Eucrate alcocki Serène, 1971

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 18-20

publication ID	https://doi.org/ 10.11646/zootaxa.2375.1.1
persistent identifier	https://treatment.plazi.org/id/03F487A8-394D-4237-7D8C-FA99F021F864
treatment provided by	Felipe
scientific name	Eucrate alcocki Serène
status

Treatment

Eucrate alcocki Serène View in CoL , in Serène & Lohavanijaya, 1973

( Figs. 2C View FIGURE 2 ; 4A–C View FIGURE 4 ; 14A–C)

Eucrate alcocki Serène 1971: 916 View in CoL (nomen nudum) [ Viet Nam]. — Serène & Lohavanijaya 1973: 71, pl. 16, figs. B, C

[ Viet Nam]. — Serène & Vadon 1981: 118, 123 [part]. — Dai et al. 1986: 372 [in key], 373, fig. 196(2), pl. 54, fig.

4 [ China] [part]. — Dai & Yang 1991: 401 [in key], 403, fig. 196(2), pl. 54, fig. 4 [ China] [part]. — Naiyanetr 1998:

78; 2007: 90 [Gulf of Thailand] [part]. — Ng et al. 2008: 78 [in list] [part]. — Yang et al. 2008: 770 [in list] [ China]

[part]. (?) Eucrate crenata var. dentata — Alcock 1900: 299 [in key], 301 [ Hong Kong]. not 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]. (= Eucrate formosensis Sakai,

1974) Eucrate maculata Yang & Sun 1979: 3 , 9, fig. 2, plate, figs. 3, 4, 8 [ China]. not Eucrate alcocki — Ng & Davie 2002: 378 [Andaman Sea coast of Thailand]. — Rajkumar et al. 2009: 832, fig. 1

[ India] (= Eucrate indica n. sp.)

Type material. Male holotype, 21.2 mm × 24.6 mm ( MNHN-B10134 ); 1 female , cl 20.8 mm [remainder of carapace damaged], same data as holotype, designated herein as paratype ( MNHN-B10133 ) .

Type locality. Viet Nam, Nhatrang Bay .

Type material of Eucrate maculata Yang & Sun, 1979 , male holotype ( BMNH J79139 View Materials ; 1 male paratype, 15.9 mm × 18.7 mm ( BMNH J79139 View Materials ; Fig. 4C View FIGURE 4 ); type locality: China, Fujian Province, Dongshan.

Material examined. Hong Kong. Unknown location, 1992: 3 males ( SWIMS CRU-92-002 ); pre-adult female ( SWIMS SML-Z-419 ) .

Viet Nam. Nhatrang Bay , R. Serène coll., 1958, ION 9688, photograph ION 911: male holotype, 21.2 mm × 24.6 mm ( MNHN-B10134 ) ; R. Serène coll., 1958, ION 44.144: 1 female paratype, cl 20.8 mm [rest of carapace damaged] ( MNHN-B10133 ) ; Institute Océanographique Nhatrang leg., récolte 2558, no. E 48.363, 13.11.1969: 1 male, 26.1 mm × 30.5 mm; récolte 2552, no. E 48.2231, 09.09.1969: 1 female, 18.2 mm × 21.4 mm ( MNHN-B10135 ) ; N. V. Luom coll., 13.11.1969, R. Serène id.: 1 male, 20.2 mm × 23.0 mm ( ZRC 1970.8.24.2); 20–30 m, 22.08.1995: 2 males, 22.5 mm × 26.7 mm, 25.3 mm × 29.2 mm, 1 female, 20.8 mm × 23.5 mm ( MNHN-B30543 ) .

Philippines. MUSORSTOM 1: stn. 1, 14°28'N, 120°42'E, 36–37 m, 18.03.1976: 1 male, 23.6 mm × 28.4 mm ( MNHN-B10346 ) GoogleMaps .

Thailand. Gulf of Thailand, Chonburi, Angsila fishing port, P. K. L. Ng coll., 29.09.1998: 1 male, 17.3 mm × 19.0 mm, 7 males, 18.9 mm × 22.1 mm, 18.9 mm × 21.9 mm, 19.0 mm × 22.5 mm, 19.4 mm × 22.1 mm, 22.0 mm × 25.2 mm, 22.00 mm × 25.3 mm, 19.0 mm × 22.3 mm, 9 females, 14.3 mm × 16.3 mm, 14.7 mm × 17.0 mm, 15.7 mm × 18.0 mm, 17.3 mm × 20.1 mm, 17.5 mm × 20.7 mm, 17.8 mm × 21.0 mm, 18. 8 mm × 22.4 mm, 18.0 mm × 21.6 mm, 19.2 mm × 23.3 mm ( ZRC 1998.1055 View Materials ); 11.1999: 1 male, 17.7 mm × 21.2 mm, 1 female, 20.6 mm × 24.2 mm ( ZRC 2000.022 View Materials ) .

Gulf of Thailand, 150 km SW of Bangkok, A. C. J. Burgers leg., 05– 18.11.1986: 1 female, 17.9 mm × 20.3 mm ( RMNH D 36596) .

Gulf of Thailand, Songkhla, Sakom fishing port, P. K. L. Ng et al. coll., 15– 17.10.2003: 1 female, 15.1 mm × 17.7 mm ( ZRC 2003.0605 View Materials ) .

Gulf of Thailand, Pattani fishing port, P. K. L. Ng et al. coll., 16.10.2003: 1 ovigerous female, 18.4 mm × 21.2 mm ( ZRC 2003.0621 View Materials ) .

Singapore. East coast, fishermen tangle nets, 5–7 m, P. K. L. Ng coll., 01.1986: 1 male, 17.5 mm × 20. 7 mm ( ZRC 1999.1189 View Materials ) .

Unknown location. Capt. E. Sirencom leg., 12.1993: 2 females, 17.4 mm × 20.6 mm, 19.7 mm × 22.9 mm ( MNHN-B22358 ) .

Diagnosis. Third anterolateral tooth absent or reduced as slight elevation, carapace with relatively long posterolateral borders ( Figs. 2C View FIGURE 2 ; 4A–C View FIGURE 4 ). P5 propodus slender ( Fig. 2C View FIGURE 2 ). Varying number of large, irregular red-brown spots across carapace, with smaller, anterior spots or dots ( Fig. 2C View FIGURE 2 ).

Remarks. Eucrate alcocki is morphologically very close to E. formosensis , E. indica n. sp., and E. sexdentata . The three species share a well developed and dorsally elevated second anterolateral tooth that sometimes has an acute tip, a third anterolateral tooth that is absent or nearly absent, even in small individuals, and long, slender ambulatory legs, the distal end of the P5 merus reaching between the second anterolateral tooth and the slight elevation that often indicates the missing third anterolateral tooth ( Figs. 2C–F View FIGURE 2 ; 4 View FIGURE 4 ; 8A, B View FIGURE 8 ; 9A View FIGURE 9 ; 10A, B View FIGURE 10 ). Sakai (1976: 537) commented that in E. alcocki and E. formosensis the P5 dactylus is “slender and markedly recurved”, whereas in E. dorsalis and E. sexdentata the dactylus is “straight and not recurved”. The distal third of the dactylus has nevertheless been found to be dorsally recurved in all species of Eucrate sensu lato.

Eucrate formosensis Sakai, 1974 , was placed in synonymy with E. alcocki by Sakai (1976) (see also Ng et al. 2001) but its unique colour pattern warrants regarding it as a separate species (see Remarks for E. formosensis below). Eucrate maculata Yang & Sun, 1979 , was similarly included as a synonym of E. alcocki by Dai & Yang (1991). Photographs of the dry male paratype of E. maculata ( Fig. 4C View FIGURE 4 ; 15.9 mm × 18.7 mm, BMNH J79139 View Materials ), however, confirm the synonymy. It is also clearly apparent from the photograph of the dorsal surface of the carapace of the holotype ( Yang & Sun 1979: plate, fig. 3; Ng et al. 2001: 34, fig. 7g). The spots diagnostic of T. alcocki can still be faintly seen on both the holotype and paratype ( Fig. 4C View FIGURE 4 ) of E. maculata .

Eucrate sexdentata has so far been unquestionably recorded only from Queensland, Australia, whereas E. alcocki is known as far south as Singapore. One feature distinguishing the two species is the complete absence of a frontal notch (or inconspicuous, if present) in E. alcocki , a character noted by Serène (in Serène & Lohavanijaya 1973: 71) when comparing his new species with E. crenata (De Haan, 1835) . The notch is well developed in E. sexdentata . Serène (in Serène & Lohavanijaya 1973) unfortunately did not compare E. alcocki with E. sexdentata although he must have seen the figures given by Campbell (1969: fig. 1). The two species also differ in their colour patterns. Whereas E. alcocki has mostly small spots across the anterior two thirds of the carapace ( Figs. 2C View FIGURE 2 ; 4A, B View FIGURE 4 ; see “Colour” below), E. sexdentata has many relatively large reddish spots on the carapace ( Campbell 1969: fig. 1B; barely visible in Fig. 10A View FIGURE 10 ). Campbell (1969: 120) described the colour pattern as “pale cream with purple-pink spots… or with two additional posterior spots”.

The G1 and G2 of E. alcocki , E. formosensis , E. indica , and E. sexdentata are similar. The G1 and G2 of E. alcocki are illustrated herein for the first time ( Fig. 14A–C).

Differences between E. alcocki and E. indica n. sp. are discussed in the description of the latter (see below).

There are also similarities between E. alcocki and E. dorsalis in terms of the salient second anterolateral teeth, but the first anterolateral teeth are much shorter than in E. dorsalis , where both the first and second teeth become shorter with size and ultimately almost disappear in large specimens ( Campbell 1969: fig. 6K).

In addition to the male holotype (MNHN-B10134), a specimen labelled as such and which was clearly shown as “type” in Serène & Lohavanijaya (1973: 71, pl. 16, fig. B), a second specimen from the type locality (MNHN-B10135) also carries a label by Serène designating it the “ holotype ”. Although this second specimen ( Serène & Lohavanijaya 1973: 71, pl. 16, fig. C), a female (erroneously referred to as a “juvenile female”), is now badly damaged, it shows the characteristics diagnostic of the species and is here recognised as a paratype.

Colour pattern. There is some variation in the pattern of spots on the carapace ( Figs. 2C View FIGURE 2 ; 4A, B View FIGURE 4 ). The dorsal surface of the carapace invariably has a varying number of large, often irregular red-brown spots across in addition to smaller spots or dots anterior to the large spots. The anterior spots vary from medium-size spots that decrease in size anteriorly to many spots of evenly small size.

The male holotype from Viet Nam ( Serène & Lohavanijaya 1973: pl. 16, fig. B) shows many small dots plus three large ones. The specimen now designated as paratype, referred to by Serène & Lohavanijaya (1973) as a “juvenile female” (see Remarks above) has many small, anterior spots plus irregular, large spots on the rest of the dorsal surface of the carapace, and small spots on the chelipeds ( Serène & Lohavanijaya 1973: pl. 16, fig. C). Serène & Lohavanijaya (1973: 71) describe the species as having “generally very bright colors, the pattern distribution of the color being variable; generally there is a larger median gastric red-brown spot and a pair of smaller but similar epigastric spots”.

Three specimens from Viet Nam collected in 1995 ( MNHN-B30543 ) still show a pattern where the size and shape of the spots are different in each of the specimens. A round or triangular central spot on the gastric region is flanked by two smaller, irregular spots in all specimens. The eight spots immediately above are relatively large in the female, much smaller in the two males. The spots are numerous and small along the anterior border of the carapace in all three specimens. Small dots are still visible on the chelipeds of the female .

According to Serène & Lohavanijaya (1973), the records of Eucrate crenata var. dentata by Alcock (1900: 299, 301) from India and Hong Kong (see also Indian list in Sankarankutty 1966: 350) may be Eucrate alcocki . However, as Alcock’s notes are so brief, we cannot be certain. Certainly they are unlikely to be Trissoplax dentata ( Stimpson, 1858) as defined here (see below). If Serène & Lohavanijaya (1973) are correct, then the Hong Kong record is probably E. alcocki whereas the Indian one is more likely to be E. indica n. sp. (see below). Chhapgar’s (1957: 39, pl. 11, figs. j, k, l) record of “ Eucrate crenata dentata ”, however, is clearly Trissoplax dentata ( Stimpson, 1858) (see below).

Distribution. Southern China ( Yang & Sun 1979, as E. maculata Yang & Sun, 1979 ), Hong Kong, Philippines, Viet Nam, Gulf of Thailand, eastern Peninsular Malaysia, Singapore. Depth: subtidal to 37 m.