Chiromantes boulengeri ( Calman, 1920 )

Naderloo, Reza & Schubart, Christoph D., 2009, Redescription and mitochondrial identification of Chiromantes boulengeri (Calman, 1920) (Decapoda: Brachyura: Sesarmidae) based on fresh material from the Persian Gulf, Iran, Zootaxa 2128, pp. 61-68 : 63-68

Chiromantes boulengeri ( Calman, 1920)

Sesarma boulengeri Calman, 1920: 63 –65, fig. A.

Chiromantes boulengeri — Apel & Türkay 1999: 133; Apel 2001: 116; Ng et al. 2008: 220, 222.

Type locality: Shat Al Arab (Basra), Iraq.

New material. 3 males ( ZUTC Brach 1151), Iran, Bahmanshir River, summer 2006, coll. E. Gholinezhad; 1 male, 1 female ( ZUTC Brach 1153), same data; 18 males, 27 females (16 ovigerous), 3 juv. (SMF-33818), Iran, Abadan, Bahmanshir River, Pole Tanki Abolhassan, 30º 21΄ 0 1.5″N, 48º 18΄ 35.9″E, 20.05.2008, coll. R. Naderloo, A. Kazemi (1 male DNA voucher).

Comparative material. Sesarma boulengeri Calman, 1920 , lectotype, 1 male (CL 23.4, CB 27.00 mm) (NHM 2002.298), largest male of the four specimens of 1919.11.14.1-4, herewith designated as lectotype), Ashar Creek, Basra, Iraq, coll. C.H. Boulenger, 1919 ( DNA voucher); paralectotypes 1 male (CL 17.8, CB 21.1 mm), 2 ovigerous females (CL 19.8-22.2, CB 23.9-26.8), (NHM 2002.299-301, remaining three specimens of 1919.11.14.1-4), Ashar Creek, Basra, Iraq, coll. C.H. Boulenger, 1919; Chiromantes boulengeri , 1 male, 1 female (NHM 1892.9.16.7.20), FAO, Persian Gulf, determined by M. Apel, 28.10.1997; 1 male (NHM 1999.124), FAO, Persian Gulf, determined by M. Apel, 28.10.1997.

Chiromantes dehaani (H. Milne Edwards, 1853) , 1 ovigerous female ( ZRC 2002.0226), Japan, Kagoshima Prefecture Satsuma Peninsula, mouth of Izaku River, 30.08.2000, leg. Suzuki, ( DNA voucher).

Sesarmops intermedium (De Haan, 1835) , 1 male (ZRC 2000.1834), Taiwan, Pingtung, Kangkou River mouth, 14.09.1999, H.-C. Liu & C.D. Schubart (DNA voucher).

Redescription. Carapace squarish (almost quadrate) ( Figs. 2 a, 3a), slightly broader than long (CL/CB about 1.17–1.20), greatest breadth slightly posterior to exorbital teeth, no anterolateral teeth; slightly convex (in particular at posterior region); surface smooth, nearly glabrous, some short setae scarcely scattered on carapace, particularly on posterolateral regions; regions well defined, arched prominent groove separating gastric from cardiac region, one pair of very small tubercles in middle of groove; two other arched, less distinct grooves in gastric region. Intestinal region distinctly depressed, separated from cardiac region by rather shallow, wide groove. Oval groove, more or less prominent, in hepatic region, just behind of orbit. Eight smooth ridges with different length on lateral region, with two short ones in between.

Front strongly deflexed, 4 lobes in frontal region, 2 middle ones larger than lateral ones; frontal edge gently curved upwards, sinuous, nearly bilobed; region between frontal lobes, frontal edge concave; low transverse elevation, somewhat fragmentary in front of middle frontal lobes, lateral angles of front rounded ( Fig. 3 b).

Basal segments of antennae, antennules separated by distinct segment ( Fig. 3 b), long setae cover three proximal segments of antenna, antennule; flagellum of antenna very short, extends shortly beyond orbital hiatus, not reaching cornea of eye.

Ischium of third maxilliped almost same size as merus, with submedian shallow groove; merus suboval, posterior surface with elevated ridge extending from inner angle of anterior margin to median part of posterior margin, with wide sulcus lateral to ridge, relatively deep groove on lateral part. Inner margins of ischium, merus with long setae; lateral margin of ischium with dense short setae, that of merus with scarce short setae; surface of merus with short bristles, that of ischium smooth without pubescence; exopod slender.

Chelipeds equal, sometimes subequal, distinctly large; ischium smooth with relatively large tooth on inner margin; outer surface of merus with finely granulated transverse ridges, inner surface smooth with longitudinal line of brown setae near inner margin, inner margin dentate on two-thirds of proximal part, subdistally roundly expanded, distally smooth, lower margin dentate, outer margin serrate. Carpus with spinelike tooth on inner margin, outer surface with granulated short ridges, with L-shaped depression on distal part. Palm ( Fig. 3 c) massive, oblique granular ridges on lower margin, on proximal part of outer surface; outer surface with small granules on lower half, large granules on middle area, sometimes 5, 6 in longitudinal row, smaller ones on upper part of outer surface; upper surface ( Fig. 3 d) with prominent 2, 3 small longitudinal granular ridges; inner surface with small granules on lower half, an oblique line of relatively large granules extending from base of immovable finger towards upper part, 2, 3 large granules on upper part. Fingers with small gap in between, widening distally; movable finger slender, relatively arched, curving gently inwards, longer than palm, small granules on dorsal margin, proximally numerous, extending distally into a row, while becoming smaller, lower. Cutting edge of movable finger with 3 large teeth: 1 proximal, 1 distal, 1 middle; cutting edge of immovable finger with 4 large teeth: 3 proximal (with distal first 2 fused), 1 distal, some low teeth between them. Tips of fingers pectinated, scalloped, that of movable finger nearly tridentate. Cheliped of female small, more narrow, otherwise possessing all features of that of male.

Walking legs medium-sized, third, second pairs longest; merus with granular transverse ridges on upper surface, upper surface of last walking legs nearly smooth with few ridges on anterior part, anterior margin serrated, with subdistal tooth, posterior margin smooth. Carpus with 2 carinae on posterior surface, 1 on anterior surface; anterior margin of carpus, propodus densely covered with short brown setae, with some large bristles in between. Propodus slightly longer than carpus, with one carina on posterior, anterior surfaces. Dactylus slender, of nearly same length as propodus, with setae on anterior, posterior margins.

Anterior margin of first thoracic sternites ( Fig. 3 e) densely covered with setae, row of relatively long setae along suture of second, third sternites; fused third, fourth sternites relatively narrow, abdominal cavity near suture of second, third sternites, reaching to coxae of chelipeds.

Male abdomen ( Fig. 3 f) widely triangular, margin of segments with short dense setae; sixth segment longer than fifth, with arched anterodistal margin; telson clearly longer than sixth segment, lateral margin proximally nearly straight, becoming strongly convex distally, forming wide triangular tip, with scarce setae.

G1 ( Fig. 3 g) straight, clear longitudinal depression on ventral surface near lateral margin; inner margin distally roundly expanded; terminal pectinated part gently bent outwards, with concave apical margin, small pectinated process ( Fig. 3 h), nearly triangular, laterally to terminal part. Genital opening ( Fig. 3 i) subdistal on ventral surface of terminal pectinated part, long setae covering terminal part, not fully concealing it, short setae along outer margin.

Female gonopore ( Fig. 3 j) in depression on anterior edge of sternite 5, attached to posterior margin of sternite 4, with elevated small operculum, directed inwards, sternite 5 scarcely covered with plumose setae. Colour. Live animals dark grey on dorsal surface of carapace; chelipeds, walking legs slightly lighter colour than carapace, ventral surface light, abdomen distinct by its light brown colour. Chelae white to light brown from anterior view. Granules on palm, fingers distinctly white, lower, inner portions of palm sometimes pale orange.

Habitat. The species was found in muddy banks of the Shat Al Arab and Bahmanshir rivers, where it digs burrows. Type material was collected from Ashar Creek near Basra (the Euphrates River) about 96 km from the sea in fresh water ( Calman, 1920). Apel & Türkay (1999) examined several other specimens deposited in the British Museum of Natural History in London, which were found together with Parasesarma plicatum in the same jar labelled as collected from “FAO” (M. Apel, personal communication). Fao is official pronunciation of Al Faw, a city about 20 km from the sea. Apel & Türkay (1999) mentioned that at this station which located at the mouth of the river, C. boulengeri coexists with P. plicatum . All recently collected adults of C. boulengeri , however, show complete independence from the sea, and it would not be possible to explain its range extension down these rivers. So far, it has been clear that this species shows no coexistence with P. plicatum , which lives in the downstream areas of the river.

Molecular results. The molecular dataset consisted of 615 aligned characters of which 479 were conserved, 99 variable, and 53 parsimony-informative. GTR+G+I with a gamma shape of 0.468 and an invariable proportion of 0.538 was selected as the best-fitting evolutionary model by MODELTEST and implemented for subsequent Bayesian analysis. The tree topology was in agreement with the one of the Maximum Composite Likelihood which is shown in Fig. 4 together with posterior probabilities and bootstrap values exceeding 50%. According to this phylogeny, the genus Chiromantes is a paraphyletic assemblage including in close relationship representatives of the genera Sesarmops and Bresedium . Most derived seem to be the East African species C. eulimene and C. ortmanni . This confirms the need of revision of this large genus (see Ng & Liu, 1999; Ng & Schubart, 2003; Ng et al., 2008; Ng & Schubart, in progress). The species Chiromantes boulengeri currently holds an outgroup position to a clade comprised of C. haematocheir (type species of the genus), C. dehaani , and Sesarmops intermedium . Apparently, no closely related species to C. boulengeri nor to Bresedium brevipes was among the here sampled taxa. Thus, there is no evidence for a close genetic relationship between the morphologically similar species C. boulengeri and C. dehaani , but rather a clustering according to geography of all the East Asian species, where a radiation of crabs from mangroves and estuaries may have taken place. This will be analysed further with additional representatives. The two sequence of C. boulengeri are genetically identical, confirming conspecific status of Calman's (1920) type from Basra ( Iraq) and the new material from Iran and the lack of genetic differentiation between river systems, probably due to the marine larval dispersal within the Persian Gulf.

Taxonomic remarks. The taxonomic position of C. boulengeri ( Calman, 1920) is not clear. It was described by Calman (1920) as Sesarma boulengeri , but Apel and Türkay (1999) placed it in Chiromantes Gistel, 1848 , by referring to a comment by Holthuis (1977). A useful account of Chiromantes has been provided by Ng & Liu (1999) who argue that the species composition of the genus is heterogeneous. In their paper, they commented that the species can roughly separated into two broad groups, with smaller groupings within each. One subgrouping includes Sesarma elongatum A. Milne-Edwards, 1869 which more recently is recognised as a member of the genus Selatium Serène & Soh, 1970 (see Hartnoll 1975; Ng et al. 2008; Schubart et al. in press), with the others in another group. A complete revision of Chiromantes is now being undertaken by P. K. L. Ng and the second author of the present paper.

In view of the genetic information and the upcoming revision of Chiromantes , it seems best to leave Sesarma boulengeri in the genus for the moment (cf. Ng et al. 2008).

Figures

FIGURE 2. Chiromantes boulengeri (Calman, 1920). Male (CL 17.3, CB 20.7 mm), Bahmanshir River (SMF- 33818). a, dorsal view; b, ventral view.

FIGURE 3. Chiromantes boulengeri (Calman, 1920). Bahmanshir River (SMF- 33818). a, carapace of male; b, frontal region of male; c, outer surface of right cheliped of male; d, upper surface of right male cheliped; e, anterior thoracic sternites (setae removed) of male; f, abdomen of male; g, right G 1 (dorsal view); h, apical part of right G 1 (ventral view); i, apical part of right G 1 (dorsal view); j, genital opening of female. Scale: a – f 1 cm, g – h 1 mm.

FIGURE 4. Reconstruction of the phylogenetic relationships of selected species of Chiromantes and other Sesarmidae according to a Bayesian analysis (5 my generations) and Maximum Composite Likelihood (5,000 pseudorepilcates) of a 615 basepair alignment of 16 S ribosomal mtDNA. Consensus tree shown with bootstrap values / posterior probabilities expressing support for the corresponding clades.