Paragathotanais diunguisus, 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 : 430-431

Paragathotanais diunguisus n. sp. Larsen & Bird

Figs 4–6

Material examined. Holotype: female, (Reg. # ZMH K-43314), ANDEEP II, sample # DZMB-HH 10395, station 135, 65°00.06'S, 42°01.19'W, 4678 m, 11 March 2002, EBS-epi. Paratype (Reg. # ZMH K-43315): non-ovigerous female (dissected), ANDEEP II, sample # DZMB-HH 10396, station 136, 64°01.88'S, 39°06.88'W, 4747 m, 11 March 2002, EBS-epi.

Diagnosis, female. Pereopods propodus with numerous distal spines; pereopods 4–6 dactylus with accessory spiniform setae (appearing as a ‘double unguis’). Uropod short (less than half as long as pleotelson), fused with basal article; exopodal process absent.

Etymology. Name is derived from the Greek, alluding to the ‘double unguis’ on pereopods 4–6.

Description. Female, holotype

Body ( Fig. 4 A,B). Heavily calcified, 7.4 times as long as wide. Cephalothorax with clear lateral shield, naked, longer than wide, marginally shorter than pereonites 1 and 2 combined. Pereonites lateral shoulders clearly defined; pereonite-1 wider than long; pereonites 2–5 longer than wide; pereonite-6 as wide as long. Pleon, including pleotelson, 0.15 times as long as total body length; all pleonites subequal and unfused. Pleotelson longer than last four pleonites combined, acorn-shaped, apex rounded, with paired setae, and covered by dorsal plate.

Antennule ( Fig. 4 C). More than half as long as carapace. Article-1 marginally longer than rest of antennule combined, with one simple and one setulose subdistal setae. Article-2 marginally shorter than half of article-1, with one long simple subdistal seta. Article-3 less than half of article-2, with one distal simple seta. Article-4 with at least three simple distal setae (broken). No indication of terminal cap-like article.

Antenna ( Fig. 4 D). Longer than antennule article-1, with five apparent articles. Article-2 (see Methods above) with three proximal spines. Article-3 with one dorsodistal seta. Article-4 longer than other articles combined, with one simple distal seta. Article-5 longer than article-2, tapering and apparently naked. Article-6 minute, with two simple distal setae.

Mouthparts. Labrum ( Fig. 4 E) narrower than clypeus, widening distally, distal edge setulose. Mandibles ( Fig. 4 F, G) with acuminate molars tipped with three slender spines. Left mandible ( Fig. 4 F) lacinia mobilis in the shape of a simple blunt spine, incisor blunt, bifurcate and with outer denticle. Right mandible ( Fig. 4 G) incisor narrower than that of left mandible, without denticles. Labium not recovered. Maxillule ( Fig. 4 H) endite with ten spiniform distal setae. Palp shorter than endite, with two terminal setae. Maxilla ( Fig. 4 I) simple, ovoid. Maxilliped ( Fig. 5 A) basis naked. Endites distally incompletely fused, with two distal setae and blunt outer process. Palp article-1 naked, article-2 with three simple setae on inner margin, article-3 with four simple setae on inner margin, article-4 only half as wide and long as article-3, with one simple outer and four simple inner setae. Epignath ( Fig. 4 J) featureless.

Cheliped ( Fig. 5 B). With large sclerite not protruding below cephalothorax ventrum. Basis attached ventrally, with small dorsal seta, about as long as merus. Merus with one medial seta. Carpus marginally longer than propodus including fixed finger, with one medioventral seta. Propodus with one wide and blunt inner seta behind dactylus insertion. Fixed finger with one simple ventral and three setae on inner margin, inner margin with prominent distal process. Dactylus as long as fixed finger, with small dorsoproximal seta.

Pereopod-1 ( Fig. 5 C) basis hardly shorter than length of four succeeding articles combined, naked. Ischium with one seta. Merus shorter than carpus, widening distally, with two ventral bayonet setae. Carpus shorter than propodus, rectangular, with two bayonet setae and one shorter spiniform distal seta. Propodus about 0.5 times as long as basis, with one long simple and one short spiniform ventral setae and numerous distal spines. Dactylus and unguis combined shorter than propodus.

Pereopod-2 ( Fig. 5 D) as pereopod-1 except propodus with short spiniform simple seta only.

Pereopod-3 ( Fig. 5 E) as pereopod-2 except basis with one setulate dorsomedial seta.

Pereopod-4 ( Fig. 5 F) basis not wider than those of pereopods 1–3, naked. Ischium with two setae. Merus with two bayonet setae, shorter than carpus. Carpus with three pinnate bayonet distal setae and one dorsodistal boneshaped seta. Propodus with three long (as long as dactylus) pinnate bayonet distal setae and multiple distal spines. Dactylus and unguis combined longer than propodus, dactylus with ventral row of spinules and one long accessory spiniform seta (more than half as long as unguis) at unguis insertion.

Pereopod-5 ( Fig. 5 G) as pereopod-4 except basis with one dorsomedial setulate setae. Dactylus with numerous spinules.

Pereopod - 6 ( Fig. 5 H, I) as pereopod-4 except basis naked, propodus with four pinnate, long distal bayonet setae (longer than dactylus).

Uropod ( Fig. 5 J) basal article fused with endopod. Exopod process completely reduced, no setae were observed but this is believed to be an artefact.

Male (not dissected)

Body ( Fig. 6 A). 7.6 times as long as wide. Cephalothorax naked, longer than wide, marginally shorter than pereonites 1 and 2 combined. Pereonites lateral shoulders clearly defined; pereonite-1 wider than long; pereonites 2–5 longer than wide; pereonite-6 as wide as long. Pleon, including pleotelson, 0.16 times as long as total body length. All pleonites subequal and unfused. Pleotelson as long as last four pleonites combined, acorn-shaped, apex rounded, with paired setae, and covered by dorsal plate.

Antennule only marginally broader than in female.

Pleopods Reduced and without setae.

Remarks. A number of species, Paragathotanais gracilis Bird & Holdich, P. macrocephalus Kudinova- Pasternak, P. spinosus Larsen, P. triunguisus n. sp. (see below), P. vikingus Bird , and an undescribed species from the Gulf of Mexico (Larsen 2005: ‘ Paragathotanais sp.’), have been recorded with the dactylus of pereopods 4–6 bearing one or two long accessory spiniform setae, giving the impression of a ‘double’ or ‘triple’ unguis. Paragathotanais diunguisus n. sp. differs (apart from the locality) from the other species by: the antenna article-2 proximal spines, a simple spiniform right mandibular incisor, and the uropod being fused to the basal article and lacking an exopodal process. The last character is also expressed in Metagathotanais and extends the variation within Paragathotanais uropod morphology. Additionally, P. diunguisus differs from P. triunguisus , P. vikingus , and the species from the Gulf of Mexico in the ‘double’ nature of the pereopod-6 unguis rather than ‘triple’, as in those species.

Figures

FIGURE 4. Paragathotanais diunguisus n. sp., female. A & B, holotype, scale bar 1.0 mm. C – J, 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, maxillule. I, maxilla. J, epignath.

FIGURE 5. Paragathotanais diunguisus n. sp., female, paratype, scale bars 0.5 mm. A, maxilliped. B, cheliped. C, pereopod- 1. D, pereopod- 2. E, pereopod- 3. F, pereopod- 4. G, pereopod- 5. H, pereopod- 6. I, same, propodus, dactylus, unguis. J, uropod.

FIGURE 6. Paragathotanais diunguisus n. sp. A, male, paratype, lateral view, scale bar 1.0 mm.