimbrai n. sp., female A & B, holotype, scale bar 1.0 mm. C – L paratype, scale bars 0.5 mm. A, habitus, dorsal view. B, habitus, lateral view. C, antennule. D, antenna. E, labrum, lateral view. F, left mandible. G, right mandible. H, labium. I, maxillule. J, maxilla. K, maxilliped. L, epignath.

FIGURE 10. Paranarthrura coimbrai n. sp. female, paratype, scale bar 0.5 mm. A, cheliped. B, pereopod- 1. C, pereopod- 2. D, pereopod- 3. E, pereopod- 4. F, pereopod- 5. G, pereopod- 6. H, uropod.