Eustomias (Haploclonus) lucenae, 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 : 4-7

publication ID	https://doi.org/ 10.1093/zoolinnean/zlad163
publication LSID	lsid:zoobank.org:pub:D261FD0-638C-46AB-AD43-B6941119E9F5Corresponding
DOI	https://doi.org/10.5281/zenodo.14552572
persistent identifier	https://treatment.plazi.org/id/03AE87AA-FFA1-FFD5-FC3D-FE0BDA19FB81
treatment provided by	Plazi
scientific name	Eustomias (Haploclonus) lucenae
status	sp. nov.

Treatment

Eustomias (Haploclonus) lucenae sp.nov.

( Figs 3 View Figure 3 , 7B View Figure 7 , 9 View Figure 9 ; Tables 1 View Table 1 and 2 View Table 2 )

Zoobank registration: urn:lsid:zoobank.org:act: 08E1C783- 06B2-4A6E-AC6B-78D0E24B014E

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

Holotype: NPM 4883, 47 mm SL, Brazil, off State of Rio Grande do Norte, ABRACOS , station AB2#39, 04°52 ʹ 27″S, 34°35 ʹ 23″W to 04°50 ʹ 53″S, 34°51 ʹ 05″W, 650–800 m, RV Antea, mid-water trawl, coll. Leandro Eduardo, Paulo Travassos, and crew, 24 April 2017, 21:49–22:37 h. GoogleMaps

Diagnosis: A species of Haploclonus with: 24 OV, 56 OC; a short barbel (9.6% SL; 83.3% HL) without appendages, lacking black spots associated with photophores on stem, ending in a well-developed, strongly asymmetric terminal bulb (0.8% SL, 6.9% HL), without terminal filaments ( Figs 3 View Figure 3 , 7B View Figure 7 ).

Description: Chin barbel shorter than head (9.6% SL; 83.3% HL) and without appendages. Barbel stem unpigmented, axis lightly pigmented in the core. Terminal bulb well developed (0.8% SL, 6.9% HL), lacking any appendages, 1.1 times deeper than long, with distinctly expanded dorsoposterior corner ( Figs 3B View Figure 3 , 7B View Figure 7 ).

Dorsal-fin rays 26, anal-fin rays 36, pectoral-fin rays three, pelvic-fin rays seven, branchiostegal rays 13, and total vertebrae 57. Linear photophores in the series: BR 10, IP 7, PV 26, VAV 14 (last five above anal-fin base), OV 24, VAL 13 (last five above anal-fin base), AC 19, IA 47, IC 66, OA, 37, OC 56 (Table 1). Postorbital organ damaged, SO small (0.4% SL, 3.2% HL). Series of small photophores along the anterior edge of the orbit extending in a straight line above PO cavity. No ventral luminous tissue. No ventral groove.

Jaws damaged, with some teeth missing: two mobile teeth retained on the premaxilla, second tooth the longest (1.3% SL, 9.7% HL). One mobile tooth retained on dentary bone (0.8% SL, 6.4% HL). Teeth on maxilla damaged.

Measurements (as a percentage of SL): body depth (behind head) 6.2, body width (at pelvic insertions) 4.9, dorsal-fin base length 13.2, anal-fin base length 23.4, predorsal length 85.1, preanal length 74.5, prepelvic length 62.3, pelvic–anal distance 12.3, snout to anus 70.2, caudal peduncle length 4.0, caudal peduncle depth 2.5, head length 11.5, snout length 4.7, eye diameter 2.3,interorbital space 3.2, and upper jaw length 10.4. Measurements (as a percentage of HL): snout length 40.7, eye diameter 20.4, interorbital space 27.8, and upper jaw length 90.7 (Table 2); SO/Eye 0.18.

Colour in alcohol: body light brown, darker dorsally and ventrally; fin rays and membranes lightly pigmented by isolated melanophores near base. Five pairs of dorsal spots (behind head, above seventh, 14th and 23rd OV, and seventh VAL), becoming less conspicuous posteriorly.

Distribution and habitat: Known only from the type locality, off Rio Grande do Norte, Brazil (Fig. 9). The holotype was collected between 650 and 800 m depth, water temperature 5.0°C, salinity 34.4, and dissolved oxygen 3.7 mL/L.

Etymology: This species is named after Dr Flávia Lucena-Frédou, Professor at the Universidade Federal Rural de Pernambuco ( Brazil), for her tireless efforts in supervising and supporting many students in the field of marine biology and conservation.

Comparison: This species is assigned to the subgenus Haploclonus on the basis of three pectoral-fin rays, seven pelvic-fin rays, low photophore and vertebral counts, no ventral groove, six paired dorsal spots, and unbranched barbel stem with little or no external pigment. However, it differs from the other members of that subgenus, except the conventionally included E. treoavasae , by the absence of the black spots associated with photophores on the barbel stem ( Gibbs et al. 1983, Prokofiev 2018). Also, E. lucenae differs from the other species of Haploclonus by its lower number of OV (24 vs. 26–30) and OC (56 vs. 59–62) ( Gibbs et al. 1983). The only species with simple barbel morphology in the subgenus are E. antea and E. simplex , with the barbel having a single distal swelling without any appendages ( Morrow and Gibbs 1964; present study). Eustomias lucenae differs from these congeners by its shorter barbel length (9.6% SL vs. 45.2% SL in E. antea and 47.3–68.6% SL in E. simplex ), prominent deep asymmetric terminal bulb with 0.8% SL, 1.1 times deeper than long (vs. almost imperceptible bulb with 0.3% SL in E. antea and prominent elongate-oval to lanceolate bulb often slightly constricted at mid-length or more proximally, 1.8–4.1% SL, 2–4 times longer than deep in E. simplex ) ( Morrow and Gibbs 1964, Sutton et al. 2020b; A.M.P., personal observations). The recently described Eustomias (Haploclonus) stamen Koeda & Ho, 2019 , has also a short barbel (19.6% SL) with relatively simple bulb morphology, but with lower fin-ray count (dorsal-fin rays 20 and anal-fin rays 32 vs. dorsal-fin rays 26 and anal-fin rays 36 in E. lucenae ) and presence of an appendage on the barbel stem and terminal filaments (both absent in E. lucenae ) ( Koeda and Ho 2019).