Eustomias (Nominostomias) bertrandi, Bárbara & Villarins & Luciano & Fischer & Artem & Prokofiev & Michael & Mincarone, 2024

Villarins, Bárbara T, Fischer, Luciano G, Prokofiev, Artem M & Mincarone, Michael M, 2023, Four new species of dragonfish genus Eustomias (Stomiiformes: Stomiidae: Melanostomiinae) from the western tropical Atlantic, with remarks on Eustomias minimus Clarke, 1999, Zoological Journal of the Linnean Society 202 (1), pp. 1-17 : 9-10

Eustomias (Nominostomias) bertrandi sp.nov.

( Figs 5 , 7E , 9 ; Tables 1 and 2 )

Zoobank registration: urn:lsid:zoobank.org:act: CBAB98BF-BD97-496B-9D0E-40E55B937587

Eustomias sp . Villarins et al. 2022: 60 [potential new species; off northeastern Brazil].

Eustomias sp . 4. – Eduardo et al. 2022: 6 [potential new species; off northeastern Brazil].

Holotype: NPM 4610, 109 mm SL, Brazil, off Fernando de Noronha Archipelago , ABRACOS, station AB2#44A, 03°52 ʹ 53″S, 32°17 ʹ 33″W to 03°52 ʹ 13″S, 32°16 ʹ 28″W, 0–850 m, RV Antea, mid-water trawl, coll. Leandro Eduardo, Paulo Travassos, and crew, 28 April 2017, 12:44–13:17 h.

Diagnosis: Species of Nominostomias with: long chin barbel (67% SL, 510.5% HL) ending in two terminal bulbs; distal bulb 2.5 times the length of the proximal bulb; distance between bulbs short (0.3% SL, 2.4% HL), 0.9 times proximal-bulb length and 0.35 times distal-bulb length; distal bulb with a short terminal filament (3.5% SL, 26.6% HL), filled with very small luminous bodies ( Figs 5 , 7E ).

Description: Chin barbel long, extending beyond the anal fin insertion (67% SL, 510.5% HL) (Fig. 5A). Barbel stem unpigmented and axis lightly pigmented. No appendages or photophores on stem. Two terminal bulbs, proximal bulb small (0.4% SL, 2.8% HL) and distal bulb larger (0.9% SL, 7% HL). Distal bulb 2.5 times length of the proximal bulb, and proximal bulb 0.4 times length of distal bulb. Distance between bulbs short (0.3% SL, 2.4% HL), 0.9 times proximal-bulb length and 0.35 times distal-bulb length. A short terminal filament (3.5% SL, 26.6% HL), filled with very small luminous bodies ( Figs 5C , 7E ).

Dorsal-fin rays 25, anal-fin rays 40, pectoral-fin rays three, pelvic-fin rays seven, branchiostegal rays 12, and total vertebrae 68. Linear photophores in the series: BR 10, IP 7, PV 32, VAV 20 (eight above anal-fin base), OV 31, VAL 20 (nine above anal-fin base), AC 19, IA 62, IC 78, OA 51, and OC 70 (Table 1). Postorbital organ large, oval, directed diagonally (1.4% SL, 10.5% HL). Suborbital organ small, rounded (0.5% SL, 3.5% HL). Small photophores randomly located on head and body. Series of small photophores along the anterior edge of the orbit extending in a straight line above PO; a few sparse aggregations of luminous spots near IV photophores and before SO. No ventral groove.

Fourteen teeth on premaxilla, with first, second, third, and sixth fixed; second tooth the longest (1.4% SL, 10.5% HL) (Fig. 5B; Table 2). Fifteen teeth on dentary, with first, second, third, and sixth fixed; second tooth the longest (1.1% SL, 8.4% HL) (Fig. 5B). Thirteen teeth on maxilla, comb-like and directed backwards.

Measurements (as a percentage of SL): body depth (behind head) 5.8, body width (at pelvic insertions) 6.0, dorsal-fin base length 13.5, anal-fin base length 24.6, predorsal length 82.6, preanal length 71.6, prepelvic length 54.3, pelvic–anal distance 15.7, pelvic-fin length 15.1, snout to anus 69.9, caudal peduncle length 3.5, caudal peduncle depth 2.1, head length 13.1, snout length 5.2, eye diameter 3.2, interorbital space 4.0, and upper jaw length 12.8. Measurements (as a percentage of HL); snout length 39.9, eye diameter 24.5, interorbital space 30.8, and upper jaw length 97.9 (Table 2); PO /Eye 0.43 and SO /Eye 0.14.

Colour in alcohol: body dark brown; fin ray membranes lightly pigmented near base by dotted melanophores. Eight paired dorsal spots between the occiput and dorsal-fin origin.

Distribution: Known only from the type locality, off eastern Fernando de Noronha Archipelago, Brazil (Fig. 9). The holotype was collected at 780 m depth, where the temperature was 4.7°C, salinity 34.5, and dissolved oxygen 3.6 mL/L.

Etymology: This species is named after Dr Arnaud Bertrand, Senior Researcher at the Institut de Recherche pour le Développement ( France), in recognition of his commitment, enthusiasm, and leadership in conducting the ABRACOS expeditions and many other marine biology-related projects.

Comparison: Like the congeners in subgenus Nominostomias , E. bertrandi has three pectoral-fin rays, seven pelvic-fin rays, the barbel stem unpigmented with no photophores, presence of bulbs and terminal filaments, ventral groove absent and high counts of photophores. Eustomias bertrandi belongs to the Nominostomias group I of Gibbs et al. (1983), particularly to the species having two separated terminal bulbs, single terminal filaments without or with very short branches, proximal bulb in the centre of the stem, and distance between bulbs <2% SL (couplet 14 in the key of Gibbs et al. 1983). Within these species, E. bertrandi is more similar to Eustomias bibulboides Gibbs, Clarke & Gomon, 1983 and Eustomias orientalis Gibbs, Clarke & Gomon, 1983 , although its barbel length is slightly longer (67% SL vs. shorter than 65% SL in E. bibulboides and E. orientalis ). Like the new species, both E. bibulboides and E. orientalis have luminous bodies (described as tiny bulblets) in the terminal filament, although varying with the size of specimens and not present in all specimens. However, E. bertrandi differs from E. orientalis by the smaller size of the proximal bulb (0.4% SL vs. 0.8–1.3% SL), the size proportion between distal and proximal bulbs (distal bulb 2.5 times the proximal bulb length vs. 0.7–1.8 times) and the shorter terminal filament (3.5% SL vs. 4.1–5.3% SL, respectively). Eustomias bertrandi differs from E. bibulboides by the size proportion between the distal and proximal bulbs (distal bulb 2.5 times the proximal bulb length vs. 0.5–1.8 times), shorter terminal filament (3.5% SL vs. usually 5–7% and maximum 11% SL), and by the lightly pigmented axis of the barbel stem (vs. densely pigmented, often black). Both E. orientalis and E. bibulboides are restricted in distribution to the North Pacific Ocean.

Within Atlantic species, E. bertrandi is most similar to E. austratlanticus and E. bibulbosus , but differs from both species in having a much shorter interbulbar distance with 0.3% SL (vs. in 2.8–3.0% SL E. austratlanticus and 2.2–4.2% SL in E. bibulbosus ), and interbulbar distance 0.35 times the distal-bulb length (vs. 2.8– 3.0 times distal-bulb length in E. austratlanticus and 2.0–7.8 times distal-bulb length in E. bibulbosus ) and 0.9 times the proximal-bulb length (vs. 2.3–8.5 times proximal bulb length in E. bibulbosus ).

Figures

Figure 5. Eustomias (Nominostomias) bertrandi, holotype, NPM 4610, 109 mm SL, Brazil, off Fernando de Noronha Archipelago, RV Antea, ABRACOS, station AB2#44A, 03°52ʹ53″S, 32°17ʹ33″W to 03°52ʹ13″S, 32°16ʹ28″W, 0–850 m. A, whole specimen (scale bar: 10 mm). B, representation of dentition (fixed teeth in black; scale bar: 10 mm). C, terminal portion of chin barbel (scale bar: 1 mm).

Figure 7. Chin barbel of the new species of Eustomias. A, terminal portion of Eustomias (Haploclonus) antea, holotype, NPM 4880, 124 mm SL. B, terminal portion of Eustomias (Haploclonus) lucenae, holotype, NPM 4883, 47 mm SL. C, terminal bulbs and complex of bulblets of Eustomias (Nominostomias) ophioglossa, holotype, NPM 4878, 162 mm SL. D, distal bulb and bulblets of Eustomias (Nominostomias) ophioglossa, holotype, NPM 4878, 162 mm SL. E, terminal portion of Eustomias (Nominostomias) bertrandi, holotype, NPM 4610, 109 mm SL. Scale bar: 1 mm.

Figure 9. Sampling location of the Eustomias from off northeastern Brazil:Eustomias antea (square); Eustomias lucenae (circle); Eustomias ophioglossa (triangle); Eustomias bertrandi (triangle); E.cf* minimus (hexagon). Abbreviations: FN, Fernando de Noronha Archipelago; RA, Rocas Atoll; RN, State of Rio Grande do Norte.