Ilyograpsus paludicola ( Rathbun, 1909 )

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 : 370-373

Ilyograpsus paludicola ( Rathbun, 1909)

( Figs. 9–12 )

Camptandrium paludicola Rathbun, 1909: 109 ; 1910: 326, Fig. 9a, b ; Tesch, 1918: 68; Shen, 1935: 31.

Ilyograpsus paludicola — Takeda & Nunomura, 1976: 84; Tirmizi et al., 1985: 24, Fig. 1 ; Tirmizi & Ghani, 1996: 143, Fig. 55; Davie, 2002: 229 (in part); Yeo et al., 2004: Sawada et al., 2005: 861 (in part), Figs. 2B, C , 4A, B ; Naruse & Kishino, 2006: 75.

Ilyograpsus nodulosus — Sawada et al., 2005: 857 (in part), Fig. 4C .

Not Ilyograpsus paludicola — Crosnier, 1965: 31, Figs. 36–37, 38a, b, 39, 59; Fishelson, 1971: 128; Kensley, 1981: 46 (list). = Ilyograpsus rhizophorae Barnard, 1955 .

Not Ilyograpsus paludicola — Hartnoll, 1975: 307 (table I), 311 (table II). =? Ilyograpsus rhizophorae Barnard, 1955 .

Not Iliograpsus (sic) paludicola — Holthuis, 1977: 161. = Ilyograpsus rhizophorae Barnard, 1955 ].

Not Ilyograpsus paludicola — Yamaguchi et al., 1976: 41, Fig. 2 (8); Nakasone, 1977: 62; Fukuda, 1978: 15; Yamaguchi et al., 1987: 31, Pl. 14, Fig. 8 ; Nakasone & Irei, 2003: 273. = Ilyograpsus nodulosus Sakai, 1983 .

Not Ilyograpsus paludicola — Vannini and Valmori, 1981: 77, Fig. 10C . = Ilyograpsus vannini Sawada, Hosogi & Sakai, 2005 .

Name bearing type. – Holotype: female (4.5 × 5.3 mm), Zoological Museum , University of Copenhagen ( ZMUC) reg. no. 7692, Lem Ngob, Gulf of Thailand, 23–27 Dec.1899, coll. Th. Mortensen. Not examined.

Material examined. – Vietnam: 1 male (cl 10.4 mm), CBM-ZC 9307 , Giao Thuy , Nam Dinh, 17 May 2001, coll. Do Van Nhuong. Indonesia: 1 male (cl 3.1 mm), 1 ovigerous female (cl 4.2 mm), CBM-ZC 9423 , Benoa Bay , Bali, 31 Aug.2001, coll. K. Wada ; 1 ovigerous female (cl 5.7 mm), ZRC 1965.7 .9.17, Padang , Sumatra, 1963, coll. R. Serène ; 4 males (cl 2.8–4.2 mm), 3 females (cl 2.8–4.9 mm), 3 ovigerous females (cl 4.0–8.0 mm), 1 juvenile (cl 2.5 mm), ZRC 1998.10.30, Bintan , Jun.1995, coll. P. K. L. Ng & L. G. S. Tan. Malaysia: 1 male (cl 3.7 mm), ZRC 1965.10 .8.3, Trengganu, Kuala Ibai , Aug.1950, coll. M. W. F. Tweedie ; 1 female (cl 4.4 mm), ZRC 1965.10 .8.6, Labuan, 1938 ; 1 female (cl 4.6 mm), ZRC 1965.10 .8.7, Prai, Province Wellesley, 1938 . Singapore: 1 ovigerous female (cl 4.1 mm), ZRC 1965.10 .8.5, Jurong River , 18 Aug.1934 . Australia: 1 male (cl 4.5 mm), QM W 19155, Camerons Beach , Northern Territory, 12°21'S 130°59.6'E, mangroves, soft mud flat, 30 Jun.1996, coll. P. Davie ; 1 female (cl 4.6 mm), QM W 25018, Reichard Creek, Darwin Harbor , Northern Territory, 12°27'S 130°50'E, estuarine, littoral, open Rhizophora forest, Nov.1998, coll. C. Salgado ; 4 males (cl 4.6–7.4 mm), QM W 29749, Darwin Harbor , Northern Territory, 2004, coll. K. Metcalfe. New Caledonia: 1 ovigerous female (cl 8.5 mm), OMNH-Ar 1656, near Nouméa , 14 Oct.1958 .

Description of male. – Carapace ( Figs. 10A, B , 11A ) suboctogonal, breadth 1.08–1.17 times length (n = 10, mean 1.13); regions well defined (degree still less than in I. nodulosus ). Postfrontal ridges distinct, often crested, separated by broad median sulcus. Epigastric ridges or tubercles present. Cardiac region with paired low elevations; branchial regions with 1 or 2 pairs of low elevations on either side of gastro-cardiac region, and few short longitudinal ridges laterally. Lateral margins generally convex, greatest carapace breadth between third anterolateral teeth. Four or five anterolateral teeth present, first tooth (external orbital tooth) largest, triangular, acute or subacute; second tooth extending as far as or slightly exceeding external orbital tooth, rounded or bluntly triangular; third tooth clearly exceeding beyond external orbital tooth, varying from blunt to acute; fourth tooth small, but clearly delineated, blunt or subacute; fifth tooth, if present, very small. prominent, distinctly less than posterior width, about 0.40 times front-orbital width and wider than orbit; anterior edge in dorsal view faintly bilobed. Upper orbital margin concave or slightly sinuous, almost transverse; lower orbital margin ( Figs. 10C , 11B ) with 2–4 lobules laterally.

Ocular peduncle ( Figs. 10A, B ; 11A, B ) reaching or slightly overreaching external orbital tooth, length about 2.2–2.3 of corneal width; cornea not dilated.

Cheliped of largest specimen (cl 10.4 mm, CBM-ZC 9307; Fig. 11C–E ) with relatively strong subdistal spine on dorsal margin of merus; inner margin of merus with or without prominent short crest; inner distal angle of merus with row of small granules. Chela 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, shorter than palm, cutting edge with well differentiated molarlike tooth proximal to midlength, otherwise weakly dentate, distal part bordered by chitinous ridge.

Cheliped of other specimens ( Fig. 10E–G ) proportionally smaller, each with distinct subdistal spine on dorsal margin of merus; anteroventral margin with or without short, smooth crest subdistally ( Fig. 10F ). Carpus with inner angle weakly produced. Chela about 2.4 times longer than high; outer surface with scattered short setae. Cutting edge of fixed finger with row of small rounded teeth in proximal 0.7 and thin chitinous ridge in distal half; dactylus slightly curved, 1.1 times longer than palm, cutting edge with row of small rounded teeth in proximal half, nearly smooth in distal half.

Ambulatory legs ( Fig. 9A ) relatively long, slender. Meri each with relatively large subdistal spine. Fourth pereopod (third ambulatory leg) ( Figs. 10I ; 11F ) with merus 3.21–4.12 times longer than broad (n = 8, mean 3.69); propodus 4.16–5.90 times longer than broad (n = 8, mean 5.14), anterior margin slightly sinuous, posterior margins slightly convex or nearly straight; dactylus 0.68–0.80 times as long as propodus (n = 8, mean 0.77). Fifth pereopod (fourth ambulatory leg) ( Figs. 10J ; 11G ) with propodus 3.03–4.27 times longer than broad (n = 9, mean 3.61), outer and inner margins fringed with short setae; dactylus shorter than propodus.

Sixth pleonal somite ( Fig. 10D ) with slightly convex lateral margins, about 2.6–2.7 times broader than long. Telson rounded terminally; breadth about 1.1–1.2 times length.

First gonopod ( Figs. 10K, L ; 11H ) slender, slightly curved mesially; terminal process ( Fig. 11I ) relatively long, slightly curved dorsally, obscured by numerous stiff setae; subterminal lobe present in largest specimen.

Description of female. – Carapace ( Fig. 12A, B ) generally similar to that of male, but with low, sometimes distinct short ridges or tubercles on gastric (1 or 2 pairs), cardiac (1 pair) and branchial (2 or 3 pairs) regions; breadth 1.09–1.19 times length (n = 12, mean 1.13); greatest carapace breadth between third anterolateral teeth. Third anterolateral tooth exceeding beyond external orbital tooth or second anterolateral tooth. Lower orbital margin ( Fig. 12C ) bordered by row of 13–18 small, unequal granules.

Ocular peduncle ( Fig. 12A, C ) reaching external orbital tooth.

Cheliped ( Fig. 12E–G ) generally similar to that of I. rhizophorae . Merus usually with distinct subdistal spine on dorsal margin. Carpus weakly elongate. Chela about 3.8 times as long as high; fixed finger weakly deflexed, cutting edge faintly dentate in proximal 0.6 and 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.

Ambulatory legs ( Fig. 9B ) relatively long, slender. Fourth pereopod (third ambulatory leg) with merus 3.17–3.79 times longer than broad (n = 7, mean 3.50); propodus 4.69–6.00 times longer than broad (n = 6, mean 5.08); dactylus 0.71– 0.89 times as long as propodus (n = 7, mean 0.82). Fifth pereopod (fourth ambulatory leg) with propodus 2.83–3.27 times longer than broad (n = 7, mean 3.27), outer and inner margins smooth, naked; dactylus shorter than propodus.

Size. – Males cl 2.5–10.4 mm; females cl 2.8–8.5 mm, ovigerous females cl 4.0– 8.5 mm.

Colour in life. – Unknown.

Distribution. – Vietnam, Malaysia, Singapore, Indonesia (Bintang, Sumatra and Bali), Northern Territory, Australia, New Caledonia, and Pakistan; found in mangrove, tidal flat and estuarine habitats.

Remarks. – Sawada et al. (2005) presented a redescription of Ilyograpsus paludicola , which is accompanied by photographs of the cephalothorax of the holotype female and of a juvenile specimen collected together with the holotype. The account provides some diagnostic characters for species recognition, including the presence of a subterminal spine on the merus of the cheliped. Therefore, there was no necessity to re-examine the holotype again. The male of Ilyograpsus paludicola is fully described in this study for the first time.

The presence or absence of a short crest on the inner margin of the merus of the cheliped is variable in the male specimens examined. In the three smallest specimens ( Bintan , Indonesia, cl 2.8, 3.1 mm, ZRC 1998.1030 ; Bali, Indonesia, cl 3.1 mm, CBM-ZC 9423 ), the crest is not differentiated. In the two specimens from Bintan (cl 3.7, 4.2 mm; ZRC 1998.1030 ), three specimens from Darwin Harbor , Northern Territory (cl 4.8–7.4 mm; QM W 27949) and one specimen from Cameron Beach , Northern Territory (cl 4.5 mm; QM W 19155), there is a distinct crest on the segment. In one specimen from Darwin Harbor (cl 4.6 mm; QM W 27949) and the largest specimen from Giao Thuy , Nam Dinh, Vietnam (cl 10.4 mm; CBM-ZC), there is no crest on the cheliped merus. It is apparent that the development of the crest could be variable in this species .

Ilyograpsus paludicola is morphologically closest to I. nodulosus and I. daviei , new species, and indeed there are misidentifications in previous literature of I. paludicola (see Synonymy). Differences between I. paludicola and the latter two species are discussed in detail under respective account of the two other species.

As mentioned before, the occurrence of Ilyograpsus paludicola in Japan has not been confirmed, although there have been supposed Japanese records of the species ( Yamaguchi et al., 1976, 1987; Nakasone, 1977; Nakasone & Irei, 2003). These Japanese records are referred to I. nodulosus .

The presence of this species in New Caledonia has been confirmed by reexamination of the single ovigerous female specimen (OMNH-Ar 1656), which was referred to I. paludicola by Takeda & Nunomura (1976) and to I. nodulosus by Sawada et al. (2005) (see Remarks of I. nodulosus ). This ovigerous specimen has the following features: the carapace is 1.11 times wider than long; the lower orbital margin bears 13 small granules; the merus of the cheliped is armed with a minute spine subdistally; the merus of the fourth pereopod is 3.19 times longer than wide; the dactylus of the fourth pereopod is 0.83 times as long as the propodus; and the propodus of the fifth pereopod is 3.14 times longer than wide. The size of the subdistal spine on the merus of the cheliped is much smaller in the specimen from New Caledonia than in the other specimens. Nevertheless, the specimen from New Caledonia is larger than other females specimens (cl 8.5 mm versus cl 2.8–4.6 mm), and therefore, the difference might be size-related. In other diagnostic respects, the specimen from New Caledonia well agrees with I. paludicola .

There have been records of I. paludicola from Pakistan, northern Arabian Sea, Indian Ocean ( Tirmizi et al., 1985, 1986; Tirmizi & Ghani, 1996), but no specimens from the Arabian Sea were available for examination. Nevertheless, morphological features of the specimens from Pakistan seem to agree with the present specimens in every diagnostic aspect. The occurrence of I. paludicola from the western Indian Ocean and the Red Sea has not been confirmed.

Figures

Fig. 9. Ilyograpsus paludicola (Rathbun, 1909). Entire animals in dorsal view. A, male (cl 4.3 mm), ZRC 1998-1030, Bintan, Indonesia; B, female (cl 8.0 mm), same lot.

Fig. 10. Ilyograpsus paludicola (Rathbun, 1909). Male (cl 4.3 mm), ZRC 1998-1030, Bintan, Indonesia. A, carapace, ocular peduncles and antennae, dorsal view; B, cephalothorax and cephalic appendages, frontal view; C, lower orbital margin, ventral view; D, pleon, ventral view; E, merus of left cheliped, outer view; F, same, ventral view; G, carpus and chela of left cheliped, dorsal view; H, left chela, outer view; I, left fourth pereopod, dorsal view (setae omitted); J, fifth pereopod, dorsal view (setae partially omitted); K, left first gonopod, ventrolateral view; L, same, dorsal view. Scale bars: A, B, D, E–J = 1 mm; C, K, L = 0.5 mm.

Fig. 11. Ilyograpsus paludicola (Rathbun, 1909). Male (cl 10.4 mm), CBM-ZC, Vietnam. A, carapace and ocular peduncles, dorsal view (setae omitted); B, left frontal to pterygostomial regions, including cephalic appendages, ventral view (setae omitted); C, left cheliped, dorsal view; D, same, merus, outer view; E, left chela, outer view; F, left fourth pereopod, dorsal view (setae omitted); G, left fifth pereopod, dorsal view; H, left first gonopod, ventrolateral view; I, same, distal part, dorsal view. Scale bars: A–H = 2 mm; H = 1 mm; I = 0.5 mm.

Fig. 12. Ilyograpsus paludicola (Rathbun, 1909). Ovigerous female (cl 8.0 mm), ZRC 1998-1030, Bintan, Indonesia. A, carapace, ocular peduncles and antennae, dorsal view (setae omitted); B, cephalothorax and cephalic appendages, frontal view; C, left frontal to pterygostomial regions, including cephalic appendages, ventral view; D, sixth pleonal somite and telson, ventral view; E, merus of left cheliped, outer view; F, carpus and chela of left cheliped, dorsal view; G, left chela, outer view; H, left fourth pereopod, dorsal view; I, left fifth pereopod, dorsal view. Scale bars: A, B, D, H, I = 2 mm; C, E–G = 1 mm.

Fig. 1. Schematic illustrations of: A, carapace; B, ambulatory leg, showing measurements and terminology. CL, carapace length; CW, carapace width; L, length; W, width.

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. 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. 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.