Desmopuntius mahakamensis Harefa, Haryono & Gustiano, 2025

Desmopuntius mahakamensis Harefa, Haryono & Gustiano sp. nov.

Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , Tables 1 View Table 1 , 2 View Table 2

Puntius sp. — Haryono 2005: 56, fig. 2 c.

Type material.

Holotype. • MZB 6132 View Materials , 53.2 mm SL; Indonesia: Borneo: Kalimantan Timur Province: Kutai Kertanegara Regency, Muara Wis Village ( 0°19'35.8"S, 116°29'37.7"E); H. Haryono; 03 July 1992 GoogleMaps . Paratypes ( N = 31). All from Indonesia: Borneo: Kalimantan Timur Province: • MZB 28243 View Materials , 1 specimen, 52.8 mm SL, same data as holotype GoogleMaps • MZB 17589 View Materials , 11 specimens, 33.7–62.5 mm SL; small stream Belayan, tributary of Mahakam River ; R. K. Hadiaty et al.; 25 April 2009 GoogleMaps • MZB 19047 View Materials , 5 specimens, 28.4–53.0 mm SL; small stream Long Tahap, tributary of Mahakam River ; R. K. Hadiaty et al., 13 July 2010 GoogleMaps . • MZB 19076 View Materials , 1 specimen, 30.5 mm SL, same data as for MZB 19047 GoogleMaps • MZB 17327 View Materials , 1 specimen, 32.7 mm SL; small stream Belayan ; R. K. Hadiaty et al.; 15 April 2009 GoogleMaps • MZB 17414 View Materials , 1 specimen, 32.6 mm SL, small stream Long Tahap, tributary of Mahakam River , R. K. Hadiaty et al.; 19 April 2009 GoogleMaps . • MZB 28447 View Materials , 11 specimens, 53.0– 75.4 mm SL, Semayang lakes, Semayang Village ( 0°10'47.9"S, 116°26'46.2"E), T. Harefa; 29 March 2025 GoogleMaps .

Diagnosis.

Desmopuntius mahakamensis can be distinguished from all congeners by the following combination of characters: anal-fin rays 5 ½; lateral line scales 26–27 (mode 26); predorsal scales 9–11 (mode 10); gill rakers 9–11 (mode 10); total vertebrae 29; axial streak present; 5–6 black lateral stripes in adults (> 30 mm SL), with stripe + 1 extending from behind the gill opening along scale row 1, reaching only to the midbody, between the origin and end of the dorsal-fin base.

Description.

Morphometric and meristic data are presented in Tables 1 View Table 1 , 3 View Table 3 . Body laterally compressed and relatively deep, with greatest depth at dorsal-fin origin. Dorsal profile continuous from head to body, with a slight hump at the nape, ascending to dorsal-fin origin, then descending to the anterior base of the caudal fin. Ventral profile continues from head to body, slightly convex through the posterior end of the anal-fin base, and then slightly concave along the caudal peduncle. Rostral and maxillary barbels present. Snout blunt. Eyes large, almost aligned with the dorsal profile of the head. Mouth subterminal; maxilla extending to, or slightly beyond, the vertical of the anterior margin of the eye. Postlabial groove deep and interrupted medially. Lateral line complete, posteriorly descending for about six scales.

Dorsal fin with 4 unbranched and 8 ½ branched rays; origin at about midbody, distal margin straight or slightly concave; last unbranched ray posteriorly serrated with 12–18 serrations. Anal fin with 3 unbranched and 5 ½ branched rays. Pectoral-fin rays with 1 unbranched and 14 * – 15 (modally 14) branched rays; fin rounded, first and second branched rays longest, not reaching pelvic-fin origin. Pelvic-fin with 1 unbranched and 9 branched rays; origin vertically behind dorsal-fin origin; unbranched ray longest, reaching only to anus. Caudal fin forked, lobes rounded to pointed at tips.

Lateral-line scales 25 + 2, 26 + 2 * (mode 26 + 2), transverse scales ½ 4 / 1 / 3 ½ from dorsal-fin origin to about two scales anterior to pelvic-fin ray; predorsal scales 9–11 (mode 10 *); circumpeduncular scales 12. Gill rakers 9–11. Total vertebrae 29.

Colouration. Fresh specimens (Adult; Fig. 4 View Figure 4 ). Dorsal side of the head dark brown, mid-lateral and ventral sides of the head greyish white. Small brown spots present below the eyes. Body with greyish-brown background, bearing 5–6 black lateral stripes: stripe 0 extending from just behind the gill opening, between scale row 0 and - 1, to the middle of the caudal-fin base posteriorly; stripe + 1 extending from behind the upper gill opening, along scale row + 1, continuing only to midbody, between the origin and end of the dorsal-fin base; stripe + 2 extending from the 5 th – 7 th of scale of row + 2 to the upper caudal-fin base; stripe + 3 extending from the nape along scale row + 3 to slightly behind the end of the dorsal-fin base; stripe - 1 extending from behind the gill opening, between scale rows - 1 and - 2, to the lower caudal-fin base; stripe - 2, extending from behind the pectoral fin along scale row - 3 to the anal-fin base, gradually decreasing in intesity anteriorly. Unbranched dorsal-fin rays dark brown, fin membrane yellowish-orange, fading posteriorly. Anal, pectoral, and pelvic fin membranes translucent. Caudal fin yellowish, becoming translucent posteriorly.

Preserved specimens (Adult; Fig. 2 View Figure 2 ). Head with dark yellowish background, slightly darker dorsally, and pale yellowish ventrally. Body ground colour dark yellowish, becoming darker dorsally and pale yellowish ventrally, extending to below the dorsal fin, and in some specimens reaching just behind the gill opening anteriorly. Body with 5–6 black lateral stripes, in positions similar to those of live specimens. Axial streak present, posteriorly overlapping lateral stripe + 1, extending anteriorly to below dorsal fin. All fins pale.

Juveniles (Fig. 3 View Figure 3 ). Head and body with dark yellowish background. In specimens < 30 mm SL, body with three interrupted lateral stripes and 4–5 vertical dark bars or spot on the dorsal side: 1 st bar accros the eye; 2 nd bar extending behind the gill opening; 3 rd bar below the first and second branched ray of the dorsal fin, sometimes continuing to the pelvic fin; 4 th bar or spot at the end the of dorsal-fin base; 5 th bar or spot at the caudal penducle. In specimens> 30 mm SL, vertical bars usually faded, and lateral stripes form a more continuous pattern, except for stripe + 1, which extends only to midbody.

Distribution.

The new species is currently known only from the Mahakam River drainage, East Kalimantan, Indonesia. Most specimens have been collected from two lakes (Wis and Jempang) and from several small streams within the Mahakam River’s tributary system (Fig. 1 View Figure 1 ).

Etymology.

The specific name, mahakamensis, is derived from the Mahakam River, the locality where the species was collected.

Linear discriminant analysis (LDA).

The LDA of seven species of Desmopuntius showed that the first two functions explained 68.32 % and 15.23 % of the variance. Five morphometric traits were identified as primary characters distinguishing the species: head length, depth at the caudal peduncle, eye diameter, postorbital length, and length of the anal-fin base (Table 4 View Table 4 ). The LDA analysis showed that all currently represented species of Desmopuntius cluster into two morphological groups: one group includes D. endecanalis , D. hexazona , D. pentazona , and D. rhomboocellatus , while the other group includes D. mahakamensis sp. nov., D. gemellus , D. johorensis , and D. trifasciatus (Fig. 8 View Figure 8 ).

Genetic divergence and phylogenetic placement.

A total of 37 COI sequences were used for phylogenetic analysis (Fig. 9 View Figure 9 ), including four newly generated sequences for D. mahakamensis and two for D. gemellus , each with a total length 651 bp. Among the Desmopuntius species studied, interspecific genetic divergence ranged from 0.2–15.2 %, while intraspecific divergence ranged from 0.0–0.3 %, based on the K 2 P model (Table 6 View Table 6 ). The mean genetic distance between D. mahakamensis and other congeners ranged from 7.2–13.0 %, with D. gemellus being the most closely related species.

The topology of the ML tree strongly supported the monophyly of the genus Desmopuntius . Within the genus, two major clades were recognised with moderately high bootstrap support (BP: 78). The first clade, the “ D. hexazona group, ” comprised four species: D. hexazona , D. rhomboocellatus , D. pentazona , and D. foerschi . The second clade, the “ D. johorensis group, ” included D. mahakamensis , D. gemellus , D. johorensis , and D. trifasciatus . Except for the node between D. hexazona and D. rhomboocellatus , most species-level nodes within Desmopuntius had poorly supported bootstrap values (BPs: <70). In addition, D. trifasciatus was nested within D. johorensis (BP: 100), and the new species D. mahakamensis was found to be closely related to D. gemellus (BP: 54).