Scorpion Spider Crab

Inachus dorsettensis (Pennant)

Cancer dorsettensis Pennant, 1777:8, pl. 9A: fig. 18.

Pseudocollodes complectens Rathbun, 1911:248, pl. 20: fig. 4 [new synonymy].

Inachus dorsettensis.—Barnard, 1950:29–30, fig. 5d–e.—Monod, 1956:526–529, figs. 715–722.

MATERIAL EXAMINED.—7 , 6 , (5 ovig.), 6.8–17.1 mm, smallest ovig. , 7.5 mm (12, USNM 135172–75; 1, AM P.17787).

Anton Bruun Cruises: E of Lourenço Marques, Sta. 370G or 372L, 112–347 m, 3 specs. Off Cape Guardafui, 70–82 m, Sta. 442, 70–80 m, 1 spec; Sta. 444, 78–82 m, 2 specs. Mouth of Gulf of Aden, Sta. 463, 75–175 m, 7 specs.

DISTRIBUTION.—Eastern Atlantic from the coast of Norway to South Africa, extending into the western Indian Ocean to Lourenço Marques, the Seychelles, and north to the mouth of the Gulf of Aden.

Inachus dorsettensis (Pennant, 1777)

Cancer Dorsettensis Pennant, 1777:8, pl. 9A: fig. 18.

Inachus dorsettensis.—A. Milne Edwards and Bouvier, 1899:45 [key], 46 [Azores]; 1900:143 [?part; Ilhas Desertas; Spanish Sahara].—Balss, 1922:72 [listed].—Bouvier, 1922:79 [Canary Islands].—Monod, 1933b:503 [p. 48 on separate; listed].—Capart, 1951:70 [part; Spanish Sahara].—Maurin, 1968a:31 [Morocco]; 1968b:489 [Mauritania].—Zariquiey Alvarez, 1968:472, figs, 157f, 159b, 160b [Spain; references].—Christiansen, 1969:100, fig. 41, map 34 [North Atlantic].—Türkay, 1976a:26 [listed], 40, fig. 34 [Portugal, Morocco].

SYNONYMS.—?Cancer dodecos Linnaeus, 1767; Macropus parvirostris Risso, 1816; Doclea fabriciana Risso, 1827.

DISTRIBUTION.—Eastern Atlantic, from the Hebrides southward to Mauritania (?), including the Azores and the Canary Islands; Mediterranean; ?South Africa. Sublittoral, from a few meters to about 110 m. All of these records require verification.

*Inachus grallator, new species

?Inachus dorsettensis.—A. Milne Edwards and Bouvier, 1900: 143 [part?: Cape Verde Islands, 75–90 and 318 m].—Doflein, 1904:72 [Banc de la Seine; Spanish Sahara].—Odhner, 1923:19 [Angola, 72–108 m].—Monod, 1956:526 [? part].—Longhurst, 1958:89 [Sierra Leone, 72–118 m].—Guinot and Ribeiro, 1962:77 [Angola, 150–220 m].

Inachus dorsettensis.—Capart, 1951:70, fig. 21, pl. 1: fig. 6, pl. 2: fig. 11 [part, not specimens from Spanish Sahara?].—Crosnier, 1970:1218. [Not Inachus dorsettensis (Pennant, 1777).]

MATERIAL EXAMINED.—Pillsbury Material: Nigeria: Sta 255, 264–269 m, 3 (includes holotype), 1 (L, W).

Undaunted Material: Angola: Sta 96, 162 m, 1 (L).

Other Material: Congo: 05°03′S, 11°23′E, 247–250 m, sandy mud, 23 Jan 1968, A. Crosnier, 3 ov (W).

DESCRIPTION.—Carapace (Figure 73a) distinctly longer than broad, length 1.06 to 1.12 times width. Gastric region of carapace with 4 tubercles in transverse row anterior to erect gastric spine. Cardiac region of carapace with erect dorsal spine. Each branchial region with shorter erect spine, not markedly recurved anteriorly, and with dorsal tubercle anterior to each spine. Hepatic lobe with 2 distinct tubercles, and smaller, less conspicuous tubercles scattered on surface. Rostrum (Figures 73b, 74b) short, spines broad, lateral margins convergent anteriorly. Eyes large, but not extending laterally beyond strong postorbital spine. Interantennular spine well developed, clearly visible in dorsal view (Figure 73a,b) overreaching rostral spines in some specimens. Branchial margin of carapace tuberculate, anteriorly continuous with free epimeral margin. Basal antennal segment (Figure 73b) with row of tubercles, posteriormost largest, anterolateral angle lacking prominent spine.

Chelipeds subequal to or slightly longer than carapace, slender, not markedly inflated (slightly inflated in some males), equal and similar in both sexes; ischium with inner row of 4 or 5 erect tubercles; merus rounded, with low, blunt spines and tubercles, primarily on ventral surface; carpus with scattered small tubercles and spinules; palm covered with small, blunt spines; dactylus much longer than palm, cutting edge lacking enlarged proximal tooth or teeth.

Second pereiopod (Figure 74c) about 4 (3.8 to 4.5, mean 4.1) times as long as carapace, very slender, merus, propodus, and dactylus each longer than carapace; dactylus unarmed, subequal to or slightly shorter than propodus. Third pereiopod not extending to end of propodus of second, overreaching carpus of second by half of propodus and all of dactylus; latter shorter than propodus, lacking subdistal spines ventrally. Fourth pereiopod extending to or slightly overreaching propodus of third; dactylus slightly curved, with 2 low, subdistal tubercles, subequal to propodus. Fifth pereiopod (Figure 74d,e) scarcely overreaching propodus of fourth by tip of dactylus; latter similar to those of third and fourth pereiopods, subequal to propodus, with 2 subapical tubercles apically. Male pleopod shown in Figure 73c.

MEASUREMENTS.—Carapace lengths of males 14.2 to 15.5 mm, of non-ovigerous females 12.7 to 13.0 mm, of ovigerous females 14.5 to 14.6 mm.

DISTRIBUTION.—West Africa, from a few localities between Nigeria and Angola. Records in the literature include the following:

Gabon: 45 mi [72.5 km] NxE of Port-Gentil, 00°S, 08°–58′E, 250–300 m (Capart, 1951).

Angola: 25 mi [40 km] WNW of Ambriz, 07°39′S, 12°47′40″E, 100 m; 8 mi [12.8 km] NxE of Baía dos Elefantes, 13°05′S, 12°46′E, 100–110 m; 18 mi [29 km] WSW of Baía dos Tigres, 16°36′S, 11°27′E, 110 m (all Capart, 1951). 16°37′S, 11°22′E, 126 m (Crosnier, 1970).

Inachus dorsettensis, commonly known as the scorpion spider crab, is a species of crab generally found on loose substrates (stony bottoms to mud) from 6 metres (20 ft) depth down to about 100 m (330 ft). It is found along the east coast of the Atlantic Ocean from Norway to South Africa, and also in the Mediterranean Sea.