Macrophthalmus japonicus (de Haan, 1838)

Barnes, R. S. K., 2010, A Review Of The Sentinel And Allied Crabs (Crustacea: Brachyura: Macrophthalmidae), With Particular Reference To The Genus Macrophthalmus, Raffles Bulletin of Zoology 58 (1), pp. 31-49 : 42

The M. japonicus group

The M. japonicus group comprises M. abercrombiei Barnes, 1966 , M. banzai Wada & Sakai, 1989 , M. definitus Adams & White, 1848 , M. depressus Rüppell, 1830 , M. japonicus (de Haan, 1838) (the type species of Mareotis ), M. setosus H. Milne Edwards, 1852 , M. pistrosinus Barnes & Davie, 2008 , M. teschi Kemp, 1919 , and M. tomentosus Souleyet, 1841 (which possesses the stridulatory apparatus) ( Fig. 4A ). In these, the front is narrow and markedly constricted, the central region of epistome bears a concavity (except in M. teschi – see below), the characteristic transverse and longitudinal branchial ridges of Mareotis are usually wellmarked, and the fingers of the male chela are elongate with the index being strongly downflexed especially in large individuals. The morphology of M. teschi appears somewhat less straightforward than seemed earlier ( Barnes, 1971) in that a north-south cline is now evident: Thai populations ( Komai et al., 1995) display a relatively parallel-sided carapace and straight central region of the epistome; in Indonesia ( Barnes, 1971) the second lateral tooth projects beyond the external orbital angle and the central region of the epistome is protuberant; whereas material examiner by the author from Selangor in peninsular Malaysia is equivalent to that from Thailand in its epistome but to that from Indonesia in the form of its anterolateral carapace teeth.

Molecular sequence data ( Kitaura et al., 2006) confirm the existence of two groupings within Mareotis but not the two identified on morphological grounds by Komai et al. (1995). Sequence analysis groups M. darwinensis and M. definitus on the one hand, but, on the other, groups M. banzai , M. japonicus , M. tomentosus , M. pacificus and M. pistrosinus , and allies them with the subgenus Venitus and the M. convexus and M. telescopicus groups of Macrophthalmus sensu stricto instead (see Fig. 6 ). The allozyme data of Horii et al. (2001), however, which did not include M. darwinensis , grouped M. definitus with M. japonicus and M. banzai in a Mareotis cluster distinct from although allied to M. convexus and the M. telescopicus group.

Figures

Fig. 4. Form of the carapace and adult male chela of subgroups of the genus Macrophthalmus IV: (a) the M. japonicus group of the subgenus Mareotis (both the relatively parallel-sided and relatively rounded carapace types), and (b) subgenus Paramareotis. Scale bars = 5mm.

Fig. 6. The relationships between and within some subgroups of Macrophthalmus suggested by the nucleotide sequence analyses of Kitaura et al. (2006).