Opistognathus ocellicaudatus, Shinohara, 2021

Shinohara, Gento, 2021, A new jawfish of the genus Opistognathus (Perciformes: Opistognathidae) from Japan, Zootaxa 4964 (1), pp. 157-168 : 158-165

publication ID	https://doi.org/ 10.11646/zootaxa.4964.1.8
publication LSID	lsid:zoobank.org:pub:E520C67B-5A3F-4625-8737-0A2CD3AD1BC1
DOI	https://doi.org/10.5281/zenodo.4741136
persistent identifier	https://treatment.plazi.org/id/00DCADDA-BE92-4C33-B7EB-1DA8348BA02A
taxon LSID	lsid:zoobank.org:act:00DCADDA-BE92-4C33-B7EB-1DA8348BA02A
treatment provided by	Plazi
scientific name	Opistognathus ocellicaudatus
status	sp. nov.

Treatment

Opistognathus ocellicaudatus sp. nov.

New Japanese name: Misaki-agoamadai

New English name: Eyespottail Jawfish

( Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 ; Table 1 View TABLE 1 )

Holotype. NSMT-P 125494 , female, 69.4 mm SL, Sagami Bay off Misaki, Kanagawa, Japan (35°08.824'N, 139°35.213'E), 67 m depth, 21 July 2017, coll. M. Kawabata, hook and line. GoogleMaps

Diagnosis. A species of Opistognathus with the following characters: dorsal fin XI, 11; anal fin II, 11; pectoral fin 21; vertebrae 10 + 16 = 26; oblique scales on body 42; supraneurals 2; 3 longitudinal dark brown stripes on body; a large dark whitish-rimmed ocellus on caudal fin; a small black blotch on opercular flap.

Description. Dorsal fin XI, 11; anal fin II, 11; pectoral fin 21; pelvic fin I, 5; caudal fin upper procurrent rays 3, segmented rays 8 + 8 (12 middle rays branched), lower procurrent rays 3; branchiostegal rays 6; vertebrae 10 (abdominal) + 16 (caudal) = 26; gill rakers 11 (upper) + 20 (lower) = 31.

Proportional measurements (% SL): predorsal length 33.6; preanal length 60.5; body depth 24.9; caudal-fin length 25.5; caudal-peduncle length 12.8; caudal-peduncle depth 13.3; head length (HL) 33.3; snout length 6.1; orbit diameter 11.1; eye diameter 9.5; interorbital width 2.5; upper-jaw length 18.3; pectoral-fin length 16.4; pelvic-fin length 16.4. Proportional measurements (% HL): snout length 18.2; orbit diameter 33.3; eye diameter 28.6; interorbital width 7.4; upper-jaw length 55.0.

Body somewhat elongate, compressed posteriorly. Head large, dorsal profile rounded in lateral view. Eyes large, oval, positioned close to dorsal profile of head. Snout short. Mouth large, slightly inferior; upper-jaw length greater than 50% HL. Maxilla extending beyond posterior margin of orbit. End of maxilla truncate.

First to 4th dorsal-fin spines shorter than other dorsal-fin spines; 9–11th spines with a small flap on tips ( Fig. 1 View FIGURE 1 ). Anal-fin origin below 1st dorsal-fin soft ray. First anal-fin spine very short, about 60% height of 2nd anal-fin spine; anal-fin soft rays gradually increasing in height to penultimate soft ray. Segmented rays of dorsal and anal fins branched distally. Pectoral fin rounded, all rays except uppermost ray branched. Pelvic fin slender, located just below pectoral-fin origin, not reaching anus when depressed; spine robust, outer 2 segmented rays unbranched. Caudal fin rounded posteriorly.

Scales absent on head and nape. Body covered by cycloid scales, except predorsal area, thorax, pectoral-fin base, and area above lateral line; longitudinal scale rows 42. Lateral line originating from upper margin of opercle, running high on body through dorsum near dorsal-fin base, reaching level with interspace between 2nd and 3rd dorsal-fin soft-ray bases. Lateral-line pores sparse ( Fig. 2 View FIGURE 2 ), in a single row terminating at 2nd (left side) or 3rd (right) dorsal-fin soft-ray base. Cephalic sensory pores relatively sparse on head, superficial neuromasts scattered on dorsal portion ( Fig. 2 View FIGURE 2 ).

Jaws with conical teeth, those on outer edge near anterior tip of both jaws enlarged ( Fig 3a View FIGURE 3 ). No teeth on vomer or palatine. Anterior naris forming a small tube, closer to posterior naris than dorsal margin of upper lip. Posterior naris crescentic, along anterior margin of eye. Gill rakers long, slender ( Fig 3b View FIGURE 3 ).

Osteology. Infraorbitals 5, including dermosphenotic ( Fig. 3c View FIGURE 3 ), 1st longest, 3rd without suborbital shelf; dermosphenotic (= 5th infraorbital in Fig. 3c View FIGURE 3 ) firmly attached to sphenotic. Nasal tube-like without spine. Premaxilla with conical teeth on anterior 4/5 of ventral surface. Maxilla long, without flexible posterior portion (sensu Smith-Vaniz, 2010: fig. 3). Supramaxilla small, on upper end of maxilla ( Fig. 4b View FIGURE 4 ). Dentary with conical teeth on anterior half of dorsal surface; 3 large ventral openings associated with mandibular sensory canal. Anguloarticular large, its anterior projection fitting into dentary notch. Retroarticular on ventroposterior corner of anguloarticular. Lateral ethmoid with 2 articular facets ventrally, connected with 1st infraorbital and palatine, respectively. Frontal bearing 2 large dorsal openings for sensory canal and 1 larger opening on suture line. Left and right parietals separated by supraoccipital. Supraoccipital crest small. Pterotic with a bony arch for cephalic sensory system. Posttemporals 2, lower element large, L-shaped. Basisphenoid crescentic. Hyomandibular broadly attached to sphenotic and pterotic. Metapterygoid as large as quadrate. Symplectic long. Entopterygoid forming a large shelf supporting eyeball. Ectopterygoid long, slender. Palatine with a robust head anteriorly. Opercle with 2 strong and 1 weak ridge. Preopercle without remarkable spines posteriorly, with 6 large openings for mandibular sensory canal. Interopercle small, pointed posteriorly. Pharyngobranchials 4 ( Fig. 3d View FIGURE 3 ), 1st rod-like, 2nd fan-like, 3rd largest (with conical teeth), 4th second largest. Ceratobranchials 5, rod-like, except 5th weakly flattened with a conical tooth plate ( Fig. 3d View FIGURE 3 ). Hypohyals 2, rod-like, connected to ceratohyal. Ceratohyal largest element in hyoid arch, connected with epihyal by interdigitation dorsally and cartilage ventrally. Epihyal second largest element. Interhyal rod-like, larger than hypohyal. Branchiostegal rays 6, long, recurved, 4 rays attached to ceratohyal, 2 to epihyal. Posttemporal forked, dorsal limb attached to epiotic, ventral limb to intercalar. Supracleithrum leaf-like. Cleithrum with a large dorsal blade, receiving supracleithrum. Postcleithra 2, upper rectangular, lower long, narrow. Scapula rectangular, a scapular foramen anteriorly. Coracoid large, with a ventral arm. Actinosts 4, uppermost smallest, lowermost largest. Supraneurals 2, tiny, 1st above 1st neural spine, 2nd just before 2nd neural spine ( Fig. 4b View FIGURE 4 ). First dorsal proximal pterygiophore inserted between 2nd and 3rd neural spines, 2nd and 3rd pterygiophores between 3rd and 4th neural spines, subsequent pterygiophores inserted singly between succeeding neural spines. First anal-fin pterygiophore before 1st haemal spine. Epurals 3, 3rd supporting 3 procurrent rays. Hypurals (except 5th) and parhypural fused to urostyle. Neural spine reduced. Haemal spine developed on preural centrum.

Color when fresh. Head brown dorsally, pale laterally and ventrally. Lower margin of upper lip and lateral surface of lower lip brown. Body pale with 3 longitudinal dark brown lateral stripes. A small black blotch on opercular flap. A blackish basal blotch between 3rd and 7th dorsal-fin spines. A brown basal blotch on 1st–6th dorsal-fin soft rays and a blackish blotch on 6th–11th (= last) soft rays. Outer margin of spinous dorsal-fin membrane whitish. A zigzag white line on side of dorsal-fin membrane, originating from 7th-spine base to last soft ray. Proximal half of anal-fin membrane white with a blackish blotch on 9th–11th (= last) soft rays. Distal half to 1/3 of fin membrane of dorsal- and anal-fin soft-rayed parts yellow. Pectoral fin light yellow. Pelvic fin yellow. Caudal peduncle with a vertical dark brown band. Caudal fin yellow with a vertical white band anteriorly, continuous with a large dark white-rimmed ocellus.

Color in alcohol. Similar to above, except yellowish areas (pectoral and pelvic fins, and parts of dorsal, anal, and caudal fins) becoming translucent.

Remarks. Opistognathus ocellicaudatus sp. nov. is easily distinguished from all valid species in the genus in having 3 longitudinal dark brown stripes on the body (1 in O. alleni and O. dipharus , 2 in O. hopkinsi , and 4 in O. decorus ; Table 1 View TABLE 1 ). Although the new species otherwise resembles O. hongkongiensis and O. pardus in having dorsal-fin rays XI, 11; anal fin rays II, 11; and vertebrae 10 + 16 ( Chan, 1966; Smith-Vaniz et al., 2012; Smith-Vaniz, pers. comm.), it differs from O. hongkongiensis in having 42 oblique body scale rows (vs. 51) and from O. pardus in having 2 supraneurals (vs. 1), in addition to the number of pectoral-fin rays (21 vs. 19 in O. hongkongiensis , 22–23 in O. pardus ). Opistognathus ocellicaudatus is further distinguished from both species in having pale cheek and opercular regions (vs. dark vertical band in O. hongkongiensis, Tashiro, 2017 : unnumbered fig.; small, irregularly shaped dark spots in O. pardus, Smith-Vaniz et al., 2012 : figs. 1–2). Although the new species is similar to O. decorus in having anal-fin rays II, 11 and pectoral-fin rays 21, it differs in the number of oblique scale rows (42 vs. 54–67) and head coloration (black blotch on opercular flap vs. many prominent dark blotches on head).

The new species is clearly distinguishable from all Indo-West Pacific species (except O. rosenbergii ) by the large dark whitish-rimmed ocellus on the caudal fin and black blotch on the opercular flap. It differs from O. rosenbergii in having a better defined ocellus and black spot, in addition to yellowish vertical fins and pelvic fin (vs. poorly defined ocellus, smaller black spot, and black vertical fins and pelvic fin; Satapoomin, 2009: unnumbered fig.; Biswas et al., 2013: fig.3).

Distribution. Known only from Sagami Bay off Misaki, Miura Peninsula (near mouth of Tokyo Bay), from 67 m depth.

Etymology. From Latin ocellus (eye) and caudatus (tail), in reference to the prominent ocellus on the caudal fin.

Biological notes. The holotype of Opistognathus ocellicaudatus sp. nov. contained mature ovarian eggs of ca. 0.9 mm longitudinal width, each bearing a single oil globule ( Fig. 5 View FIGURE 5 ). Fine adhesive threads aided in forming loose clumps of eggs. The level of egg maturity suggested that the new species may be a summer spawner in Sagami Bay.

The type locality of Opistognathus ocellicaudatus sp. nov. is close to the northern limit of distribution of Opistognathidae in the Indo-West Pacific, all species having been recorded from south of Tokyo Bay ( Aizawa & Doiuchi, 2013). Because the Japanese coastline near the mouth of Tokyo Bay is influenced by the warm Kuroshio Current, before the latter changes course to an easterly direction away from Japan, the new species is likely to be distributed south of Tokyo Bay in warm waters, rather than in more northern waters influenced by the cold Oyashio Current.