Johnius javaensis, Lin & Pogonoski & Fahmi & Wibowo & Chao & Seymour, 2025

Lin, Bai-an, Pogonoski, John J., Fahmi,, Wibowo, Kunto, Chao, Ning Labbish & Seymour, Mathew, 2025, Johnius javaensis, a new species of croaker (Acanthuriformes, Sciaenidae) from the southern coast of Java, Indonesia, ZooKeys 1259, pp. 169-183 : 169-183

Johnius javaensis sp. nov. Lin, Pogonoski, Fahmi, Wibowo, Chao & Seymour, 2025

Figs 2 , 3 , 4 , 5 , 6 , 7 , Table 2 New English common name: Java croaker New Indonesian name: Gulamah Jawa

Johnius heterolepis (text, in part; figure incorrectly duplicated from Nibea soldado ): White et al. (2013: 236) ( Indonesia).

Type material.

Holotype. • MZB 28379 , 121 mm SL, female, Cilacap , Central Java, Indonesia, 19 October 2008 . Paratypes. • CSIRO H 7697-11 , 115 mm SL, male, collected with holotype ; • CSIRO H 8376-12 , 112 mm SL, Cilacap , Central Java, Indonesia ( 23 March 2010) ; • CSIRO H 9285-33 , 114 mm SL, Cilacap , Central Java, Indonesia ( 01 July 2004) ; • MZB 28380 , 87 mm SL, Palabuhanratu , West Java, Indonesia ( 19 March 2010) .

Diagnosis.

A new species of Johnius characterized by five vesicular mental barbels on the chin, 11 or 12 swim-bladder appendages, and the ventral margin of the sagitta head expanded into a distinct convexity.

Description.

Dorsal fin X + I, 32 (X + I, 30–32); anal fin II, 7; pectoral fin rays 18 (17–18); caudal fin rays 17; pored lateral line scales 48 (46–48); scale rows above lateral line 5 (4–5), below 8 (7–8); outer gill rakers of 1 st arch 6 + 1 + 12 = 19 (5–6 + 1 + 11–12 = 17–19); vertebrae 11 + 14, last well-developed pleural rib on 10 th vertebra, first anal proximal radial between 11 th – 12 th vertebrae; swim-bladder appendages 11–12. Proportions as % of SL: head length 28.4 (25.9–27.2); eye diameter 5.4 (5.8–6.1); body depth 31.7 (27.1–29.2); body width 18.4 (14.5–16.7). Proportions as % of HL: eye diameter 18.9 (22.2–22.6); snout length 27.0 (24.4–25.5); interorbital width 26.2 (25.2–27.6); post-orbital length 58.1 (53.1–57.1); maxillary length 35.5 (34.2–35.9); second anal spine length 30.8 (34.5–40.1).

Body moderately deep, dorsal profile evenly arched, ventral profile rather flat; head conical, 25.9–28.4 % of SL. Snout bluntly rounded, projecting in front of upper jaw; three upper and three marginal snout pores; underside of lower jaw with five mental pores, median mental pore with two small openings inside, very closely positioned. Five vesicular mental barbels at chin, with anterior pair of mental barbels on both sides of anterior point of inner mental pore, one middle mental barbel at the posterior end of median mental pore, and posterior pair of mental barbels at the posterior end of outer mental pore. Mouth inferior with upper jaw longer than lower jaw, upper jaw extending posteriorly to below middle of eye or hind margin of pupil. Upper jaw with a single, outer row of teeth slightly enlarged, and an inner band of small, conical teeth. Lower jaw with broad band of uniformly small, conical teeth. Eye circular, eye diameter small in holotype (18.9 % of HL) and moderately large in paratypes (22.2–22.6 % of HL). Eye diameter smaller than interorbital width. Anterior and posterior nostrils circular and somewhat ovate, respectively, just anterior to eye; posterior nostril twice the size of the anterior. Gill rakers short and stiff, its length approximately 31.4–46.2 % of gill filament length at angle of the gill arch. Scales large, cycloid on head (except operculum), throat, membrane of dorsal, anal and caudal fins; body scales ctenoid, ctenii well developed. Opercular scales a mix of cycloid and ctenoid. Third or fourth dorsal spine longest. First soft ray of pelvic fin with short filament. Second anal-fin spine stiff, its length 59.6–74.9 % of first anal-fin ray and 30.8-40.1 % of head length. Caudal fin rhomboid. Sagitta thick and triangular; ostium of sulcus in head with long axis lying obliquely to sagitta; cauda expanded and deepened as hollow cone; outer surface with crest-like elevations; ventral margin of sagitta head expanded to a distinct convexity. Swimbladder hammer-shaped, with 11 or 12 pairs of arborescent diverticula attached to anterior and lateral sides of main chamber, becoming tubular posteriorly. First anterior pair of diverticulae pierces through septum transversum, reaching to the base of cranium (basioccipital and exoccipital bones). Drumming muscles restricted to male (absent in female) and positioned on the lateral body cavity wall.

Coloration (based on color photographs of paratypes when fresh).

Body greyish dorsally; upper two-thirds of body darker, separated from whitish to greyish belly by a distinct line. Line darkish to greyish, with darkish dots from base of pectoral fins to base of caudal fin and essentially parallel to pectoral fin. Dorsal fin dusky, with small dots; pectoral-fin darkish to greyish, with one black dot on upper end of axil; pelvic fins yellowish, with sparse, small darkish dots; anal fin yellowish, with dense, small darkish dots; caudal fins darkish. Color in preservative (all type material): head, body and fins brownish tan; first dorsal and anal fins with dense, small darkish dots.

Geographical distribution.

All specimens of the new species were collected from the west and central coast of southern Java, Indonesia.

Etymology.

The specific name ‘‘ javaensis ’’ is proposed, as all collected specimens were from the west and central of southern Java.

Comparisons.

The new species belongs to the subgenus Johnius ( Johnius) , which exhibits uniformly-sized lower jaw teeth or the inner rows of lower jaw teeth molariform. The Southeast Asia region, including Java, harbors three species that possess mental barbels, J. javaensis sp. nov., J. macropterus , and J. amblycephalus . The new species can be readily separated from J. macropterus and J. amblycephalus in having five vesicular mental barbels on the chin, while the other two species only have one mental barbel (Fig. 8 ; Table 3 ). Additionally, the new species can also be readily distinguished from similar congeners without barbels in the region (Table 3 ). Johnius javaensis sp. nov. can be distinguished from J. heterolepis in having more dorsal-fin rays (30–32 vs 25–28) and fewer swim-bladder appendages (11-12 vs 14). The new species can be separated from J. hypostoma in having fewer scale rows below the lateral line (7 or 8 vs 9 or 10), more swim-bladder appendages (11 or 12 vs 9–10), and a smaller interorbital width (25.2–27.6 % vs 28.0–34.0 % of head length). Furthermore, Johnius javaensis sp. nov. can be differentiated from J. laevis Sasaki & Kailola, 1991 in having body scales with well-developed ctenii. The new species can be distinguished from J. macrorhynus (Lal Mohan, 1976) in having fewer scale rows below the lateral line (7 or 8 vs 10–14), more lower gill rakers (11 or 12 vs 5–8), and fewer swim-bladder appendages (11 or 12 vs 13–16) (Table 3 ).

Phylogeny of Johnius javaensis sp. nov.

Based on the ML tree analysis, the Johnius species with mental barbels are non-monophyletic and merit further investigation. Johnius javaensis sp. nov. is sister to J. macropterus with high bootstrap values (Fig. 9). The intraspecific K 2 P distance in the 521 - bp COI gene sequences for the new species are 1.83 % (0.77-2.56 %) (Table 4 ). The K 2 P distance between J. javaensis sp. nov. and J. macropterus is 8.18 % (7.76-8.84 %), which is lower than the distance between J. javaensis sp. nov. and the other 19 Johnius species in this study, averaging 19.01 % (12.68 % - 30.53 %), giving high confidence in species relationships (Table 4 ). Our analysis reveals substantial interspecific divergences among the 21 Johnius species, with an average K 2 P distance of 18.78 % ± 5.79 % (range: 1.96 % – 32.24 %). Notably, the exceptionally low genetic distance (<2 %) between J. taiwanensis Chao, Chang, Chen, Guo, Lin, Liou, Shen & Liu, 2019 and Johnius sasakii Hanafi, Chen, Seah, Chang, Liu & Chao, 2022 suggests potential taxonomic ambiguity and warrants further investigation (Table 4 ).

Remarks.

Johnius javaensis sp. nov. is a small sciaenid; the holotype (121.0 mm SL) is mature, with fully developed gonads. The specimens were collected from coastal fish markets, but the specific habitat preferences of this species are unknown.

Figures

Figure 2. Holotype of Johnius javaensis sp. nov., MZB 28379, 121 mm SL, Cilacap, Central Java, Indonesia. A. Preserved specimen; B. Digital radiograph of preserved specimen.

Figure 3. Five vesicular mental barbels of Johnius javaensis sp. nov. at chin. A, D, B, E. Lateral views; C, F. Ventral views; A – C. MZB 28379, holotype, 121 mm SL; D – F. CSIRO H 8376-12, paratype, 112 mm SL. (I) anterior pair of mental barbels, (II) middle mental barbel, (III) posterior pair of mental barbels. Not to scale.

Figure 4. First gill arch on right side of Johnius javaensis sp. nov., CSIRO H 8376-12, paratype, 112 mm SL.

Figure 5. Swimbladder (ventral view) of Johnius javaensis sp. nov., CSIRO H 8376-12, paratype, 112 mm SL.

Figure 6. Right side of sagitta of Johnius javaensis sp. nov. A. Medial view; B. Lateral view, CSIRO H 8376-12, paratype, 112 mm SL.

Figure 7. Fresh specimen of Johnius javaensis sp. nov. CSIRO H 7697-11, paratype, 115 mm SL, male, Cilacap, Central Java, Indonesia.

Figure 8. Comparison of the single short mental barbel in Johnius macropterus and J. amblycephalus. A – C. J. macropterus, CSIRO H 7370-09, 85 mm SL; D – E. J. amblycephalus, CSIRO H 7245-05, 182 mm SL; A, B, D, E. Lateral views; C, F. Ventral views. Scale bars: 1 cm (A, D); others not to scale.