Gigantactis watermani Bertelsen, Pietsch & Lavenberg, 1981

Mincarone, Michael Maia, Afonso, Gabriel Vinícius Felix, Di Dario, Fabio, Eduardo, Leandro Nolé, Frédou, Thierry, Lucena-Frédou, Flávia, Bertrand, Arnaud & Pietsch, Theodore Wells, 2021, Deep-sea anglerfishes (Lophiiformes: Ceratioidei) from off northeastern Brazil, with remarks on the ceratioids reported from the Brazilian Exclusive Economic Zone, Neotropical Ichthyology 19 (2), pp. 1-28 : 19-21

Gigantactis watermani Bertelsen, Pietsch & Lavenberg, 1981

( Figs. 5 , 6A , 7 )

Diagnosis. Twenty species of Gigantactis are recognized (two of doubtful validity: G. ovifer Regan & Trewavas, 1932 and G. filibulbosus Fraser-Brunner, 1935 ), of which 14 are reported for the Atlantic. Gigantactis watermani differs from G. elsmani , G. kreffti , and G. perlatus by the length of the illicium (130–490% SL, rarely less than 200%, vs. 60–120% SL); from G. golovani , G. macronema , and G. gargantua (North Pacific and eastern South Indian Ocean) by the escal filaments (distal escal filaments simple, without posterior filaments on or below its base vs. esca with distal filaments branched, several filaments emerging from and below its base); it further differs from G. gargantua by the pigmentation of distal escal filaments (heavily pigmented for more than one-half their length vs. lightly pigmented for less than one-fifth their length) and position of proximal escal filaments (restricted to the anterior margin of the escal bulb vs. not restricted to the anterior margin of escal bulb); from G. ios , G. longicauda , G. macronema , G. microdontis (eastern Pacific), and G. savagei (eastern North Pacific) by the presence of a group of anterior filaments arising from the base of esca (vs. absence), escal bulb structure (distal part of escal bulb bearing four or five pairs of stout filaments along posterior margin vs. filaments of distal part of escal bulb different from above), and length of caudal-fin rays (second and seventh greater than 50% SL vs. longest caudal-fin rays less than 40% SL); from G. herwigi by the number of filaments at esca base (10 vs. less than 10), number of pair of filaments on the distal part of escal bulb (four or five, each with a pigmented swollen base vs. four, each gradually tapering and only faintly pigmented at base); from G. longicirra by the number and length of the dorsal-fin rays (4–7, all about equal in length vs. 8-10, the first and last distinctly longer than intermediate rays) and length of the first and eighth caudal-fin rays (less than 40% vs. 60–100% SL); and from G. gibbsi , G. gracilicauda , G. meadi , G. vanhoeffeni , and G. paxtoni (western South Indian Ocean and western South Pacific) by the absence of a darkly pigmented, spinulose distal prolongation in the esca (vs. presence of dark pigment) (Pietsch, 2009).

Geographical distribution. Only two metamorphosed females of Gigantactis watermani were previously known, one from the eastern Tropical Atlantic ( ISH 2330 /71, 1º04’N 18º22’W) and another from the western Tropical Pacific , off New Caledonia (Pietsch, 2009). The specimen collected off seamounts of Rio Grande do Norte State, between depths of 700 and 1,113 m, represents the third known female specimen of the species and the first record in the South Atlantic ( Fig. 5 ) .

Remarks. Morphological and meristic data of the specimen agree with the description provided by Bertelsen et al. (1981) for the holotype, but some slightly differences were noted in its escal anatomy. The esca is bilaterally asymmetric, with four stout, tapering filaments present on the left side and five filaments present on the right side. The base of the most proximal filament of the right side is, however, reduced, with the structure mostly represented by the swollen, dark pigmented proximal part and a tiny unpigmented narrow tip ( Fig. 7 ). In addition, the left filament of the most distal pair of filaments is secondarily branched, resulting in three filaments for this pair. In the holotype, the filaments of the most distal pair have a single branch. Bertelsen et al. (1981) also indicated the presence of 12 narrow unpigmented filaments on the anterior margin base of the escal bulb, but 14 filaments are present in the specimen examined ( Fig. 7 ), a number that is within the range noted by Pietsch (2009: 467) for the species.

One additional small-sized specimen ( NPM 3836 , 6 mm SL) of Gigantactis collected off Rio Grande do Norte State, between depths of 35 and 100 m, was identified only to genus ( Fig. 5 ) .

Material examined. NPM 4424 , 1, 170 mm ( Fig. 6A ) , RV Antea, sta. AB2/59A, 3°38’01.6”S 36°31’46.3”W to 3°38’36.1”S 36°17’49.7”W, 700–1,113 m, 5 May 2017, 21:57–22:37 h.

Figures

FIGURE 5 | Records of the Caulophrynidae, Gigantactinidae, and Linophrynidae in Brazilian waters: Caulophryne sp. (pentagon), Gigantactis longicirra (square), Gigantactis vanhoeffeni (cross), Gigantactis watermani (triangle), Gigantactis sp. (diamond), Rhynchactis sp. (star), Linophryne arborifera (circle). Full symbols represent specimens collected during the ABRACOS surveys and open symbols are records from the literature (see text). Selected Brazilian States and oceanic islands are RN – Rio Grande do Norte, BA – Bahia, ES – Espírito Santo, RJ – Rio de Janeiro; SPA – Saint Peter and Saint Paul Archipelago, FN – Fernando de Noronha Archipelago, RA – Rocas Atoll. Dashed line represents the outer limit of the Brazilian Exclusive Economic Zone.

FIGURE 6 | Species of the Gigantactinidae reported in this study: A. Gigantactis watermani, NPM 4424, 170 mm SL; B. Rhynchactis sp., NPM 4425, 113 mm SL. Scale bars = 10 mm.

FIGURE 7 | Esca of Gigantactis watermani, NPM 4424, in left ventrolateral view. Arrows indicate the secondary branching of the left filament of the most distal pair of filaments (upper left) and the reduced base of the most proximal filament of the right side (lower right). Scale bar = 5 mm.