Oneirodes amaokai Ho & Kawai

Ho, Hsuan-Ching, Kawai, Toshio & Amaoka, Kunio, 2016, Records of deep-sea anglerfishes (Lophiiformes: Ceratioidei) from Indonesia, with descriptions of three new species, Zootaxa 4121 (3), pp. 267-294 : 287-289

Oneirodes amaokai Ho & Kawai , sp. nov.

New English name: Amaoka's dreamer Figs. 16 , 17 A–B; Table 2

Holotype. HUMZ 191135 (1, 61.8), st. 32, 3°42.15'N, 94°44.55'E – 3°43.31'N, 94°44.33'E, off Sumatra, Indonesia, 833–896 m, 21 Oct. 2004.

Diagnosis. A species of Oneirodes with relatively long illicium (56.5% SL), 12–13 pectoral-fin rays and unique escal morphology: anterior appendage complete absent; pair of filamentous anterolateral appendages; single medial appendages with 3 main filamentous branches; slender filamentous posterior appendage, branched distally; no lateral appendage.

Description. Morphometric and meristic data are provided in Table 2 . Dorsal-fin rays 6; pectoral-fin rays 12 (right side)/13 (left side); anal-fin rays 4; caudal-fin rays 9.

Body slightly elongate, laterally compressed, body depth about half of body length, excluding caudal-fin; caudal peduncle narrow, its depth 12.6% SL. Head moderately large, its length 42.6% SL, depth 41.6% SL and width 28.2% SL; dorsal margins of frontals convex, frontal space narrow, narrowest distance between outer margins of frontals 10.4% SL. Sphenotic spines well developed.

Illicium relatively long compared to most congeners, 56.3% SL. Esca bulb small, its width 2.9% SL, its length excluding appendages 3.7% SL. Eye very small. Mouth large, its cleft extending well pass eye, upper jaw length 34.0% SL and lower jaw length 41.9% SL. Lower jaw with well developed symphysis. Quadrate and articular spines well developed, former twice as long as latter. Pectoral-fin lobe short and broad, shorter than longest ray of fin.

Teeth slender, recurved and depressible; teeth on upper jaw 40 (20 on each side), longest teeth 3.9% SL; teeth on lower jaw 44 (22 on each side), longest teeth 4.5% SL; vomerine teeth 6 (3 on each side), outermost tooth largest, 2.1% SL. Epibranchial teeth absent; second and third pharyngobranchials well toothed.

Escal appendage pattern uncertain, but likely pattern B of Pietsch (1974:34, fig. 60B): anterior appendage absent; pair of filamentous anterolateral appendages, each bifurcated distally; single medial appendages with 3 filamentous branches, its medial branch slightly stronger than other two, with 4 secondary branches and its side branches bifurcated; terminal papilla conical, with distal black spot; large posterior pore posteriorly at base of terminal papilla; and single slender filamentous posterior appendage, with 2 secondary filaments distally.

Opercle bifurcated, axes of forks forming narrow angle, about 15°; upper fork of opercle simple and relatively short, 10.7% SL; lower fork 26.7% SL; ratio of lengths of dorsal to ventral forks 0.40. Subopercle relatively short 9.5% SL, its ventral end rounded, dorsal end narrow and bluntly pointed, posterodorsal margin convex, not indented.

Coloration. Uniformly blackish; inter-radial membranes transparent; appendages on esca colorless.

Etymology. Named in honor of Dr. Kunio Amaoka, Professor Emeritus of Hokkaido University, for his numerous contributions to ichthyology.

Distribution. Known only from the holotype collected in eastern Indian Ocean off Sumatra, Indonesia, at depths of 833– 896 m.

Discussion. Ho & Shao (2004) described Oneirodes pietschi , the first species lacking an anterior escal appendage. Later, Ho et al. (2008) recorded the species from Indian Ocean. Prokofiev (2014) described a second species with this characteristic, Oneirodes parapietschi based on a single specimen collected in the eastern Pacific Ocean.

Oneirodes amaokai sp. nov. is the third species among the congeners that lacks anterior appendage on the esca. It differs from O. pietschi in having 12–13 pectoral-fin rays (vs. 14–16 in O. pietschi ); a slightly longer illicium, 56.3% SL (vs. 37–49% SL); a pair of filamentous anterolateral escal appendages with distal branches (vs. appendages simple, never branched); a single filamentous medial appendage with three main branches that are considerably longer than the escal bulb length (vs. a pair of branched medial appendages, both shorter than the escal bulb length); a slender filamentous posterior appendage that is considerable longer than escal bulb length (vs. a compressed, terminally expanded posterior appendage, about equal to the esca); and a smaller ratio of length of upper and lower forks of opercle (0.40 vs. 0.45–0.57), reflected by the relatively short upper fork of opercle.

The new species differs from O. parapietschi in having a longer illicium, 56.3% SL (vs. 44.4% SL); anterolateral appendages branched distally (vs. simple); a single filamentous medial appendage with three main branches, all considerably longer than the escal bulb length (vs. a pair of branched medial appendages, both shorter than the escal bulb length); and a slender filamentous posterior appendage, considerable longer than the esca (vs. a compressed, terminally expanded posterior appendage, about equal to the esca).

Although only described on the basis of the sole holotype, the species can be clearly distinguished from its two closely similar congeners and requires a new name.

Figures

FIGURE 16. Oneirodes amaokai Ho & Kawai, sp. nov., HUMZ 191135, holotype, 61.8 mm SL, fresh.

FIGURE 17. Oneirodes amaokai Ho & Kawai, sp. nov. A. drawing of esca. B. opercle and subopercle. Both from the holotype. See Fig. 15 for abbreviations.