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.

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.

Morphometric and meristic data are summarized in Table 1. General appearances presented on Fig. 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.

Figure 3. 

Illustrations of Betta iaspis sp. nov. A MZB.26963, 19.5 mm SL male holotype, freshly preserved after collection in field (laterally inverted) B male, live coloration, not preserved (laterally inverted) C male holotype, in stress coloration immediately after capture (laterally inverted) D female, in courtship coloration, not preserved (laterally inverted).

Male (Fig. 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. 4C), 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.

Figure 4. 

Type locality photographs for B. iaspis A freshly collected specimens of male from type locality in dry season (laterally inverted), coll. Mulyadi Tjoa Hong Tjai B photograph of remaining puddles in the forest in dry season, photograph by Mulyadi Tjoa Hong Tjai 2023 C the surface of the type locality appear to be dried-up in dry season, while the mud beneath the thick layer of dead leaves often remain moist D this area will turn to swamp in rain season, photograph by Agus 2022 E type locality in Jambi, a small forest swamp directly adjacent to a huge oil-palm plantation.

Female (Fig. 4D). 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.

Male (Fig. 3, Suppl. material 2: fig. S1): 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. S1): Head and body coloration similar to male, but posterior edge of body after anus dark brown. All fins coloration similar to male.

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).

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

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.

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). 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.

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. 4C), 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 B2ab (iii), based on its very restricted distribution area in a single forest peat swamp (< 30 km²) and the fact that this habitat has already been facing direct threats from human activities.

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; Suppl. material 1: table S2). 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 K2P < 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.

Holotype. MZB.26964, 18.5 mm SL, male; Indonesia, Sumatra Island, Riau, Oil palm plantation; colls. Mulyadi Tjoa Hong Tjai, Nov. 2023. The exact locality withheld to avoid potential pressure on the wild population of ornamental fish industry. Qualified researchers can request information from the first author or MZB. Paratypes. NCUMB.65326, 28 specimens, 22.4–28.4 mm SL; same data as for holotype; colls. Mulyadi Tjoa Hong Tjai & Johan Raharjo. Jun. 2022.

Betta mulyadii sp. nov. differs from its congeners in the B. coccina group by the following unique combination of characters: fewer dorsal-fin rays (8*–10) and subdorsal scales (5*-6); shorter dorsal-fin base (9.89–15.1% SL, mean 12.5%); male with reddish body; without green iridescent mid-lateral body patch; unpaired fins red without significant marks (dorsal and caudal fins with bright bluish margins).

Morphometric and meristic data are summarized in Table 1. General appearances presented in Fig. 5. Head rounded and small. Body slender (at dorsal-fin origin 18.7%–22.0% SL, mean 19.9%), not compressed at caudal peduncle (12.9%–16.5% SL). Dorsal fin narrow (total 8*–10 rays), base short (9.89–15.1% SL with 5*–6 subdorsal scales) and placed significantly far back (predorsal length 58.1–65.9% SL). Dorsal fin pointed with elongated posterior rays, sometimes reaching caudal-fin base in mature males. Anal fin situated ~ ½ body (preanal length 38.1%–43.5% SL), base long (48.9%–58.9% SL). Anal fin with total 27*–29 rays, pointed, posterior rays elongated, sometimes 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 i-I-4+5-I-i). 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 29–30*, plus two or three scales on caudal-fin base; predorsal scales 19–21*; postdorsal scales 9–12 (modal 10); 7–8* scales in transverse series at dorsal fin origin.

Figure 5. 

Illustrations of Betta mulyadii sp. nov. A MZB.26964, 18.5 mm SL male holotype, freshly preserved B male holotype, in stress coloration immediately after capture C breeding male with a bubble-nest, not preserved (laterally inverted) D female, in courtship coloration, not preserved E Bmale, live coloration, not preserved (laterally inverted).

Male (Fig. 5B, C, E). Head reddish with iridescent greenish/golden patches, dorsum reddish with iridescent greenish/golden patches. 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. Body uniformly reddish with weak iridescent blue patches on some scales (absent in stressed or preserved specimens), dorsum reddish with iridescent greenish/golden patches. No distinct dark stripes or iridescent patches on body flank. Dorsal-fin simply red with a bright bluish margin. Caudal fin simple red with a bright bluish margin on the upper half (sometimes also present on the lower half). Anal fin simply red (rarely with a bluish margin). Pectoral fin hyaline. Pelvic fin red with whitish filamentous ray.

Female (Fig. 5D). Head and body coloration similar to male, but less reddish. All fin colorations similar to male, but bluish margin less distinct.

Male (Suppl. material 2: fig. S2): Head yellowish brown, dorsum brownish, no bar present on opercle. Body and dorsum uniformly yellowish brown. Unpaired fin uniformly dark reddish without distinct margin. Pectoral fin hyaline. Pelvic fin red with hyaline filamentous ray.

Female (Suppl. material 2: fig. S2): Head and body coloration similar to male. All fin colorations similar to male, but more brownish.

Betta mulyadii sp. nov. can be easily distinguished from the closely related phylogenetic sister species Betta iaspis sp. nov. by the following combination of characters: uniformly reddish body (vs blackish), simple reddish anal fin (vs blackish with reddish patches on posterior part), dorsal-fin inter-radial membrane without dark marks (vs present). It is also distinct from other congeners of the same phylogenetic branch 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 differs from its most morphologically similar species B. rutilans by the presence of a bright bluish margin on dorsal and anal fins (vs absence/indistinct), elongated anal-fin posterior rays reaching half-length of caudal fin in mature males (vs slightly pointed but not significantly elongated), fewer dorsal-fin rays (8*–10 vs 11–12*), fewer subdorsal scales (5*–6 vs 9*–10) and shorter dorsal-fin base (7.5–19.1% SL vs 20–23%). It also differs 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 and B. tussyae by fewer lateral scales (29*–30 vs 30–31). It can be differentiated from B. brownorum by the lack of an iridescent mid-lateral blotch (vs presence); from B. hendra by a reddish body and fins (vs iridescent bluish/greenish), absence of distinct bar on opercle (vs prominent red parallel bars), fewer transverse scales 7–8* (vs 8–10).

Betta mulyadii sp. nov. is currently known only from an area in Riau, Sumatra Island (Fig. 1).

The species is named after Mulyadi Tjoa Hong Tjai, who discovered this species and contributed much first-hand field information on this genus during the last 30 years. Previously the species was widely known by the common name “api-api” given by the discoverer, which means flame/fire in Bahasa Indonesia referring to the reddish body and lanceolate caudal fin.

The species was first recorded by Mulyadi Tjoa Hong Tjai in Duri in 2012. Currently it is still only found in this area, which is severely disturbed by human activities. Most of the nearby regions have been converted into oil-palm plantations or occupied by oil wells. Thus, we have not yet been able to record this species outside the type locality, which is a broken tiny swamp located inside an oil-palm plantation and adjacent to several running oil wells (Fig. 6). Further studies will be necessary to explore potential remaining population and habitats of this endangered species.

Figure 6. 

Type locality photographs for B. mulyadii A swamp shaded by secondary shrubs B a tiny swamp surrounded by a huge oil-palm plantation C freshly collected specimens of male B. mulyadii from type locality, coll. Mulyadi Tjoa Hong Tjai.

All the syntopic fish species recorded from the habitats include Betta cf. pugnax (Tan & Ng, 2005) and Rasbora einthovenii.

Oil-palm plantations and the petroleum industry have severely destroyed the environment in Duri, especially forest peat swamps. During the field survey in 2023, little original forest peat swamps could be found in this region. The type locality of the new species is in poor condition, original forest no longer exists, and the remaining swamp is shaded by secondary shrubs. Biodiversity is very low, which is expected since it is inside a large oil-palm plantation (Fig. 6B). Few conservation efforts for freshwater fish are known there, since it is also a petroleum industry area. Immediate in-situ and ex-situ conservation is highly recommended for this species. Thus, following the IUCN Red List Categories and Criteria (v. 3.1), we propose Betta mulyadii sp. nov. be listed as Critically Endangered B2ab (iii), based on its very restricted distribution area in a single swamp (< 5 km²) and the extremely high likelihood of becoming extinct due to the current existence of surrounding oil-palm plantations and oil wells.

The consensus phylogenetic tree based on the mitochondrial Cyt b suggests that Betta mulyadii sp. nov. is a monophyletic group distinct from its sister group Betta iaspis sp. nov. by an uncorrected p-distance of 4.35% (Fig. 7; Suppl. material 1: table S2). Betta mulyadii sp. nov. is also distinct from other congeners in the same branch for which Cyt b is available with a p-distance ranging from 5.75% to 7.19% (Suppl. material 1: table S2), and distinguished from the remaining species in the other branch with a p-distance ranging from 19.2%–22.0% (Suppl. material 1: table S2). These results suggest that genetic differences among the new species and its congeners are indicative of divergence at a species level. Betta mulyadii sp. nov. also differs from all known Betta species in its unique morphological characters (see above Diagnosis and Comparison). Thus, based on both molecular and morphological analysis in the current study, this fish from Riau, Sumatra is formally recognized as a distinct species.

Figure 7. 

Phylogenetic tree of Betta species based on Cyt b using ML approaches. The two new species in the phylogenetic tree are highlighted in red (photograph of Betta persephone Jambi: Mulyadi Tjoa Hong Tjai).