Nephropsis rahayuae, Chang & Chan & Kumar, 2020

Chang, Su-Ching, Chan, Tin-Yam & Kumar, Appukuttannair Biju, 2020, A new clawed lobster of the genus Nephropsis Wood-Mason, 1872 (Crustacea: Decapoda: Nephropidae) from the Indonesian deep-sea cruise, SJADES 2018, Raffles Bulletin of Zoology 68, pp. 50-55 : 52-54

Nephropsis rahayuae , new species

( Figs. 1 , 3A, B )

Material examined. Holotype: male (cl 23.8 mm), south of Java, SJADES 2018, stn CP 33, 7°42.912′S, 107°36.559′E, 525– 312 m, 29 March 2018 ( MZB Cru 5053) . Paratype: 1 male (cl 15.8 mm), south of Java, SJADES 2018, stn CP 20, 6°42.320′S, 105°08.682′E, 325–362 m, 27 March 2018 ( ZRC 2020.0126 ) .

Description. Carapace finely granulated ( Fig. 1A, B ). Rostrum 0.6–0.7 times as long as carapace length, tip slightly

curved upwards, bearing a pair of lateral spines just behind mid-length; median groove extending anteriorly beyond lateral rostral spines. Subdorsal carinae finely denticulate, without distinct spines. Supraorbital and antennal spines well-developed, post-supraorbital spine absent. Cervical, postcervical and hepatic groove distinct. Postcervical groove U-shaped in dorsal view, with median straight part 0.7 times as wide as carapace width at same position. Intermediate and lateral carinae present but indistinct. Gastric tubercle near supraorbital spines, their distance about 0.3 times the distance between gastric tubercle and postcervical groove. Distance between orbital margin and postcervical groove 1.5–1.6 times the distance between postcervical groove and posterior margin of carapace.

Pereopod I finely granulate ( Fig. 1C, D ), densely pubescent on dorsal surface; fingers 0.8–0.9 times as long as palm; carpus with an anteroventral spine, a small subdistal spine on outer-lower margin, inner surface with a distal spine on upper margin and a subdistal spine at lower margin of carpus; merus bears a small subdistal spine dorsally, a strong anteroventral spine on inner margin, and a small subdistal

spine on outer surface. Pereopod II unarmed ( Fig. 1E ), dorsal and ventral margins covered with long setae; carpus 0.9–1.0 times palm length. Pereopod III overreaching distal end of rostrum, less stout than pereopod II; carpus 0.6–0.7 times as long as palm; merus about two times as long as carpus. Pereopod IV and V smooth, non-chelate; dactylus 0.6–0.7 times as long as propodus.

Pleon generally smooth ( Fig. 1A, B ), with some granules, covered with short soft hairs. Pleonal somites II–VI bearing dorsal median carina but with those on somites II–IV rather indistinct. Posterior margin of somite V unarmed. Anterior margin of pleuron II strongly convex and lacking spine, terminating ventrally in a blunt or sharp angle. Anterior margins of pleura III–V moderately convex, each ending ventrally as a long spine. Telson without erected dorsal spine near base. Uropod generally smooth ( Fig. 1A, B ), sparsely covered with short soft hairs. Posterior angle of uropodal protopod armed with a spine. Uropodal exopods with conspicuous, fully formed diaeresis.

Etymology. The new species is named after Dwi Listyo Rahayu, the Indonesian chief scientist of the SJADES 2018 deep-sea cruise.

Colouration in life. Body generally whitish ( Fig. 3A, B ) and covered with light brown pubescence. Rostrum, dorsal carapace, distal parts of pereopods II to V, uropodal endopods, lateral margin of pleonal tergites, and margins of telson pale

orange to reddish. Antennular flagella reddish. Antennal flagella whitish but with distal portion becoming orange-red. Eyes whitish. Chela of pereopod I slightly pinkish.

Distribution. Only known from southwestern Java, Indonesia, at depths of 312– 525 m.

Remarks. The SJADES material is very similar to N. carpenteri by having one pair of lateral rostral spines, lacking post-supraorbital spine and pleon with a median carina. Nephropsis carpenteri has so far been known with certainty only from India and Myanmar ( Wood-Mason, 1885; Alcock, 1901; Macpherson, 1990; Holthuis, 1991; Watabe & Iizuka, 1999; Radhakrishnan et al., 2019). The access of recently collected material of N. carpenteri from Myanmar (NTOU M02248 ) and India (DABFUK/AR-ACH-6) allows detailed comparisons with the present two specimens taken from southern Java. Their colourations are very similar ( Fig. 3 ). Although the Java form is whiter than the India material and the exopod of uropod almost entirely whitish instead of reddish, two specimens from Myanmar show either a red (only photograph without specimen examined) or white (NTOU M02248 ) exopod. Nevertheless, the two Java specimens differ from the India and Myanmar materials of N. carpenteri by the intermediate and lateral carinae on the carapace being rather indistinct ( Fig. 1B ), and the post-cervical groove being U-shaped in dorsal view (with the median straight part 0.7 times as long as the carapace width at the same position; Fig. 1A ). The two specimens of N. carpenteri from India and Myanmar have well-marked intermediate and lateral carinae on the carapace ( Fig. 2A ), and the post-cervical groove is somewhat V-shaped in dorsal view (with the median straight part 0.3–0.4 times as long as the carapace width at the same position; Fig. 2G ). The carpus of the large cheliped (pereopod I) is less spiny in the Java form (no dorsal spine, 1 spine at lower margin of inner surface; Fig. 1C, D ) than in the India and Myanmar material (1 dorsal spine, 2–3 spines at lower margin of inner surface; Fig. 2C, D ). On the other hand, the rostrum ( Fig. 1A, B ) and carpus of pereopod II ( Fig. 1E ) appear to be longer in the Java form (rostrum longer than half carapace length, carpus of pereopod II 0.9–1.0 times as long as palm) than in N. carpenteri material from India and Myanmar (rostrum less than half carapace length, carpus of pereopod II 0.7–0.8 times as long as palm; Fig. 2A, E ) (also see Alcock & Anderson, 1894; Alcock, 1901; Macpherson, 1990). Moreover, the dorsal carinae on the pleonal somites II to IV are less distinct in the Java form ( Fig. 1A ) as compared to the India and Myanmar material ( Fig. 2B ).

Comparisons on the barcoding COI gene sequence (638 657 bp) showed that the two SJADES specimens have 99.8% similarity with each other, while the two India and Myanmar specimens have 99.7% similarity with each other. However, the Java form has 8.3–8.5% sequence divergence from the topotypic N. carpenteri material (i.e., from the Bay of Bengal). Such a high COI sequence divergence (i.e.,>5%) is generally considered to be the interspecific difference in decapod crustaceans ( Jones & Macpherson, 2007; Chan et al., 2009; Malay et al., 2012; da Silva et al., 2013; Komai et al., 2019). As both morphological and genetic differences can be found between the Java material and N. carpenteri , the Java form is determined to be a distinct species with the new name N. rahayuae , new species.

Other than N. carpenteri , N. rahayuae , new species, is also close to N. aculeata from the western Atlantic ( Macpherson, 1990; Holthuis, 1991). These three species differ from the congeners by a combination of characters: having one pair of lateral rostral spines, lacking a post-supraorbital spine, pleon bearing a median carina, no erect dorsal spine on the telson, and uropodal exopod with diaeresis. Nephropsis rahayuae , new species, can be readily distinguished from N. aculeata (see Holthuis, 1974, 1991) by the distance between the supraorbital spine and gastric tubercle being about 0.3 times the distance between gastric tubercle and postcervical groove ( Fig. 1A, B ) (versus about 0.5 times in N. aculeata ), and the dorsal median carina on the pleonal somites II–IV being rather indistinct ( Fig. 1A ) (versus these being distinct in N. aculeata ). Moreover, the carpus of pereopod II is shorter than the palm in N. rahayuae , new species ( Fig. 1E ) but distinctly longer than the palm in N. aculeata . The COI sequence divergence between N. rahayuae , new species, and N. aculeata is as high as 17.1–17.2%.

Figures

Fig. 1. Nephropsis rahayuae, new species, holotype, male (cl 23.8 mm), MZB Cru 5053. A, carapace and pleon, dorsal view; B, same, lateral view; C, left cheliped I, dorsal view; D, same, lateral view; E, left pereopod II, lateral view. ★: position of dorsal spines; ▲: position of spines at lower margin of inner surface.

Fig. 3. A, B, Nephropsis rahayuae, new species, holotype, male (cl 23.8 mm), MZB Cru 5053; C, D, Nephropsis carpenteri Wood-Mason, 1885, Sakthikulangara fishing harbour, India, male (cl 22.1 mm), DABFUK/AR-ACH-6.

Fig. 2. Nephropsis carpenteri Wood-Mason, 1885. A–F, Myanmar, ovigerous female (cl 32.9 mm), NTOU M02248; G, Sakthikulangara fishing harbour, India, male (cl 22.1 mm), DABFUK/AR-ACH-6. A, carapace and pleon, lateral view; B, pleon, dorsal view; C, left cheliped I, dorsal view; D, same, lateral view; E, left pereopod II, lateral view; F, anterior part of carapace, dorsal view; G, carapace, dorsal view. ★: position of dorsal spines; ▲: position of spines at lower margin of inner surface.