Macrophthalmus grandidieri A. Milne-Edwards, 1867

Naderloo, Reza, Türkay, Michael & Apel, Michael, 2011, Brachyuran crabs of the family Macrophthalmidae Dana, 1851 (Decapoda: Brachyura: Macrophthalmidae) of the Persian Gulf, Zootaxa 2911, pp. 1-42 : 15-19

Macrophthalmus grandidieri A. Milne-Edwards, 1867

( Figs. 8 a–f, 9a–d, 21a–b)

Macrophthalmus Grandidieri A. Milne-Edwards 1867: 285 .

Macrophthalmus grandidieri — Crosnier 1965: 127, figs. 230, 235. — Hywel-Davies 1994: 29, 37, 48. — Apel 2001: 108, 109.

Macrophthalmus (Macrophthalmus) grandidieri — Barnes 1967: 23; 1970: 233, fig. 6a–c; 1971: 40 (in key); 2010: 35 (in key), 40. — Lewinsohn 1977: 73, 74.

Macrophthalmus (Macrophthalmus) sulcatus grandidieri — Pretzmann 1974: 438, figs. 1, 4.

Macrophthalmus brevis — Nobili 1906b: 318.

Type locality. Zanzibar.

Material examined. Persian Gulf: Iran: 1 juv. ( SMF 38538), Bandar-Abbas, E. city, 27º 11'N, 56º 21'E, muddy sand flat, 23.04.2008, R. Naderloo, A. Kazemi & A. Keykhosravi; 1 juv. ( SMF 38537) Qeshm I., 3 km E. of Kuweii, 26° 57'N, 56° 00'E, 0 5.05.2008, R. Naderloo & A. Kazemi

Gulf of Oman: 1 male, 1 female ( SMF 26291), Oman, Qurm near Muscat, sandy bank of water channel, 0 7.1994, A. Hywel-Davies.

Comparative material. South Africa: 2 males, 2 females (NHM 1928:1:2:117–118), Durban, Stebbing collection; 2 males (NHM 1913:2:14:11–12), Durban, coll. W.T. Calman, det. R.S.K. Barnes. East Africa: 66 males, 43 females (20 ovig.) (NHM 1971:50), Tanzania, Dar Es Salam, Tanganyika, R.G. Hartnoll, 1971; 1 male, 4 females (ovig.) (NHM 1973:81), Madagascar, Nosy Be, muddy sand, 10.1971, R.G. Hartnoll; 1 male (NHM 1973:99), Madagascar, Tulear, muddy sand, 10.1971, R.G. Hartnoll; 2 males, 3 females (2 ovig.) (NHM 1955:3:5:109–112), Port E. Africa, Manque Ferry, Morrumbene Estuary, mangroves, J.H. Dey; 1 male, 2 females ( SMF 25150), Kenya, between Mombasa and Malindi, 12.1985, W. Baumeister.

Redescription. Carapace ( Fig. 21a ) very much wider than long (CB/CL = 2.1), relatively convex, microscopic granules regularly on carapace, some slightly larger granules on epibranchial region, usually in transverse row; transverse row of small granules on posterior region, extending parallel to posterior margin, granules extensively lined. Regions well defined; furrows defining gastric, epibranchial regions remarkably deep. Front narrow, about 0.16 times as wide as carapace; anterior edge smooth, very slightly concave, not bi-lobed, frontal furrow faint.

Lateral margin ( Figs. 8 a, b) with three distinct teeth including exorbital angle; first tooth remarkably smaller than second, elongatedly triangular, directed outwards; second largest, broadly triangular, directed forwards, separated from former by long U-shaped notch; third smallest, directed forwards; posterolateral margin nearly straight, slightly converging posteriorly.

Eyestalks ( Figs. 8 a, b) narrow, not reaching tip of exorbital angle; upper orbital margin convex, sloping outward, regularly granular, granules small, nearly of same size; lower margin with relatively large granules, of different size, directed inwards.

Third maxilliped large, ischium about twice as long as merus, inner margins of ischium, merus with long brown setae, outer margin without setae, outer surface smooth.

Chelipeds ( Figs. 8 c, e) nearly equal. Merus with dense patch of long setae on inner upper margin, inner upper, lower margins smooth, posterior margin with small granules. Carpus with small granules medially on upper inner margin, large spine-shaped tooth on inner distal margin, directed forwards, sometimes with small accessory one. Palm ( Figs. 8 c) long, about 1.7 times as long as high in distal portion; outer surface smooth, with longitudinal ridge on lower portion, running from proximal part to near base of immovable finger, curving downward dorsally, finely granular, granules smaller dorsally; lower margin deflexed on base of immovable finger, covered with small granules; upper margin with very small granules; inner surface ( Fig. 8 e) with patch of dense setae on upper portion of palm, continuing to inner surface of fingers; with large spine-shaped tooth on proximal portion, small granules around it, lower proximal portion densely covered with small granules, distal lower portion depressed; upper margin with row of large granules, conical, decreasing in size distally. Movable finger ( Fig. 8 c) long, relatively narrow, curved downward, upper margin with small granules; cutting edge without differentiated tooth, small round teeth along it. Immovable finger ( Figs. 8 c, d) short, moderately deflexed; with median differentiated tooth, subquadrate, directed forwards, some small teeth distally along cutting edge.

Cheliped of females small, long setae on posterior, lower inner margin of merus, margins of carpus; upper margin of palm finely granular, lower margin faintly granular; lower half of outer surface with depression, upper half finely granular; inner upper margin of manus, fingers with long setae; cutting edges with numerous small teeth.

Walking legs medium-size, relatively narrow. Merus with anterior, posterior margins serrated, small subdistal tooth on anterior margin of merus of second, third, posterior margin minutely denticulate distally; third largest, merus of third about 3.2 times as long as wide; dense patch of setae proximally on anterior margin of second. Propodus as long as dactylus; fourth walking leg very small, unarmed, with long setae on posterior, anterior margins of all segments.

Posteromedian margin of epistome strongly convex, bearing faint ridge on anterior part of buccal cavity.

Male abdomen ( Fig. 8 f) broadly triangular, with segments 3, 4 of same length, slightly shorter than segment 5; segment 5 as long as segment 6, with lateral margins gently converging; lateral margins of segment 6 moderately swollen proximally; telson very slightly longer than segment 6, lateral margins strongly converging distally, apically rounded.

Male G1 ( Fig. 9 a) moderately long, curving outwards proximally, distal portion depressed laterally; apical chitinous process ( Fig. 9 b) short, curved laterally, lateral surface with depression, apical margin concave; distal opening ( Fig. 9 c) distally on mesiodorsal part; long setae around apical part, long plumose setae sparsely along lateral, ventral surface.

Female gonopore ( Fig. 9 d) having markedly elevated margins, fissure on anterolateral corner; operculum relatively large, directed laterally.

Remarks. Apel (2001) examined material from the Persian Gulf identified as M. grandidieri by several authors ( Basson et al. 1977; Clayton 1986; Jones 1986; Vousden 1987). It appeared, however, that all specimens examined had to be assigned to Macrophthalmus sulcatus H. Milne-Edwards, 1852 . There were only one male and one female (SMF 26291) from the Muscat area in northern Oman (Gulf of Oman) collected by A. Hywel-Davies, which could be convincingly assigned to M. grandidieri . Two juveniles were collected from Bandar-Abbas and Qeshm I., which are assigned to M. grandidieri being the first record of the species from the Straits of Hormuz, while it has not been recorded from the inner Persian Gulf.

There are several good characters that allow distinguishing between M. grandidieri and M. sulcatus . Macrophthalmus sulcatus has the carapace markedly wider than M. grandidieri . The CB/CL ratio of M. sulcatus is about 2.3, that of M. grandidieri about 2.1. The eyestalks of M. sulcatus are longer, reaching beyond second lateral tooth, whereas those of M. grandidieri do not even reaching the exorbital angle. Furthermore, the granules on the posterior surface of the carapace in M. sulcatus are relatively larger than those of M. grandidieri , and even the epibranchial granules of M. sulcatus are more distinct. The genital apparatus of males and females of these two species are, however, very similar, not allowing to easily distinguish them using the morphology of the G1, the shape of the gonopore, or the male and female abdomen. This similarity is most remarkable in the shape of the G1 ( Figs. 9 a–c, 20a–c).

Tesch (1915) described a new species, M. Hilgendorfi based on a single male from Zanzibar deposited in RMNH. This species is very similar to M. grandidieri , but according to Tesch’s drawing, it has a clearly wider front. Barnes (1977) synonymised M. hilgendorfi with M. grandidieri without any discussion. Ng et al. (2008), however, listed it amongst the valid species of the genus.

Biology. Macrophthalmus grandidieri is a medium-size species (specimens from the Gulf of Oman: male CL = 12.16, CB = 24.86 mm, female CL = 12.99, CB = 27.02 mm) that inhabits only the mid intertidal zone with a relatively firm sandy substrate. In mangrove stands it is restricted to the seaward fringe on the sandy bank of the water channels, where it was recorded from mangroves near Muscat in Gulf of Oman ( Hywel-Davies 1994). Hywel- Davies (1994) recorded 15 specimens per m2 on an exposed sandy bank of a mangal channel near Muscat (Gulf of Oman). Otherwise not much data is available regarding the biology of this species in the northern Indian Ocean, including the Red Sea and the Arabian Sea.

Emmerson (1994) collected ovigerous females of M. grandidieri throughout the year in a mangrove estuary in Transkei, South Africa. The number of females always exceeded that of males, with a female/male ratio of 1.4. The continuous breeding activity is quite unusual for ocypodoid crabs, most of which have seasonal reproductive cycles ( Emmerson 1994).

Geographical distribution. Western Indian Ocean: South Africa, East Africa, Red Sea, Persian Gulf, Gulf of Oman.

Figures

FIGURE 8. Macrophthalmus grandidieri A. Milne-Edwards, 1867: a, c, e, f, male (SMF 26291); b, d, male (NHM 1973: 50). a, posterior surface of carapace, left side; b, posterior surface of carapace, left side; c, cheliped of male, outer surface; d, immovable finger with differentiated tooth; e, cheliped of male, inner surface; f, male abdomen.

FIGURE 9. Macrophthalmus grandidieri A. Milne-Edwards, 1867: a – c, male (SMF 26291); d, female (SMF 26291). a, G 1 of male, ventral surface (right); b, apical part of the same G 1, lateral surface; c, apical part of the same G 1, dorsal surface; d, female gonopore.

FIGURE 21. a, b: Macrophthalmus grandidieri A. Milne-Edwards, 1867, male (SMF 26291), a, posterior surface; b, ventral surface; c, d: Macrophthalmus sulcatus H. Milne-Edwards, 1852, male (SMF 36885), c, posterior surface; d, ventral surface.