Eucrate tripunctata Campbell, 1969

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 40-47

Eucrate tripunctata Campbell, 1969

( Figs. 12A–F ; 13A–F ; 15J–L)

Eucrate tripunctata Campbell, 1969: 119 [in key], 127, figs. 2, 4 [Queensland, Australia]. — Guinot 1971: 1080 [in list] — Davie 2002: 199 [in list]. — Ng et al. 2008: 78 [in list].

(?) Eucrate crenata — Nobili 1903: 35 [ Singapore]. — Tirmizi & Ghani 1982: 107, fig. 3; 1996: 77 [in key], 80, fig. 31 [ Pakistan]. [not Eucrate crenata (De Haan, 1835) ]

Type material. Male holotype (QM W3034), 2 male paratypes, 26.7 mm × 33.8 mm, cl 27.0 mm [rest of carapace damaged], 1 pre-adult female paratype, 16.8 mm × 20.7 mm, 1 female paratype, 29.6 mm × 37.6 mm (QM W1070, Fig. 15J–L; AM: see Davie 2002: 199) .

Type locality. Australia, Queensland, Moreton Bay.

Material examined. Thailand. Gulf of Thailand, Songkhla, Sakom fishing port, 3 males, 24.3 mm × 29.4 mm, 37.0 mm × 47.0 mm, 37.5 mm × 47.2 mm, 2 ovigerous females, 34.9 mm × 45.5 mm, 35.6 mm × 44.8 mm ( ZRC 2003.0606 ). – 1 male, 38.0 mm × 48.9 mm ( ZRC 2003.0191 ) .

Singapore. No data: 1 male, 41.4 mm × 52.6 mm ( ZRC 1985.1378 ); K. L. Yeo coll. , 8– 15.06.1990: 1 male, 32.6 mm × 41.0 mm ( ZRC 1991 . 0341) .

Tuas, trawling, W. M. Lee coll., 8– 18.09.1982: 1 male, 38.1 mm × 47.8 mm, 3 females, 38.0 mm × 48.8 mm, 38.3 mm × 49.0 mm, 33.8 mm × 41.7 mm ( ZRC 1984.7844 – 7847 ) ; C. M. Yang coll., 12.08.1982: 1 male, 32.5 mm × 40.0 mm ( ZRC 1984.5796 ) ; 09.05.1984: 1 ovigerous female, 32.3 mm × 40.0 mm, 1 female, 35.4 mm × 45.2 mm ( ZRC 1984 : 6315–6316) .

(?) Changi Beach Club , 3 m, D. C. Yeo coll., 01.01.2002: 1 female, 13.6 mm × 16.0 mm ( ZRC 2002.0248 ). – Cyrene Reefs, Southern Islands, Singapore, P. F. Clark coll., 10.3.2005: 1 male, 7.0 mm × 8.3 mm ( ZRC 2008.066 ) .

Australia, Queensland, Moreton Bay , Mud I., dredging, V. F. Collin coll., 7.06.1940: 2 males paratypes, 26.7 mm × 33.8 mm, cl 27.0 mm [rest of carapace damaged], 1 pre-adult female paratype, 16.8 mm × 20.7 mm, 1 female paratype, 29.6 mm × 37.6 mm ( QM W1070 ) .

Diagnosis. Third anterolateral tooth visible (except large individuals), carapace with relatively short posterolateral borders ( Figs. 12 ; 13A–C ). P5 propodus noticeably short, wide ( Figs. 12 , 13C ). Proportionally short ambulatory legs ( Figs. 12 ; 13C ). G1 is straight along median portion ( Fig. 15J). Colour pattern varying from light gray-brown anterior third of carapace ( Fig. 12A–C ) to various patterns of bright colours ( Fig. 12D– F ).

Remarks. Diagnostic of E. tripunctata are arched anterolateral borders with the two anterolateral teeth that are short, rounded and very similar in appearance to the outer orbital tooth ( Figs. 12A–E ; 13A–D ; Campbell 1969: fig. 4B, K, L). The second anterolateral tooth is triangular in small individuals; the third short but always visible even in the largest individuals. The ambulatory legs are also proportionally short ( Figs. 12 ; 13C ), the P5 not reaching the third anterolateral tooth when folded. The P2–P5 meri are short, wide and the P5 propodus conspicuously short and broad ( Fig. 13C ; Campbell 1969: fig. 4G). The male telson is very long and slender, longer than abdominal somite 6 ( Campbell 1969: fig. 4J), the G1 is straight along the median portion ( Fig. 15J; Campbell 1969: fig. 4H, I), in contrast to being sinuous as in other species of Eucrate .

Campbell (1969: 128) referred to E. tripunctata the four Mergui Archipelago ( Myanmar [= Burma]) specimens identified “with some hesitation” as E. affinis Haswell, 1882 , by De Man (1887: 89, pl. 5, figs. 5–7), as well as the single specimen of the same collection identified by Alcock (1900: 300) as E. crenata var. affinis . Eucrate affinis is a junior synonym of Trissoplax dentata ( Stimpson, 1858) (see below). Campbell’s decision was made on account of the restriction of the cheliped tomentum to “the upper border of the wrist of the cheliped”, the proportions of the P5 propodus, and the similarity between the outer orbital teeth and the first two anterolateral teeth. Based solely on De Man’s description and his figures, however, it is clear that the specimens do not belong to E. tripunctata . The anterolateral teeth, described by De Man (1887: 90, pl. 5, fig. 5) as “rather acute”, do not resemble the conspicuously short teeth of E. tripunctata , a feature that is observed even in pre-adults ( Campbell 1969: fig. 4K, L). Furthermore, the male telson ( De Man 1887: pl. 5, fig. 6) is shorter than that in E. tripunctata . Alcock’s specimen was described as being “more sculptured” than that of E. crenata , which is in sharp contrast to the smoother carapace of E. tripunctata .

A relatively small female from Singapore ( Fig. 12D ; 13.6 mm × 16.0 mm, ZRC 2002.0248) had more prominent anterolateral and outer orbital teeth than those of the much larger specimens available or of a smaller male (cw 8 mm) shown by Campbell (1969: fig. 4L). The teeth were similarly prominent, however, in a small male from Singapore ( Fig. 12E, F ; 7.0 mm × 8.3 mm, ZRC 2008.066).

Nobili (1901: 35) identified a Singapore specimen as E. crenata and described it as having a large spot on the gastric region and two adjacent, irregular spots. The specimen may have belonged instead to E. tripunctata . Eucrate crenata has never been recorded from or near Singapore.

Also possibly identical to E. tripunctata are specimens reported from Pakistan by Tirmizi & Ghani (1996: 82). Their colour pattern (“dark purplish red, with chelipeds and legs white, the carapace [with] a band of white … on the anterior and lateral borders” is indeed similar to that of E. tripunctata . Their figures also show similarities with E. tripunctata , because of the short and rounded anterolateral teeth that are similar in appearance to the outer orbital teeth.

Colour pattern. Campbell (1969: 128, fig. 4K) described alcohol-preserved specimens as “pale cream with three large reddish spots on carapace … median spot of variable extent sometimes coalescing with the two smaller lateral spots”. In some of the Singapore and Thailand specimens the anterior third of the carapace is light gray-brown without a clear trace of spots ( Fig. 12A–C ), except some of the males, where there are hints of large coloured spots ( Fig. 12B, C ). The chelipeds, and sometimes the anterior margin of the carapace, of large specimens have red-brown dots ( Fig. 12A–C ). The carapaces of smaller specimens show various patterns of bright colours ( Fig. 12D–F ).

Distribution. Gulf of Thailand, Singapore, Australia (Queensland). Depth: shallow subtidal.

Genus Euryplax Stimpson, 1859

Euryplax Stimpson, 1859: 60 . — Rathbun 1918: 16 [in key], 34 [diagnosis], 34 [key to species]. — Tesch 1918: 41 [in list]. — Guinot 1969b: 512 [discussion]; 1971: 1080 [in list, list of species]; 1984: 95. — Karasawa & Kato 2003a: 151 [in list]; 2003b: 130 [in list], 139 [in list]. — Ng & Castro 2007: 44 [in list]. — Ng et al. 2008: 78, 79 [in list]. — De Grave et al. 2009: 33 [in list].

Diagnosis. Carapace ( Figs. 16A ; 17A, B ; 18C ) transversely rectangular, wider than long, dorsal surface smooth without clear indication of regions; anterolateral borders straight, nearly parallel to each other; front wide, straight or slightly lobed, with small median notch, transverse sulcus along margin. Two obtuse or acute, often nearly equal, anterolateral teeth posterior to rounded, obtuse, outwardly or anteriorly oriented outer orbital tooth. Small notch on inner portion of thin supraorbital border ( Figs. 16A ; 17A, B ; 18C ); short, triangular median lobe on thin suborbital border ( Figs. 16C ; 17C, E ; 18A ), inner suborbital tooth absent. Orbits long (shorter than front but longer than half front length); eye peduncles long, slightly longer than large, spherical corneas ( Figs. 16C ; 17A–C ; 18A ). Basal antennal article immobile, disto-lateral process absent, orbital hiatus closed excluding antennal flagellum from orbit ( Fig. 16C ; Guinot 1969b: fig. 41). Anteroexternal margin of third maxilliped merus auriculiform ( Figs. 17C ; 18A ). Cheliped fingers moderately slender, shorter than propodus, light in colour ( Figs. 16B ; 18C ); carpus with tooth on inner margin; short tomentum may be present along anterodistal margins of merus, carpus ( Fig. 18C ). Dorsal margins of ambulatory legs (P2–P5) meri, carpi, propodi unarmed, dactyli slender, smooth, setose. P5 propodus proportionally stout, subcylindrical, margins fringed with long, simple setae; P5 dactylus proportionally slender ( Fig. 16A ), margins fringed with long, simple setae, short teeth. Thoracic sternum wide; thoracic suture 2/3 complete, straight ( Fig. 17D ); 4/5, 6/7, 7/8 interrupted, 5/6 complete; thoracic sternites 7, 8 overlapping over penis ( Figs. 16E ; 17G ); median groove on thoracic sternites 7, 8 ( Figs. 16E ; 17G ). Sterno-abdominal cavity of male deep, nearly reaching anterior margin of sternite 4 ( Figs. 17D, G ). Male abdomen proportionally wide, triangular (not T-shaped), proportionally narrow telson ( Figs. 16D ; 17E ); somite 3 transversely longer than somites 4–6, not reaching inner margins of P5 coxae; small portion on each side of thoracic sternite 8 left exposed by closed abdomen even if somite 2 transversely longer than somite 3 ( Figs. 16F ; 17F ; 18D ). Press-button of male abdominal-locking mechanism as large tubercle near thoracic suture 4/5 ( Fig. 17D ) (small tubercle present in pre-adult females). G1 long, slender, slightly sinuous, acuminate apex, with many denticles ( Figs. 18D ; 20A, B ); G2 less than one-third of G1, straight, apex with 2 unequal processes ( Fig. 20C ). Male genital opening (gonopore) coxal, protected by enlarged, widened episternite 7; coxo-sternal disposition of long penis, protected by overlapping episternite 7, thoracic sternite 8 ( Figs. 16E ; 17G ). Female abdomen relatively narrow, not covering outer portions of thoracic sternum ( Fig. 18A ). Vulva small, ovoid, extending from margin of thoracic suture 5/6 to median portion of sternite 6 far from median axis of thorax; covered by soft membrane, sternal vulvar cover absent ( Fig. 18B ).

Type species. Euryplax nitida Stimpson, 1859 (by monotypy, gender feminine) [Opinion 85, Direction 37].

Remarks. Euryplax is noteworthy for the protection of the proximal portion of the penis by the partial closure of thoracic sternites 7 and 8 ( Figs. 16E ; 17G ; also see Guinot 1969b: fig. 39; Castro et al. 2010: 8 C, D). Stimpson (1859: 60) had noted this in his description of E. nitida : “Verges [penis] of the male arising from the coxae of the posterior feet, and passing to the abdominal appendages through canals in the sternum”. The penis of Euryplax is protected by episternite 7 extending close to but never fusing with thoracic sternite 8, thus never forming a closed channel as in the case of Sotoplax robertsi Guinot, 1984 , a goneplacoid now placed in its own family (see Castro et al. 2010). Penial protection in Euryplax may be considered an extreme case among euryplacids, where the penis is protected only by a concavity along the posterior portion of thoracic sternite 7, an expansion of episternite 7, and the transversely wide abdominal somite 3 of the closed abdomen. Another peculiarity of Euryplax that departs from most other euryplacids is that somite 3 of the male abdomen, although transversely longer than somites 4–6, does not reach the inner margins of the P5 coxae ( Figs. 16F ; 17F ; 18D ). Furthermore, a small portion on each side of thoracic sternite 8 is left exposed by the closed abdomen even if somite 2 transversely longer than somite 3 ( Figs. 16F ; 17F ; 18D ; Rathbun 1918: fig. 11a; Guinot 1969b: figs. 39, 47).

The significance of the shape of the abdomen and sternal protection of the penis in Euryplax and the Euryplacidae in general is discussed below (“Evolution of Penial Protection in the Euryplacidae ”).

Euryplax bevisi Stebbing, 1921 (Stebbing 1921: p. 14, pl. II), described from Natal, South Africa, does not belong in Euryplax (see Barnard 1950: 283; Guinot 1969b: 512; Ng et al. 2008: 78, 79) or in the Euryplacidae . It is a portunid, as previously suggested by Barnard (“reminds one very much of a Thalamita ”). However, the unusual carapace depicted by Stebbing (1921: pl. II) is a problem as no known Thalamita species has such elongated proportions. Euryplax bevisi was subsequently designated as the type species of Lipkeplax Števčić, 2005 , which was included in a list of “new genera incertae sedis” ( Števčić 2005: 134) without any indications as to their inclusion in any particular supra-generic taxa. The generic name is unavailable since it was not accompanied by a description or definition to differentiate it from other genera (International Code of Zoological Nomenclature, Article 13.1).

The holotype of E. bevisi Stebbing, 1921 , was recently found in the NHM and examined by the second author. The specimen, measuring 22.8 mm × 13.8 mm, collected by A. L. Bevis, was dismembered and there is a label indicating it was once dried. However, all the key characters are intact, including the gonopods. Ng & Clark (in press) showed that the species is clearly a portunid of the genus Thalamita (see Barnard 1950: 283; Guinot 1969b: 512; Ng et al. 2008: 78, 79), and is a senior synonym of Thalamita dakini Montgomery, 1931 , which is known from many parts of the Indo-West Pacific ( Apel & Spiridonov 1998; Retamal 2004). There is thus no basis for Števčić (2005) establishing a new genus for the species.

Species included.

Euryplax nitida Stimpson, 1859

Euryplax polita Smith, 1870

The genus is restricted to the Western Atlantic and Tropical Eastern Pacific regions.

Figures

FIGURE 12. Fresh colours of Eucrate tripunctata Campbell, 1969. A, female (34.9 mm × 45.5 mm) (ZRC 2003.0606), Thailand, Gulf of Thailand (specimen slightly tilted when photographed); B, male (24.3 mm × 29.4 mm) (ZRC 2003.0606), Thailand, Gulf of Thailand; C, male (37.5 mm × 47.2 mm) (ZRC 2003.0606), Thailand, Gulf of Thailand; D. female (13.6 mm × 16.0 mm) (ZRC 2002.0248), Singapore; E, F, male (7.0 mm × 8.3 mm) (ZRC 2008.066), Singapore.

FIGURE 13. Eucrate tripunctata Campbell, 1969; A, female (29.6 mm × 37.6 mm) (QM W1070), Australia, Queensland, Moreton Bay; B, male (26.7 mm × 33.8 mm) (QM W1070), Australia, Queensland, Moreton Bay; C–F, male (38.0 mm × 48.9 mm) (ZRC 2003.0191), Thailand, Gulf of Thailand. A–C, overall views; D, frontal view showing orbits and antennae; E, anterior portion of male thoracic sternum and abdomen; F, outer surface of right chela.

FIGURE 16. Euryplax nitida (Stimpson, 1859); A–F, male neotype of Heteroplax nitidus Stimpson, 1859 (7.1 mm × 11.3 mm) (UF 15166), Florida, Gulf of Mexico, west of St. Petersburg. A, overall view; B, outer surface of chelae; C, frontal view showing orbits and antennae; D, anterior portion of male thoracic sternum and abdomen; E, sternal protection of penis; F, posterior portion of male thoracic sternum and abdomen. Abbreviations: a1–a3, a6 = male abdominal somites 1, 2, 3, 6, respectively; cx5 = coxa of fifth pereopod (P5); es7 = episternite 7; G1 = first male pleopod; mg = median groove; p = penis; s4–s8 = thoracic sternites 4 to 8, respectively; t = telson.

FIGURE 17. Euryplax nitida Stimpson, 1859; A, C, G, male (7.2 mm × 10.4 mm) (RMNH D 15769), Florida, Marco Beach; B, D, female (USNM 276579), Gulf of Mexico, off Florida; E, F, male (13.9 mm × 23.2 mm) (MNHN-B8732), Brazil, Dertero (?). A, B, dorsal views of carapaces; C, third maxillipeds; D, anterior portion of male sterno-abdominal cavity and G1; E, anterior portion of male thoracic sternum and abdomen; F, posterior portion of male thoracic sternum and abdomen; G, posterior portion of male sterno-abdominal cavity and G2. Abbreviations: a1–a3 = male abdominal somites 1, 2, 3, respectively; cx5 = coxa of fifth pereopod (P5); es7 = episternite 7; G1 = first male pleopod; G2 = second male pleopod; mg = median groove; p = penis; pb = press-button of male abdominal-locking mechanism; s4–s8 = thoracic sternites 4 to 8, respectively.

FIGURE 18. A, B, Euryplax nitida Stimpson, 1859; A, female (USNM 276579), Gulf of Mexico, off Florida, ventral view of carapace; B, female (10.1 mm × 7.1 mm) (LACM), Colombia, Atlantic coast, ventral view of carapace; C, D, Euryplax polita Smith, 1870; male (18.9 mm × 33.8 mm) (LACM), Perú, Tumbes; E, F, Frevillea hirsuta (Borradaile, 1916); E, male lectotype of Goneplax hirsutus Borradaile, 1916 (10.5 mm × 15.2 mm) (NHM 1917.1.29.148–9); F, female paralectotype of Goneplax hirsutus Borradaile, 1916 (12.0 mm × 17.8 mm) (NHM 1917.1.29.148–9). A, ventral view; B, D, female sterno-abdominal cavity; C-F, overall view; D; male sterno-abdominal cavity. Abbreviations: a3 = male abdominal somite 3; G1 = first male pleopod; G2 = second male pleopod; pb = press-button of male abdominallocking mechanism; s4–s8 = thoracic sternites 4 to 8, respectively; v = vulva. Photo credits: B, C, D by J. Martin (LACM); E, F by P. Crabb (NHM).

FIGURE 20. Gonopods of Euryplax and Frevillea species. A–C, Euryplax nitida Stimpson, 1859; A, B, G1; C, G2 (after Guinot 1969b: figs. 56, 57); D–F, Frevillea hirsuta (Borradaile, 1916): D, E, G1; F, G2 (after Guinot 1969b: figs. 58, 59).