Quadrella boopsis Alcock, 1898

Ng, Peter K. L., 2017, Two new records of the coral symbiont crab genus Quadrella Dana, 1851, from Taiwan, with notes on the taxonomy of Q. boopsis Alcock, 1898 (Crustacea: Brachyura: Trapeziidae), Zootaxa 4324 (3), pp. 571-580 : 572-578

Quadrella boopsis Alcock, 1898

( Figs. 1–3 )

Quadrella boopsis Alcock, 1898: 227 .— Alcock & Anderson 1899: pl. 38 fig. 1.— Sakai 1965: 163, fig. 19, pl. 80 fig. 4; 1976: 512, pl. 184 fig. 2.— Serène 1973: 201; 1975: 514, figs. 5–12, pl. 2; 1984: 287, fig. 191, pl. 41 fig. A.— Sakai 1976: 512, pl. 184 fig. 2.— Kensley 1981: 45.— Takeda 1982: 194, fig. 574.— Miyake 1983: 140, 235, pl. 47 fig. 5.—1998: 140, 235, pl. 47 fig. 5.— Castro 1999a: 95; 1999b: 32, fig. 1: 66.—Castro et al. 2004: 55, 56.—Ng et al. 2008: 185. Quadrella bispinosa Borradaile, 1902: 266 , fig. 58.— Barnard 1950: 819.— Guinot 1967: 275.— Serène 1968: 89.—1973: 198.— Galil & Takeda 1985: 197, fig. 1.— Galil 1986: 278, figs. 3 A–D.— Yamaguchi et al. 1987: 30. Quadrella boopsis boopsis — Serène 1968: 89.

Quadrella aff. boopsis — Serène 1973: 202, figs. 2, 14–16.

Not Quadrella boopsis — Galil 1986: 281, figs. 4A, B (= Quadrella reticulata Alcock, 1898 ).

Material examined. (All collected from Tubastraea micrantha , Taiwan).1 ovigerous female (13.05 × 11.64 mm) ( ZRC 2015.285 ), Siauliukiu diving spot, South Bay, southern Taiwan, coll. C.- W. Lin, 17 December 2013; 1 female (with bopyrid) (14.90 × 12.20 mm) , 1 female (6.05 × 7.05 mm) ( ZRC 2015.287 ), Bluehole diving spot diving spot, South Bay, southern Taiwan, coll. C.- W. Lin, 18 March 2014 ; 1 females (8.32 × 7.44 mm) (NMMBCD4079), Siauliukiu diving spot, South Bay, southern Taiwan, coll. C .- W. Lin, 0 6 February 2014; 1 young female (7.15 × 6.40 mm) (NMMBCD4080), Bluehole diving spot, South Bay, southern Taiwan, coll. C .-W. Lin, 18 March 2014; 1 ovigerous female (10.76 × 9.23 mm) (NMMBCD4081), 82.7 diving spot, north-eastern Taiwan, coll. C.- W. Lin, 18 July 2014; 1 male (5.87 × 5.24 mm) ( ZRC 2015.286 ), Independent Rock diving spot, South Bay, southern Taiwan, coll. C .-W. Lin, 22 November 2014.

Diagnosis. Dorsal surface of carapace, chelipeds and ambulatory legs variously covered with plumose setae, denser, more prominent in individuals exceeding 10 mm carapace width ( Figs. 1 , 2 ). Carapace usually with 1 anterolateral spine, gently curved anteriorly, sometimes with small intermediate spine ( Figs. 1 , 3A ). Tips of frontal teeth rounded, median teeth longer, separated by deep cleft; internal orbital angle rounded ( Fig. 2A ) or with short spinules ( Fig. 2B ), always with short submarginal spine ( Fig. 2A, B ). Carpus of cheliped with 2 spines on anterior margin and 1 on inner angle ( Fig. 1 ). Merus of cheliped short, less than two-thirds carapace length, anterior margin lined with 5–9 small and large sharp teeth ( Fig. 2C, D ). Propodus of P2–P5 unarmed; dactylus of P2–P5 3–4 times longer than wide, posterior margin with 3–11 low to distinct teeth ( Fig. 3C–F ). Suture between male and female thoracic sternites 2 and 3 distinct, complete. G1 slender, distinctly sinuous, distalmost surface with 8 or 9 spines ( Serène 1975: figs. 7–12; Serène 1984: fig. 191).

Variation. Among the variously-sized Taiwanese specimens, the dorsal surface of the carapace is distinctly more convex and appears more swollen in larger specimens ( Fig. 1B ) compared to smaller ones ( Fig. 1A ). The internal orbital angle in smaller specimens is rounded and almost smooth ( Fig. 2A ) but is spinular in larger ones ( Fig. 2B ), although the submarginal spine is always distinct.

Remarks. Castro (1999b: 33, 36) noted that carapace and appendages of specimens recorded by Serène (1975: pl. 2B’, F) from Saparua Island, east of Ambon in Indonesia, and Miyake (1983: pl. 47 fig. 5; 1998: pl. 47 fig. 5) and Nakamura (1996: 50) from Japan were tomentose; whereas those from Madagascar, Maldives and Japan he examined lacked or had only a few long setae (see also Serène 1975: pl. 2A, B; Serène 1984: pl. 41A). We believe this is at least partly associated with size. Smaller specimens from Taiwan about 10 mm in carapace width tend to be more glabrous, with only scattered tufts of plumose setae on the carapace and appendages ( Figs. 1A , 2A ). Larger specimens 13 mm in carapace width are more pubescent, with distinctly denser setae over these surfaces ( Figs. 1B , 2B–D ). These plumose setae are easily removed, even with gentle brushing. As such, it is possible older records of the species or specimens examined by other workers may have had these setae accidentally removed during cleaning. Fresh specimens, like those examined here, are distinctly pubescent, even though these setae never obscure the surface or margins.

The absence or presence of an additional tooth between the external orbital tooth and the lateral carapace tooth has been discussed at length by Castro (1999b: 34–35), and we agree with him that this character varies too much to be taxonomically useful. Of the six specimens examined, one female (7.15 × 6.40 mm, NMMBCD4080) has an additional small tooth on the right margin but none on the left ( Fig. 3A ).

The ambulatory propodi are all unarmed, lined only with stiff setae; with the number of teeth or denticles on the flexor margin of the dactylus varying from 3 to 11 ( Fig. 3C–F ). These dactylar teeth all appear eroded to differing degrees.

All the present specimens were collected from the sun coral, Tubastraea micrantha (Ehrenberg, 1834) (Cnidaria: Anthozoa: Scleractinia : Dendrophylliidae ). These are non-reef building, ahermatypic, azooxanthellate corals typically found in waters 20–25 m deep.

Colour. The present specimens from Taiwan are relatively consistent in their colour, although there is some variation associated with size. The dorsal surface of the carapace and chelipeds are orange to light orange, with the ambulatory legs yellowish-orange in life. The margins of the carapace and distal margins of the pereopodal meri and propodi are dark orange to red, giving them a banded appearance ( Figs. 1 , 2 ). This contrasting pattern is more distinct in smaller specimens ( Fig. 1A ), with larger ones having the carapace and chelipeds more reddish-orange ( Fig. 1B ). This generally agrees with the colour reported by other workers (see Borradaile 1902; Sakai 1965, 1976; Takeda 1982; Nakamura 1996). In smaller specimens (carapace width about 10 mm), the chela and fingers are uniform orange ( Fig. 1A ) but the distal third of the fingers becomes white in large specimens ( Fig. 1B ). Serène (1975: 518) reported that his Indonesian specimens, which were collected from an unidentified black dendrophylliid coral, were a dark brownish-violet with the fingers of the chela white. This colouration may be because of its host.

Castro (1999b: fig. 1) figured a specimen from French Polynesia that had a spotted carapace and in which the merus of the cheliped also appears to be proportionately longer (cf. Figs. 1 , 2C, D ). The identity of these specimens should be re-confirmed.

Figures

FIGURE 1. Quadrella boopsis Alcock, 1898. In situ in coral, Taiwan. A, female (10.76 × 9.23 mm) (NMMBCD); B, male (5.87 × 5.24 mm) (ZRC 2015.286).

FIGURE 2. Quadrella boopsis Alcock, 1898, colours in life. A, female (8.32 × 7.44 mm) (NMMBCD); B, ovigerous female (10.76 × 9.23 mm) (NMMBCD); C, female (14.90 × 12.20 mm, with bopyrid) (ZRC 2015.287); D, female (6.05 × 7.05) (ZRC 2015.287); E, ovigerous female (13.05 × 11.64 mm) (ZRC 2015.285); F, male (5.87 × 5.24 mm) (ZRC 2015.286). All specimens from Taiwan.

FIGURE 3. Quadrella boopsis Alcock, 1898, overall habitus, Taiwan. A, male (5.87 × 5.24 mm) (ZRC 2015.286); B, ovigerous female (10.76 × 9.23 mm) (ZRC 2015.287); C, ovigerous female (13.05 × 11.64 mm) (ZRC 2015.285).