Nephropsis stewarti Wood-Mason, 1872

Chang, Su-Ching, Chan, Tin-Yam & Kumar, Appukuttannair Biju, 2020, Deep-sea clawed lobster Nephropsis stewarti Wood-Mason, 1872 species complex in the Indo-West Pacific (Crustacea, Decapoda, Nephropidae), with description of a new species, ZooKeys 1008, pp. 37-60 : 37

Nephropsis stewarti Wood-Mason, 1872 Figures 1 , 4A-F

Nephropsis Stewarti Wood-Mason 1872: 151 (type locality: Andaman Sea); 1873: 60; 1874: 40, pl. 4-1-3, 5, 7; 1885: 71; Alcock 1894: 230; 1901: 159; Anderson 1897: 96; Alcock and Anderson 1899: 286.

Nephropsis stewartii .- Alcock and Anderson 1894: 161; 1896: pl. 27-figs 1, 1a; Lloyd 1907: 3; Ramadan 1938: 124, text-fig. 1; Thomas 1979: 43.

Nephropsis stewarti Not Nephropsis Stewarti .-De Man 1916: 112, pl. 3-fig. 17. [= Nephropsis serrata Macpherson, 1993].

Nephropsis stewarti .- Calman 1925: 21; Barnard 1950: 531; Holthuis 1991: 45 (in part), fig. 80; Macpherson 1990: 312 (in part), figs 5e, 10, 11c, d, 16e; Zarenkov 2006: 93 (in part); Radhakrishnan et al. 2019: 112, fig. 3.22.

Nephropsis stewarti ? Nephropsis Stewarti .- Balss 1925: 208.

Nephropsis stewarti Not Nephropsis stewarti .- Kubo 1965: 629, unnumbered fig.; Miyake 1982: 77, pl. 26-1; Baba 1986: 153, fig. 103; Chan and Yu 1988: 8, pl. 1A; 1993: 83, unnumbered photo.; Holthuis, 1991: 45 (in part); Wadley and Evans, 1991: 39, unnumbered photo; Macpherson 1993: 63; Chan 1997: 415; Jones and Morgan 2002: 83, unnumbered photo; Davie 2002: 391; Zarenkov 2006: 93 (in part), fig. 19; Chang and Chan 2019: 50 (in part), fig. 7. [= Nephropsis grandis Zarenkov, 2006].

Nephropsis stewarti Not Nephropsis stewarti .- Macpherson 1990: 312 (in part). [? = Nephropsis grandis Zarenkov, 2006 and/or Nephropsis pygmaea sp. nov.].

Nephropsis stewarti Not Nephropsis stewarti .- Chang and Chan 2019: 50 (in part). [= Nephropsis pygmaea sp. nov.].

Nephropsis stewarti Not Nephropsis stewarti .- Chang and Chan 2019: 50 (in part), figs 2C, D. [= Nephropsis serrata Macpherson, 1993].

Material examined.

Neotype: Andaman Sea • male cl 46.2 mm; RV "Dr. Fridtjof Nansen" stn 135, 12°21.96'N, 96°37.32'E, 514 m, 23 May 2015 (NTOU M02249).

Other material.

Andaman Sea • 1 male cl 42.3 mm; RV "Dr. Fridtjof Nansen" stn 68, 14°03.72'N, 94°19.08'E, 457 m, 10 May 2015 (NTOU M02250) • 1 female cl 42.6 mm; commercial trawler, 09°34'65"N, 92°43'21"E, 320 m, 13 Nov. 2017 (DABFUK/AR-ACH-7). Andaman Islands • 1 male cl 38.4 mm, 1 female cl 33.7 mm; A185, commercial trawler, 13 Nov. 2017 (DABFUK/AR-ACH-8). INDIA • 1 male cl 47.0 mm; Sakthikulangara fishing harbor, Kollam district, Kerala, commercial trawler, Nov. 2013 (DABFUK/AR-ACH-9) • 1 male cl 50.8 mm, 2 ovigerous females 42.4 and 48.7 mm; 4 Mar. 2019 (DABFUK/AR-ACH-10) • 2 ovigerous females cl 46.8 and 49.2 mm (DABFUK/AR-ACH-11). Mozambique • 1 male cl 52.7 mm; Mainbaza stn CP3138, 25°12.13'S, 35°21.07'E, 700-707 m, 10 Apr. 2009 (MNHN IU-2018-5063).

Diagnosis.

Rostrum bearing one pair of dorsolateral teeth usually situated near mid-length of rostrum. Carapace with subdorsal carinae granulate, without distinct spine or tooth-like process; supraorbital and antennal spines present, lacking post-supraorbital spine; post-cervical groove U-shaped in dorsal view; intermediate and lateral carinae well marked. Large cheliped (pereiopod I) with inner surface of palm lacking distinct spines; carpus with strong distoventral, ventro-outer distal (rarely absent), and dorso-inner distal spines, inner surface with dorsal margin generally bearing 2-4 spines, outer surface without distinct spines; merus bearing subdistal dorsal, subdistal outer and distoventral spines. Pleon finely granulate, without median carina; pleura lacking spine on anterior margins. Telson without erected dorsal median spine near base. Uropodal exopods with complete diaeresis.

Description.

Body covered with long or short pubescence, rather thick on anterior two pereiopods, dorsal carapace, and pleonal tergum.

Carapace finely granulated (Fig. 1A, B ); rostrum 0.4-0.5 × as long as carapace, with 1 pair of teeth usually situated near mid-length of rostrum; subdorsal carinae granulate, without distinct spine or tooth-like process; supraorbital and antennal spines well developed, post-supraorbital spine absent; cervical, postcervical, and hepatic grooves present, with post-cervical groove U-shaped in dorsal view; intermediate and lateral carinae both well marked; gastric tubercle located near supraorbital spine, their distance being approximately 0.4 × distance between gastric tubercle and post-cervical groove; distance between orbital margin and post-cervical groove 1.2-1.5 × longer than the distance between post-cervical groove and posterior margin of carapace.

Large cheliped (pereiopod I), generally granulate (Fig. 1C-E ) but less granular in females; inner surface of palm granular but without distinct spines; chela 3.0-4.0 × as long as wide, males generally having relatively longer chela (> 3.5 ×), whereas females having shorter chela (<3.5 ×); carpus with strong distoventral spine, ventro-outer distal spine (rarely absent) and dorso-inner distal spine, inner surface with dorsal margin bearing 2-4 (rarely 1) spines, outer surface without distinct spines; merus bearing subdistal dorsal spine, subdistal outer spine and distoventral spine.

Pereiopod II with carpus 0.5-0.7 × palm length. Pereiopod III with carpus 0.4-0.5 × as long as palm; merus 1.4-2.1 × as long as carpus. Pereiopods IV and V with dactyli 0.4-0.6 × as long as propodi.

Entire pleon finely granulate (Fig. 1A, B ) without median carina; pleura lacking spine on anterior margins, each terminating ventrally into blunt to sharp spine. Telson without erected dorsal median spine near base. Uropodal exopods with complete diaeresis.

Eggs spherical and 2.2-2.7 mm in diameter.

Distribution.

Known with certainty in the western to northeastern Indian Ocean from the eastern coast of South Africa to the Andaman Sea. Found at depths of 250-1520 m and perhaps even 1720 m, but mostly less than 1000 m (see Alcock 1901; Macpherson 1990; Zarenkov 2006).

Color in life.

Body varies from whitish to reddish (Fig. 4 ; Radhakrishnan et al. 2019: fig. 3.22). Eyes and antennal peduncle always whitish. Distal parts of pereiopods II-V, pleopods always reddish. Large cheliped and pleonal tergum, whitish to orange. Pleonal pleura and uropods purple to reddish. Antennal and antennular flagella orange to reddish. Pubescence grayish to reddish. Eggs orange.

Remarks.

Although the present Indian specimens have a very reddish color, a comparison with Andaman Sea topotypic specimens and material from Mozambique Channel revealed wide color variations in N. stewarti , from whitish to reddish (Fig. 4 ). Specimens with different colors in the western and northern Indian Ocean are genetically very similar, with 1.0% or less sequence divergence in 16S (Table 2 ). However, large genetic divergences (16S sequence divergence 3.8-7.3%) exist between the material from the western and northern Indian Ocean, and that from the western Pacific (including the South China Sea and Arafura Sea) and northwestern Australia (Table 2 ). Such genetic differences are greater than those between N. rosea Bate, 1888 and N. aculeata Smith, 1881 (3.1-3.7%) and between N. serrata Macpherson, 1993 and N. stewarti s.l. (lowest 2.8%).

Nephropsis grandis , previously considered to be a synonym of N. stewarti , has a type locality in the Arafura Sea ( Zarenkov 2006). Of the three characteristics proposed by Zarenkov (2006: table 1) to separate N. grandis from N. stewarti , the shape of the distal part of the rostrum has been shown to be variable. The subdistal outer spine on the merus of the large cheliped is present in all of the western and northern Indian Ocean specimens (Fig. 1C, D ) but can be present or absent in the western Pacific and northwestern Australia material (Figs 2C, D , 3C, D ). The degree of development of the lateral carina on the carapace is similar in all the Indo-West Pacific material (Figs 1B , 2B , 3B ). However, the intermediate carina on the carapace is well developed in all of the western and northern Indian Ocean material (Fig. 1A, B ) but is indistinct in the western Pacific and northwestern Australia specimens (Figs 2A, B , 3A, B ). Moreover, a pair of lateral rostral teeth is usually situated around the mid-length of the rostrum in the western central Indian Ocean material (with only one exception; a cl 42.3 mm ovigerous female of DABFUK/AR-ACH-10) but mostly in a position distinctly posterior to the middle of the rostrum in the specimens from the western Pacific and northwestern Australia (except in three specimens; one in N. grandis : NTOU M02177, and two in N. pygmaea sp. nov.: NTOU M02168, NTOU M02262).

Nephropsis stewarti was originally described from a single female specimen lacking large chelipeds, and collected from Ross Island of the Andaman Islands ( Wood-Mason 1873, 1874). Soon after its discovery, many more specimens of this species were collected in India (see Alcock 1901); however, the holotype (supposed to have registration number 1404) is no longer extant, although having been held by the Zoological Survey of India, Calcutta (S Mitra, Zoological Survey of India, Calcutta, personal communication). As the N. stewarti species complex has now been found to contain at least three species, in order to fix the identity of N. stewarti , a recently collected Andaman Sea specimen (NTOU M02249) with color (Fig. 4E ) and genetic information (Table 1 ) and that is very close to the type locality, is herein selected as the neotype of this species. The neotype fits well with the description of the holotype ( Wood-Mason 1873, 1874), particularly in terms of the eye being rudimentary, bearing one pair of lateral rostral teeth, exopod of uropod with distinct diaeresis, and generally being similar to the figures provided for the holotype (Fig. 1A, B ; Wood-Mason 1874: pl. 4-1-3).

Because material from northwestern Australia in the eastern Indian Ocean is now considered to belong to N. grandis instead of N. stewarti , re-examination of the specimens from northeastern Sumatra in the eastern Indian Ocean, reported by Balss (1925), will be necessary to determine if they represent N. stewarti , despite being collected near the type locality of the latter species. Re-examination of the " N. stewarti " material, reported by Chang and Chan (2019), revealed that all but one female (NTOU M02162) from the South China Sea belong to either N. grandis or the new species described below. This particular female specimen has the subdorsal carina on the carapace bearing small spines; therefore, it actually represents N. serrata (also see Tables 1 , 2 ).

Although a red or white body color is thought to be specific for Nephropsis (see Chang and Chan 2019), this is not the case for N. stewarti . The Indian material appears to be much redder (Fig. 4A, B ; Wood-Mason 1885; Alcock and Anderson 1899; Radhakrishnan et al. 2019: fig. 3.22) and has more distinct granules on the pleon, sometimes even arranged like a median carina. Thomas (1979), however, mentioned that his N. stewarti material from the Gulf of Mannar had a greenish-yellow color and deep red appendages. Color photographs are available for two of the Andaman Sea specimens examined (NTOU M02249, M02250). One (Fig. 4F ) has a rather white body like the Mozambique specimen (MNHN IU-2018-5063, Fig. 4C, D ), except for the pereiopods II to V, which are entirely pale purple. The neotype (Fig. 4E ) has a body that is generally pale orange (which is intermediate between red and white). Color information on more specimens from different areas of the central western Indian Ocean will be necessary to understand whether material from the same locality also exhibits large variations in body color for this species.

Figures

Figure 1. Nephropsis stewarti Wood-Mason, 1872, Andaman Sea, RV ' Dr. Fridtjof Nansen' stn 135, neotype male cl 46.2 mm (NTOU M 02249) A carapace and pleon, dorsal B same, lateral C left pereiopod I, chela to distal part of merus, dorsal D same, lateral E same, ventral. Pubescence and setae omitted ● Position of spines on inner surface of palm ◇ position of spines on dorsal margin of outer surface of carpus ♦ position of spines on dorsal margin of inner surface of carpus ⏹ dorso-inner distal spine of carpus △ ventro-outer distal spine of carpus ◻ distoventral spine ✰ subdistal dorsal spine of merus ★ position of subdistal outer spine of merus.

Figure 2. Nephropsis grandis Zarenkov, 2006, Tanimbar Islands, Arafura Sea, KARUBAR stn CP 59, neotype male cl 64.1 mm (MNHN IU- 2017 - 9001) A carapace and pleon, dorsal B same, lateral C left pereiopod I, chela to distal part of merus, dorsal D same, lateral E same, ventral. Pubescence and setae omitted ● Position of spines on inner surface of palm ◇ position of spines on dorsal margin of outer surface ♦ position of spines on dorsal margin of inner surface ⏹ dorso-inner distal spine of carpus △ ventro-outer distal spine of carpus ◻ distoventral spine ✰ subdistal dorsal spine of merus ★ position of subdistal outer spine of merus.

Figure 3. Nephropsis pygmaea sp. nov., Donggang, Pingtung County, Taiwan, holotype male cl 25.6 mm (NTOU M 01898) A carapace and pleon, dorsal B same, lateral C left pereiopod I, chela to distal part of merus, dorsal D same, lateral E same, ventral, pubescence and setae omitted ● position of spines on inner surface of palm ◇ position of spines on dorsal margin of outer surface ♦ position of spines on dorsal margin of inner surface ⏹ dorso-inner distal spine of carpus △ ventro-outer distal spine of carpus ◻ distoventral spine ✰ subdistal dorsal spine of merus, ★ position of subdistal outer spine of merus.

Figure 4. A-F Nephropsis stewarti Wood-Mason, 1872 A, B Sakthikulangara fishing harbor, India, ovigerous female cl 42.4 mm (DABFUK / AR-ACH- 10) C, D Mozambique, MAINBAZA stn CP 3138, male cl 52.7 mm (MNHN IU- 2018 - 5063) E Andaman Sea, RV ' Dr. Fridtjof Nansen' stn 135, neotype male cl 46.2 mm (NTOU M 02249) F Andaman Sea, RV ' Dr. Fridtjof Nansen' stn 68, male cl 42.3 mm (NTOU M 02250) A, C, E, F dorsal habitus B, D lateral habitus E, F photographed by PN Psomadakis.