Taxonomy & naming
Betta iaspis was formally described by Ding, Lei, Haryono, Shi and Zhang in 2025 in the journal ZooKeys. The holotype is a male (MZB.26963, 1 in SL) collected from a forest peat swamp in Jambi, Sumatra, Indonesia. Eschmeyer's Catalog of Fishes is the governing authority for the valid name.
The species belongs to the Betta coccina species group, a complex of small, crimson-tinged fighting fishes distributed across Sundaland. Phylogenetic analysis of the cytochrome b gene placed B. iaspis closest to B. mulyadii, described simultaneously from the same region, from which it diverges by 4.35%; divergence from more distant coccina-group relatives runs from 5.40 to 6.32% (or 19.2–22.0% depending on how the comparison group is framed). The two simultaneously described species were distinguished by coloration, meristics, and molecular data.
Morphology
Betta iaspis is a small species reaching a maximum known standard length of 1 in (approximately 1 inch). The holotype male measured 1 in SL. Fin-ray counts recorded in the original description include 8–10 dorsal soft rays and 27–28 anal soft rays.
Males display a reddish-brown head, a dark dorsum, and a posterior body that shows faint blue iridescence. The iris carries patches of bluish iridescence. The dorsal, pelvic, and caudal fins are red with blue margins; the anal fin is blackish with a small number of red patches. Females resemble males in basic pattern but show less intense coloration overall; breeding females display dark lateral body stripes. The species is most readily separated from its sister taxon B. mulyadii by the distinctive blackish anal fin with only sparse red patches, a character noted by multiple observers following the description.
Habitat
The entire known range of Betta iaspis is a single forest peat swamp in Jambi province, Sumatra, Indonesia. The habitat is a shallow, shaded swamp within intact peat-swamp forest — the kind of environment that supports high endemism among Sundaland fishes because each patch is effectively isolated from neighbouring drainages by intervening uplands.
Water chemistry measured at the type locality during the dry season was strongly acidic and extremely soft: pH 5.0 and total dissolved solids of only 12 ppm, with a temperature of 86 °F. These are classic blackwater peat-swamp conditions — tannin-stained, low-conductivity, high-temperature water poor in dissolved oxygen. Like all members of the family Osphronemidae, B. iaspis possesses the labyrinth organ, a suprabranchial accessory breathing structure that allows it to gulp atmospheric air and survive in the oxygen-depleted waters typical of this habitat. During the dry season the swamp partly desiccates; field observations suggest the fish survive the dry period in moist mud beneath accumulated dead leaves, resuming normal activity and reproduction when the rains refill the swamp. Syntopic species recorded at the locality include Betta simorum, Boraras maculatus, Rasbora einthovenii, and Sphaerichthys osphromenoides — a characteristic peat-swamp assemblage.
Feeding
No specific dietary study has been published for Betta iaspis. By analogy with well-documented coccina-group relatives, the species is presumed to be a carnivore or micropredator, feeding on small aquatic invertebrates — chironomid larvae, microcrustaceans, and other fauna of the peat-swamp leaf litter — as well as terrestrial insects that fall onto the water surface.
In captivity, coccina-group bettas generally require or strongly prefer live and frozen small invertebrates: Daphnia, Artemia nauplii, Tubifex, small bloodworm, and similar items. Their small mouth and the fine fauna of their native habitat mean they are not well suited to accepting coarse prepared foods without acclimation. Frequent small feedings reflect the opportunistic foraging style of these fishes in nature.
Mating
Betta iaspis is a bubble-nesting species. Males of bubble-nesting Betta build a raft of mucus-bound air bubbles at the water surface, typically anchored beneath a broad leaf or along the bank, and use this structure as the focal point of courtship and parental care. The labyrinth organ, which allows the male to breathe atmospheric air, is directly implicated in bubble production: the fish gulps air, coats each bubble with oral mucus, and places it into the nest.
Courtship follows the pattern seen across bubble-nesting Betta: a displaying male extends his fins, intensifies body and fin coloration, and manoeuvres to position himself beneath or beside a receptive female near the nest site. Females signal receptivity through posture and coloration; gravid females of coccina-group species often show the dark lateral stripes documented in the field notes for B. iaspis. Mating activity in the wild coincides with the rainy season, when the swamp refills and conditions are most stable.
Breeding
Following the bubble-nest mating embrace typical of the group, the female releases eggs that are caught and placed into the nest by the male. He then guards the nest and the developing eggs, retrieving any that fall and aerating the nest by blowing fresh bubbles into it. Parental care is exclusively paternal; the female plays no role in guarding the eggs or fry and is typically removed by breeders to prevent aggression.
Field observations in the type locality indicate the species reproduces normally in the rainy season, when the habitat refills after the seasonal dry period. For specialist hobbyists attempting to breed coccina-group species, replicated conditions typically include very soft, acidic water (pH 5.0–6.0, extremely low conductivity), warm temperatures (82–86 °F), low flow, and the provision of broad-leaved surface cover to anchor the bubble nest. Fry of coccina-group bettas are among the smallest in the genus and require very fine live foods — infusoria, vinegar eels, or rotifers — as first foods before graduating to Artemia nauplii.
In the aquarium
Betta iaspis is not yet established in the broader ornamental trade as of the time of its description in 2025, and captive specimens are extremely rare. Interest in the species exists among specialist coccina-group keepers, given the group's popularity with Betta enthusiasts attracted to their small size, vivid coloration, and complex behaviour.
Successful maintenance of B. iaspis, should captive stock become available, would require replication of its extreme blackwater conditions: very soft, acidic water (pH around 5.0, TDS below 20 ppm), warm temperature (82–86 °F), gentle or negligible filtration, surface access for the labyrinth organ, and a tannin-rich environment created by peat filtration or dried leaf litter. The species' tiny adult size (under 1 in SL) means it is suitable only for small, species-specific setups and would be at risk from even mildly aggressive tankmates. As with all coccina-group bettas, males are intolerant of one another; pairs or trios with extra females are the standard approach. Given the species' extreme rarity and critical conservation situation in the wild, any hobbyist stock should be treated as a conservation asset and bred carefully.
Conservation
At the time of its formal description in 2025, Betta iaspis had not yet received an official IUCN Red List assessment. However, the original description explicitly proposed a Critically Endangered status under criterion B2ab(iii), based on an area of occupancy estimated at less than 19 mi² concentrated in a single forest peat swamp, combined with ongoing and projected habitat loss. The threats identified are concrete and severe: oil-palm plantation irrigation and coal mining operations in the Jambi region of Sumatra are actively encroaching on or directly altering the hydrology of peat-swamp habitats across the region.
The species' biology compounds its vulnerability. Seasonal desiccation of the type locality swamp already pushes the population to a physiological extreme during the dry season; any further drainage or hydrological disruption would eliminate the habitat entirely. Its known range is, as far as can be determined, a single swamp with no known satellite populations. If confirmed by a formal IUCN assessment, Critically Endangered would place B. iaspis among the most threatened freshwater fishes in the world by range size. Peat-swamp forests in Sumatra have experienced severe deforestation rates in recent decades, and the species' extreme habitat specificity leaves no buffer against further loss.