Uroptychus nitidus

Uroptychus nitidus (A. Milne Edwards, 1880) (Figs. 5–7) Diptychus nitidus A. Milne Edwards, 1880: 62 (part) (off Guadeloupe, off Dominica, off Martinique, off St Lucia, off St Vincent, off Florida, 161–1342 m; see Baba & Wicksten (2017a) for review). Uroptychus nitidus.— Baba & Wicksten 2017a: 253, figs 1, 2, 23A (see references in the revision of U. nitidus complex; designation of lectotype and paralectotypes). Type material. Lectotype: Martinique, BLAKE Stn 200, 14°31'55"N, 61°07'28"W, 863 m, 7 February 1879: female 7.1 mm (MCZ CRU-2756) [examined]. Other material examined (eastern Atlantic). Guinea Bissau. GB1219 Stn L53, 10°01'55"N, 17°25'01"W, 909 m, 30 November 2019: 1 male 13.5 mm (carapace broken, ICM-CBMR-D002842, sequenced, GenBank Acc. No. PQ654351), 3 ovigerous females 9.6–11.9 mm (ICM-CBMR-D002843). Sierra Leone, off Freetown. GALATHEA Stn 17, 7°17'N, 13°28'W, 1290 m, mud, 10.XI.1950: 2 males 9.3 mm, another male not measured (ZMUC CRU-11635). Other material examined (western Atlantic). Bahamas, Global Explorer ROV, F.G. Walton Smith R/V, Stn NWP 101–bb, 25°51'41.73"N, 77°16'57.41"W, 1731 m, 27 March 2009: 1 ovigerous female 8.7 mm (USNM 1532599, sequenced, GenBank Acc. No. PQ654359). — Gulf of Mexico, Louisiana, R/V Pelican Stn GoMRI-III-02, 27°34'8.46"N, 89°50'15.45"W, 1125–1148 m, 16 November 2012: 1 male 6.8 mm (USNM 1532600, sequenced, GenBank Acc. No. PQ654360). — Florida, R/V PELICAN Stn GoMRI-V-28, 24°20'51.50"N, 83°54'28.45"W, 1200 m, 11 September 2014: 1 male 4.8 mm (USNM 1532601, sequenced, GenBank Acc. No. PQ654361). — Caribbean Sea, Colombia, R/V OREGON, Cruise 92 Stn 4913, 12°09'N, 72°47'W, 183 m, 01 June 1964: 1 male 9.2 mm (USNM 1662453, sequenced, GenBank Acc. No. PQ654362). Comparative material. Uroptychus concolor (A. Milne Edwards & Bouvier, 1894): Off the coast of Sahara [now Western Sahara], TALISMAN Stn 80, 23°52'N, 19°37'W [Greenwich longitude 17°17'W], 1139 m: lectotype, male 10.9 mm (MNHN Ga507 [currently MNHN-IU-2016-534]). NW Spain, Bank of Galicia. INDEMARES Stn GOC8, 42°37'59.88"N, 11°28'59.88"W, 1565 m, 25 July 2011: 1 ovigerous female 7.2 mm (ICM-CBMR-D000322), sequenced, GenBank Acc. No. PQ65435, 1 female 8.0 mm (ICM-CBMR-D000324), sequenced, GenBank Acc. No. PQ654358; 1 female 9.0 mm (ICM-CBMR-D000323), sequenced, GenBank Acc. No. PQ654357.—Stn DR31, 42°58'59.88"N, 11°57'59.76"W, 1671 m, 25 July 2011: 1 male 13.1 mm (ICM-CBMR-D000282), sequenced, GenBank Acc. No. PQ654353, 2 ovigerous female 9.6 (ICM-CBMR-D000283), sequenced, GenBank Acc. No. PQ654354, 11.8 mm (ICM-CBMR-D000284), sequenced, GenBank Acc. No. PQ654355. Atlantis Seamount. SEAMOUNT 2, Stn DW 261, 34°22.37’N, 30°27.79’W, 1190–1340 m, 03 February 1993: 3 males 7.4–12.0 mm (CEAB-CRU 1993A). — Stn DW262, 34°23.36’N, 30°29.06’W, 1000–1160 m, 03 February 1993: 6 males 6.1–13.6 mm; 2 ovigerous females 10.5, 11.7 mm (CEAB-CRU 1993B). Genetic data. Intraspecific sequence divergence (COI): 1.5% (western and eastern Atlantic specimens). Interspecific sequence divergence is on average: 6% (U. concolor); 15% (U. rubrovittatus) (see Fig. 1). Remarks. The taxonomic status of Uroptychus nitidus was verified by Baba & Wicksten (2017a), based on examination of all syntypes and a large series of specimens from the western Atlantic. Morphologically, the present specimen from Guinea Bissau is only slightly different from the western Atlantic specimens in the ornamentation of the carapace dorsum (Fig. 5): small tubercles are scattered on the lateral surface in small specimens or distributed all over the surface in large specimens (versus obsolescent or nearly absent). However, molecular data indicate that the genetic distance (COI gene) between the western and eastern Atlantic specimens is minor at around 1.5% (Fig. 1), which suggests that this morphological variability is merely intraspecific. Among the squat lobster collection of the Galathea Expedition made available to KB (cf Baba 2005), two specimens taken at Station 17 off Freetown, Sierra Leone (ZMUC CRU-11635) were provisionally identified as Uroptychus nitidus considering its range was presumed to be restricted to the western Atlantic (Baba, unpubl.). This material was not included in that report, which treated the Indo-Pacific species. This identification of the Guinea Bissau specimen is now accepted, being corroborated by the present molecular analysis. Uroptychus nitidus resembles U. concolor (A. Milne Edwards & Bouvier, 1894) from the northeastern Atlantic, which was originally described as Diptychus nitidus var. concolor A. Milne Edwards & Bouvier, 1894. Chace (1942) noted that U. nitidus can be separated from U. concolor by the depressed P1, the carpus in particular; the height-breadth ratio of the P1 carpus is 0.6–0.7 in U. nitidus (see Baba & Wicksten 2017a), 0.8 in U. concolor (in accordance with the material here examined). A further diagnostic character is proposed here considering the relative size of the ultimate compared to penultimate spine of the P2–4 dactyli: the ultimate spine is subequal to the penultimate in U. nitidus (see Baba & Wicksten 2017a: fig. 2F, H, J; Fig. 7C, F, H in this paper), distinctly smaller in U. concolor (Figs. 8H, 11B, 11D, 11F), the latter confirmed by examination of the lectotype and additional material from off northeastern Atlantic. The genetic distance between U. nitidus and U. concolor is on average 6% for COI, and these species are highly divergent from U. rubrovittatus (15%) (Fig. 1). Distribution. Gulf of Mexico, Caribbean Sea, and Brazil. The present material extends its range to the western coast of Africa. The specimens from the coasts of Guinea Bissau and Sierra Leone were collected at 909–1290 m. The occurrences in the West Atlantic range between 161 and 1362 m (Baba & Wicksten 2017a).