Leucicorus lentibus, 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 : 545-548

Leucicorus lentibus n. sp.

Table 1 , Figs. 1C , 2D , 3G , 5

Holotype (and only specimen): ZMUC P 771812, 170 mm SL, female, off Hawaiʽi, 20°01’N, 154°05W, R / V Vityaz, cr. 29, st. 4313, Sigsbee trawl, 5385–5390 m, 1 Feb. 1959.

Diagnosis. Dorsal fin with 105 rays, anal fin with 87 rays and 64 (14+50) vertebrae. Transversal scale rows above origin of anal fin 20 (up to 27 rows in presumable life photographs). Reduced squamation on occiput, preopercle and opercle. Diameter of black eye 13% head length with large eye lens of 57% of black eye diameter. Otolith with flat inner and convex outer face; OL:OH = 1.73.

Comparison. L. lentibus seems most similar to L. atlanticus with the reduced head squamation and a comparable number of transversal scale rows; however, it differs from L. atlanticus by having more dorsal- (105 vs. 82–93) and anal-fin rays (87 vs. 68–80) and a more slender otolith (OL:OH = 1.73 vs 1.2–1.55). It differs from L. lusciosus by having reduced head squamation, fewer transversal scale rows (20 vs. 35–40) and fewer dorsal- (105 vs. 110–114) and anal-fin (87 vs. 96–99) rays. It differs from L. gerringerae for its reduced head squamation, and by having more dorsal- (105 vs 97) and anal-fin (87 vs 73–80) rays and the flat inner and convex outer face of the otolith (vs convex inner face and slightly convex to flat outer face). It differs from all the three congeners in the presence of a large eye lens (57% of black eye vs 0–10%).

Description. The principal meristic and morphometric characters are shown in Table 1 . Body elongate and compressed with tapering tail; head broad and flat with a slight concavity above the eyes; head bones thin and fragile. Diameter of black eye 13% head length; the distinct, light, oval lens is 57 % the diameter of the black eye. Opercular spine thin and broadly pointed. Scales and scale pockets show a fully scaled body; 20 transversal scale rows from anal-fin origin; head with reduced squamation on occiput, preopercle and opercle. Dorsal-fin origin above anterior part of pectoral fin; anal-fin origin distinctly closer to tip of snout than to base of caudal fin; pelvic fins each with two tightly joined rays. Mouth terminal with upper jaw ending below posterior part of orbit. Anterior gill arch with four knob-like rakers on upper branch, one long raker in the angle and lower branch with nine long and four knob-like rakers; longest gill raker 3–4 times the length of the longest gill filament; two pseudobranchial filaments. After sixty-two years of preservation in alcohol the specimen is brownish grey with blue eye balls.

Axial skeleton (based on radiographs). Precaudal vertebrae 14, all with pointed neural spines. Anterior neural spine half the length of the second one. The six anterior neural spines slightly depressed. Basis of neural spines 4–14 enlarged. Parapophyses on precaudal vertebrae 8–14. Pleural ribs on precaudal vertebrae 3–14. Epineurals not observed.

Dentition.All dentigerous bones with many close-set, pointed teeth in irregular rows. Premaxillae and dentaries with teeth along their full length. Vomer boomerang-shaped. Palatines spindle-shaped. A single long and narrow basibranchial tooth patch.

Otolith ( Fig. 3G ). Large otolith of 8.2 mm in length (holotype) with slender, droplet-like shape (otolith length: height = 1.73). Ventral rim shallow; dorsal rim with broad, rounded, predorsal angle; anterior rim broadly rounded; posterior tip slightly tapering, rounded. Inner face nearly flat; outer face convex; otolith height: thickness = 1.9. Sulcus straight, shallow, narrow, with single well-defined colliculum; otolith length: sulcus length = 2.18; sulcus length: height = 4.4. Sulcus connected to the anterior-dorsal rim via collicular crest. Ventral furrow very close to ventral rim of otolith; dorsal depression small.

Distribution ( Fig. 5 ). Known from the holotype caught in a bottom working trawl at a depth 5385–5390 m off Hawaii.

Etymology. From lentibus (Latin) = lens bearing, referring to the presence of a large eye lens.

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.