Eucrate formosensis Sakai, 1974

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 30-32

Eucrate formosensis Sakai, 1974

( Figs. 2E, F ; 8A–F ; 14J–L)

Eucrate formosensis Sakai, 1974: 94 [ Taiwan]. — Ng et al. 2008: 78 [in list]. Eucrate alcocki — Sakai 1976: 535 [in key], 536, pl. 192, fig. 2 [ Taiwan]. — Ng et al. 2001: 34 [discussion], fig. 7g

[colour] [ Taiwan]. — Hsueh & Huang 2001: 130 [in key], 132, figs. 8G, 16 [ Taiwan]. (not Eucrate alcocki Serène , in

Serène & Lohavanijaya, 1973) Eucrate crenata — Shen & Jeng 2005: 150, 152, colour photographs [ Taiwan]. [not Eucrate crenata (De Haan, 1835) ]

Type material. Unknown. No specimens of E. formosensis Sakai, 1974 , are listed as part of T. Sakai’s material deposited at the Kanagawa Perfectural Museum ( Muraoka 1998) or at the Forschunginstitut Senckenberg, Frankfurt, so it is probable that the type material is no longer extant.

Type locality. Taiwan, Kaoshiung County .

Material examined. Taiwan. Kaoshiung County, Tung-Kang fishing port, P. K. L. Ng coll., 05.08.1996: 2 females, 13.6 mm × 15.9 mm, 22.2 mm × 27.1 mm ( ZRC 1993.739 ) .

Taichung County, Wuchi fishing port, gill net, 15 m, 06.12.1991: 1 male, 22.9 mm × 28.3 mm ( ZRC 2008.1355 ) .

Penghu Bay, Y. L. Shen coll., 6.10.2007: 1 male, 19.8 mm × 24.1 mm (ASIZ-74623) .

Diagnosis. Third anterolateral tooth absent or reduced as slight elevation, carapace with relatively long posterolateral borders ( Figs. 2E ; 8A, B ). P5 propodus slender ( Figs. 2E, F ; 8A, B ). Small red-brown dots through most of carapace ( Fig. 2E ), larger spots in juveniles ( Fig. 2F ).

Remarks. Eucrate formosensis was described as a new species mostly on account of its unique colour pattern ( Sakai 1974: 94). Although it was distinguished by Sakai from E. sexdentata , with which it shares the general shape of the carapace, and E. dorsalis , the colour pattern of the new species was the only reliable way to identify it.

No differences were found in the morphology of the G1 of the three species. The G1 of E. formosensis ( Fig. 14J, K) and E. dorsalis ( Fig. 14G, H) were described by Sakai (1976: 537) as being slender and thin along the anterior half of their lengths, in contrast to that of E. sexdentata ( Fig. 15D, E), where it was described as slender and thin only along the anterior third. Examination of the G1 of several specimens of the three species did not show any reliable differences.

Sakai (1976) could not find any morphological differences between E. formosensis and E. alcocki and placed his species in synonymy with the later (see Ng et al. 2001: 34). Both species are indeed morphologically very similar but the colour pattern of E. formosensis , small red-brown spots throughout most of the carapace and chelipeds ( Fig. 2E, F ), is different from that of E. alcocki ( Fig. 2C ). We opt to retain E. formosensis as a distinct species as originally described by Sakai until additional material is collected and/or DNA analysis is carried out.

The whereabouts of the holotype of E. formosensis is unknown (see above). The only type specimen was collected by T. Watabe of the Manazuru Marine Laboratory ( Sakai 1974: 94) and it is possible that the specimen was returned to the collector. Although we believe the type is probably no longer extant, we also do not see an urgent need to select a neotype as the species is not known outside Taiwanese waters, and fresh specimens cannot be mistaken for any other species owing to their distinct coloration.

Colour pattern. Small red-brown dots throughout at least the anterior half of the carapace ( Fig. 2E ; Sakai 1976: pl. 192, fig. 2 [colour]; Ng et al. 2001: fig. 7g; Shen & Jeng 2005: 150, 152, [colour photographs], as E. crenata ). The dots remain visible for a relatively long time in specimens preserved in alcohol.

Li Kuan-Xin from the Peikuan Crab Museum in northern Taiwan gave the second author a photograph ( Fig. 2F ) of an unidentified Eucrate species collected off Tahsi, Ilan Province, which we believe is E. formosensis . Unfortunately, the specimen was not preserved after it died in an aquarium. The dense pattern of similarly sized spots on the specimen, which was about 1.5 cm in carapace width, is characteristic of E. formosensis . We are of the opinion that the spots get proportionately smaller as the specimen grows in size, eventually developing into the finely spotted pattern seen in adults ( Fig. 2E ). The absence of larger spots on the carapace of the small Taiwanese specimen argues against it being E. alcocki .

Distribution. Only known from Taiwan thus far. Depth: shallow subtidal to at least 15 m.

Figures

FIGURE 2. Fresh colours of Eucrate species. A, B, E. crenata (De Haan, 1835); A, male (22.5 mm × 27.1 mm) (ZRC 2002.0493), China, Qingdao; B, male, Hong Kong, not preserved; C, E. alcocki Serène, in Serène & Lohavanijaya, 1973, ovigerous female (18.4 mm × 21.4 mm) (ZRC 2003.0621), Thailand, Pattani, Thailand; D, E. indica n. sp., female, Persian Gulf, not preserved; E, F, E. formosensis Sakai, 1974; E, female (22.2 mm × 27.1 mm) (ZRC 1993.739), Taiwan, Kaohsiung, Taiwan; F, juvenile, northern Taiwan, not preserved. Photo credits: B by D. Poon; D by R. Naderloo (Forschunginstitut Senckenberg, Frankfurt); E by K. Li.

FIGURE 8. Eucrate formosensis Sakai, 1974; A, C–F, male (19.8 mm × 24.1 mm) (ASIZ-74623), Taiwan, Penghu; B, female (22.2 mm × 27.1 mm) (ZRC 1993.739), Taiwan, Kaohsiung. A, B, overall views; C, anterior portion of male thoracic sternum and abdomen; D, posterior portion of male thoracic sternum and abdomen; E, frontal view showing orbits and antennae; F, outer surface of right chela.