Eucrate sexdentata Haswell, 1882

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 35-37

Eucrate sexdentata Haswell, 1882

( Figs. 10A–F ; 15D–F)

Eucrate sexdentatus Haswell, 1882a: 548 ; 1882b: 86 [Queensland, Australia].

Eucrate sexdentata — Campbell 1969: 118 [in key], 120, fig. 1 [Queensland, Australia]. — Griffin & Campbell 1969: 150 [Queensland, Australia]. — Guinot 1971: 1080 [in list]. — Davie 2002: 199 [in list]. — Ng et al. 2008: 78 [in list].

(?) Eucrate sexdentata — Alcock 1900: 299 [in key], 301 [ Myanmar = Burma].

not Pseudorhombila vestita var. sexdentata ( Pseudorhombila haswelli Miers, 1884 ) — Miers 1884: 240, pl. 24, fig. B [Arafura Sea]. [= Homoioplax haswelli ( Miers, 1884) ]

Type material. Dry male lectotype, 8.3 mm × 10.5 mm ( AM P719 ; Fig. 10E ); 1 female paralectotype, 9.5 mm × 10.6 mm ( AM P719 ; Fig. 10F ) .

Type locality. Australia, Port Denison , off Holborn I., 36 m.

Material examined. Australia, Queensland, stn. 9–79, 20.09.79: 5 males , 22.8 mm × 26.6 mm, 2 females ( LACM) .

Queensland, Moreton Bay, muddy bottom, 25 m, N. Coleman coll., 06.1986: 1 male, 19.6 mm × 23.1 mm, 2 pre-adult females, 13.7 mm × 15.7 mm, 15.0 mm × 16.9 mm (QM W16032); east of Mud I., trawling, S. Cook coll., 22.10.1979: 1 male, 20.1 mm × 23.2 mm (QM W12057) .

Diagnosis. Third anterolateral tooth absent or reduced as slight elevation, carapace with relatively long posterolateral borders ( Fig. 10A, B, E, F ). P5 propodus slender ( Fig. 10A, B ). Large purple-pink spots on anterior two-thirds of dorsal surface of carapace ( Fig. 10A, B ; Campbell 1969: fig. 1B).

Remarks. Characteristic of E. sexdentata is the presence of only two anterolateral teeth posterior of each outer orbital tooth ( Fig. 10A, B, E, F ), the third tooth is absent, leaving only a slightly elevated margin, even in the two pre-adult females that were examined. The second anterolateral tooth is acute and dorsally projecting. Also diagnostic are the relatively long posterolateral margins ( Fig. 10A, B, E, F ) and the long and slender P2–P5 ( Fig. 10A, B ), the distal end of the P5 merus reaching the proximal portion of the second anterolateral tooth, the tip in pre-adults. These characters, however, are shared with E. alcocki and E. formosensis . Differences among the three species are discussed in the Remarks for E. alcocki .

The type material of Eucrate sexdentatus Haswell, 1882 , consists of two dry syntypes (male, 8.3 mm × 10.5 mm; female, 9.5 mm × 10.6 mm [ AM P719 ]). Neither could be examined on loan because of their very fragile condition. Colour photographs of the specimens, however, clearly show that they agree well with Haswell’s description as well as with the Australian specimens on hand. The dry male specimen ( Fig. 10E ) is hereby designated as the lectotype and the dry female ( Fig. 10F ) as paralectotype. The mesobranchial regions of the male paralectotype are visibly inflated, making the posterolateral borders of the carapace prominently more convex than in the female. A handwritten label glued underneath the slide where the specimens are kept reads “ 1 specimen distorted by parasites” (H. Stoddart, personal communication). The swellings on both sides of the carapace are symmetrical to each other but this does not preclude that both sides were parasitised by bopyriids. In the more recently collected specimens examined, however, the posterolateral borders of the carapace are slightly more convex in males ( Fig. 10A ) than in females ( Fig. 10B ), so this may be normal sexual dimorphism .

The identification by Alcock (1900: 301) of a male specimen from the Gulf of Martaban (Andaman Sea coast of Myanmar [= Burma]) as E. sexdentata is questionable. The species has only been reported from Queensland, Australia, and it is possible that Alcock was mistaken since he based his identification solely from Haswell’s description. Neither the short description ( Haswell 1882a: 548) nor a longer discussion of the species ( Haswell 1882b: 86) included illustrations. A character given in Alcock’s (1900: 299) key, “dactylus of last pair of legs almost styliform”, also applies to E. alcocki , which has been recorded from several locations in the Andaman Sea (see Material examined for E. alcocki ) and which had not been described until well after Alcock’s lifetime. Nevertheless, Alcock clearly stated in his key that the Myanmar ( Burma) specimen had only two anterolateral teeth [“three teeth (including the orbital angle)”], a character diagnostic of E. sexdentata . Specimens of E. alcocki of the same size as Alcock’s male (11.5 mm × 13.5 mm) do show three anterolateral teeth unlike specimens of E. sexdentata .

Colour pattern. “Pale cream with purple-pink spots” on the anterior two-thirds of the dorsal surface of the carapace, decreasing in size anteriorly (barely visible in Fig. 10A, B ; Campbell 1969: 120, fig. 1B).

Distribution. Queensland, Australia and, questionably, Myanmar [= Burma] ( Alcock 1900). Depth: shallow subtidal to 180 m ( Campbell 1969).

Figures

FIGURE 10. Eucrate sexdentata Haswell, 1882; A, C, D, male (19.6 mm × 23.1 mm) (QM W16032), Australia, Queensland, Moreton Bay; B, female (15.0 mm × 16.9 mm) (QM W16032), Australia, Queensland, Moreton Bay; E, dry male lectotype of E. sexdentatus Haswell, 1882 (8.3 mm × 10.5 mm) (AM P719), Australia, Port Denison, Holborn I.; F, dry female paralectotype of E. sexdentatus Haswell, 1882 (9.5 mm × 10.6 mm), same data as paralectotype. A, B, overall views; C, frontal view showing orbits and antennae; D, anterior portion of male thoracic sternum and abdomen; E, F, dorsal views of carapaces. Photo credits: E, F by R.T. Springthorpe © (AM).