Leucicorus gerringerae, Schwarzhans & Nielsen & Mundy, 2022

Schwarzhans, Werner W., Nielsen, Jørgen G. & Mundy, Bruce C., 2022, Revision of the circumglobal deep-sea genus Leucicorus (Teleostei, Ophidiidae) with two new species, Zootaxa 5100 (4), pp. 541-558 : 544-545

Leucicorus gerringerae n.sp.

Table 1 , Figs. 1B , 2B , 3E–F , 5

Leucicorus atlanticus: Sêret & Andreata 1992: 92 ; Mincarone et al. 2008: 57.

Material examined (2 specimens, SL 214–235 mm).

Holotype: VIMS 42888, 235 mm SL, male, Silver Abyssal Plain, 23°20–22.5’ N, 68°23–29.4’ W, R / V Columbus Iselin , cr. CI-8113, st. D018, 45’ OT, 5303–5387 m, 25 May 1981.

Paratype: MNRJ 52795 , male, 214 mm SL, off Brazil, 21°39’S, 31°47’W , R / V Marion Dufresne, cr. MD-55, st. 26 CP 44, beam trawl, 4500–4510 m, 18 May 1987 .

Diagnosis. Dorsal fin with 97 rays, anal fin with 73–80 rays and 62 (13–14 + 48–49) vertebrae. Head squamation extensive on opercle, preopercle and occiput. 25 scales transversely across trunk above the anal-fin origin. Bluish eyes large (15–19% HL), without lens. Otolith elongate (OL:OH = 1.62), with inner and outer faces equally convex.

C omparison. L. gerringerae is most similar to L. lusciosus with the extensive head squamation; however, it differs from L. lusciosus by having fewer dorsal-fin (97 vs. 110–114) and anal-fin (73–80 vs. 87–99) rays, larger head scales (2.0– 2.5 mm vs ~ 1 mm) and fewer scales across trunk above beginning of anal fin (25 vs. 35–40). It differs from L. lentibus by having an extensive head squamation, fewer rays in dorsal (82–94 vs. 105) and anal (73–80 vs. 87) fins and by lacking an eye lens. It differs from the sympatric L. atlanticus in having complete head squamation (vs reduced on occiput), higher number of dorsal-fin rays (97 vs 82–93), larger eye size (15–19% HL vs 10–13.5% HL except one eye in one case 18.4% HL), and the more elongate otolith (OL:OH = 1.62) with equally convex inner and outer faces (vs roundish otolith, OL:OH = 1.2–1.55, with flat inner face and strongly convex outer face).

Description. The principal meristic and morphometric characters are shown in Table 1 . The description is based on the holotype; characters in which the paratype differ from the holotype are given in brackets. Body elongate and compressed with tapering tail; head broad with dorsal profile straight except for a slight concavity above eyes; head bones thin and fragile. Anterior nostril placed midway between upper lip and posterior nostril and the larger posterior nostril close to orbit. Orbit equal in length to snout. Black eye about 15 to 19% of HL; no eye lens discernible. Opercular spine thin and pointed. Body fully scaled, with 25 scale rows transversely above beginning of anal fin, head with scales on opercle, preopercle and occiput. Dorsal-fin origin above anterior part of pectoral fin; anal-fin origin below dorsal fin ray 21(19), much closer to tip of snout than to base of caudal fin and with a preanal length ca. 40% SL. Pelvic fins each with two tightly joined rays. Pectoral fins placed on midbody. Mouth terminal; upper jaw ends below posterior edge of orbit; supramaxilla well developed. Anterior gill arch with four knob-like and one long raker on upper branch, one long raker in the angle between upper and lower branches and lower branch with nine(7) long and five(6) knob-like rakers; longest gill raker almost three times as long as longest gill filament. 2–4 pseudobranchial filaments. The color is brownish grey except for the bluish eyes.

Axial skeleton (based on radiographs). Precaudal vertebrae 14(13) all with pointed neural spine tips. Anterior neural spine half the length of second spine whereafter the neural spines decrease in length. Six anterior neural spines somewhat depressed. Bases of neural spines 5–14(5–13) enlarged. Parapophyses on precaudal vertebrae 5–14(4–13). Pleural ribs on precaudal vertebrae 3–13(2–12). Epineurals not observed.

Dentition. All dentigerous bones with many, small and pointed teeth arranged in irregular rows. Dentaries and premaxillae with teeth along their entire length with decreasing rows posteriad. Palatines with spindle shaped dentition and vomer ‘boomerang’-shaped with rather few teeth. One median basibranchial tooth patch, 6.5 mm long, 2.5 mm broad anteriorly and 0.8 mm broad posteriorly, with dentition similar to that on dentaries.

Otolith ( Fig 3E–F ). Large otoliths up to 10.5 mm in length (holotype) with slender, droplet-like shape (otolith length: height = 1.62). Ventral rim shallow; dorsal rim with broad, obtuse, predorsal angle; anterior rim broadly rounded; posterior tip slightly tapering. Inner face about as convex as outer face; otolith height: thickness = 2.3. Sulcus slightly inclined, shallow, narrow, with single well-defined colliculum; otolith length: sulcus length = 2.28– 2.88; sulcus length: height = 3.3–4.5. Sulcus connected to anterior-dorsal rim via indistinct channel. Ventral furrow variably expressed; no distinct dorsal depression.

Distribution ( Fig. 5 ). Known from two localities (north of the Bahama Isl. and west of Rio de Janeiro) caught abyssally (4500 to 5303 m).

Etymology. The species is named after Dr. Mackenzie Gerringer (State University of New York at Geneseo, USA) for her contribution to the knowledge of the biology of hadal fishes.

Figures

FIGURE 1. A) Leucicorus atlanticus Nielsen, 1975, holotype, ZMUC P771813, 154 mm SL, 19°00’N, 80°38’W. B) Leucicorus gerringerae n. sp., holotype, VIMS 42888, 235 mm SL, 23°20–22.5’ N, 68°23–29.4’ W. C) Leucicorus lentibus n. sp., holotype, ZMUC P771812, 170 mm SL, 20°01’N, 154°05’W. D) Leucicorus lusciosus Garman, 1899, ZMUC P771814, 225 mm SL, 17°42’S, 78°59’W. E) Leucicorus lusciosus Garman, 1899, radiograph of holotype, MCZ 28680, 245 mm SL, 14° 46’N, 98°40’W.

FIGURE 2. Head drawings (lateral and top): A) Leucicorus lusciosus Garman, 1899, ZMUC P771814, 225 mm SL, 17°42’S, 78°59’W. B) Leucicorus gerringerae n. sp., holotype, VIMS 42888, 235 mm SL, 23°20–22.5’ N, 68°23–29.4’ W. C) Leucicorus atlanticus Nielsen, 1975, holotype, ZMUC P771813, 154 mm SL, 19°00’N, 80°38’W. D) Leucicorus lentibus n. sp., holotype, ZMUC P771812, 170 mm SL, 20°01’N, 154°05W.

FIGURE 3. Otolith drawings: A–D) Leucicorus atlanticus Garman, 1899; A, holotype, ZMUC P771813 (A1 anterior view, A2 medial view, A3 dorsal view); B, ZMUC P77585 (B1 medial view, B2 dorsal view); C, VIMS 06857 (C1 medial view, C2 dorsal view); D, BMNH 2020.11.16.1 (D1 medial view, D2 dorsal view). E–F) Leucicorus gerringerae n. sp.; E, holotype, VIMS 42888 (E1 anterior view, E2 medial view, E3 dorsal view); F, MNRJ 52795 (medial view). G) Leucicorus lentibus n. sp., holotype, ZMUC P771812 (G1 anterior view, G2 medial view, G3 dorsal view). H–I) Leucicorus sp.; H, SMF 28854, 85 mm SL (H1 medial view, H2 dorsal view); I, SMF 28854, 75 mm SL (I1 medial view, I2 dorsal view). J–K) Leucicorus lusciosus Garman, 1899; J, SIO 81–148 (J1 anterior view, J2 medial view, J3 ventral view); K, ZMUC P771814, medial view.

FIGURE 5. Distribution map of Leucicorus species.