Oneirodes quadrinema Ho, Kawai & Amaoka, sp. nov.

Oneirodes quadrinema Ho, Kawai & Amaoka, sp. nov.

New English name: Indonesian Dreamer

Figs. 14 A–B, 15A–B; Table 2

Holotype. HUMZ 194478 (169.0), st. 9, 8°19.1'S, 109°1.9'E – 8°18.9'S, 109°0.3'E, off Java, 814 m, 6 May 2005.

Paratypes. HUMZ 193748 (1, 130.2), st. 29, 8°31.3'S, 110°25.0'E – 8°30.8'S, 110°23.6'E, off Java, Indonesia, eastern Indian Ocean, 755–770 m, 13 May 2005. HUMZ 193893 (1, 104.6) and HUMZ 193894 (1, 69.5), st. 22, 8°18.8'S, 110°13.1'E – 8°18.2'S, 110°11.3'E, off Java, Indonesia, eastern Indian Ocean, 755–770 m, 13 May 2005.

Diagnosis. A species of Oneirodes differing from all described species in having relatively few teeth in jaws, 17–22 total teeth (8–11 on each jaw) and the following combination of escal morphology: long, internally pigmented anterior appendage, with 2–4 black-tipped branches, its total length 15.6–19.1% SL; pair of filamentous anterolateral appendages arising from either side at base of anterior escal appendage, subequal or slightly longer than anterior escal appendage; single broad-based medial appendage with four main branches, each branch with many secondary branches and filaments; short and cylindrical posterior appendage; and blunt terminal papilla with a distal spot.

Description. Morphometric and meristic data of the type series are provided in Table 2. The following data are for the holotype, followed by those of all types where differences exist, except as indicated.

Dorsal-fin rays 6 (104.6 mm paratype with 7); anal-fin rays 4; pectoral-fin rays 16/16 (16–18); caudal-fin rays 9.

Body slightly elongate, laterally compressed, profile oblong in lateral view; body depth about 1.5 in body length excluding caudal-fin; caudal peduncle narrow, 14.0% (8.5–15.0%) SL.

Head moderately large, its length 37.3% (37.3–44.0%) SL, depth 34.8% (34.8–43.7%) SL, and width 27.6% (27.6–32.4%) SL; dorsal margins of frontals convex, frontal space narrow, narrowest distance between outer margins of frontals 10.2% (10.2–17.6%) SL. Sphenotic spines well developed.

Illicium relatively short, 15.6% (14.7–18.7%) SL; posterior end of pterygiophore protruding from dorsal midline of trunk. Esca bulb small, its width 3.6% (3.6–4.9%) SL, length excluding appendages 4.7% (4.7–6.2%) SL. Eye very small. Mouth large, its cleft extending well past eye posteriorly, upper jaw length 30.7% (30.7– 34.4%) SL and lower jaw length 36.2% (36.2–45.5%) SL. Lower jaw with well developed symphysis. Quadrate spine well developed, distinctly larger than articular spine. Pectoral-fin lobe short and broad, shorter than longest ray of fin. Pectoral-fin relatively long, 19.0–22.0% SL.

Teeth slender, recurved and depressible; relatively scattered and few in number, in 1 or 2 irregular rows; teeth on upper jaw 22 (19–22; 9–11 on each side), longest teeth 3.0% (3.0–5.2%) SL; teeth on lower jaw 20 (17– 22; 8–11 on each side), longest teeth 3.7% (3.7–5.9%) SL; 3 vomerine teeth (4 in all three paratypes), 2 teeth on each side (one side of holotype with 1), outer tooth about twice size of inner one, 3.2% (3.2–6.3%) SL. Epibranchial teeth absent; second and third pharyngobranchials well toothed.

Morphology of esca almost identical in all four types, except for minor variations. Escal appendage pattern B of Pietsch (1974, fig. 60B). Escal bulb pigmented internally with black butterfly-shaped pattern on top.

Anterior appendage elongate, cylindrical and internally pigmented, its length including all branches 15.6% (15.6–19.1%) SL; terminus of holotype with 4 slender branches, arranged in one row on distal and posterior margins, branch lengths 14.1–21.7% of the total length of anterior appendage, all pigmented distally, uppermost 2 slightly stronger than other 2, lowermost branch thinnest; 3 short lateral filaments slightly below branches; terminus of 69.5 mm paratype a pair of slender distally pigmented branches and three slender filaments; those of other two paratypes comprising three similar branches, branch lengths 12.8–20.3% of the total length of anterior appendage, without filaments.

Single broad-based, highly branched medial escal appendage, its base connected to that of anterior appendage and covered on most surface of esca, with four main branches arranged in two symmetrical pairs, those inner pair slightly stronger than those in outer pair; each branch bearing as many as 6 secondary branches and filaments. Conical posterodorsally directed terminal papilla (directed dorsally in 69.5 mm paratype), with a distal pigmented spot.

Anterolaterally branched appendage arising from either side at base of anterior appendage, total length 20.8% (17.4–20.8%) SL (partly damaged in 105 mm paratype); divided into 3 branches proximally and 2–3 short filaments at undivided base in holotype; appendage of paratypes divided into two main branches slightly above base, each simple or with 1–2 secondary branches and filaments.

Short, simple, cylindrical posterior appendage (compressed in holotype which might be artificial), its length 2.4% (2.2–3.5%) SL, slightly more than half of escal length excluding appendage. Lateral appendage absent.

Large posterior pore between terminal papilla and posterior appendage.

Opercle bifurcated, upper fork in holotype bilobed, simple in paratypes; length of upper fork of opercle 11.7% (11.7–13.6%) SL; length of lower fork 25.3% (25.3–27.0%) SL; ratio of lengths of dorsal and ventral forks 0.47% (0.45–0.52%) SL.

Subopercle elongate, 13.5% (13.5–16.0%) SL, its ventral end broad and rounded, dorsal end narrow and bluntly pointed, posterodorsal margin convex, not indented.

Coloration. Uniformly deep brownish to blackish; inter-radial membranes of all fins transparent except for the bases. Distal portion and appendage of esca pale or transparent, except as indicated above.

Etymology. From the Latin quadro meaning four and the Greek nema meaning tread or appendage, the name refers to the four main branches on medial escal appendage, a diagnostic character of the species.

Distribution. Known from the type series collected in the eastern Indian Ocean off Java, Indonesia, at depths of 755– 814 m.

Discussion. Although the medial escal appendage of O. quadrinema sp. nov. can be divided into four main branches, that are somewhat arranged in two symmetrical pairs, their bases are fused and not clearly divided into two independent appendages as in most congeners. Four species were previously recognized as sharing the possession of a single unpaired medial appendage: O. macronema (Regan & Trewavas, 1932), O. clarkei Swinney & Pietsch, 1988, O. pithales Orr, 1991 and O. haplonema Stewart & Pietsch, 1998. Of these, O. quadrinema sp. nov. is most similar to O. haplonema in having a relatively long anterior appendage and a pair of anterolateral escal appendages.

The new species can be distinguished from O. haplonema in having fewer jaw teeth, 19–22 on the upper jaw (vs. 34) and 17–22 on the lower jaw (vs. 42); 6 or 7 dorsal-fin rays (vs. 5); and a different escal appendage pattern: a broad-based branched medial appendage (vs. narrow-based and unbranched); anterolateral appendage relatively long, subequal to or longer than the anterior appendage (vs. about one-third length of anterior appendage); branches on anterior appendage all black distally (vs. colorless); and a conical terminal papilla (vs. an elongate terminal papilla).

It can be distinguished from O. macronema and O. clarkei in having a much longer anterior escal appendage, considerably longer than the illicium (vs. much shorter than the escal bulb). It differs from O. macronema and O. epithales in having a pair of anterolateral appendages (vs. absent); and from O. clarkei and O. epithales in having a simple, unbranched posterior escal appendage (vs. appendage branched distally).

Oneirodes quadrinema sp. nov. is also similar to O. heternema (Regan & Trewavas, 1932), O. macrosteus Pietsch, 1974 and O. eschrichtii Lütken, 1871 in having similar escal morphological pattern. It differs from O. heteronema in having a simple posterior escal appendage (vs. appendage branched distally) and a very long anterior escal appendage (vs. appendage shorter than the esca); from O. macrosteus in having a simple posterior escal appendage (vs. appendage branched distally), a relatively long medial and anterolateral appendages (vs. appendages short); and from O. eschrichtii in having a remarkably long anterior escal appendage (vs. appendage shorter than the esca) and presence of anterolateral appendages (vs. appendages absent).

It may be also similar to a recent described species, Oneirodes sipharum Prokofiev, 2014, in the form of the escal pattern. The new species differs from O. sipharum mainly in having anterolateral appendages (vs. absent) and a less-branched and internal-pigmented anterior appendage (vs. highly branched appendage without pigmentation). Although O. sipharum also has few jaw teeth (20 on the upper jaw and 13 on the lower jaw), the sole holotype is a very small juvenile (14 mm SL) whereas the types of Oneirodes quadrinema sp. nov. are well-developed adults. Thus, this character is not comparable between these two species. It is notable that Oneriodes species exhibit strong ontogenetic changes and/or intraspecific variation in escal morphology (Pietsch, 1974). Hence, describing new species based on juvenile specimens may be inadequate and is not recommended.

All types of Oneirodes quadrinema sp. nov. have nearly identical escal appendage morphology and similar numbers of jaw teeth. However, some proportional measurements, such as head length, head depth, lower jaw length, size of escal bulb and length of jaw teeth have clear negative trend with growth, whereas other proportions do not seem to change with growth (Table 2).