Macrophthalmus (Mareotis) crinitus Rathbun, 1913

Teng, Shao-Jyun & Shih, Hsi-Te, 2015, A new species of Macrophthalmus Desmarest, 1823 (Crustacea: Decapoda: Brachyura: Macrophthalmidae) from Taiwan, with notes on four new records, Zootaxa 4058 (4), pp. 451-470 : 459-460

Macrophthalmus (Mareotis) crinitus Rathbun, 1913

( Figs. 5 , 6 )

Macrophthalmus sp. — De Man 1902: 495.

Macrophthalmus pacificus— Rathbun 1910b: 307, pl. 1(3). (not M. pacificus Dana, 1851 )

Macrophthalmus crinitus Rathbun, 1913: 619 , pl. 75(3) [type locality: Ambon, Moluccas, Indonesia]; Tesch 1915: 192; Kemp 1919: 390, pl. 24(7); Chhapgar 1957: 515.

Macrophthalmus (Mareotis) crinitus— Barnes 1970: 236; 1971: 22, fig. 5; Vannini & Valmori 1981: 220 (?); Takeda 1981: 73; Barnes 2010: 41 , fig. 3C; Rahayu & Nugroho 2012: 27 , fig. 1C, D.

Not Macrophthalmus crinitus— Barnes 1967: 221, fig. 7, pl. 2c (= M. darwinensis Barnes, 1971 ).

Material examined. 1 ♂ (7.7 mm, soft-shelled) (NCHUZOOL 14758), Shanyuan, Taitung, coll. S.-J. Teng, 27 July 2014.

Comparative material. 3 ♂♂ (15.5–16.2 mm), 2 ♀♀ (5.1, 15.0 mm) (NCHUZOOL 14759), Camiguin, northern Mindanao, Philippines, 30 Aug. 2003; 4 ♂♂ (12.7–15.6 mm), 2 ♀♀ (8.2, 14.0 mm, incl. 1 ovig.) ( ASIZ BOHOL), Cabantian, Bohol, Philippines, coll. H.-C. Liu, 15 May 2004; 1 ♂ (carapace broken), 1 ovig. ♀ (14.9 mm) (NCHUZOOL 14760), Gerokgak, Bali, Indonesia, coll. H.-T. Shih, 18 July 2014.

Diagnosis. Carapace ( Fig. 5 A) with first two anterolateral teeth large, third tooth small. First anterolateral tooth broad, subrectangular, directed forwards, outwards, pointed; anterior margin with pointed granules continuous with those on upper orbital border; lateral margin straight or convex, with pointed granules; separated from second tooth by wide V-shaped incision. Second anterolateral tooth conspicuously broad, directed outwards, projecting beyond first tooth. Third anterolateral tooth pointed. Posterolateral margins of carapace with rounded or pointed granules, obscured by dense setae. Largest carapace width across lateral margins, diverging posteriorly. Eyestalks short; cornea extending to base of first anterolateral tooth. G1 ( Fig. 5 B–D) with apical chitinous process short, curved.

Coloration. The color is grayish according to Chhapgar (1957). Our preserved specimens showed gray chelipeds and legs, but deep gray on carapace, with pterygostomian region dark brown.

Distribution. Gulf of Aden, India (Okha), Myanmar (Mergui Archipelago), Indonesia ( Molucas: Ambon, Halmahera, Ternate), Australia (Darwin), Japan (Amami-Oshima, Ryukyu Islands), Philippines (Mindanao), and Taiwan (Taitung). This is a new record for Taiwan.

Habitat. Sandy mud substrate of seaward fringe of mangrove forests ( Rahayu & Nugroho 2012).

Remarks. The specimen collected from Taitung in eastern Taiwan is a soft-shelled juvenile, but the morphology ( Fig. 5 A–D), especially the characters of anterior lateral teeth and shape of carapace, agrees with the description of this species ( Rathbun 1913: 619; Barnes 1971: 22) and with the specimens from Philippines and Indonesia ( Fig. 5 E–L; see comparative material). Specimens from Taiwan form a clade with specimens from Philippines and Indonesia, based on molecular evidence ( Fig. 11 ), which supports the identity of Taiwanese specimen.

Other characters of M. crinitus , based on the adult specimens from Philippines and Indonesia, is as follows. Cheliped stout ( Fig. 5 F). Outer surface of palm smooth, without ridge, inner surface of palm, fingers and merus of cheliped heavily setose. Dactylus armed with big differentiated tooth on cutting edge. Female gonopore with suboval operculum ( Fig. 5 L), directed mesially, forward, projecting slightly; depression on sternite anteromesial to operculum indistinct.

This species is morphologically similar to M. definitus , but can be distinguished by the setae on the chelipeds. The inner surface of the merus and palm of M. crinitus is densely covered with long setae, but M. definitus only has long setae densely covering the inner surface of the palm, none on the merus. The immovable finger of M. crinitus is stouter than that of M. definitus . There is also a differentiated tooth each on inner cutting edges of both fingers of M. definitus , but M. crinitus has a well-defined tooth only on the dactylus. The setae on the surface of the carapace of M. crinitus is denser than that of M. definitus .

Figures

FIGURE 5. Macrophthalmus (Mareotis) crinitus Rathbun, 1913. A – E, ♂ (CW 7.7 mm), NCHUZOOL 14758, from Taitung, Taiwan; A, part of the broken carapace; B – D, terminal segment of right G 1. B, ventral view; C, dorsal view; D, outer view. E – L, ♂ (CW 15.6 mm), ASIZ BOHOL, from Philippines; E, carapace; F, palm of left chela; G, male abdomen; H – K, terminal segment of right G 1, H, ventral view; I, dorsal view; J, outer view; K, inner view. L, ♀ (CW 14.0 mm), ASIZ BOHOL, from Philippines, gonopore.

FIGURE 6. Macrophthalmus (Mareotis) crinitus Rathbun, 1913. A – D, soft-shelled and broken ♂ (CW 7.7 mm), NCHUZOOL 14758, Taitung, Taiwan; E – H, ♂ (CW 15.6 mm), ASIZ BOHOL, Philippines. A, E, dorsal view; B, a part of carapace showing the anterolateral teeth; C, F, G, ventral view; D, H, frontal view.

FIGURE 11. A Bayesian inference (BI) tree of the macrophthalmid species and outgroups used in this study, based on the combined 16 S rRNA and cytochrome oxidase subunit I (COI) genes. See Table 1 for details of the specimens. Probability values at the nodes represent support values for BI and maximum likelihood (ML).