Gnathophausia gracilis Willemoes-Suhm, 1875

Meland, Kenneth & Aas, Pål Øyvind, 2013, A taxonomical review of the Gnathophausia (Crustacea, Lophogastrida), with new records from the northern mid-Atlantic ridge, Zootaxa 3664 (2), pp. 199-225 : 204-206

Gnathophausia gracilis Willemoes-Suhm, 1875

( Fig. 3 )

Gnathophausia gracilis Willemoes-Suhm, 1875: 33 –34, 37.—G.O. Sars 1885:48–50.—W.M. Tattersall 1939:223–224.—Fage 1941: 27–30.—O.S. Tattersall 1955: 39–40.—Casanova 1996a: 129.—Price et al. 2009: 923–928

Gnathophausia gracilis var. brevispinis— Wood-Mason and Alcock 1891a: 187. Gnathophausia brevispinis Wood-Mason and Alcock, 1891b: 269 –270.—Faxon 1895: 216–218. Gnathophausia dentate Faxon, 1893: 217–218.

Gnathophausia bidentate Illig, 1906: 229 –230.

Diagnosis. Body slender. Carapace small; rostrum tridentate, long and slender, equaling carapace in length, denticulate; posterodorsal spine short; distinct cervical sulcus; dorsal keel armed with anteriorly curved denticles along posterior end; lateral extensions of carapace produced into two unequal posterolateral spines on each side, upper spine being largest and equal in length to posterodorsal spine; upper lateral keels absent; lower lateral keels continuous, extending into upper posterolateral spines; antennal spines present; supra-orbital spines small; branchiostegal expansions large and acutely triangular. Eyes long and slender. Antennal scale slender, terminal lobe small, outer edge serrated at distal end, outer spine equal or longer than apex in length. Abdominal somites one and two equipped with conspicuous dorsal projections, pleura of somites one to six produced into two ventral spines. Telson linguiform, armed with spiniform setae, apex quadridentate, posterior margin takes on form of two spines, flanked by one small and one large conspicuous pair of spiniform setae on side. Obtains lengths up to 100 mm (G.O. Sars 1885; O.S. Tattersall 1955).

Distribution. G. gracilis is widely distributed in the tropical waters of the world. It has only on rare occasions been collected north of the tropic of cancer, and extends southward to 15°S (O.S. Tattersall 1955). From the Atlantic Ocean G. gracilis is reported from the Canaries, Cape Verde Islands and Gulf of Guinea in the east, through St. Helena in the mid-Atlantic, and extending to the West Indies, Gulf of Mexico, northward to the south of Bermuda in the west (Illig 1930; Fage 1941; Price et al. 2009; O.S. Tattersall 1955). From the Indian Ocean G. gracilis has been recorded from the Cocos Islands, south of Ceylon, Bay of Bengal, the Arabian Sea, and north of Madagascar (Fage 1941; Wood-Mason and Alcock 1891b). Pacific Ocean records are from the Gulf of Panama, Galapagos Islands, mid Pacific, the Philippines, and East Indian Archipelago (Fage 1941; Hansen 1912). G. gracilis is distributed at bathypelagic depths, most common at depths between 1500 and 2000 m (O.S. Tattersall 1955).

Remarks. First described by Willemoes-Suhm from the “Challenger” station 107 between Africa and Brazil at a depth of 2744 m (Willemoes-Suhm 1875), and later fully described and figured by G.O. Sars (1885). Gnathophausia brevispinis , G. dentate, and G. b i d e n t a t e are considered subjective junior synonyms of G. gracilis .

G. gracilis is easily recognized from other Gnathophausia species by the conspicuous spines on anterior abdominal somites and the shape and armature of the telson’s apex.

Figures

FIGURE 3. Gnathophausia gracilis Willemoes-Suhm, 1875. Adult male: A, lateral view; B, dorsal view; C, antenna (with scale and proximal part of flagellum); D, telson and uropod (dorsal view); E, apex of telson (from G. O. Sars 1885: pl. VII, figs. 6 – 10).