Opistognathus cryos, Su & Ho, 2024

Su, Yo & Ho, Hsuan-Ching, 2024, A new species of the jawfish genus Opistognathus from Taiwan, northwestern Pacific Ocean (Perciformes, Opistognathidae), ZooKeys 1220, pp. 165-174 : 165-174

Opistognathus cryos sp. nov.

Figs 1 , 2 , 3 , Tables 1 , 2 New English name: Frozen jawfish New Chinese name: 冷鋒後頷鱚

Opistognathus sp. 1: Smith-Vaniz 2023: 72, fig. 103.

Type locality.

Taiwan, Peng-hu Islands, Chih-kan beach , ca 23°40'12"N, 119°36'10"E, 25 February 2022, H.-C. Ho leg.

Type specimen.

Holotype: NMMB-P 36179 , 65.1 mm SL.

Diagnosis.

A species of Opistognathus differing from its congeners in having the following combination of characters: upper jaw rigid, without a distinct flexible lamina posteriorly; dorsal-fin rays XI, 11; anal-fin rays II, 10; gill rakers 10–11 + 1 + 19–22 = 31–33; scale rows in lateral series 55; vertebral formula 10 + 16 = 26; dorsal-fin interdigitation pattern S / S / 1 / 1 + 1 / 1 /; lateral-line ends at base of fourth segmented dorsal-fin ray (15 th in total rays); head, nape, dorsal-fin base above lateral line, throat, chest, and pectoral-fin base scaleless; upper two preopercular and fifth mandibular pores bipored; vomer edentate; head mottled with small, dark blotches; dorsal fin with eight blotches along its base; distal portion of membrane between dorsal-fin spines white; body with five horizontal, dark stripes; nape with two dark blotches in front of dorsal-fin origin; and caudal fin with five narrow, dark bands.

Description.

Meristic and morphometric data are provided in Tables 1 , 2 . Paired characters are presented as left / right whenever available.

Dorsal-fin rays XI, 11. Anal-fin rays II, 10. Pectoral-fin rays 19 / 19. Pelvic-fin rays I, 5 / I, 5. Principal caudal-fin rays 8 + 8, with innermost 6 + 6 rays branched; procurrent caudal-fin rays 4 on both upper and lower lobes. Gill rakers 11 + 1 + 19 = 31 / 10 + 1 + 22 = 33. Scale rows in lateral series 55 / 55. Vertebrae 10 + 16 = 26. Dorsal-fin interdigitation pattern S / S / 1 / 1 + 1 / 1 /; anal-fin interdigitation pattern / 1 / 1 / 1 / 1 / 1 /.

Body slender, depth at anal-fin origin 4.2 in SL; both dorsal and ventral profiles of body flat. Head large, length 2.5 in SL; anterior profile of head rounded, gently curved to dorsal-fin origin. Eyes large, eye diameter 3.0 in HL. Two nostrils, anterior one a short tube with small flap; posterior one without flap, situated immediately in front of eye. Preoprecle and opercle covered by skin, their posterior margins without spines; single, small flap present on upper end of opercle.

Mouth lower in position, slightly oblique, forming ca 10 ° angle with body axis. Jaws terminal, with lower jaw slightly included. Upper-jaw length 1.5 in HL, its end exceeding 0.8 in eye diameter behind posterior margin of orbit; posterior margin of maxilla truncated, without distinct flexible lamina; its anterior margin without crenulae. Supramaxilla present, greatest width about one-third of maxilla. Premaxilla with two or three rows of small canine teeth anteriorly; posterior portion forming single row of conical teeth, their size decreasing posteriorly. Dentary with small canine teeth forming two or three rows anteriorly and single row posteriorly. Vomer and palatine without teeth.

Body scales cycloid. Scales absent on head, nape, dorsal-fin base above lateral line, throat, chest, and pectoral-fin base (Fig. 2 ). Lateral-line terminus below 4 th / 4 th or 15 th / 15 th in soft ray or total elements of dorsal fin, respectively; lateral-line pores arranged in irregular series along embedded lateral-line canals. Cephalic sensory pores rather sparsely scattered (Fig. 2 ); upper-two preopercular pores bipored, others simple; fifth mandibular pore bipored, others simple.

Dorsal fin with long base, originated at vertical through upper end of gill slit; its distal nearly straight, with slight elevation on soft rays; no distinct notch between spines and soft rays. Pectoral-fin tip pointed; its origin at same horizontal through lower margin of eye; its tip reaching near vertical through anal-fin origin. Pelvic fin elongated, its origin below second dorsal-fin spine and in advance of pectoral fin; its tip reaching anal-fin origin when adpressed; outermost segmented ray not bounded to adjacent ray, with incision on interradial membrane. Anal-fin base moderately long, its posterior end slightly anterior to that of dorsal fin; its origin below first and second dorsal-fin soft rays (between 12 th and 13 th total dorsal-fin rays); fin rays gradually longer posteriorly; its distal margin nearly straight. Caudal fin rounded, slightly pointed; its length 1.4 in HL. Caudal peduncle broad, depth 2.8 in HL.

Coloration.

When preserved (Fig. 1 A, B ), body pale, with one horizontal dark line near dorsal-fin base, and four rows of thinner dark lines on lateral side of body above anal-fin base. Head pale, scattered with irregularly sized dark blotches on operculum, upper and lower jaws, and infraorbital; their sizes smaller than pupil. Nape with two dark blotches in front of dorsal-fin origin (Fig. 1 C ). Dorsal fin dusky, with eight dark blotches along its base, slightly extending onto dorsum; distal end of fin spines white; soft rays with two horizontal, dark stripes. Caudal fin dusky, with five narrow, dark bands. Anal, pectoral, and pelvic fins dusky. Oral cavity, including underside of tongue pale.

Osteology.

Pleural ribs present on fourth to tenth vertebra; epineurals present and epipleurals absent. Caudal skeleton consists of four plates, including three hypurals and one parhypural; hypural 1 and 2 fused; hypural 3 and 4 fused; hypural 5 present (Fig. 3 ).

Etymology.

The specific name cryos , is from the Greek “ κρύος ” meaning cold or chilled, indicating that the holotype was collected during a cold snap in 2022. The common name “ frozen jawfish ” is also a reference to the fantasy film “ Frozen ” produced by Walt Disney Animation Studios.

Distribution.

The holotype was collected ashore from the northern portion of the Peng-hu Islands, western Pacific Ocean. Another possible record from Japan ( Smith-Vaniz 2023) may suggest a wide distribution in the northwestern Pacific Ocean.

Figures

Figure 1. Preserved specimen of Opistognathus cryos sp. nov., holotype, NMMB-P 36179, 65.1 mm SL A on black background B on white background C dorsal view of nape. Photos by Y. - C. Hsu.

Figure 2. Head pores and adjacent area of Opistognathus cryos sp. nov., holotype, NMMB-P 36179, 65.1 mm SL, with scaled area shaded in gray A dorsal view B lateral view. Abbreviations: AN = anterior nostril; PN = posterior nostril. Dotted lines indicate dorsal- and pectoral-fin bases. Anterior to left. Figure not to scale.

Figure 3. X-radiograph of Opistognathus cryos sp. nov., holotype, NMMB-P 36179, 65.1 mm SL.