Neognathophausia ingens

Neognathophausia ingens (Dohrn, 1870)

(Figs. 1–5)

Lophogaster ingens Dohrn, 1870: 610, pl. 31, figs. 12–14.

Gnathophausia inflata Willemoes-Suhm, 1873: in MS (nomem nudum).

Gnathophausia calcarata G. O. Sars, 1883: 5 –6; 1885: 35, pl. IV; Ortmann 1906: 30, pl. I (2a–f).

Gnathophausia bengalensis Wood-Mason & Alcock, 1891: 269.

Gnathophausia doryphora Illig, 1906: 227 –228, fig. 1A–D.

Gnathophausia ingens— G. O. Sars, 1883: 4.— Illig 1930: 407 –408, figs. 11–12.— W.M. Tattersall 1939: 224 –225.— Fage 1941: 15 –24, figs. 20, 24–25; Nouvel 1943: 9–12, pl. I (4).— W.M. Tattersall 1951: 25 –26.— O. S. Tattersall 1955: 31 – 35.—Clarke 1961: figs. 1–8.— Pequegnat 1965: 402 –403, 406, 408, figs. 3–4, 8, tables 1–2.—Casanova 1977: 328–330.— Kathman et al. 1986: 160 –161.—Escobar-Briones & Soto 1991: table 1.— Casanova 1996: 129; Casanova et al. 1998: 60.— Serejo et al. 2007: Tabs. 3, 4.— Price et al. 2009: 923 –928.— Meland & Aas 2013: 203, fig. 2.— Gunalan & Kumar 2014: 123, Figs. 1, 3–4, tables 1 and 2.

Neognathophausia ingens — Petryashov, 1992: 47 –48.— Petryashov 2005: 959, 968–969, Fig. 3.— Petryashov 2007: Tab. 2; 2015: figs. 5, 6.— Wittmann & Wirtz 1998: 512.— Dürr & González 2002: 367, Tab. 3.— Haroun & Garrido 2003: 68.— Wittmann et al. 2004: 1261, table I.— Serejo et al. 2007: 142, Tab. 2.—Wittmann et al. 2007.—Wittmann & Riera 2012: 70–71.

Type locality. Off the west coast of Africa.

Material examined. One female (CL, 10.1 cm), Thiago EJ II, St. 23#1 (32°22.173’S, 50°13.829’W), 330 m, coll. Luiz F.R. Moro, 14/II/2018 (UFRGS 6587); one female (CL, 8.7 cm), Thiago EJ II, St. 24 (32°29.967’S, 50°16.941’W), 237 m, coll. Luiz F.R. Moro, 14/II/2018 (UFRGS 6588); one male (CL, 8.1 cm), REVIZEE Pesca, Bahia II, St. E0547 (21°46.57’S, 39°53.35’W), 1105 m, coll. N.O. Thalassa, 06/VII/2000 (MNRJ 15042); one male (CL, 10 cm) and one US (3.5 cm), REVIZEE Pesca, Bahia II, St. 0 538 (20°27.667’S, 39°38.101’W to 20°32.771’S, 39°37.65’W), 1680 m, coll. N.O. Thalassa, 02/ VI /2000 (MNRJ 15041); one female (CL, 8.1 cm), REVIZEE Pesca, Bahia II, St. E0524 (19°43.663’S, 38°39.838’W to 19°42.684’S, 38°44.568’W), 925 m, coll. N.O. Thalassa, 27/VII/2000 (MNRJ 15043).

Diagnosis. See Meland & Aas (2013).

Description. Carapace: smooth; rostrum triangular, short and weakly denticulate, surpassing antennal scale laterally and covering eyestalks partially (Figs. 1A, B, 2A); dorsal ridge at the basis of rostrum unarmed (Fig. 2A); dorsal keel interrupted in the middle region, extending anteriorly onto the rostrum and posteriorly onto the posterodorsal margin (Fig. 1A); upper and lower lateral keels continuous (Fig. 2A); cervical groove U-shaped (Fig. 1A); posterodorsal spine reduced (Fig. 1A, B); posterior margin of carapace emarginate with postero-lateral angles terminating in long and sharp spines (Fig. 1A, B).

Eyes: large, reaching the end of the third antennular peduncle (Fig. 1B); cornea distinctly semi-ellipsoidal, occupying about 1/3 of whole eye (Figs. 1A, B, 2A).

Antennule: antennular peduncle three-segmented; first and third segments about 2.3x as long as second; all segments bearing plumose setae (Fig. 2B).

Antenna: antennal scale small and subovate, tapering into sharply pointed apex, unsegmented; external margin with 8 teeth and a short apical spine (Fig. 2C).

Mandible: mandibular palp three-segmented; second segment about 2.9x as long as first, about 1.6x as long as third (Fig. 2D); first and second segments bearing simple setae (Fig. 2 D-3), third segment bearing plumose setae (Fig. 2 D-2) and row of feathered setae (Fig. 2 D-1); incisive process bearing five teeth, lacinia mobilis bicuspidate (Fig. 2E).

Maxillule: base with 11 spines, endite covered by plumose setae, retroverted palp bi-articulated bearing long simple setae (Fig. 2F).

Maxilla: sympodite consisting of three few distinct segments, coxa with a simple endite, basis with a bilobate endite, all covered by plumose setae along their margins; endopod two-segmented, covered by plumose setae, distolateral margin of first segment with one spine; exopod rounded, outer margin with plumose setae (Fig. 2G).

Thoracopods: first thoracopod with endopod five-segmented, short and robust, covered by simple setae, exopod small, ribbon-type, covered by simple setae, base bearing a long leaf-like epipod (Fig. 3A); second thoracopod robust, exopod short, about 0.4x endopod length (Fig. 3B); third thoracopod robust, exopod short, about 0.4x endopod length, inner margin of dactylus armed with nine spines (Fig. 3C); fourth thoracopod slender, exopod short, about 0.5x endopod length, inner margin of dactylus armed with 11 spines (Fig. 3D); fifth thoracopod slender, exopod short, about 0.4x endopod length (Fig. 3E); sixth thoracopod slender, exopod short, about 0.5x endopod length (Fig. 3F); seventh thoracopod slender, exopod short, about 0.6x endopod length (Fig. 3G); eighth thoracopod slender (Fig. 3H), exopod short, about 0.7x endopod length; all dactyli of endopods with one strong spine on apex, inner margin with 8–11 spines; oostegites leaf-like increasing in size posteriorly.

Pleon: pleural plates produced into two spines (Fig. 4A); epimera of sixth somite fused in the mid-ventral line into heart-shaped plate (Fig. 4B); all pleopods well developed, birramous in both sexes; exopods and endopods composed by 58–64 and 46–49 segments respectively, bearing compound setae (Fig. 4 C–G).

Tail fan: telson linguiform, about 3.5x as long as broad at its base, dorsal surface with two longitudinal keels (Fig. 4H), lateral margins with irregularly distributed spines (Fig. 4H), apex crescent-shaped (Fig. 4H, I); uropods shorter than telson, inner margin of sympodite unarmed (Fig. 4J, K).

Distribution. Neognathophausia ingens is considered a cosmopolitan species, but does not occur in polar and sub-polar waters (Meland & Aas 2013). Along the Atlantic coast of South America it has been recorded for the Brazilian coast and east of La Plata region in Argentina (Fig. 5) (Tattersall 1951; 1955; Serejo et al. 2007; Meland & Aas 2013).

Bathymetric distribution. Occurring from 125 to 3391 m depth, being usually found between 600 to 1.500 m (Meland & Aas 2013).

Ecology. In the marine food webs, N. ingens feeds mainly on fishes (Hopkins et al. 1994) and is an important food source in the diet of fishes of the family Berycidae (Dürr & Gonzalez 2002) and the sperm whale Physeter macrocephalus Linnaeus (Best 1999). Regarding reproductive ecology, this species is considered semelparous (Childress & Price 1978).

Remarks. This species was first recorded from Brazil by Serejo et al. (2007) from the state of Bahia (BA) to Rio de Janeiro (RJ) (922–1815 m depth). However, a review of the material deposited in the MNRJ showed that there is no record for the state of Bahia. Therefore, the occurrence of N. ingens in Brazil has been limited to the states of Espirito Santo, Rio de Janeiro and Rio Grande do Sul (Fig. 5). The new records of N. ingens increases the southernmost limit for the species in Brazil about 1188 km. This contribution provides for the first time, illustrations and descriptions of the mandible (Fig. 2D, E), thoracopods 3–8 and dactyli 2–8 (Fig. 3 B–H), pleopods 1–5 (Fig. 4 C–G), and sympodite of uropod in dorsal view (Fig. 4K). The new illustrations could be useful for further taxonomic studies.