Betta iaspis, Ding & Lei & Haryono & Shi & Zhang, 2025

Betta iaspis sp. nov.

Figs 3 View Figure 3 , 4 View Figure 4 , Suppl. material 2: fig. S 1

Type material.

Holotype. MZB.26963 , 22.0 mm SL, male; Indonesia, Sumatra Island, Jambi, forest peat swamp; colls. Mulyadi Tjoa Hong Tjai, Nov. 2023 . The exact locality is withheld to avoid potential pressure on the wild population of ornamental fish industry. Qualified researchers can request the information from the first author or MZB. Paratypes. NCUMB.65334 , 30 specimens, 17.7–23.9 mm SL; same data as for holotype; colls. Mulyadi Tjoa Hong Tjai Jun. 2022 .

Diagnosis.

Betta iaspis sp. nov. differs from its congeners in the B. coccina group by the following unique combination of characters: less dorsal-fin rays (8–10 *) and subdorsal scales (5–6 *); shorter dorsal – fin base (7.5–19.1 % SL, mean 11.7 %); male with dark blackish body; without green iridescent mid-lateral body patch; dorsal-, pelvic- and caudal fins red without significant marks; blackish anal fin with reddish patches on posterior part.

Description.

Morphometric and meristic data are summarized in Table 1 View Table 1 . General appearances presented on Fig. 3 View Figure 3 . Head rounded and small. Body slender (at dorsal-fin origin 18.2 % – 22.3 % SL, mean 19.9 %) not compressed at caudal peduncle (11.9 % – 20.5 % SL). Dorsal fin narrow (total 8–10 * rays), base short (7.5–19.1 % SL with 5–6 * subdorsal scales) and placed significantly far back (predorsal length 57.8–67.7 % SL). Dorsal fin pointed with elongated posterior rays, sometimes reaching caudal-fin base in mature males. Anal fin situated ~ ½ body (preanal length 39.7 % – 47.0 % SL), base long (47.9 % – 57.8 % SL). Anal fin with total 27 * – 28 rays, pointed, posterior rays elongated, often reach half-length of caudal fin in mature males. Caudal fin lanceolate in males, rounded in females, with i-ii rudimentary, I simple principal, 4 + 5 branched principal, I simple principal, i-ii rudimentary rays (modal ii-I- 4 + 5 - I-ii). Pectoral fin rounded with 12–14 (modal 13) rays. Pelvic fin with one spine, one simple and four branched rays, simple ray filamentous. Lateral scales 28 * – 30, plus two or three scales on caudal-fin base; predorsal scales 19–21 *; postdorsal scales 9–11 (modal 10); 7–8 * scales in transverse series at dorsal fin origin.

Live coloration.

Male (Fig. 4 View Figure 4 ). Head reddish brown, dorsum dark brown. Opercle without distinct bar in neutral mood, two barely recognizable pale reddish twin bars on opercle in aggressive or breeding mood. Iris with iridescent bluish patches. Anterior edge of body reddish brown, belly area brown, posterior edge of body after anus blackish with pale flush of iridescent blue (less distinct reddish brown in stressed or preserved specimens, Fig. 4 C View Figure 4 ), dorsum dark brown. No distinct dark stripes or iridescent patches on body flank. Dorsal fin simple red with a bright bluish margin (blackish basal spots presented on inter-radial membrane of some specimens). Caudal fin simple red with a bright bluish margin on the upper half. Anal fin blackish with reddish patches on posterior part. Pectoral fin hyaline. Pelvic fin red with whitish filamentous ray.

Female (Fig. 4 D View Figure 4 ). Head and body coloration similar to male, but blackish part less intense. All fins coloration similar to male, but blackish black spots more intense on dorsal fin. In breeding condition, dark stripes can be observed on the body.

Preserved coloration.

Male (Fig. 3 View Figure 3 , Suppl. material 2: fig. S 1): Head dark brown, dorsum blackish, no bar present on opercle. Anterior edge of body yellowish brown, posterior edge of body after anus pale blackish (dark brown in juvenile specimens), dorsum dark brown. Dorsal fin simple red without distinct margin (indistinct blackish spots presented on inter-radial membrane of some specimens). Caudal fin simply red without distinct margin. Anal fin blackish with reddish patches on posterior part. Pectoral fin hyaline. Pelvic fin red with hyaline filamentous ray.

Female (Suppl. material 2: fig. S 1): Head and body coloration similar to male, but posterior edge of body after anus dark brown. All fins coloration similar to male.

Comparison.

Betta iaspis sp. nov. can be easily distinguished from other members of the B. coccina group by the following combination of characteristics: shorter dorsal-fin base (7.5–19.1 % SL), fewer subdorsal scales (5–6) and its unique caudal-fin coloration (blackish with reddish patches on posterior part); it also differs from its most similar congeners B. persephone and B. miniopinna by the presence of red dorsal- and caudal fins (vs dark greenish / bluish); filamentous elongated posterior rays of anal fin (vs pointed but not filamentous). It can also be distinguished from B. burdigala , B. coccina , B. livida , B. tussyae , and B. uberis by lack of iridescent greenish / bluish streaks / patches on inter-radial membrane of unpaired fins (vs presence); differs further from B. burdigala and B. uberis by fewer dorsal-fin rays (8–10 * vs 14–17), from B. coccina by whitish pelvic fin tips (vs black), from B. livida by fewer lateral scales (28 * – 30 vs 30–31); from B. tussyae by presence of iridescent blue on body flank (vs absence). It also differs from B. brownorum and B. rutilans by blackish body color (vs reddish magenta), further distinct from B. brownorum by lack of iridescent mid-lateral blotch (vs presence), from B. rutilans by presence of bright bluish margin on dorsal- and caudal fin (vs absence / indistinct). It can be differentiated from B. hendra by absence of distinct bar on opercle (vs prominent red parallel bars), less transverse scales 7–8 * (vs 8–10), blackish or reddish unpaired fins (vs greenish / bluish).

Distribution.

Betta iaspis sp. nov. is currently only known from one single forest peat swamp in Jambi, Sumatra Island (Fig. 1 View Figure 1 ), which is adjacent to a huge oil palm plantation.

Etymology.

A Latin noun iaspis is derived from the Greek ἴασπις, for the gemstone jasper, which is usually red or green / blue in color, referring to the distinct combination of the fish’s iridescent bluish / greenish body and reddish fins.

Field notes.

Specimens were collected from a small forest peat swamp, which can be partly dried-up in the dry season. Similar to its congeners B. persephone in Malaysia ( Schaller 1986), Betta iaspis sp. nov. also survives through the dry season, particularly in the dried-up area of the swamp, by hiding in the moist mud beneath the dead leaves on the ground (Fig. 3 View Figure 3 ). In the rainy season, when the habitat is filled again with water, they come back to surface and reproduce normally like other members of the group. Certain water parameters were recorded in dry season: pH 5.0, total dissolved solids in water 12 ppm, water temperature 29.8 ° C.

All syntopic fish species recorded from the type locality are as follows: Betta simorum Tan & Ng, 1996 , Boraras maculatus ( Duncker, 1904) , Rasbora einthovenii ( Bleeker, 1851) , Sphaerichthys osphromenoides Canestrini, 1860 .

Conservation status.

Oil-palm plantations and coal mining activities have severely affected the natural habitats in Jambi, especially forest peat swamps along Batang Hari River ( Rustiadi et al. 2018). The Lagan region, the distribution area of Betta iaspis sp. nov., is facing the same challenges. During the field survey in 2023, we noticed that the type locality is immediately adjacent to a huge oil-palm plantation (Fig. 4 C View Figure 4 ), whose irrigation activities have aggravated the drought of the forest swamp. Although the species has evolved a successful survival strategy against nature drought, it will fail eventually if the continuing deterioration of the habitat’s hydrological conditions cannot be stopped by proper conservation efforts. Thus, following the IUCN Red List Categories and Criteria (ver. 3.1), we propose Betta iaspis sp. nov. be listed as Critically Endangered B 2 ab (iii), based on its very restricted distribution area in a single forest peat swamp (<30 km 2) and the fact that this habitat has already been facing direct threats from human activities.

Molecular analysis.

The consensus phylogenetic tree based on the Cyt b suggests that Betta iaspis sp. nov. is a monophyletic group distinct from its sister group B. mulyadii sp. nov. by an uncorrected p-distance of 4.35 % (Fig. 7 View Figure 7 ; Suppl. material 1: table S 2). Betta iaspis sp. nov. is also distinct from other congeners in the same branch for which Cyt b is available, with a p-distance ranging from 5.40 % – 6.32 %, and significantly distinguished from the remaining species in the other branch with a p-distance ranging from 19.2 % – 22.0 %. These results indicate that the genetic differences between the new species and its congeners exceed the intraspecific differences observed (<2 % in the current study, <1 % in related labyrinth fish species like Parosphromenus spp. [ Shi et al. 2021] or K 2 P <0.5 % in Channa argus [ Zhou et al. 2019]) (<2–3 % in previously published comparable data by COI gene by Fahmi et al. 2020 and Panijpan et al. 2014). Morphologically, Betta iaspis sp. nov. differs from all known Betta species (see above Diagnosis and Comparison). Thus, based on both a significant morphological diagnosis and a Cyt b divergence consistent with that, we are confident that these specimens from Jambi, Sumatra, represent a valid novel species.