Ilyograpsus daviei, Komai & Wada, 2008

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 : 376-379

Ilyograpsus daviei , new species

( Figs. 13–15 )

Ilyograpsus paludicola — Davie, 2002: 229 (in part). Ilyograpsus nodulosus — Sawada et al., 2005: 857 (in part).

Material examined. – Holotype - male (cl 7.3 mm), QM W 15556a, Boggy Creek, Myrtletown, Brisbane , Queensland, 27°24’S 153°08’E, under rocks near low tide mark, 12 Jul.1998, coll. J. Short et al.

Paratypes: 1 ovigerous female (cl 10.2 mm), QM W 5265 , Jackson Creek , Queensland, 12 Oct.1972, coll. B. M. Campbell ; 3 males (cl 5.0–7.0 mm), 1 female (cl 6.1 mm), 8 ovigerous females (cl 6.0–8.0 mm), QM W 15554a, Boggy Creek, Myrtletown, Brisbane , Queensland, burrows in mud bank, 12 Jul.1988, coll. J. Short ; 1 male (cl 5.2 mm), 1 ovigerous female (cl 8.4 mm), QM W 15556b, same data as holotype ; 1 male (cl 6.3 mm), 1 ovigerous female (cl 8.3 mm), QM W 23889, same locality, estuarine, littoral, 29 Jul.1997, coll. P. Davie & J. Short.

Non-type: 2 young males (cl 3.3, 3.3 mm), 1 female (damaged), QM W 15554b, Boggy Creek , Myrtletown, southeast Queensland, in burrows in mud bank, coll. J. Short et al .

Description of male. – Carapace ( Fig. 14A, B ) suboctogonal, breadth 1.12–1.19 times length (n = 6, mean 1.15); regions relatively weakly defined. Postfrontal ridges distinct, 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 with few short longitudinal ridges laterally. Lateral margins generally convex, greatest carapace breadth between third anterolateral teeth. Four anterolateral teeth present, first tooth (external orbital tooth) largest, triangular, acute or subacute; second tooth slightly exceeding external orbital tooth, rounded or bluntly triangular; third tooth clearly exceeding beyond external orbital tooth or second anterolateral tooth, varying from blunt to acute; fourth tooth small, but clearly delineated, blunt or subacute. Front distinctly less than posterior width, about 0.4 times front-orbital width, wider than orbit; anterior edge in dorsal view faintly bilobed. Upper orbital margin concave or slightly sinuous, almost transverse; lower orbital margin ( Fig. 14C ) with 3–5 lobules laterally.

of small, blunt teeth almost over entire length, distal part bordered by thin chitinous ridge. Dactylus nearly straight, subequal in length to palm, cutting edge with low molar-like tooth proximal to midlength, otherwise weakly dentate, distal part bordered by chitinous ridge.

Cheliped of smaller males (cl 3.3–5.0 mm) similar to that of I. paludicola .

Ambulatory legs ( Fig. 13A ) relatively short, stout. Meri broadened distally, each with relatively large subdistal spine. Fourth pereopod (third ambulatory leg) ( Fig. 14I ) with merus about 2.47–3.02 times longer than broad (n = 5, mean 2.88), anterior margin slightly sinuous, posterior margin slightly convex; propodus 3.27–3.58 times longer than broad (n = 5, mean 3.44); dactylus 0.64–0.87 times as long as propodus (n = 5, mean 0.80). Fifth pereopod (fourth ambulatory leg) ( Fig. 14J ) with propodus 2.00–2.87 times longer than broad (n = 5, mean 2.43), outer and inner margins fringed with short setae; dactylus subequal to or slightly longer than propodus.

Sixth pleonal somite ( Fig. 14D ) with straight or faintly sinuous lateral margins, about 2.5–2.7 times broader than long. Telson rounded terminally; breadth about 1.1–1.2 times length.

First gonopod ( Fig. 14K ) moderately slender, very slightly curved; terminal process ( Fig. 14L ) moderately long, slightly curved dorsally, partially obscured by numerous stiff setae; subterminal lobe not delineated.

Description of female. – Carapace ( Fig. 15A ) generally similar to that of male; breadth about 1.15–1.21 times length (n = 11, mean 1.19); greatest carapace breadth between

Ocular peduncle ( Fig. 14A ) reaching or slightly falling short of external orbital tooth, length about 2.0–2.3 of corneal width; cornea not dilated.

Cheliped ( Fig. 14E–H ) of larger males (cl 5.2–7.3 mm) with merus bearing small subdistal spine on dorsal margin and distinct crest on anterior surface adjacent to inner margin. Chela about 1.80–2.00 times as long as high; ventral margin faintly sinuous; inner surface of palm with covering of dense setae extending onto fingers; fingers leaving proximal hiatus when closed; fixed finger not deflexed, cutting edge with row third anterolateral teeth. Third anterolateral tooth exceeding beyond external orbital tooth or second anterolateral tooth. Lower orbital margin ( Fig. 15B ) bordered by row of 13–18 small granules becoming larger and more widely spaced laterally.

Pleon and telson ( Fig. 15 ) similar to those of other congeneric species.

Merus of cheliped ( Fig. 15D ) with distinct subdistal spine on dorsal margin. Chela ( Fig. 15E ) with fixed finger slightly deflexed, cutting edge not dentate; dactylus with nearly smooth cutting edge.

Ambulatory legs similar to those of males; meri broadened distally. Fourth pereopod with merus 2.24–2.77 times longer than broad (n = 10, mean 2.56); propodus 3.18–3.85 times longer than broad (n = 10. mean 3.41); dactylus 0.72–0.86 times as long as propodus (n = 10, mean 0.80). Fifth pereopod with propodus 2.05–2.45 times longer than broad (n = 9, mean 2.09); dactylus subequal to or slightly longer than propodus.

Size. – Males cl 5.0– 7.3 mm; females cl 6.0– 10.2 mm, ovigerous females cl 6.0–10.0 mm.

Distribution. – Known with certainty only from Queensland, Australia.

Remarks. – The present new species is similar to I. paludicola and I. nodulosus particularly in the general shape of the carapace. Nevertheless, I. daviei is differentiated from the latter two species by the less clearly defined carapace regions and the distinctly stouter ambulatory legs ( Table 1). Particularly, the fifth pereopod is relatively stout in the new species. From I. nodulosus , I. daviei can be separated further by the different ornamentation of the lower orbital margin in females, the merus of the cheliped with a subdistal spine on the dorsal margin and with a short subdistal crest on the anteroventral margin, and the more elongate terminal process of the first gonopod.

The material referred to I. nodulosus by Sawada et al. (2005) contains specimens from Brisbane, Queensland, where the occurrence of the present new species has been confirmed. We consider that the specimens used by Sawada et al. (2005) could be referred to I. daviei , and thus the reference is included in the synonymy of the present new species.

Etymology. – The new species is named in honour of our esteemed colleague, Peter J. F. Davie of the Queensland Museum, in recognition of his great contributions to the systematics of the Decapod Crustacea in the Indo-Pacific region.

Figures

Fig. 13. Ilyograpsus daviei, new species. Entire animals in dorsal view. A, male (cl 7.3 mm), holotype, QM W 15556, Boggy Creek, Myrtletown, Brisbane, Queensland, Australia; B, female (cl mm), paratype, QM 15554, same locality.

Fig. 14. Ilyograpsus daviei, new species. Holotype, male (cl 7.3 mm), QM W 15556, Boggy Creek, Myrtletown, Brisbane, Queensland, Australia.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, pleon, ventral view; E, merus of right cheliped, outer view; F, same, dorsal view; G, carpus and chela of right cheliped, dorsal view; H, right chela, outer view; I, right fourth pereopod, dorsal view; J, right fifth pereopod, dorsal view; K, left first gonopod, ventral view;; L, same, distal part, dorsal view. Scale bars: A, B, E–I = 2 mm; C, D = 1 mm; K, L = 0.5 mm.

Fig. 15. Ilyograpsus daviei, new species. Paratype, female (cl 7.3 mm), QM W 5265, Queensland, Australia. A, carapace, ocular peduncles and antennae, dorsal view; B, left lower orbital margin and external orbital tooth, ventral view; C, sixth pleonal somite and telson, ventral view; D, merus of left cheliped, outer view; E, left chela, outer view; F, right fourth pereopod, dorsal view (setae omitted); G, right fifth pereopod, dorsal view. Scale bars: A, C, E–G = 2 mm; B = 1 mm.