Johnius sasakii, Hanafi & Chen & Seah & Chang & Liu & Chao, 2022

Hanafi, Norhafiz, Chen, Meng-Hsien, Seah, Ying Giat, Chang, Chih-Wei, Liu, Shang Yin Vanson & Chao, Ning Labbish, 2022, Johnius sasakii, a new species of croaker (Perciformes: Sciaenidae) with a key to Johnius from East Malaysia, Borneo, Zootaxa 5116 (3), pp. 393-409 : 397-405

Johnius sasakii sp. nov.

( Fig. 2 , Table 2–4 )

Holotype. NMMB-P 34733 , 1 [111 mm SL], fish landing port at Bako, Sarawak collected by Norhafiz Hanafi on 17 March 2017.

Paratypes. NMMB-P 34734 , 1 (110 mm SL), fish landing port at Betangor , Sarawak, Malaysia, collected by Norhafiz Hanafi, 14 March 2017 . NMMB-P 34735 , 3 (103–108 mm SL), fish landing port at Sandakan , Sabah, Malaysia, collected by Norhafiz Hanafi, 27 February 2017 . NMMB-P 34736 , 1 (134 mm SL), fish landing port at Bintulu , Sarawak, Malaysia, collected by Norhafiz Hanafi, 9 March 2017 . NMMB-P 34737 , 5 (122–147 mm SL), fish landing port at Bintulu , Sarawak, Malaysia, collected by Norhafiz Hanafi, 11 March 2017 . NMMB-P 34738 , 4 (105–118 mm SL), fish landing port at Miri , Sarawak, Malaysia, collected by Norhafiz Hanafi, 7 March 2017 . NMMB-P 34739 , 3 (100–146 mm SL), fish landing port at Kota Kinabalu , Sabah, Malaysia, collected by Norhafiz Hanafi, 4 March 2017 .

Diagnosis. A species of Johnius distinguished by the following combination of characters: number of total outer gill rakers on first arch, 4–6 (mode 5) + 8–10 (mode 9) = 13–15; second anal-fin spine short and stiff, 7–10% of SL (usually 8–10%); body moderately deep, 25–29% of SL (usually 26–28%); first anal-fin ray length, 9–13% of SL (usually 10–12%); anal-fin base length short, 7–10% of SL (mode 9%); pre-anal length, 67–74% of SL (usually 70–71%); scale rows above lateral line, 4–6 (mode 5); body scales moderately large and ctenoid; snout bluntly rounded.

Description. Counts and measurements of the type specimens are shown in Table 2 and 3 . The following data is provided for the holotype first, followed by the size range and mean for the 17 paratypes.

Body moderately deep, 27% of SL, dorsal and ventral profiles evenly arched. Snout bluntly rounded, about 23% of HL, slightly projecting in front of upper jaw. Three upper and three marginal snout pores. Three pairs of mental pores, anterior pair with two small openings, very closely positioned. No mental barbel. Upper jaw (premaxilla) with, a single, outer row of closely spaced villiform teeth, and an inner band of small, conical teeth, comprising seven anterior and six posterior rows. Lower jaw (dentary) with broad band of uniformly small, conical teeth, comprising five or six anterior and three or four posterior rows. Eye moderately large, 21% of HL, circular. Anterior and posterior nostrils circular and somewhat ovate, respectively, just before eye, the latter twice the size of former. Gill rakers short and slender, 15% of ED; gill filaments approximately 3.75 times longer than gill rakers at angle of gill arch ( Fig. 3 ). Scales rather large, cycloid on head (except occiput), throat, membrane of soft dorsal, anal, and caudal fins; body scales ctenoid, ctenii well developed, having only radiated marginal grooves (smooth to touch). Third dorsal-fin spine longest. First soft ray of pelvic-fin with a short filament, with a dim black spot on upper pectoral-fin base. Second anal-fin spine short, stiff, 10% of SL, or 32% of HL, about ⅔ of first anal-fin soft ray. Caudal fin rhomboid. Swim bladder hammer-shaped, with 15 arborescent appendages along entire lateral surface ( Fig. 4 ). Sagitta in medial view is typical Johninae pattern ( Fig. 5 ) (see Trewavas, 1977).

Color when fresh. Based on color photographs of the type material of Johnius sasakii sp. nov. with head and upper body iridescent mauve or bronze, creamy white on lower lateral and ventral surfaces ( Figs. 2 , 6A ). Roof mouth lining whitish. Upper operculum appearing darkish owing to a densely pigmented branchial cavity. Peritoneum of anterior abdominal cavity punctuated with black pigmentation. Spinous and soft dorsal-fins dusky brownish hyaline, a basal quarter of both pale; upper part of pectoral-fin dusky brownish hyaline, pelvic-fin slightly mottled anteriorly, a few rays creamy-white distally; anal-fin slightly mottled dusky brownish; caudal fin brownish hyaline, dark distally.

Color in preservative. Head and upper body brownish tan, the lower part of body and operculum whitish-yellow; fins brownish tan, dorsal and caudal fins with black margins.

Geographic distribution. All known specimens of the species were collected from the coast of Sabah and Sarawak, East Malaysia.

Etymology. Named in honor of the ichthyologist, Dr Kunio Sasaki, Professor at Kochi University, Japan, who has made significant contributions to the taxonomy of Sciaenidae and Johnius .

Comparisons. Johnius sasakii sp. nov. resembles J. belangerii , J. weberi and J. coitor in possessing slightly enlarged teeth on upper jaw and villiform teeth at the inner row on lower jaw (including molariform teeth on inner rows lower jaw for J. macrorhynus ), in having no mental barbel, and dorsal-fin spines IX–XI; meanwhile J. sasakii sp. nov. is most similar to J. heterolepis , J. carouna , and J. macrorhynus in possessing scale rows above lateral line from dorsal-fin origin 4–8 (usually 5–6); scale rows below lateral line from anal-fin origin 6–14 (usually 6–10); and scales moderately large.

Johnius sasakii sp. nov. can be separated from the most similar species, J. heterolepis , by the following combination of characters: snout profile more blunted (vs. more pointed); gill raker length more shorter, stiff (vs. moderately long, slender); fewer outer gill rakers on the lower limb of the first arch (mode 9 vs. mode 10); more outer gill rakers on the upper limb of the first arch (mode 5 vs. mode 4); shorter anal-fin base length (mode 9% vs. 10% of SL); shorter first anal-fin ray length (10–12% vs. 12–13% of SL); and higher number of scale rows above and below the lateral line (mode 5 and 10 vs. mode 4 and 7), respectively ( Fig. 6 , Table 3 ).

Johnius sasakii sp. nov. can also be differentiated from J. carouna by total outer gill rakers of first arch 13–15 vs. 16–18; number of lower limb outer gill rakers, 8–10 (mode 9) vs. 10–12 (mode 11); second anal-fin spine length rather shorter, 7–10% of SL (usually 8–10%) vs. 11–14% of SL (usually 11–12%); body depth slightly deeper, 25–29% of SL (usually 26–28%) vs. 23–28% of SL (usually 24–26%); first anal-fin ray length shorter, 9–13% of SL (usually 10–12%) vs. 11–15% of SL (usually 13–14%); anal-fin base length shorter, 7–10% of SL (mode 9%) vs. 9–11% of SL (mode 10); and pre-anal length slightly longer, 67–74% of SL (usually 70–71%) vs. 66–70% of SL (usually 67–68%) ( Table 3 and 4 ), respectively. Johnius sasakii sp. nov. can be further be differentiated from J. macrorhynus : by dentition of lower jaw villiform (vs. molariform teeth on inner rows); higher number and structure of lower gill rakers on the first arch (8–10, short and slender vs. 7–8, short and stumpy); second anal-fin spine length short and stiff (24.9–35.6% of HL vs. 16.8–27.8% of HL rather short and slender) ( Fig. 6 , Table 4 ).

Molecular comparison. To clarify the taxonomic status of J. sasakii sp. nov., we compared sequences of two genetic markers (16S mtDNA and S7 nDNA) with similar morphological Johnius species. Based on pairwise K2P genetic distances ( Table 5 and 6 ), J. sasakii sp. nov. is clearly differentiated from J. carouna by 16S:19.3%, S7: 8.4%; J. macrorhynus by 16S: 16.7%, S7: 8.1%; J. heterolepi s by 16S:10.4%, S7: 5.8%; J. amblycephalus by 16S:21.2%, S7: 10.9%; and the outgroup D. russelli by 16S:24.8%, S7: 12.6% respectively.

The NJ and ML trees obtained high support of bootstrap value (BS>90%) based on mtDNA and nDNA markers shared identical topologies where the specimens of J. sasakii sp. nov. grouped together in a monophyletic clade, which can be separated from the other Johnius species ( Figs. 7 and 8a ). The concordant phylogenetic topology derived from both mtDNA and nDNA markers indicate that the sister species of J. sasakii sp. nov. is the J. heterolepis ( Figs. 7 and 8a ), meanwhile J. carouna and J. macrorhynus form a sister group to J. sasakii sp. nov. and J. heterolepis . In addition, haplotypes of partial nDNA S7 intron can be separated from J. carouna by three fixed nucleotide differences ( Fig. 8b ), indicating a significant level of genetic variation can be inferred from nuclear gene between J. sasakii sp. nov. and J. carouna .

Remarks. We did not record J. latifrons Sasaki 1992 and J. trachycephalus (Bleeker 1851) from Malaysian waters during our survey, however, these species were included by Sasaki (2000) based on Sasaki (1992) concerning on J. latifrons , and Trewavas (1977) on J. trachycephalus from Thailand and Vietnam. Because we have no confirmed records of J. latifrons and J. trachycephalus in Malaysian waters, we included it in the key to the species. Only eight species of Johnius (Johnius) have been reliably documented from Malaysian waters ( Sasaki 2000; 2001).

Figures

FIGURE 2. Holotype of Johnius sasakii sp. nov., (A) Fresh specimen, (B) preserved specimen, NMMB-P 34733, 111 mm SL, Bako, Sarawak, Malaysia, 17 March 2017, collected by Norhafiz Hanafi, fish market.

FIGURE 3. First gill arch on left side of Johnius sasakii sp. nov. (paratype: NMMB-P 34739, 146 mm SL).

FIGURE 4. Swimbladder of Johnius sasakii sp. nov. (paratype, NMMB-P 34739, 146 mm SL), with 14 pairs of lateral appendages followed by a hammer-shape, with a number of arborescent appendages along the entire lateral surface (ventral view).

FIGURE 5. Inner surface of sagitta of Johnius sasakii sp. nov., paratype, NMMB-P 34739, 146 mm SL.

FIGURE 6. Photographs of the comparative materials. (A) Johnius sasakii sp. nov.; NMMB-P 34738, paratype, 114 mm SL, (B) Johnius heterolepis NMMB-P 35556, 105 mm SL, (C) Johnius carouna, NMMB-P 34743 141 mm SL and (D) Johnius macrorhynus; NMMB-P 34744, 116 mm SL.

FIGURE 7. Phylogenetic trees reconstructed using the mtDNA 16S genes of five Johnius (Johnius) species. Values above the branches are respective bootstrap values from 5000 replications for the Neighbour-Joining (NJ) and Maximum-Likelihood (ML) analyses. Bar indicates genetic distances of 0.02.

FIGURE 8. (A) Phylogenetic trees reconstructed using the nDNA S7 genes of 5 Johnius (Johnius) species. Values above the branches are respective bootstrap values from 5000 replications for the Neighbour-Joining (NJ) and Maximum-Likelihood (ML) analyses. Bar indicates genetic distances of 0.02. (B) Three nucleotide differences (black arrow) at the sites 215, 308, and 354 nucleotides in the homozygote nuclear gene S7 of J. sasakii sp. nov.