Johnius Bloch, 1793

Hanafi, Norhafiz, Chen, Meng-Hsien, Chang, Chih-Wei, Chao, Ning Labbish & Seah, Ying Giat, 2024, Taxonomic review of the genus Johnius (Perciformes: Sciaenidae) from East Malaysian waters, with comments on newly recorded Johnius species, Zootaxa 5550 (1), pp. 85-117 : 90-94

Synonyms and invalid names of nominal species of Johnius Bloch, 1793

Several taxonomic names of Malaysian species often used in the literature have been identified as questionable identifications. Table 3 lists all Johnius species found in Malaysian sources, along with their current status. Sasaki (1999) acknowledged J. glaucus and J. goldmanni as nomen dubium. Mohsin et al. (1996) and Chin et al. (1998) misidentified and photographed J. dussumieri as J. amblycephalus , whereas J. glaucus and J. goldmanni are junior synonyms of J. carouna and J. borneensis ( Sasaki, 1999) . However, since J. elongatus is exclusively found in Indian coastal waters, the species described and photographed by Atan et al. (2010) was misdiagnosed as J. macrorhynus . Johnius carutta Bloch, 1793 ; J. dussumieri ( Cuvier, 1830) ; J. elongatus Lal Mohan, 1976 ; and J. macropterus (Bleeker, 1853) are all valid names that are exclusively found in the Indian Ocean. Meanwhile, J. latifrons ( Sasaki, 1992) and J. trachycephalus (Bleeker, 1850) are also valid species endemically dispersed in the Gulf of Thailand. One additional species, Johnius trewavasae Sasaki, 1992 was discovered for the first time in Malaysia, increasing its known range to south-eastern Malaysia (Borneo shoreline).

Several references in Table 3 have been revised and corrected from the East Malaysia literature review ( Mohsin et al., 1996; Chin et al., 1998; Sasaki, 2000; Mohamad Faisal, 2009; Lim, 2009; Ambak et al., 2010; Matsunuma et al., 2011; Kimura et al., 2015; Ng et al., 2015; Atan et al., 2010; Shah, 2017; Lim et al., 2018; Seah et al., 2021) with Fig. 2 were provided to show the spatial distribution of Johnius species in the East Malaysian waters. Descriptions and identification keys were also utilised to cross-check against all species, as described by Trewavas (1977), Lal Mohan (1984), Sasaki (1992, 1999, 2001), and Fricke et al. (2023).

Integrated identification of East Malaysian Johnius species

Morphological measurements. The sheared PCA analysis ( Fig. 3 ) of the factor loadings data ( Table 4 ) revealed that size contributed to 26.4% of the observed variance. Sheared PC2 and PC3 accounted for 19.61% and 6.79%, respectively, of the observed variance. The loadings of both components were similar on sheared PC2. The highest loadings were observed at gill raker length (GRL/ED) (0.74) in eye diameter (ED) and maxillary length (MxL/HL) (0.37) in head length (HL). For PC3, the loadings were highest at the second spine anal ray length (2ndAL/HL) (0.0.87) in head length (HL).

The scatterplot clusters with 95% confidence interval polygons for Johnius species from East Malaysia were compared to assess morphological divergence ( Fig. 3 ). The PCA of the morphometric data indicated substantial overlap among the studied characteristics. Upon plotting PC1 versus PC2, several clusters were apparent, indicating a well-structured variance in morphometric traits across the studied species. This differentiation allowed for a clear distinction between interspecific species and individuals that were previously classified as the same species. The principal component analysis (PCA) results reveal the presence of 11 Johnius species with distinct physical characteristics in the seas of East Malaysia.

Molecular phylogeny. The COI sequences that were aligned included a total of 613 base pair sequence characters. Among them, 51 characters provided useful information for parsimony analysis, 52 characters were varied but did not contribute to parsimony analysis, and 472 characters remained constant throughout. The NJ analyses generated phylogenetic trees with consistent structures but varying bootstrap support (BS) values ( Fig. 4 ). The COI sequencebased phylogenetic tree identified six main lineages consisting of 11 species, excluding J. macrorhynus ( Fig. 4 ). The first lineage included taxa of Dendrophysa russelli as an outgroup, followed by the subsequent lineage, J. amblycephalus , which served as a basal species with a significant bootstrap support (BS:100%) value. Whereas the third and fourth lineages comprised of taxa of J. plagiostoma (BS: 100%), followed by J. borneensis with modest bootstrap support (BS: 35%). Furthermore, the fifth clade, which includes J. coitor (BS: 23%), is separated into two distinct groups (BS: 15%). This clade independently diverges from J. carouna and J. heterolepis as a sister clade (BS: 30%). Additionally, there are derived clades consisting of J. sasakii (BS: 13%) and J. weberi (BS: 13%), both of which independently diverged from their respective sister clades, J. trewavasae and J. belangerii (BS: 21%) ( Table 5 ). Nevertheless, the genetic differences within this lineage make it possible to identify all species of Johnius from East Malaysia, which forms a highly monophyletic clade. The validity of this finding is reinforced by the inclusion of further morphological statistical analysis and genetic evidence data provided in this study ( Fig. 4 and Table 5 ).

Systematics

Genus Johnius Bloch, 1793

Johnius Bloch, 1793 , Naturg. Ausland. Fische (pt. 7), p. 132 — type Johnius carutta Bloch , designated by Gill , 1861, Proc. Acad. Nat. Sci, Philadelphia, p. 85.

Bola Hamilton, 1822 , Fish. Ganges, p. 173 — type Bola coitor Hamilton , designated by Jordan, 1917, Genera of Fishes , p. 114. Syn. nov.

Wak Lin, 1938 , Lingnan. Sci. J., 17 (2) p. 378 —substitute name for Bola Hamilton allegedly preoccupied by Bola Gunther ; type by original designation Bola coitor Hamilton.

Diagnosis. This genus Johnius is distinguished from other Sciaenidae genera by the following combination of feature states: (2) Barbel presents or missing, median with the median mental pore at the front of its base; (3) Hammer head in the form of a swimbladder right behind the transverse septum. A lateral branch extends to the anterolateral face of the pectoral arch at the intersection of the cleithrum and supracleithrum, where its palmate twiglets sit between the bone and the skin; (4) swimbladder appendages without dorsal limbs; (5) Sagitta, with the tadpole pattern’s long axis obliquely or nearly at right angles to the otolith’s long axis The otolith’s anterior section is thick. (6) Vertebrae 25 (10–12 abdominal, 13–15 caudal), exceptionally 24 (10+14); (7) The inferior apophyses of the fourth vertebra join below the haemal canal to form an arch to which the swimbladder is linked; (8) Predorsal bone two or three; (9) Scaly soft dorsal and anal fins; and (10) the presence of a large foramen in the prootic bone ( Hanafi et al., 2023).

Figures

FIGURE 2. Spatial distribution and species composition in sites of collection samples of Johnius species in East Malaysia (Acronym sites: Tawau (TWU); Sandakan (SKN), Beluran (BLRN), Kota Kinabalu (KK), Miri (MIRI), Bintulu (BNT), SIBU (SIBU), Betangor (BGR), Sarikei (SRK), Bako (KBA), Goebilt (GBT) and Kuching (KCH).

FIGURE 3. Scatterplots with 95% confidence interval ellipses of the sheared second principal component (PC2) and sheared third principal component (PC3) of morphometric data on Johnius from East Malaysia waters. Johnius amblycephalus (1, black dots), J. belangerii (2, blue plus), J. borneensis (3, violet square), J. coitor (4, brown fill square), J. macrorhynus (5, gold cross), J. heterolepis (6, coral circle), J. carouna (7, aqua diamond), J. carouna (8, gray star), J. sasakii (9, green triangle), J. plagiostoma (10, maroon dash), and J. weberi (11, orange bar).

FIGURE 4. Neighbor-joining phylogenetic tree of Johnius based on COI sequences. Bootstrap values (neighbor-joining [NJ]/ maximum likelihood [ML]) are shown on the nodes.