Acanthacaris tenuimana Bate, 1888

Chang, Su-Ching, Wang, Teng-Wei & Chan, Tin-Yam, 2015, First record of the Nephropid genus Acanthacaris Bate, 1888 (Crustacea: Decapoda: Nephropidae) from Taiwan, Zootaxa 4032 (5), pp. 595-599 : 595-598

Acanthacaris tenuimana Bate, 1888 ( Figs. 1 , 2 )

Phoberus tenuimanus Bate, 1888: 171 [type locality: New Guinea].

Acanthacaris tenuimana .— Bate, 1888: pl. 21.— Holthuis, 1974: 752.— Holthuis, 1984: NEPH Acant 2, unnumbered figs.— Hayashi & Ogawa, 1985: 220, fig. 1. — Macpherson, 1990: 293.— Holthuis, 1991: 28, figs 39b, 42.— Griffin & Stoddart, 1995: 232.— Chan, 1998: 988, unnumbered fig.— Davie, 2002: 389. — Chan, 2010: 156, fig. 2B.

Acanthocaris tenuimana .— Bate, 1888: pl. 22.

Phoberus caecus sublevis .—Wood-Mason in Wood-Mason & Alcock, 1891: 197 [type locality: Laccadive Sea]. — Alcock & Anderson, 1894: 161.— Anderson, 1896: 96.

Phoberus caecus tenuimanus .— Alcock, 1901: 156.— Alcock & McArdle, 1902: pl. 60.

Acanthacaris tenuimanus .— Bruce, 1974: 303, figs. 1, 2.

Acanthacaris opipara . — Burukovsky & Musij, 1976: 1811, figs. 1, 2 [type locality: near Durban, South Africa].

Phoberus brevirostris . — Tung et al., 1985: 379, fig. 1 [type locality: East China Sea].— Tung et al., 1988: 48, fig. 47.

Acanthacaris cf. tenuimana .— Watabe & Miyake, 2000: 31, fig. 3.

Material examined. S.W. Taiwan, “Ocean Researcher 1”, stn CST 5, 22°33.06’N, 119°42.01’E, 1290–1300 m, 31 May 2015, 1 male cl. 125.0 mm ( NTOU M01873 ).

Description. Entire body covered with fine spines. Rostrum longer than half carapace length, overreaching antennular peduncle but not reaching tip of scaphocerite; armed with 5 (2 rather indistinct) dorsal and 8 ventral teeth. Carapace with median, subdorsal, supraorbital and antennal carinae; subdorsal carina less distinct than supraorbital carina, reaching slightly behind orbit and bearing 1 pair of strong spines at anterior part; supraorbital carina strongly ridged, with strong spine followed by 6–7 spines; antennal spine strong, situated immediately behind anterior margin of carapace and followed by 5 distinct spines as well as some spinules. Eye strongly reduced, failed to reach middle of basal antennular segment; stalk immovable. Antennular peduncle more or less extending to middle of scaphocerite. Antennal peduncle slightly falling short of tip of scaphocerite, second segment bearing strong ventromesial spine distally.

Abdominal tergites and pleura densely packed with sharp posteriorly pointed spines; first pleuron small and rounded; second to fifth pleura large and bluntly pointed ventrally; sixth pleura subtriangular. Telson rather squarish; lateral margin bearing 10–12 spines, distal spine much larger than second distal spine on right side but similar in size on left side; posterior margin denticulate. Uropods longer than wide; exopod larger than endopod and bearing diaeresis.

First cheliped (right side missing) slender but greatly elongated; fingers 1.85 times as long as palm, occusal margin armed with long and short oblique teeth at regular intervals; outer margin of movable finger bearing numerous spinules as well as some larger spines; outer margin of fixed finger uniformly covered with spinules. Second cheliped densely covered with spinules, fingers slightly shorter than palm, carpus as long as merus. Third cheliped much more robust but shorter than second cheliped, palm about 1.5 times as long as fingers, merus with 1 large and 2–3 small anterodorsal spines. Third cheliped and last two pereiopods also packed with distinct spines but less dense than anterior chelipeds. Fourth pereiopod with propodus about 3 times as long as dactylus, merus nearly 2 times as long as carpus, bearing 1–2 strong anterodorsal spines. Fifth pereiopod similar to fourth pereiopod.

Coloration. Uniformly pinkish with distal part of scaphocerite, basal antennal segment, ventral part of basal rostrum, dorsal carpus and distal parts of merus of first cheliped, most parts of propodus and dactylus of right fifth pereiopod, and articulate surface of first abdominal tergum whitish.

Distribution. Indo-West Pacific: southwestern Indian Ocean near Natal, Mozambique, Madagascar, Laccadive Islands, Indonesia (Makassar Strait and western Kepulauan Aru), eastern Australia, New Caledonia, the Philippines, South and East China Seas, Japan and now Taiwan. At depths of 600–2161 m.

Remarks. The two species of Acanthacaris can be readily separated by the fingers of the large chela as long as palm in A. caeca but distinctly longer than plam in A. tenuimana ( Holthuis 1991) . The large cheliped in the Taiwanese specimen is typical of the Indo-West Pacific species.

This lobster has a very large size but it appears that those from the Indian Ocean are larger and can reach a carapace length of 212 mm (from Madagascar, see Macpherson 1990). Material reported from the West Pacific is at most 157 mm carapace length (from eastern Australia, Griffin & Stoddart 1995). Moreover, there are some morphological differences reported amongst the Indo-West Pacific material (see Burukovsky & Musij 1976; Hayashi & Ogawa 1985; Tung et al. 1985; Macpherson 1990) and altogether four names have been created for them. Wood-Mason and Alcock (1891) used the name A. sublevis (i.e. Phoberus caecus sublevis ) for the Indian material but later admitted that it is the same as A. tenuimana ( Alcock, 1901) . Another name A. opipara was given to the material from the southwestern Indian Ocean by Brukovsky & Musij (1976) for having longer fingers in the large chelae (2 times as long as palm vs. about 1.5 times as long as palm in the type of A. tenuimana from the western Pacific). On the other hand, A. brevirostris described from the East China Sea by Tung et al. (1985) has the rostrum (about half carapace length) shorter than the other material from the Indo-West Pacific (longer than half carapace length) and with less rostral teeth (0 dorsal and 1–2 ventral vs. 3 dorsal and 5–6 ventral rostral teeth). Nevertheless, after examining a series of specimens, Macpherson (1990) considered that all these are likely to be intraspecific variations. Although the present specimen was collected in southern Taiwan and not far from the East China Sea, it has a longer rostrum with more rostral teeth than Tung et al.’s (1985) A. brevirostris and similar to the typical A. tenuimana . On the other hand, the Taiwanese specimen has the fingers of the large chela 1.85 times as long as palm, and this is intermediate between Bate’s (1888) A. tenuimana from the southwestern Pacific and Burukovsky & Musij’s (1976) A. opipara from the southwestern Indian Ocean. Literature review indeed suggests that material from the Indian Ocean generally has slightly longer fingers in the large chelipeds (1.71–2.0 times as long as palm, Alcock & McArdle 1902; Bruskovsky & Musij 1976) than those from the western Pacific (1.25–1.70 times as long as palm, not including the present specimen, Bate 1888; Bruce 1974; Hayashi & Ogawa 1985; Tung et al. 1985; Griffin & Stoddart 1995). Nevertheless, the rareness of Acanthacaris in the Indo-West Pacific hinders further evaluation on their taxonomy. But as commented by Holthuis (1984, 1991), if the Indo-West Pacific material are separated into two species, the name A. sublevis instead of A. opipara should be used for the Indian Ocean form.

The present specimen was collected near a deep-sea cold seep. However, there is no report on Acanthacaris directly associated with deep-sea chemosynthetic habitats (see Martin & Haney 2005; Desbruyères et al. 2006). There is only one report of this lobster from the vicinity of a hydrothermal vent but in area not affacted by hydrothermalism ( Watabe & Miyake 2000). Whether A. tenuimana really enter cold seep will need further investigations.

Figures

FIGURE 1. Acanthacaris tenuimana Bate, 1888, southwestern Taiwan, 1290 – 1300 m, male cl 125.0 mm, (NTOU M 01873). A, lateral view; B, dorsal view.

FIGURE 2. Acanthacaris tenuimana Bate, 1888, southwestern Taiwan, 1290 – 1300 m, male cl 125.0 mm, (NTOU M 01873). A, anterior carapace and appendages, dorsal view; B, left major cheliped (tip slightly broken), mesial view. Scale bars: 3 cm.