Macrophthalmus dentipes Lucas, 1836

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 : 7-11

Macrophthalmus dentipes Lucas, 1836

( Figs. 4 a–e, 5a–f, 10a–b)

Macrophthalmus dentipes Lucas 1836: 551 . — Holthuis 1995: 401.

Macrophthalmus pectinipes — Guerin-Méneville 1838: 1, pl. 23. — Alcock 1900: 377. — Chhapgar 1957b: 512. — Barnes 1970: 237, fig. 10. — Pretzmann, 1971: 31; 1974: 442. — Tirmizi 1981: 109. — Titgen 1982: 253 (in list). — Jones 1986: 159, pl. 45. — Tirmizi & Ghani 1996: 121, fig. 46.

Macrophthalmus (Venitus) dentipes — Apel & Türkay 1999: 135. — Apel 2001: 110. — Barnes 2010: 33 (in key), 43.

Type locality. Bombay (= Mumbay), India

Material examined. Persian Gulf: Iran: 3 males ( ZUTC Brach1163), Hormozgan, Bandar-Khamir, 28º 48'N, 55º 38'E, mangroves, 31.11.2005, R. Naderloo; 3 females ( ZUTC Brach1172), Hormozgan, Khor-Khalasi, 25º 35'N, 58º 08'E, mud flat behind mangroves, 26.10.2006, R. Naderloo; 4 males ( ZUTC Brach1186), Hormozgan, Bandar-Khamir, 28º 48'N, 55º 38'E, muddy sandy shore, east of fishery jetty, 14.04.2006, R. Naderloo; 7 females (ovigerous) ( ZUTC Brach1210), Khuzestan, Mahshahr, Fishery jetty (Majidieh), 30º 28'N, 49º 11'E, muddy shore, 17.04.2006, R. Naderloo; 4 males, 2 females ( ZUTC Brach1211), Khuzestan, Shah Abdollah, 30º 10'N, 50º 05'E, sandy mud-flat, 14.04.2006, R. Naderloo; 3 males, 2 females ( ZUTC Brach1238), Khuzestan, Shah Abdollah, 30º 10'N, 50º 05'E, sandy mud-flat, 14.04.2006, R. Naderloo; 1 male (CL = 28.35 CB = 28.15), 1 female ( SMF 36863), Bandar-Abbas, E. of city, 27º 08'N, 56º 20'E, muddy sand flat with shell, 23.04.2008, R. Naderloo, A. Kazemi & A. Keykhosravi; 3 males, 3 females ( SMF 36866), Bandar-Khamir, E. of fishery Jetty, 26º 56'N, 55º 36'E, Khor, muddy flat, 24.04.2008, R. Naderloo, A. Kazemi & A. Keykhosravi; 1 male ( SMF 36864) Qeshm I., N. coast, 3 km W. of Kuweii, 26º 57'N, 56º 00'E, muddy flat, 13.01.2008, R. Naderloo & M. Türkay; 2 males, 1 female, 10 juv. ( SMF 36865), Bandar-Khamir, E. of fishery Jetty, 26º 56'N, 55º 36'E, Khor, muddy flat, 24.04.2008, R. Naderloo, A. Kazemi & A. Keykhosravi.

Kuwait: 1 male (NHM 1978.194), Kuwait Bay, west coast of Sulaibikhat, near mangroves, 16.04.1978, D. Clayton; 1 female (NHM 1978.195), mud flat creek at Al-Jahra, Clayton & Vaughan.

Iraq: 4 males (NHM 1892.9.16.2-6), Fao, W.D. Cumming, examined by Barnes (1971).

Comparative material. Arabian Sea: 1 male, 3 females ( SMF 26095), Oman, Filim, W. of Barr al-Hikman, 20º 36.592'N, 58º 11.217'E, muddy flat and mangroves, 14.01.2001, M. Apel; 4 males, 1 female (NHM 1889:6:17:83-87), Pakistan, Sind, F. Day, examined by Barnes (1971).

Redescription. Carapace ( Fig. 4 a) moderately wider than long (CB/CL = 1.6–1.7), slightly convex; large granules scattered on entire posterior surface except in narrow median, frontal regions, granules on branchial regions high, longitudinal row of 6–8 high granules on epibranchial region, granules on median regions low, round. Regions well defined; furrows wide, moderately deep, normally beset with dense setae. Frontal region remarkably deflexed downward, smooth; front very narrow, about 0.06–0.07 times as wide as carapace, strongly constricted medially; anterior edge remarkably concave, bi-lobed, frontal furrow markedly deep.

Lateral margin of carapace ( Fig. 4 a) with 3 distinct teeth (including exorbital tooth); first nearly subquadrate, with posterior margin smooth, curved forward; second triangular, with smooth margin, higher than first, greatest width of carapace between second lateral teeth; third very small, directed forwards; posterolateral margin nearly straight, slightly converging posteriorly, with small granules, beset with long setae; posterior margin with very small granules.

Eyestalks narrow ( Fig. 4 a), long, but not reaching to exorbital angle; upper orbital margin fairly convex, regularly granular, granules large, high, pointed, directed laterally; lower orbital margin ( Fig. 4 b) with round granules on inner third, 5–6 long tubercles on outer portion of margin forming stridulating ridge.

Third maxillipeds leaving small gap between; ischium slightly more than twice the length of merus, inner margin of ischium, merus with long setae, outer margins with short setae, outer margin of ischium completely straight, outer margin of merus sharply sloping distally; outer surface of ischium, merus smooth, elliptical row of long setae proximally on outer surface of ischium.

Chelipeds nearly equal, sometimes subequal, remarkably long in large specimens ( Fig. 4 f). Merus ( Fig. 4 e) long; inner upper margin with distinct stridulating ridge, large granules along it, larger distally, with scarce setae; inner lower margin with small granules, continuous with lower surface; upper margin with small granules on proximal portion, with scarce setae. Carpus smooth on outer surface, inner upper margin with denticles, distally larger, small granules along inner portion of these denticles. Palm long ( Figs. 4 c, d, f), about 1.8–2.3 times as long as high in proximal portion; outer surface smooth ( Figs. 4 c, f) without longitudinal ridge; inner surface ( Fig. 4 d) smooth, patch of dense setae on upper portion, parallel to upper margin; lower margin nearly smooth; upper margin with large granules on proximal portion, smaller distally. Fingers remarkably curved inward distally, movable finger with upper margin smooth, long setae densely along inner surface of upper margin, continuous on upper, outer surface, cutting edge with subproximal differentiated tooth, small teeth distally; immovable finger narrow, with relatively large teeth on cutting edge, long setae along inner surface.

Cheliped of females small; outer surface of palm smooth, longitudinal ridge short, extending from base of immovable finger to proximal half; upper margin with small granules, with long setae; lower margin smooth, with relatively short setae; fingers distinctly long, slightly less than 1.5 length of palm; cutting edge faintly tuberculate, chitinous distal margin long, more than half of length of finger, long setae on inner surface of fingers.

Walking legs moderately long; second, third longest, with margins of segments more granular than those of first, fourth. Merus long, that of third leg about 4 times as long as wide; merus of first, second, third walking legs with subdistal tooth on anterior margin, 3–4 large denticles distally on posterior margin, merus of females with large denticles on anterior margin. Carpus of first walking leg, with longitudinal ridge, that of second, third with two ridges of long granules on anterior margin, carpus of third with one distinct large denticle distally on posterior margin. Propodus of second with small denticles on anterior, posterior margins; propodus of third with small denticles on anterior margin, large, spine-shaped denticles on posterior margin; dense setae on upper portion of anterior surface of carpus, propodus of third.

Posteromedian margin of epistome nearly straight, short longitudinal ridge on anterior part of buccal cavity.

Male abdomen ( Fig. 5 d) with segments 3, 4 of same length, slightly shorter than segment 5; segments 5, 6 nearly of same length, with lateral margins nearly straight; lateral margins of segment 6 with small depression at one third distal portion; telson very slightly longer than segment 6, lateral margins strongly converging distally, apically rounded.

Female abdomen ( Fig. 5 e) with large telson, slightly longer than segment 6, distinctly wider than half length of segment 6.

Male G1 ( Fig. 5 a) moderately stout, slightly curved outward medially; distal half relatively narrowing, with apical chitinous process ( Figs. 5 b, c) remarkably long, narrow, curved outward at about 45°; distal opening ( Fig. 5 b) large, distinct, subdistal on dorsal portion of apical process; long feather-shaped setae densely set along lateral margin, long setae around apical process.

Female gonopore ( Fig. 5 f) on outer wall of depression, directed mesially, anterior margin distinctly rounded, elevated, outer margin slightly convex; operculum small, directed laterally.

Remarks. Barnes (1970) first recorded M. dentipes from the Persian Gulf at Al-Faw (Fao), Iraq. Barnes (1970), like many preceding authors, referred to this species using the junior synonym M. pectinipes Guerin-Méneville 1838 , and assigned it to the subgenus Venitus Barnes, 1967 . Pretzmann (1971) recorded the species from Bandar-Abbas at the Iranian coast, Jones (1986) from Kuwait, both following Barnes (1970) using the name M. pectinipes . The older name M. dentipes , however, was overlooked until Holthuis (1995) revived M. dentipes as the valid name by showing that M. pectinipes is an objective synonym of M. dentipes , and therefore must be replaced by the latter. Apel & Türkay (1999) and Apel (2001) listed M. dentipes from the Persian Gulf with reference to the records by Barnes (1971) and Jones (1986).

Biology. Macrophthalmus dentipes is the largest ocypodid crab (largest male CL = 40.11, CB = 66.20 mm, largest female CL = 40.55, CB = 65. 56 mm) inhabiting the mid and low intertidal zones in muddy sand/sandy mud substrates ( Jones 1986; Al-Zaidan et al. 2006) in the region. This burrowing crab occurs especially in soft muddy substrates at depths of more than 60 cm. The Macrophthalmus zone extends from the middle part of the mudskipper ( Periophthalmus waltoni ) zone downwards to the low littoral ( Clayton 1986). Macrophthalmus dentipes digs large burrows with an opening of approximately 10 cm in diameter, which sometimes can be confused with those of mudskippers, but in this crab the burrows entrance is marked by a sloppy, light-coloured mud pool with a mound of excavated mud Whereas, the species has not been recorded from the Arabian side on the western and southern parts of the Persian Gulf, it is a common species of muddy sand/sandy mud substrates along the northern and northeast coasts including Kuwait ( Jones 1986; Clayton 1986) and the Iranian coast. The population density of this species was estimated based on burrow counts. In the muddy flat of Bandar-Khamir east to the fishery jetty (26º 56'N, 55º 36'E) an average of 10 burrows were present per 5 m 2, whereas near Mahtabi Police station (26º 46'N, 55º 20'E) in sandy mud substrate an average of 20 burrows per 5 m 2 was counted.

The pereopods of males of M. dentipes grow faster compared to the carapace, therefore large males have remarkably long legs, and long chelipeds in particular. Barnes (1970), in his detailed description, only mentioned the abnormal growth of the merus of the pereopods, but the rapid development of all segments was observed in the present study, which can be clearly detected in the remarkably long palm of the cheliped in large males ( Fig. 4 f). Furthermore, large males have more granules on the posterior surface of the carapace, which are markedly high in comparison to the low and round granules of carapace of small males.

Geographical distribution. Northern Indian Ocean: northern and eastern Persian Gulf, Oman (Gulf of Masirah), Pakistan, west coast of India. A record from Malaysia by Henderson (1893) is highly questionable and probably based on misidentified material.

Figures

FIGURE 4. Macrophthalmus dentipes Lucas, 1836: a – f, male (SMF 36863); f, male (SMF 26095). a, posterior surface of carapace, left side; b, lower orbital margin of male, right; c, cheliped of male, outer surface; d, cheliped of male, inner surface; e, merus of male cheliped, inner surface; f, cheliped of male outer surface.

FIGURE 5. Macrophthalmus dentipes Lucas, 1836: a – d, male (SMF 36863); e, f, female (SMF 26095). a, G 1, ventral surface (right); b, apical part of the same G 1, dorsal surface (right); c, apical part of the same G 1, ventral surface (right); d, male abdomen; e, female abdomen, penultimate segment and telson; f, female gonopore, right.