Ilyograpsus rhizophorae Barnard, 1955

Komai, Tomoyuki & Wada, Keiji, 2008, A Revision Of The Estuarine Crab Genus Ilyograpsus Barnard, 1955 (Crustacea: Decapoda: Brachyura: Macrophthalmidae), With Descriptions Of A New Genus And One New Species, Raffles Bulletin of Zoology 56 (2), pp. 357-384 : 361-365

Ilyograpsus rhizophorae Barnard, 1955

( Figs. 2–5 )

Ilyograpsus rhizophorae Barnard, 1955: 26 , Fig. 8a–g ; Kensley, 1981: 46 (list); Sawada et al., 2005: 862.

Ilyograpsus paludicola – Crosnier, 1965: 31, Figs. 36, 37, 38a, b, 39, 59; Fishelson, 1971: 128. Not Ilyograpsus paludicola ( Rathbun, 1909) .

Iliograpsus (sic) paludicola – Holthuis, 1977: 161.

Ilyograpsus vannini Sawada, Hosogi & Sakai, 2005: 853 (in part), Fig. 5B, D, F .

Name bearing type. – Holotype: male (6.5 × 7.5 mm) ( South African Museum , Cape Town, A10913), Inhambane, Mozambique, in mangrove swamps, coll. University of Cape Town, Jul.1954. Not available for study.

Material examined. – Ethiopia: 3 males ( CL 5.0– 6.5 mm), 1 nonovigerous female ( CL 7.4 mm), paratypes of Ilyograpsus vannini ( RMNH D 26501), Israel South Red Sea Expeditions 1962/2996, Melita Bay, Gulf of Zula, south of Massawa, mangrove swamps with Avicennia marina (Forskål) , 0 to 0.5 m deep at low tide, 14 Apr.1962. Madagascar: 1 ovigerous female ( CL 7.2 mm) (MNHN- B 12842), Tuléar, mangrove swamps, coll. A. Crosnier, 1 ovigerous female ( CL 5.3 mm) ( MNHN-B 12843); 1 non-ovigerous female ( CL 4.4 mm), 2 ovigerous females ( CL 5.2, 5.3 mm) ( MNHN-B 12845), same locality, coll. Derijard; 1 male ( CL 3.8 mm) ( MNHN-B 12846), Nosy Bé, mangrove swamps, coll. A. Crosnier.

Description of male. – Carapace ( Figs. 3A , 4A ) suboctogonal, breadth 1.21–1.33 times length (n = 4, mean 1.27); regions only faintly indicated in general, but gastrocardiac groove distinct. Postfrontal ridges low, straight, separated by broad median sulcus. Epigastric ridges absent. Lateral margins generally convex, greatest carapace breadth between external orbital teeth or third anterolateral teeth. Four anterolateral teeth present, first tooth (external orbital tooth) largest, subacute; second tooth extending as far as or slightly exceeding external orbital tooth, rounded or bluntly pointed; third tooth laterally extending as far as or clearly exceeding beyond external orbital tooth, varying from blunt to acuminate; fourth tooth tiny, but clearly demarcated, blunt or subacute; sometimes slight notch present posterior to fourth tooth. Mesobranchial region with some short striae. Front prominent, distinctly narrower than base of front, 0.30–0.35 times front-orbital width (n = 4) and wider than orbit; anterior margin faintly bilobed in dorsal view. Upper orbital margin sinuous, slightly oblique; lower orbital margin ( Fig. 3B ) with 2 or 3 lobules laterally.

surface weakly granular; inner surface naked. Chela about 2.4 times as long as high; ventral margin faintly sinuous; outer surface of palm smooth; inner surface of palm with patch of dense setae extending onto fingers; fingers leaving proximal hiatus when closed; cutting edge of fixed finger with row of small, triangular teeth almost over entire length, distal part bordered by thin chitinous ridge; dactylus nearly straight, about 1.2 times longer than palm, cutting edge with well differentiated molar-like tooth medially and few obtuse teeth proximal to molar-like tooth and row of tiny teeth in distal 0.3, distal part bordered by chitinous ridge.

Cheliped of smallest male (cl 3.8 mm, MNHN-B 12846; Fig. 4B, C ) with merus slightly curved, without patch of setae on anterior surface; dorsal margin with small subdistal spine; no short subdistal crest on anteroventral margin; posterior surface nearly smooth to slightly granular. Outer and dorsal surfaces of carpus nearly smooth or slightly granular; inner surface naked. Chela about 2.5 times as long as high; ventral margin slightly sinuous; outer surface of palm with scattered short setae; inner surface of palm with covering of numerous setae in distal half extending onto fingers; fingers leaving very narrow hiatus when closed, each with row of setae on outer and inner surfaces; cutting edge of fixed finger with row of small teeth; dactylus slightly curved, about 1.1 times longer than palm, cutting edge with row of small teeth, but without prominent tooth.

Ambulatory legs moderately long, slender ( Fig. 2 ). Meri each with moderately large subdistal spine on anterior margin. Fourth pereopod (third ambulatory leg) ( Fig. 3H ) with merus 3.48–3.84 times longer than broad (n = 2), both anterior and posterior margins slightly convex; propodus 4.38–4.47 times longer than broad (n = 2); dactylus 0.74–0.80 (n = 2) times as long as propodus. Fifth pereopod (fourth ambulatory leg) ( Fig. 3I ) with propodus 2.81 times longer than broad (n = 1); dactylus slightly shorter than propodus.

Sixth pleonal somite ( Fig. 3D ) with slightly convex or nearly straight lateral margins, about 2.0–2.1 times broader than long. Telson rounded; breadth about 1.4–1.5 times length.

First gonopod ( Fig. 3J–L ) relatively slender, slightly sinuous Ocular peduncle ( Fig. 3A ) reaching external orbital tooth, length about 2.2–2.3 of corneal width; cornea slightly dilated.

Cheliped of large males (cl 6.3, 6.5 mm; RMNH D 26501) relatively large ( Fig. 3E–G ). Merus not markedly curved in dorsal view; posterior surface with granules sometimes forming short vertical rows; dorsal margin with small subdistal spine, inner surface with prominent short crest adjacent to inner-ventral margin; inner-distal angle with row of prominent granules. Carpus with inner angle weakly produced; dorsal margin delimited by row of granules; outer in ventrolateral view; terminal process relatively long, slender, tube-like, weakly directed laterally, partially obscured by stiff setae; obtuse subterminal lobe delineated.

Description of female. – Carapace ( Fig. 5A, B ) generally similar to that of male; breadth 1.21–1.32 times length (n = 6, mean 1.26); greatest carapace breadth between third anterolateral teeth. Third anterolateral tooth exceeding beyond external orbital tooth or second anterolateral tooth. Lower orbital margin ( Fig. 5C ) bordered by row of 13–18 granules becoming larger and more widely spaced laterally.

Ocular peduncle ( Fig. 5A ) reaching external orbital tooth.

Cheliped ( Fig. 5F–H ) slender. Merus with small subdistal spine on dorsal margin. Carpus short. Chela about 3.8 times as long as high; outer surface faintly granular particularly dorsally and ventrally, dorsal margin slightly delimited by row of granules; inner surface of palm naked; fingers leaving very narrow hiatus when closed, with row of stiff setae on outer and inner surfaces in distal half; fixed finger slightly deflexed, cutting edge faintly dentate in proximal 0.6, remaining distal part bordered by thin chitinous ridge; dactylus slightly curved, cutting edge faintly denticulate in proximal 0.7, bordered by thin chitinous ridge in distal 0.3.

Fourth pereopod (third ambulatory leg) with merus 2.52 times longer than broad (n = 1); propodus 3.56 times longer than broad; dactylus 0.77 times as long as propodus. Fifth pereopod (fourth ambulatory leg) with propodus 3.59 times longer than broad; dactylus slightly shorter than propodus.

Size. – Males cl 3.8–6.5 mm; females cl 5.0– 7.4 mm, ovigerous females cl 5.2–7.2 mm.

Distribution. – Western Indian Ocean: Ethiopia, Mozambique and Madagascar; mangrove swamps.

Remarks. – Barnard (1955) noted resemblance between his new taxon Ilyograpsus rhizophorae Barnard, 1955 , and Camptandrium paludicola Rathbun, 1909 , but he concluded that I. rhizophorae should belong to Grapsinae . Tesch (1918) had assigned Camptandrium paludicola to the Varuninae , Grapsidae . Later, Crosnier (1965) synonymized I. rhizophorae with Camptandrium paludicola , although the genus was maintained as valid. Recently, Sawada et al. (2005) reinstated I. rhizophorae as a valid species, but the authors’ action was only based on a comparison of the original description of I. rhizophorae with the holotype (female) and one juvenile specimen of I. paludicola . They referred the specimens from Madagascar, identified with I. paludicola by Crosnier (1965), to their new taxon I. vannini , although they did not actually examine the specimens used by Crosnier (1965). Naruse & Kishino (2006) followed the action by Sawada et al. (2005) in recognizing I. rhizophorae as valid.

During this study, we tried to obtain information on the holotype of I. rhizophorae from the South African Museum. Unfortunately, because of the loan policy of the museum, direct examination of the holotype on loan was not possible. Although the original description and figures of Barnard (1955) is not fully detailed in the view point of the modern standard, some diagnostic characters are still apparent. These characters include the obscurely defined regions of the carapace, prominent anterolateral teeth of the carapace, and the elongate, relatively slender terminal lobe of the male first gonopod. The present specimens from Madagascar studied by Crosnier (1965) and the paratypes of Ilyograpsus vannini from Ethiopia agree rather well with the holotype of I. rhizophorae in these respects. Furthermore, all collecting localities, including the type locality of I. rhizophorae , are on the coasts of the western Indian Ocean. Therefore, we concluded to refer the present specimens from Madagascar and Ethiopia to I. rhizophorae .

Our comparison with the original description of I. vannini led us to conclude that I. rhizophorae and I. vannini , now represented only by the holotype, might be specifically distinct. Differences are seen in the shape of the carapace and the development of the anterolateral teeth on the carapace ( Table 1). In the female specimens of I. rhizophorae , the carapace width is 1.21–1.32 of the carapace length, rather than 1.15 in I. vannini . The upper orbital margin appears more strongly oblique in I. vannini than in I. rhizophorae . The anterolateral teeth are more developed in I. rhizophorae than in I. vannini . The external orbital tooth reaches or slightly overreaches the distal margin of the cornea in the former specimens, but it does not reach the distal corneal margin in I. vannini . The second and third anterolateral teeth are more strongly developed in I. rhizophorae than I. vannini ; the third anterolateral tooth clearly exceeds beyond the second tooth in the former specimens, rather than only extending as far as the second tooth in I. vannini .

Ilyograpsus rhizophorae is easily distinguished from other three congeneric species, I. daviei new species, I. nodulosus and I. paludicola by the poorly defined regions of the carapace and the relatively broader carapace (1.21–1.33 times wider than long vs. 1.05–1.21 times) ( Table 1). The postfrontal ridges are less clearly demarcated in I. rhizophorae than in the other three species. There are no traces of epigastric ridges or tubercles in I. rhizophorae , whereas, in the latter three species, the carapace has at least traces of epigastric ridges or tubercles. The upper orbital margin is slightly oblique in I. rhizophorae , rather than transverse in the other three species. The terminal process of the first gonopod is well developed in I. rhizophorae , I. paludicola and I. daviei , new species, but the curvature of the process is different between I. rhizophorae and the other two species. In I. rhizophorae , the terminal process is curved laterally, whereas it is curved slightly dorsally in the latter two species.

Flores et al. (2003) described the first zoeal stage of I. paludicola from East African coast. During this study, however, the occurrence of I. paludicola in the western Indian Ocean has not been verified. It is highly likely that the authors were describing larvae of I. rhizophorae .

Figures

Fig. 2. Ilyograpsus rhizophorae Barnard, 1955. Male (cl 6.4 mm), paratype of Ilyograpsus vannini Sawada, Hosogi & Sakai, 2005, RMNH-D 26501, south of Massawa, Gulf of Zula, Ethiopia. Entire animal in dorsal view.

Fig. 3. Ilyograpsus rhizophorae Barnard, 1955. Male (cl 6.5 mm), paratype of Ilyograpsus vannini Sawada, Hosogi & Sakai, 2005, RMNH- D 26501, south of Massawa, Gulf of Zula, Ethiopia: A, carapace, ocular peduncles and antennae, dorsal view (setae omitted); B, left lower orbital margin and external orbital tooth, ventral view; C, anterior part of thoracic sternum, ventral view; D, pleon, ventral view; E, left cheliped, dorsal view; F, same, merus, outer view; G, same, chela, outer view; H, left fourth pereopod, dorsal view; I, left fifth pereopod, dorsal view; J, left first gonopod, ventral view; K, same, ventrolateral view; L, same, distal part, dorsal view. Scales: A = 2 mm; B–I = 1 mm; J–L = 0.5 mm.

Fig. 4. Ilyograpsus rhizophorae Barnard, 1955. A, male (cl 5.0 mm), paratype of Ilyograpsus vannini Sawada, Hosogi & Sakai, 2005, RMNH-D 26501, south of Massawa, Gulf of Zula, Ethiopia; B–E, male (cl 3.8 mm), MNHN-B 12846, Nozy Bé, Madagascar. A, left part of carapace, left ocular peduncle and antenna, dorsal view; B, left cheliped, dorsal view; C, same, chela, outer view; D, right first gonopod, dorsal view; E, same, ventrolateral view. Scale bars: A, B, D = 1 mm; C, E = 0.5 mm.

Fig. 5. Ilyograpsus rhizophorae Barnard, 1955. A–E, I, J, ovigerous female (cl 7.2 mm), MNHN-B 12842, Tuléar, Madagascar; F, H, ovigerous female (cl 5.3 mm), MNHN-B 12843, same locality; G, female (cl 7.4 mm), paratype of Ilyograpsus vannini Sawada, Hosogi & Sakai, 2005, RMNH-D 26501, south of Massawa, Gulf of Zula, Ethiopia. A, carapace, ocular peduncles and antennae, dorsal view; B, anterior part of cephalothorax, including left ocular peduncles and antennae, frontal view; C, left lower orbital margin, ventral view; D, pleon, ventral view; E, left third maxilliped, ventral view; F, left cheliped, dorsal view; G, same, merus, outer view; H, same, chela, outer view; I, right fourth pereopod, dorsal view; J, right fifth pereopod, dorsal view. Scale bars: A, D, F = 2 mm; B, C, E, G, I, J = 1 mm; H = 0.5 mm.

Fig. 8. Ilyograpsus nodulosus Sakai, 1983. Female (cl 7.8 mm), SINH-Cr 1474, Nada, Urado Bay, Kochi, Kochi Prefecture, Japan. A, carapace, ocular peduncles and antennae, dorsal view (setae omitted); B, cephalothorax and cephalic appendages, frontal view; C, left lower orbital margin, ventral view; D, sixth pleonal somite and telson, ventral view (setae omitted); E, merus of left cheliped, outer view; F, carpus and chela of left cheliped, outer view; G, left fourth pereopod, dorsal view; H, left fifth pereopod, dorsal view. Scale bars: A, D = 2 mm; B, E–H = 1 mm; C = 0.5 mm.