Paranarthrura cousteaui García-Herrero & Esquete & Cunha 2021, sp. nov.

Paranarthrura cousteaui sp. nov.

urn:lsid:zoobank.org:act: 3AFA3BE0-25D4-4FDC-B03F-57B7F75F27D1

Figs 2–5

Diagnosis

Preparatory male

Paranarthrura with antenna six-articled. Maxilliped endite with one seta. Cheliped carpus with one long midventral seta. Pereopods 4–6 basis with one penicillate seta. Presence of rudimentary pleopods fused to each pleonite. Uropod endopod bi-articulated; exopod shorter than endopod article 1.

Neuter

As preparatory male, but without pleopods (Fig. 2G).

Etymology

This species is named in honour to Jacques-Yves Cousteau (1910–1997), for his life-long intensive work in raising awareness to the sea life and great contributions to the knowledge of the marine environment.

Material examined

Holotype PORTUGAL • preparatory ♂ (tergal plate on pereonite 4 broken); West Iberian Margin, Nazaré Canyon; 39°35.80′ N, 9°24.25′ W; depth 897 m; 11 Sep. 2006; stn 64PE252_43bc1; MNCN 20.04/12538.

Paratype PORTUGAL • 1 preparatory ♂ (dissected); same collection data as for holotype; MNCN 20.04/12539.

Other material

PORTUGAL • 1 manca II; West Iberian Margin, Setúbal Canyon; 38°17.10′ N, 9°06.00′ W; depth 970 m; 17 Sep. 2006; stn 64PE252_61bc3; DBUA0002189.01 • 1 manca II; West Iberian Margin, Cascais Canyon; 38°27.89′ N, 9°28.51′ W; depth 935 m; 18 Sep. 2006; stn 64PE252_36bc1; DBUA0002189.02 • 1 neuter (broken specimen); West Iberian Margin, off Sines; 37°49.98 N, 9°28.49 W; depth 1001 m; 10 Sep. 2006; stn 64PE252_56bc3; DBUA0002189.03.

Description

Preparatory male (MNCN 20.04/12538)

BODY (Fig. 2A–B). Well calcified, 6.2 times as long as wide (holotype length: 2.1 mm; width 0.33 mm). Cephalothorax without eyes or eye lobes, subrectangular posteriorly, narrower anteriorly, 0.20 of body length. Rostrum (Fig. 2A, C) absent. Pereon 0.62 of body length, pereonites decreasing in width posteriorly. Pereonites 1–6: 0.5, 0.6, 0.6, 0.9, 0.9 and 0.7 times as long as wide respectively, each with hyposphaenium (Fig. 2B); pereonites 2–6 subhexagonal. Coxal setae visible in dorsal view. Pleon 0.14 of body length, with five free pleonites. Pleonite 5 longest, 0.3 times as long as previous, with anterodorsal and lateral seta (Fig. 2B). Pleotelson semicircular, 0.04 of body length, carrying a pair of setae in posterior margin. Uropods not visible in dorsal view.

ANTENNULE (Fig. 2C). Four-articled. About as long as cephalothorax, 5.2 times as long as wide. Article 1, 2.8 times as long as wide, with one subdistal seta and three short medial penicillate setae on outer margin. Article 2, 2.1 times as long as wide, with one short subdistal seta on inner margin, one long dorsodistal penicillate seta, and one long subdistal seta on outer margin. Article 3, 0.9 times as wide as long, with two distal setae on inner margin and one subdistal seta on outer margin. Article 4, 2.7 times as long as wide, with six long and one short distal setae.

ANTENNA (Fig. 2D, ventral view). Six-articled, 7.5 times as long as wide. Article 1 fused with body, not visible on dorsal view. Article 2, 1.4 times as long as wide, with dorsodistal seta. Article 3, 1.1 times as long as wide, with dorsodistal seta. Article 4 longest, 3.9 times as long as wide, with three subdistal setae. Article 5 naked, 2.8 times as long as wide. Terminal article 0.3 times as long as previous, with five distal setae.

MOUTHPARTS. Labrum (Fig. 3A–C) conical on ventral view, not compressed, longer than wide and distally setulose. Mandible right (Fig. 4A) and left similar and reduced, without molar process or lacinia mobilis; incisor denticulate. Labium not recovered. Maxillule (Fig. 4B–C) endite setulose distally, with eight distal setae, four shorter and four longer; palp with two distal setae. Maxilla not recovered. Maxilliped (Fig. 4D) basis fused, elongate, 1.6 times as long as wide, with one seta near the palp insertion. Endites not fused, with one inner distal short seta each. Palp article 1, 1.5 times as long as wide, naked. Article 2, 1.0 times as long as wide, with three inner setae, one of them longer. Article 3, 1.4 times as long as wide, 1.5 times as long as previous, with three inner setae. Article 4, 2.1 times as long as wide, distally setulose, with four simple and two pinnate setae.

CHELIPED (FigS 4E, 5A–B). Attached via ventral pseudocoxa, naked, 1.4 times as long as wide. Basis 1.2 times as long as wide, seta not seen. Merus subtriangular, 0.9 times as long as wide, with midventral seta. Carpus 1.7 times as long as wide, with two midventral setae, short and long, and two short middorsal and posterodorsal setae. Propodus 2.0 times as long as wide, ventral protuberance with one ventral seta and inner row of three setae near ventral margin. Cutting edge of fixed finger coarse, not distinct claw, with three setae, near dactylus insertion. Dactylus and unguis not fused, together 3.3 times as long as wide. Dactylus with one simple dorsal seta.

PEREOPOD 1 (Fig. 5C). Coxa with seta. Basis 4.1 times as long as wide, naked. Ischium wider than long, naked. Merus twice as long as wide, with ventrodistal spine, reaching about half-length of carpus. Carpus 2.6 times as long as wide, bearing three serrate spines: one dorsodistal and two ventrodistal. Propodus slightly curved, 4.7 times as long as wide, ventral margin proximally with four spinules,

bearing three subdistal simple setae, two ventral, and one dorsal. Dactylus and unguis together 1.1 times as long as propodus, unguis 0.53 times as long as dactylus.

PEREOPOD 2 (Fig. 5D). Coxa with anterior seta. Basis naked, 6.2 times as long as wide. Ischium wider than long, with ventral seta. Merus 1.7 times as long as wide, with long, ventrodistal simple spine, as long as carpus. Carpus 2.0 times as long as wide, bearing three serrate spines, one dorsodistal and two ventrodistal. Propodus slightly curved, 3.7 times as long as wide, with small dorsodistal spiniform apophysis, ventral margin with four spinules, bearing one subdistal simple spine. Dactylus and unguis combined 1.3 times as long as propodus, unguis 0.6 times as long as dactylus.

PEREOPOD 3 (Fig. 5E). Similar to pereopod 2, except for: basis 3.9 times as long as wide. Merus 2.1 times as long as wide, with spine reaching just 80% length of carpus. Carpus 2.7 times as long as wide. Propodus 3.5 times as long as wide. Dactylus and unguis combined 1.5 times as long as propodus.

PEREOPOD 4 (Fig. 5F). Coxa with anterior seta. Basis 3.2 times as long as wide, with one midventral penicillate seta. Ischium wider than long, with two ventral setae. Merus 1.7 times as long as wide, bearing two ventrodistal simple spines (both 50% length of carpus). Carpus 2.4 times as long as wide, bearing three subdistal serrate spines. Propodus 3.1 times as long as wide, with dorsodistal spiniform apophysis, two ventrodistal and one dorsodistal simple spines. Dactylus and unguis combined 1.7 times as long as propodus, unguis 0.5 times as long as dactylus.

PEREOPOD 5 (Fig. 5G). Similar to pereopod 4, except for: basis 3.6 times as long as wide. Merus 1.84 times as long as wide. Carpus with an extra distal simple seta. Unguis broken

PEREOPOD 6 (Fig. 5H). Similar to pereopod 4, except for: Basis 3.7 times as long as wide. Merus 1.6 times as long as wide, bearing two ventrodistal serrate spines. Carpus 2.8 times as long as wide. Propodus 3 times as long as wide, with dorsodistal spiniform apophysis, two distal serrate spines in dorsal margin and two distal serrate spines in ventral margin. Dactylus and unguis together 1.4 times as long as propodus.

PLEOPODS (Fig. 2B, F). Rudimentary, uniramous, naked and fused to pleonites, with faint fusion line.

UROPODS (Fig. 2B, E). Biramous. Exopod fused to protopod, with long and short distal setae, not reaching beyond mid-length of endopod article 1. Endopod bi-articulated, 2.7 times as long as wide. Article 1, 1.5 times as long as wide, with two distal setae on outer margin, one of them penicillate. Article 2, 1.0 times as long as wide, bearing one subdistal long setae on inner margin and four distal setae, one of them shorter.

Manca II

Antennule with aesthetasc, only two setae on pereopod 1 propodus; only one seta on pereopod 5 ischium; pleopods absent (Fig. 2G); uropod endopod article 1 naked, terminal article with four setae only.

Remarks

For most of the species of Paranarthrura the males were described with their original description, exceptions being Paranarthrura bacescui Kudinova-Pasternak, 1986, Paranarthrura coimbrai Larsen & Bird, 2013, Paranarthrura fortispina Sieg, 1986 and Paranarthrura meridionalis Sieg, 1986 (see Kudinova-Pasternak 1986; Sieg 1986b; Larsen et al. 2013). However, males of P. fortispina were later described (Jóźwiak & Błażewicz-Paszkowycz 2011). The presence of pleopods is common and one of the main differences with females, together with the body length and relative size of the pleon. Because of the poor condition of the neuter specimens in our collection, we describe P. cousteaui sp. nov. from a preparatory male holotype.

Paranarthrura cousteaui sp. nov. is distinguished from the other species of the genus by the unique combination of the following characters: post-cheliped sclerites unfused; presence of one long midventral seta in cheliped carpus; presence of dorsal seta on cheliped dactylus; presence of one penicillate seta in the basis of pereopods 4–6; one seta in the maxilliped endite uropod endopod bi-articulated and uropod exopod shorter than endopod article 1.

From the 19 species of the genus, only ten have a uropod endopod bi-articulated. These are: Paranarthrura angolensis Guerrero-Kommritz, Schmidt & Brandt, 2002; P. arctowskii Jóźwiak & Błażewicz-Paszkowycz, 2011; P. bacescui Kudinova-Pasternak, 1986; P. bispinosa Larsen, 2005; P. coimbrai Larsen & Bird, 2013; P. crassa Bird & Holdich, 1989; P. fortispina Sieg, 1986; P. insignis Hansen, 1913; P. lusitanus Bird & Holdich, 1989 and P. tenuimanus Larsen, 2005. Of these, three species have been found in the North-East Atlantic (P. crassa, P. insignis and P. lusitanus). Bird & Holdich (1989) noted the relevance of the cephalothorax shape and chelipeds setae to distinguish among these three sympatric species. Like P. cousteaui sp. nov., P. crassa presents a maxilliped basis with endites not fused, cheliped carpus with long midventral seta and strong chela; it differs from the new species in having a stouter antennule with different chaetotaxy (group of four penicillate subdistal setae instead of just two), presence of strong lacinia mobilis in the left mandible, two setae in the endite of maxilliped, the post-cheliped sclerites clearly visible dorsally, and non-serrated spines in pereopods 4–6. Paranarthrura insignis shares with P. cousteaui sp. nov. the following characters: post-cheliped sclerites unfused ventrally; pereopod 1 chaetotaxy on carpus, propodus, dactylus and unguis and chaetotaxy on chela. It can be distinguished by the following characters: post-cheliped sclerites hardly visible dorsally; antennule article 1 considerably shorter than the three others combined; protuberance from ventral margin of chelipedal propodus with two setae and uropodal endopod article 1 shorter than article 2. Paranarthrura lusitanus shares with P. cousteaui sp. nov. the post-cheliped sclerites unfused ventrally. It can be distinguished in having a shorter body (1.4 vs 2.1 mm); shorter cheliped, less prominent from ventral view; post-cheliped sclerites hardly visible dorsally; presence of two subdistal penicillate setae in antennule article 1; presence of two penicillate setae in the basis of pereopod 6.

Paranarthrura angolesis from the South East Atlantic shares with P. cousteaui sp. nov. the following characters: post-cheliped sclerites not fused, presence of serrate spines on pereopods and number and relative length of uropod endopod article; it can be distinguished from the new species by the endopod with “setose setae” (sensu Guerrero - Kommritz et al. 2002), a more slender chela (2.5 times as long as broad, instead of 2.1) and four setae on maxilliped articles 2 and 3 instead of three. Paranarthrura bispinosa from the Gulf of Mexico, shares with P. cousteaui sp. nov. the short uropod exopod not as long as endopod article 1 and penicillate setae on the basis of the pereopods 4–5 and the presence of distoventral spiniform apophysis in pereopods 2–3 propodus; it differs by the maxilliped endites fused to basis, presence of several penicillate setae on antennule (five in article 1 and two in article 2) and antenna (three in article 3 and one in article 4), cheliped chaetotaxy (absence of midventral seta in merus, subdistal setae in carpus and dorsal in propodus, and presence of one midventral seta in carpus and one dorsal seta in dactylus) and slender chela. Paranarthrura tenuimanus also from the Gulf of Mexico, has very short setae on maxilliped endite, no long seta on cheliped carpus and no dorsal spine on dactylus.

Paranarthrura cousteaui sp. nov. can be distinguished from species with a two-articled uropod endopod from other geographic locations as follows: P. arctowskii from the Antarctic has post-cheliped sclerites unfused medioventrally two setae on maxilliped endite, and a longer uropod exopod; and P. bacescui from the Indian Ocean show relatively longer uropod endopod segments.

Distribution and ecology

Paranarthrura cousteaui sp. nov. was found in the three Portuguese canyons sampled and at the open slope off Sines (Southern distribution limit), between 897 and 1001 m depth, in silty clay and, in Setúbal Canyon, amongst arborescent foraminifera (see de Stigter et al. 2007 for more environmental information of sampling sites). Paranarthrura cousteaui sp. nov. was found sympatric with other tanaidacean species: Atlantapseudes curvatus Esquete & Cunha, 2017 and Typhlamia sandersi (Kudinova-Pasternak, 1985) at the open slope off Sines; A. curvatus, P. intermedia Kudinova-Pasternak, 1982, Collettea sp. and Typhlotanais sp. at Setúbal Canyon; Anarthruridae (undetermined) and Pseudotanais falcicula Bird & Holdich, 1989 at Cascais Canyon and Collettea sp. at Nazaré Canyon. Original descriptions of these species can be found in Kudinova-Pasternak (1982, 1985), Bird & Holdich (1989), and Esquete & Cunha (2017).