Johnius medidentatus Geenita, Pavan-Kumar, Bhushan, Devi & Jaiswar, 2025

Johnius medidentatus Geenita, Pavan-Kumar, Bhushan, Devi & Jaiswar sp. nov.

Figs 2 a, b, c View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 d View Figure 5 , 6 c View Figure 6 , Table 2 Proposed common name: Moderate-toothed croaker View Table 2

Type material.

Holotype. India • 1, 141 mm SL; Kalamukku Fishing Harbour , off Kerala coast, Arabian sea; 9°59.03'N, 76°14.56'E; 23 Dec. 2023; K. Geenita leg.; trawl landings; BNHS MF 77 GoogleMaps .

Paratypes. India • 2, 123– 134 mm SL; same data as for holotype; CF 1 KL 0123 – CF 1 KL 0124 GoogleMaps • 2, 114– 141 mm SL; same data as holotype; CF 1 KL 0126 – CF 1 KL 0127 GoogleMaps .

Non-types. India • 3, 145– 158 mm SL; Penthakata Beach , Puri, Odisha; 19°48.11'N, 85°51.00'E; 28 Mar. 2024; K. Geenita leg.; gill net landings; CF 1 OD 0120 – CF 1 OD 0122 GoogleMaps • 2, 93–95 mm SL; Mandapam Harbour , Tamil Nadu; 9°16.55'N, 79°09.07'E; 30 Aug. 2024; K. Geenita leg.; trawl net landings; CF 1 TN 0118 – CF 1 TN 0119 GoogleMaps • 1, 94 mm SL; Malpe Fishing Harbour , Karanataka; 13°20.91'N, 74°42.00'E; 20 Oct. 2024; K. Geenita leg.; trawl net landing; CF 1 KA 0125 GoogleMaps .

Diagnosis.

A species of Johnius ( Johnieops) with the following combination of characters: body oval shaped; enlarged teeth in the inner row of lower jaw moderate in size; slightly longer pre-anal length, 68.5–73.5 % SL; moderately large eye, 21.8–30.1 % HL; scales below lateral line, 11–13 (mode 12); total number of outer gill rakers on first gill arch 5–8 (mode 7) + 10–15 (mode 13) = 17–24 (mode 21).

Description.

Counts and measurements of the holotype and paratype with non-type specimens are presented in Table 2 View Table 2 . For meristic counts, the modal values are given in brackets.

A small-sized fish with oval-shaped body, more or less compressed laterally, dorsal and ventral profiles evenly curved, nearly equal. Head moderate, 24.9–32.6 % of SL, with five rostral and five marginal pores, the skin around the latter forming weak lobes along its edge. Mental pore in three pairs, first pair lateral to tip of lower jaw but in “ false pit ”. Snout evenly convex till origin of dorsal fin but never projecting. Jaws end equally at tips. Upper jaw, 43.6–54.7 % of HL, and lower jaw, 40.6–52.8 % of HL. Eyes round, moderately large, 21.8–30.1 % of HL. Inter-orbital length moderate, 25.7–32.1 % of HL. Mouth terminal. Upper jaw with spaced and enlarged teeth in outer row, teeth in inner row in 1–2 bands; lower jaw with moderately large and spaced teeth in inner row, small teeth in 1–2 rows in outer row, unregular teeth pattern at tip of lower jaw. Cleft of upper jaw extending till rear end of iris of eye. Pre-opercle finely serrated. Opercle with two flat spines near upper end. Pre-dorsal length, 26.2–31.2 % of SL, pre-pectoral length, 27.2–31.7 % of SL, pre-pelvic length, 27.6–34.6 % of SL and pre-anal length, 68.5–73.5 % of SL. Pectoral fin origin almost in vertical line of first dorsal fin insertion, its tip ending almost near 2 nd – 3 rd soft dorsal fin ray. Anal fin origin between 10 th – 12 th ray of second soft dorsal fin. Caudal fin rhomboidal, covered with small scales. Scales on snout, check and operculum cycloid, elsewhere ctenoid. Base of first dorsal fin, whole of second dorsal fin, pectoral fin and anal fin covered with small cycloid scales. Gill rakers lanceolate. Sagital otolith typical triangular shaped “ johnius-type ” with a tadpole shaped impression, caudal deepened as a hollow cone (Fig. 3 View Figure 3 ). Gas bladder hammer-shaped with 12–15 pairs of lateral arborescent appendages (Fig. 4 View Figure 4 ).

Coloration.

In fresh condition, the body is grey with a silverish sheen and a bluish tinge, below pale whitish, the first dorsal fin is dark, and the second dorsal fin is grey. Pectoral, pelvic, anal, and caudal fins pale yellow, with dusky spots and a few dusky spots on upper lips. In formalin specimens, slightly darker, dusky spots on the body and on the fins.

Etymology.

The species is named “ medidentatus ’’ with reference to the moderate-size teeth in the inner row of the lower jaw (Latin origin, medius = middle or moderate; dentatus = toothed).

Distribution.

This species has a wide distribution along the Indian Coastline: off Mumbai coast, Karnataka, Kerala coast, Tamil Nadu, Andhra Pradesh, Odisha, West Bengal; both from the east and west coasts of India.

Identification key to the genus Johnius ( Johnieops) found in Indian waters

Comparisons

The genus Johnius has been divided into two subgenera, Johnieops and Johnius , based on the pattern of teeth on the upper and lower jaw. The new species described herein comes under the subgenus Johnieops , i. e., having enlarged and spaced teeth in the outer row of the upper jaw and enlarged teeth on the inner row of the lower jaw ( Lal Mohan et al. 1984). The new species differs from all congeners found in Indian waters but shares slightly similar body morphology with J. plagiostoma (Fig. 5 View Figure 5 ). Johnius medidentatus can be easily differentiated from J. plagiostoma by having first pair of mental pores in a false pit (vs. separated by symphysis), absence of a mental process at lower jaw (vs. present), presence of moderately enlarged teeth in inner row of lower jaw (vs. well enlarged teeth), higher number of scales below the lateral line (11–13, mode 12 vs. 9–11, mode 10) and fewer number of total gill rakers (17–24, mode 21 vs. 22–26, mode 25) (see Table 3 View Table 3 ). It differs from J. borneensis by having a rounded snout (vs. pointed from dorsal view) ( Hanafi et al. 2022, 2024; Sasaki 2022), absence of strong anterior teeth in the outer row of the upper jaw (vs. present) ( Chao et al. 2019; Sasaki 2022), moderately enlarged teeth in the inner row of the lower jaw (vs. well enlarged teeth), relatively shorter snout (15.3–22.9 % HL vs. 20.4–26.2 % HL), higher number of gill raker in the lower limb of the first gill arch (10–15, mode 13 vs. 9–13, mode 11), higher number of total gill raker (17–24, mode 21 vs. 14–21, mode 17) (see Tables 3 View Table 3 , 4 View Table 4 ). It differs from J. dussumieri in having larger eye (21.8–30.1 % HL vs. 15.7–22.4 % HL), interorbital area not flattened (vs. flattened), longer pre-anal length (68.5–73.5 % SL vs. 59.75–69.94 % SL) (see Table 4 View Table 4 ). Out of these three species found in Indian waters, J. dussumieri have comparatively smaller enlarged teeth in the inner row of the lower jaw, the other two, i. e., J. borneensis and J. plagiostoma have prominent and larger enlarged teeth in the inner row of the lower jaw. In comparison to all three, our new species has moderately sized teeth, larger than J. dussumieri but relatively smaller than J. plagiostoma and J. borneensis (Fig. 6 View Figure 6 ).

J. medidentatus sp. nov. differs from J. distinctus (Tanaka, 1916) from Japan, China and Taiwan most prominently by absence of conspicuous white streak along the lateral line (vs. present), lesser number of scales above lateral line (6–7 vs. 7–11), longer upper jaw length (43.6–54.7 % HL vs. 38–43 % HL) ( Sasaki 1999). From Johnius dorsalis (Peters, 1855) which is distributed from South Africa, East Africa to Madagascar, it differs by having shorter interorbital length (25.7–32.1 % HL vs. 29–39 % HL), though slightly overlapping but never exceeded 32 %, longer upper jaw length (43.6–54.7 % vs. 34–46 %), first spinous dorsal fin naked (vs. fully covered with small scales) ( Sasaki 1997, 1999). The new species differs from J. novaeguineae (Nichols, 1950) from New Guinea and Northern Australia by having three pair of mental pores, and first pair not separated by symphysis (vs. one pair only and separated by symphysis), lesser scales above lateral line (6–7 vs. 8–9), lesser scales below lateral line (11–13 vs. 14–19), lesser upper gill raker count (5–8 vs. 8–11), lesser lower gill raker count (10–15 vs. 16–18), lesser number of total gill raker (17–24 vs. 24–29), larger eye (21.8–30.1 % HL vs. 11–16 % HL), smaller interorbital length (25.7–32.1 % HL vs. 33–42 % HL) ( Trewavas 1977; Sasaki 1999). It differs from J. pacificus Hardenberg, 1941 , from the northern Pacific coast of New Guinea by having larger eyes (21.8–30.1 % HL vs. 16–23 % HL), longer upper jaw length (43.6–54.7 % HL vs. 39–45 % HL). Even though there is slight overlapping of the morphometric characters, J. pacificus has a restricted distribution and is known to occur only along the coast of New Guinea ( Sasaki 1999; Froese and Pauly 2024). It differs from J. philippinus Sasaki, 1999 from Philippines by having longer upper jaw length (43.6–54.7 % HL vs. 37–44 % HL), lesser snout length (15.3–22.9 % HL vs. 24–29 % HL) and appendages on the swim bladder well-branched (vs. poorly branched) ( Sasaki 1999).

Molecular analysis

A final aligned sequence length of 551 bp after trimming the gaps at the ends were used in molecular analysis. In the maximum likelihood phylogenetic tree, individuals of Johnius medidentatus formed a distinct cluster with high bootstrap support (> 80 %) (Fig. 7 View Figure 7 ). This clade was positioned as a sister group to J. borneensis from India and other regions with a 10.1 % genetic divergence in K 2 P value. The new species exhibits on an average 8.8 % genetic divergence with J. distinctus followed by J. dussumieri (9.2 %), J. novaeguineae (15.9 %) and J. plagiostoma (21.9 %). Further, the new species exhibited intraspecific divergence value of 0.2 % (Table 5 View Table 5 ).