Rayllianassa amboinensis

Komai, Tomoyuki, Fujita, Yoshihisa & Maenosono, Tadafumi, 2014, Additional record of Rayllianassa amboinensis (de Man, 1888) from Japan, and description of a new species from Okinawa Island, Ryukyu Islands (Crustacea: Decapoda: Axiidea: Callianassidae), Zootaxa 3835 (4), pp. 549-563 : 551-554

Rayllianassa amboinensis (de Man, 1888)

( Figs. 1 , 2 )

Callianassa amboinensis de Man 1888: 480, pl. 20, fig. 4.— Zehntner 1894: 194.— Holthuis 1958: 35.— Poore & Griffin 1979: 248, fig. 14.— Sakai 1984: 96, figs 1, 2; 1988: 53 (key), 57, fig. 1; 1999: 35 (key), 38; 2005: 71.— Ngoc-Ho 1991: 283, fig. 1; 2005; 68, fig. 12.—Tudge et al. 2000: 143.— Davie 2002: 458.— Poupin 2003: 23 (list).— Poore 2008: 172.

Callianassa (Calliactites) amboinensis .— Borradaile 1903: 545.

Callianassa (Trypaea) amboinensis .—de Man 1928: 107 (key), 165, pl. 18, fig. 28–28c.

Callianassa ngochoae Sakai 1999: 36 (key), 49.

Rayllianassa amboinensis .— Komai & Tachikawa 2008: 43, figs 13–15.

? Callianassa amboinensis — Samadi et al. 2010: 462.

Notiax amboinensis .— Sakai 2011: 382.

Notiax ngochoae .— Sakai 2011: 385.

Material examined. Off Kamiura, Kushimoto, 20–30 m, 10 November 2001, commercial lobster net, associated with unidentified sponge, 1 ovigerous female (cl 7.6 mm), coll. K. Nomura, CBM-ZC 11937; TRV “Toyoshiomaru”, 2009-3 cruise, stn 2-2, N of Mage Island, Ohsumi Islands, 30°49.60’N, 130°50.20’E, 124–125 m, 19 May 2009, beam trawl, 1 ovigerous female (cl 5.8 mm), CBM-ZC 11074; TRV “Toyoshio-maru”, 2005-4 cruise, stn 8, W of Itoman, Okinawa, 26°08.34’N, 127°32.03’E, 69 m, 22 May 2005, dredge, coll. T. Komai, 1 ovigerous female (cl 6.6 mm), CBM-ZC 11015; TRV “Toyoshio-maru”, 2013-4 cruise, Ohshima-shin-sone Bank, Amami Islands, 28°52.46’N, 129°32.93’E, 169–174 m, hard bottom with many sponges and soft corals, 29 May 2013, dredge, coll.

T. Komai, 1 ovigerous female (cl 4.7 mm), CBM-ZC 11938; Ohmine, Naha, Okinawa, 0.5–1 m at low tide, 27 April 2013, coll. T. Maenosono, 6 females (cl 2.8–5.8 mm), 3 ovigerous females (cl 3.2–4.7 mm), CBM-ZC 12163; Sesoko Islet, Okinawa, 0.5–1 m at low tide, 12 May 2013, coll. T. Maenosono, 1 female (cl 3.4 mm), CBM-ZC 12164; Inanse, Urasoe, Okinawa, 0.5–1 m at low tide, 7 July 2012, 1 female (cl 7.3 mm), CBM-ZC 12165.

Description. See de Man (1928), Sakai (1984), Ngoc-Ho (1991) and Komai & Tachikawa (2008).

Coloration in life. Body and appendages generally milky white, second and third pleomere brownish, telson and uropods yellowish. Eggs light tan. See Fig. 1 .

Distribution. Widely distributed in the Indo-West Pacific: Ambon, Indonesia (de Man 1888; Zehntner 1894); Eylath, Israel ( Holthuis 1958); Dampier Archipelago, Western Australia ( Poore & Griffin 1979; Poore 2008); Heron Island, Queensland, Australia ( Sakai, 1984); Port Essington, Northern Territory, Australia ( Sakai 1988); New Caledonia ( Ngoc-Ho 1991); Japan ( Komai & Tachikawa 2008; this study); Philippines ( Ngoc-Ho 2005); Marquesas Islands, French Polynesia ( Ngoc-Ho 2005); Easter Island ( Poupin 2003); shallow subtidal to 183 m.

Habitat. Habitat of Rayllianassa amboinensis has not been specified, although Sakai (2005: 71) and Poore (2008: 172) recorded sponges, corals, and gorgonians as by-catch fauna.

In the present series, three specimens (CBM-ZC 11015, 11074, 11937), collected by dredge, came from hard bottoms with many sponges and alcyonaceans, and of them one specimen (CBM-ZC 11015) was found in an unidentified sponge. The specimen from Kushimoto (CBM-ZC 11937) was also living in an unidentified sponge.

Specimens from subtidal zone in Okinawa (CBM-ZC 12163–12165) were all found to be associated with an unidentified species of alcyonacean soft coral. Openings of burrows were found on the upper surface of the soft coral, of which the diameter was 3–4 mm. It was found that individuals stayed in a small chamber between the base of soft coral and the rock substratum. More than one individual could inhabit in a single colony of soft coral. It remains unknown how the shrimp constructs and maintains their burrows such an unusual habitat.

Remarks. The present specimens agree generally with the previous descriptions and/or figures of Rayllianassa amboinensis by de Man [1928, as Callianassa (Trypaea) , including the holotype], Poore & Griffin (1979, as Callianassa ), Sakai (1984, as Callianassa ; 1988, as Callianassa ), Ngoc-Ho (1991, as Callianassa ; 2005, as Callianassa ), and Komai & Tachikawa (2008). Some characters are known to exhibit intraspecific variation ( Poore & Griffin 1979; Sakai 1984; Ngoc-Ho 2005; Komai & Tachikawa 2008; Poore 2008): the rostrum varies from obtuse to sharply triangular; the ventral margins of meri of chelipeds are convex and minutely denticulate or nearly straight to slightly concave with or without denticles; the posterior margin of the telson is unarmed or armed with a minute median spine; and the ventral margin of the propodus of the third pereopod is smoothly convex to undulate. These variations are also seen in the present series of specimens from Japan. It is interesting to note that the variation of the shape of cheliped meri seem to correlate with bathymetric range. In the present series, ventral margins of cheliped meri are convex (cf. Fig. 2 D) in 11 specimens from shallow subtidal zone (CBM-ZC 12163–12165), whereas those are nearly straight or faintly sinuous (cf. Fig. 2 E) in four specimens from deeper zone (CBM-ZC 11937, Kushimoto, 20–30 m; CBM-ZC 11074, N of Mage Island, 124–125 m; CBM-ZC 11015, W of Itoman, Okinawa, 69 m; CBM-ZC 11937, Ohshima-shin-sone Bank, Amami Islands, 169–174 m). Examination of more specimens, in particular, comparison of molecular markers, is advisable to determine if two separate species are actually represented in the current R. amboinensis .

Sakai (1999) established a new taxon Callianassa ngochoae Sakai, 1999 , for a male specimen from New Caledonia, referred to C. amboinensis by Ngoc-Ho (1991), although he did not actually examine that specimen. He differentiated his new taxon from C. amboinensis by the relatively shorter ultimate segment of the antennular peduncle (citing as 1.5 times as long as the penultimate segment versus 3.0 times as long), the merus of major cheliped with a serrated and convex ventral margin (versus not serrated nor convex), and the telson being slightly longer than broad (versus about as long as broad). Later, Sakai (2005) admitted that his (1999) action was wrong, and put C. ngochoae in the synonymy of C. amboinensis . Ngoc-Ho (2005: 69–71) argued in detail that the characters cited by Sakai (1999) were based on misinterpretation or intraspecific variation, and also placed C. ngochoae in the synonymy of C. amboinensis . However, Sakai (2011: 382, key; 384) resurrected C. ngochoae as a valid species (as Notiax ngochoae ), although his notation given in the synonymy of Notiax is quite confusing [There Sakai noted that C. amboinensis , the type species of Rayllianassa , is identical with C. ngochoae (as Neaxius ngochoae )]. Furthermore, he attributed most previous records of Callianassa amboinensis to Notiax ngochoae , although only the specimen reported by Ngoc-Ho (1991) was originally considered to represent Callianassa ngochoae (cf. Sakai 1999: 49). The only differentiating character cited by Sakai (2011) is the proportion of the ultimate segment of the antennular peduncle, “three times” as long as the penultimate segment in “ Notiax amboinensis ”, while “1.5–2 times” as long as the penultimate segment in “ Notiax ngochoae ”. However, according to de Man (1928), the ultimate segment of the antennular peduncle was about 2.6 times as long as the penultimate segment in the holotype of Callianassa amboinensis , 2.5 times as long in the specimen from “Siboga” station 133. Ngoc-Ho (2005) specifically noted that, in the specimen designated as the holotype of C. ngochoae , the ultimate segment of the antennular peduncle is actually 2.4 times as long as the penultimate segment. In the present series, the ratio varies from 2.0 to 3.1. Thus Sakai’s (2011) action loses ground. We follow Ngoc-Ho (2005) to place C. ngochoae under the synonymy of Rayllianassa amboinensis at present.

Sakai (2011) gave a lengthy critical comment against the description of the male first and second pleopods of Ngoc-Ho’s (1991) specimen made by Komai & Tachikawa (2008). However, Komai & Tachikawa (2008) only highlighted more details of those appendages than Ngoc-Ho (1991) did, finding that there were actually two rami on the second pleopod, which was not mentioned by Ngoc-Ho (1991).

Samadi et al. (2010: 462) mentioned the occurrence of Callianassa amboinensis in the sunken-wood associated communities in deep water (the depth range is included in 100–1500 m, although not specified for the species) in the Southwest Pacific, but the identification might be questionable. The present species is a shallow water inhabitant (0.5–183 m), as has been shown by many references (de Man 1888, 1928; Zehntner 1894; Holthuis 1958; Poore & Griffin 1979; Sakai 1984, 1988, 1999; Ngoc-Ho 1991, 2005; Poore 2008; Komai & Tachikawa 2008; this study), burrowing in sponges or alcyonacean soft corals (this study).

In Japanese waters, this species was recorded from the Ogasawara Islands ( Komai & Tachikawa 2008). The present specimen from Kushimoto, Kii Peninsula (CBM-ZC 11937), extends the known geographical range of the species to further north to Honshu Island of Japan.

Figures

FIGURE 1. Rayllianassa amboinensis (de Man, 1888), ovigerous female (cl 4.7 mm), CBM-ZC 11938, entire animal in lateral view, showing coloration in fresh.

FIGURE 2. Rayllianassa amboinensis (de Man, 1888). A – D, ovigerous female (cl 4.0 mm), CBM-ZC 12163; E, ovigerous female (cl 6.6 mm), CBM-ZC 11015. A, carapace and left cephalic appendages, lateral view; B, sixth pleomere and telson, dorsal view; C, left third maxilliped, lateral view (setae omitted); D, E, merus of major (right) cheliped, lateral view. Scale bars: 1 mm for A, B, D, E; 0.5 mm for C.