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Unresolved name

Surf Crab

Acanthonyx lunulatus

Comprehensive Description

provided by Smithsonian Contributions to Zoology
Acanthonyx lunulatus (Risso, 1816)

Acanthonyx lunulatus.—Capart, 1951:84, fig. 26.—Monod, 1956:517, figs. 709, 710.—Rossignol, 1957:78, 116 [key].—Forest and Gantès, 1960:356.—Gauld, 1960:72.—Rossignol, 1962:122.—Guinot and Ribeiro, 1962:76.—Ribeiro, 1964:20.—Chace, 1966, fig. 13a–d [Mediterranean].—Forest and Guinot, 1966:106.—Zariquiey Alvarez, 1968:466, figs. 7d, 153e,f, 154i,j [Spain; references].—Kensley, 1970:181.—Penrith and Kensley, 1970b:252, 260.—Uschakov, 1970:455 [listed].

SYNONYMS.—Maia glabra Latreille, 1836; Acanthonyx viridis O. Costa, 1838; Gonosoma viridis O. Costa, 1844.

MATERIAL EXAMINED.—Pillsbury Material: None.

Other Material: Madeira: SE coast near Agua de Pena, 32°41′N, 16°46′W, 0–25 m, diving, 9 Mar 1976, Onversaagd Sta 27, 1 (L).

DISTRIBUTION.—Mediterranean Sea and adjacent Atlantic, from Portugal to South-West Africa, generally in shallow water, littoral and subtidal. Records since 1956 include the following.

Morocco: Rabat, Temara, Skhirat, Oued Cherrat, David, Tillet [?], Sidi Moussa, Agadir, and Foum Assaka (all Forest and Gantès, 1960).

Cape Verde Islands: Matiota, São Vicente, beach and shore, and Tarrafal do Monte Trigo, Santo Antão (Guinot and Ribeiro, 1962; Ribeiro, 1964).

Guinea: No specific locality (Uschakov, 1970).

Ivory Coast: Lagoon of Abidjan, 05°16′12″N, 04°00′20″W (Forest and Guinot, 1966).

Ghana: Tenkpobo to Dixcove (Gauld, 1960).

São Tomé: Ilhéu Macao (as îlot dos Cocos), 3–8 m, and Sant'Ana, shore (Forest and Guinot, 1966).

Congo: Pointe Indienne (Rossignol, 1957). Baie de Loango and near Pointe-Noire (Rossignol, 1962).

Angola: Baía do Lobito, shore; Praia das Conchas, Moçâmedes, shore; and Baía das Vacas, Benguela, shore (all Guinot and Ribeiro, 1962).

South-West Africa: Rocky Point, 18°59′S, 12°29′E (Kensley, 1970; Penrith and Kensley, 1970b). Kunene River mouth, 17°15′S, 11°45′E, and Möwe Point, 19°23′S, 12°42′E (Kensley, 1970).

Möwe Point is the southernmost record for Acanthonyx on the West African coast.

*Acanthonyx minor, new species

?Acanthonyx brevifrons.—Balss, 1914:101 [not A. brevifrons A. Milne Edwards, 1869].

MATERIAL EXAMINED.—Pillsbury Material: Annobon: Sta 271, shore, 6 (includes holotype), 4 (1 ov) (L, W). Sta 273, shore, 1 (L).

DESCRIPTION.—Carapace (Figure 64a,f,i) smooth, rather wide, length 1.1 to 1.3 times greatest width in adults, about 1.5 times width in juveniles. Greatest width at level of anterior anterolateral teeth in juveniles (Figure 64i), at level of posterior anterolateral teeth in adults (Figure 64a,f). Surface of carapace coarsely pitted, with normal elevations: 2 protogastric, 1 mesogastric, 1 cardiac, all low, each bearing 2 or more broad setae. Rostral teeth elongate-triangular, separated by wide, V-shaped sinus, rostrum not markedly depressed (Figure 60d). Dorsal surface of carapace, behind rostrum, with normal 2 divergent rows of curved, hook-shaped hairs. Preorbital tooth short, blunt, much shorter than rostral teeth. Orbital margin continuing gradually into anterior margin of first anterolateral tooth, latter not distinctly set off as in A. lunulatus. Orbital margin with small tooth or lobe situated about halfway between eye and first anterolateral tooth (Figure 64a,f); this tooth absent in all other Atlantic species of Acanthonyx, present in all but smallest specimens of A. minor (Figure 64i). First anterolateral tooth large, wide, rounded apically, second and third teeth distinct, smaller, subequal; each tooth with several broad setae. Eyes relatively large, in comparison with those of A. lunulatus of similar size. Ventral surface of carapace with subhepatic tooth behind orbit.

Basal segment of antennal peduncle with distinct outer anterolateral tooth (Figure 64b). Antennal peduncle variable in length, shorter than or slightly longer than rostrum.

Cheliped of adult female (Figure 64c) small. Fingers almost as long as palm (measured along upper surface). Cutting edges dentate, with only slight gape proximally. Palm smooth. Carpus globular, smooth, bearing no carinae or tubercles, shorter than palm, much shorter than merus. Latter smooth except for 2 blunt tubercles on basal half.

Walking legs similar to those of other Acanthonyx species, but dactylus appearing more slender, with tip less strongly curved, terminating in slender apex, posterior margin with 7 or 8 small but distinct teeth. Second pereiopod (first walking leg) dactylus about as long as propodus (measured dorsally). Latter 4 times as long as high, outer surface ending in disc-like projection covering base of dactylus. Posterior margin of propodus with low tubercle or prominence near midlength ornamented with strong, stiff hairs. Carpus as long as propodus, much shorter and narrower than merus. First walking leg longer than remainder, latter of similar shape but decreasing in size posteriorly. Fifth pereiopod (Figure 64e) shortest. Dactylus slightly longer than propodus, more robust than that of second leg. Propodus about 2.5 times as long as wide. Tubercle on posterior margin low but distinct because of tuft of hairs. Carpus distinctly shorter than propodus, merus about as long as propodus.

Male abdomen (Figure 64g) narrow. Telson tongue-shaped. Sixth somite broad proximally, distinctly narrowing at telson. Abdomen of largest females very broad, reaching to bases of legs; sixth somite widest.

First male pleopod as shown in Figure 64h. It does not differ significantly from that of A. sanctaehelenae Chace from Saint Helena (Chace, 1966, fig. 12f).

MEASUREMENTS.—Carapace lengths of males 1.7 to 3.4 mm, of non-ovigerous females 1.8 to 3.8 mm, of the ovigerous female 3.7 mm.
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bibliographic citation
Manning, Raymond B. and Holthuis, L. B. 1981. "West African Brachyuran crabs." Smithsonian Contributions to Zoology. 1-379. https://doi.org/10.5479/si.00810282.306