Eucrate indica, Castro & P. K. L. Ng, 2010

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 32-35

publication ID 10.11646/zootaxa.2375.1.1

persistent identifier

treatment provided by


scientific name

Eucrate indica

sp. nov.

Eucrate indica View in CoL n. sp.

( Figs. 2D View FIGURE 2 ; 4D–F View FIGURE 4 ; 9A–F View FIGURE 9 ; 15A–C)

Eucrate alcocki View in CoL — Ng & Davie 2002: 378 [Andaman Sea coast of Thailand]. — Rajkumar et al. 2009: 832, fig. 1 [ India]. (not Eucrate alcocki Serène View in CoL , in Serène & Lohavanijaya, 1973)

(?) Eucrate crenata var. dentata — Alcock 1900: 299 [in key], 301 [ India]. — Sankarankutty 1966: 350 [in list; India].

Type material. Male holotype, 23.8 mm × 28.4 mm ( ZRC 2001.1058 View Materials ; Figs. 4E View FIGURE 4 , 9 View FIGURE 9 , 15A–C); 1 female paratype, 17.6 mm × 20.8 mm ( ZRC 1999.0135 View Materials ), 1 male paratype, 20.1 mm × 24.2 mm, 1 female paratype, 20.0 mm × 24.2 mm ( ZRC 1998.1119 View Materials ), 1 male paratype, 18.1 mm × 21.8 mm, 1 female paratype, 13.5 mm × 17.1 mm ( ZRC 2001.1058 View Materials ) .

Type locality. Thailand, Andaman Sea coast, Phuket I. fishing port

Material examined. India. Tamil Nadu, fish landing opposite Vellar estuary, A. S. Fernando & P. K. L. Ng coll., 24.03.2001: 1 male, 22.3 mm × 27.3 mm, 1 female, 22.8 mm × 28.3 mm ( ZRC 2001.0867 View Materials ) . – Chennai [Madras], Kasimedu fishing port, shrimp trawlers, Z. Jaafar coll., 23.11.2004: 1 male, 21.5 mm × 26.7 mm, 1 ovigerous female, 18.5 mm × 23.1 mm ( ZRC 2004.0764 View Materials ) . – Bay of Bengal , D. Rajkumar leg., 06.2006: 1 male, 23.8 mm × 29.1 mm ( MNHN-B30155 ) .

Thailand. Andaman Sea , Phuket I., Pichai fishing port, P. K. L. Ng coll., 04.1997: 1 female paratype, 17.6 mm × 20.8 mm ( ZRC 1999.0135 View Materials ) . – N. K. Ng et al. coll., 17– 20.01.2000: carapace, 18.6 mm × 23.2 mm ( ZRC 2000.0764 View Materials ) . – Phuket I. fishing port, S. Chaitiamwong et al., 1 male paratype, 20.1 mm × 24.2 mm, 1 female paratype, 20.0 mm × 24.2 mm ( ZRC 1998.1119 View Materials ) . – Phuket I. fishing port, P. K. L. Ng et al. coll., 17.02.2001: male holotype, 23.8 mm × 28.4 mm, 1 male paratype, 18.1 mm × 21.8 mm, 1 female paratype, 13.5 mm × 17.1 mm ( ZRC 2001.1058 View Materials ) .

Peninsular Malaysia. Andaman Sea Coast, between Penang and Langkawi, trawling, C. P. How & C. O. Lau coll., 12.11.1991: 1 female, 15.3 mm × 19.0 mm ( ZRC 1992.10458 View Materials ) .

Diagnosis. Third anterolateral tooth absent or reduced as slight elevation, carapace with relatively long posterolateral borders ( Figs. 2D View FIGURE 2 ; 4D–F View FIGURE 4 ; 9A View FIGURE 9 ). P5 propodus slender ( Figs. 2D View FIGURE 2 ; 9A View FIGURE 9 ). Irregular, large, red-brown spots on median portion of carapace ( Figs. 2D View FIGURE 2 ; 4D–F View FIGURE 4 ; 9A View FIGURE 9 ).

Description. Carapace ( Figs. 2D View FIGURE 2 ; 4D–F View FIGURE 4 ; 9A View FIGURE 9 ) transversely hexagonal, wider than long (1.19 wider than long in male holotype), anterolateral borders arched, dorsal surface without clear indication of regions; front wide, with median notch, deep transverse sulcus along margin. Three anterolateral teeth posterior to short, triangular outer orbital tooth (first short, triangular, obtuse tip; second largest, slender, acute; third short, barely noticeable). Orbits short ( Fig. 9C View FIGURE 9 ), shorter than front (0.6 frontal width in holotype), conspicuous notch between front, orbit; conspicuous notch on median portion, shallower notch on outer portion of curved, thick supraorbital border; suborbital border ( Fig. 9B View FIGURE 9 ) sinuous, with short, obtuse inner suborbital tooth, short median lobe; eye peduncles short (0.2 frontal width in holotype), as long as corneas; large, spherical corneas. Basal antennal article slightly immobile, with disto-lateral process so that orbital hiatus is closed excluding antennal flagellum from orbit.

Posterior margin of epistome lobular; lateral lobes large, with sinuous margins, separated from median portion by deep fissure; median portion with 2 lobes separated by deep fissure ( Fig. 9C View FIGURE 9 ). Anterior margin of endostome well demarcated from buccal cavern, endostomial ridges low. Pterygostomian region with low granules. Third maxillipeds ( Fig. 9B View FIGURE 9 ) completely closing buccal cavern; ischium rectangular with deep submedian line; merus relatively square in shape but anteroexternal part angular, rounded; exopod long, reaching to just before anterior edge of merus with long flagellum.

Cheliped fingers ( Fig. 9D View FIGURE 9 ) moderately stout, slightly longer than swollen propodus, distal portion light in colour. Inner (dorsal) margin of carpus with large tooth; short tomentum on anterior margin of carpus; outer (dorsal) margin of merus with large, obtuse tooth, row of short tubercles. Dorsal, ventral margins of ambulatory legs (P2–P5) with short tubercles, dorsal margins of carpus with long, simple setae; dactyli long, slender; P5 merus ( Fig. 9A View FIGURE 9 ) long, moderately slender (16.2 mm long in holotype), ventral margin slightly curved, distal end reaches past third anterolateral tooth but not second anterolateral tooth when folded against carapace; P5 propodus (9.8 mm long, 3.0 mm wide in holotype), proportionally stout, subcylindrical; inner, outer margins fringed with row of numerous short, simple setae; P5 dactylus (9.5 mm long, 2.0 mm maximum width in holotype) proportionally slender, subcylindrical, fringed with short, simple setae.

Thoracic sternum ( Fig. 9E View FIGURE 9 ) wide, thoracic suture 2/3 complete, convex; 3/4 deep, short, interrupted; 4/5, 6/7, 7/8 interrupted, 5/6 complete; median groove on thoracic sternites 7, 8. Sterno-abdominal cavity of male deep, nearly reaching anterior margin of sternite 4. Press-button of male abdominal-locking mechanism as tubercle near thoracic suture 4/5.

Male abdomen ( Fig. 9E View FIGURE 9 ) narrow, slender (T-shaped), lateral margins of somites 4–6 abruptly narrowing from somite 3 to transversely narrow, pointed telson; somite 3 reaching inner margins of P5 coxae ( Fig. 9F View FIGURE 9 ); no portions of thoracic 8 exposed by closed abdomen, somite 2 slightly transversely shorter than somite 3. G1 long, slender, sinuous, acuminate apex, with small denticles ( Figs. 15A, B); G2 ( Fig. 15C) less than one-third of G1, straight, with 2 processes: one long, tip obtuse; second much shorter, tip acute. Male genital opening (gonopore) coxal; coxo-sternal disposition of long penis, protected by concave posterior portion of thoracic sternite 7.

Vulva ovoid, extending across anterior portion of sternite 6 close to median axis of thorax; covered by soft membrane, sternal vulvar cover absent.

Colour pattern. Two large, irregular, red-brown spots on the median portion of the dorsal surface of the carapace, each flanked by two smaller, vertically placed spots ( Figs. 2D View FIGURE 2 ; 4D–F View FIGURE 4 ; 9A View FIGURE 9 ; see Remarks below). The central or lateral spots may coalesce into a single lateral spot ( Fig. 4E View FIGURE 4 ). All spots may also coalesce, forming irregular patterns bearing a striking resemblance to letters or numbers ( Fig. 2D View FIGURE 2 ). Small red-brown spots are located along the anterior border of the carapace and dorsal surface of chelipeds.

Etymology. Indica from India and Indian Ocean, to denote the distributional range of this species in contrast to two similar species, Eucrate alcocki in China and southwestern Asia, and E. formosensis in Taiwan.

Remarks. The populations that had been identified as “ E. alcocki ” from the Indian and western Pacific oceans are clearly different in their carapace colour patterns. In true E. alcocki from China, Vietnam, Gulf of Thailand and Singapore, there are consistently one to six large spots or blotches on the median portion of the carapace, and the anterior portion has numerous smaller spots ( Figs. 2C View FIGURE 2 ; 4A, B View FIGURE 4 ). In specimens from the Indian Ocean and as far west as the Andaman Sea coast of Thailand and the northern Straits of Malacca (Phuket I., Langkawi, and Penang islands), there are usually six large spots arranged transversely across the median portion of the carapace and numerous smaller spots on the anterior portion of the carapace. This colour pattern is consistent for the large series of specimens examined.

There are also several morphological differences. Specimens from the Indian Ocean have proportionately wider carapaces (width to length ratio 1.18–1.26, n = 13, mean = 1.21; 1.09–1.29, n = 32, mean = 1.16 in E. alcocki ) ( Figs. 2D View FIGURE 2 , 4D–F View FIGURE 4 for E. indica ; Figs. 2C View FIGURE 2 , 4A, B View FIGURE 4 for E. alcocki ), the frontal margin is generally more prominent, well produced, and with a distinct median notch ( Figs. 4D–F View FIGURE 4 ; 9C View FIGURE 9 ) (less prominent, with the median notch shallow or barely visible in E. alcocki , Figs. 4A–C View FIGURE 4 ), the cleft between the frontal margin and inner suborbital tooth is deep and pronounced ( Fig. 9C View FIGURE 9 ) (shallow in E. alcocki ), and the supraorbital border has a deep and prominent notch ( Figs. 4D–F View FIGURE 4 ; 9C View FIGURE 9 ) (shallow and less distinct in E. alcocki , Figs. 4A–C View FIGURE 4 ). As such, we are of the opinion that the Indian Ocean material should be referred to as a separate species.

As has been discussed earlier under E. alcocki , the record of Eucrate crenata var. dentata by Alcock (1900: 299, 301) from India (see also list of Indian taxa in Sankarankutty 1966: 350) may be Eucrate indica n. sp. as well. Serène & Lohavanijaya (1973) had suggested it may be E. alcocki .

The geographic distributions of E. indica n. sp. and E. alcocki are noteworthy as, E. indica n. sp. is found in the Persian Gulf, Indian Ocean, and the Andaman Sea, whereas E. alcocki is found on the Gulf of Thailand and the western Pacific Ocean. A similar pattern has also been observed for several other species of brachyurans, with one species occurring in the Indian Ocean (e.g. the xanthid Liagore erythematica Guinot, 1971 , the calappid Calappa bilineata Ng, Lai & Aungtonya, 2002 , the portunid Portunus reticulatus (Herbst, 1799)) and a close species present in the Pacific ( Liagore rubromaculata (De Haan, 1835) , Calappa philargius (Linnaeus, 1758) , Portunus pelagicus (Linnaeus, 1758) , respectively) (see Ng et al. 2002; Ng & Chen, 2004; Ng et al. 2008; Lai et al. 2010).

Distribution. Persian Gulf, India, Andaman Sea coasts of Thailand and Peninsular Malaysia. Depth: shallow subtidal.














Eucrate indica


Eucrate alcocki

Rajkumar, M. & Vasagam K. K. P. & Li, X. & Sun, J. 2009: 832
Ng, P. K. L. & Davie, P. J. F. 2002: 378
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