Taxonomy & naming
Macropodus lineatus was described by Nguyen, Ngo & Nguyen in 2005 from specimens collected in Phong Nha-Ke Bang National Park, Quang Binh Province, central Vietnam. The holotype measures 2 in SL (the illustrated specimen 2 in SL), with paratypes ranging from 1.5–2 in SL. Eschmeyer's Catalog of Fishes (Catalog of Fishes, CAS) recognises the valid name as Macropodus lineatus Nguyen, Ngo & Nguyen, 2005.
The genus Macropodus belongs to the family Osphronemidae (gouramis and allies) within the suborder Anabantoidei — the labyrinth fishes. The paradisefishes of Macropodus are distributed across East and Southeast Asia, and M. lineatus represents the group's reach into the limestone karst uplands of central Vietnam. Its closest relatives within the genus are not formally established in the accessible English-language literature, but the species' morphology and range place it among the smaller, more recent additions to a genus still under active revisionary study.
Morphology
FishBase records a maximum total length of 4.5 in TL (approximately 3 in SL) for Macropodus lineatus, consistent with the paratype size range of 1.5–2 in SL documented in the original description. This makes it a small to mid-sized paradisefish, broadly comparable in body length to some of the smaller members of the genus.
Specific morphological detail for this species is sparse in the accessible literature. As a member of Macropodus it is expected to display the family's characteristic labyrinth organ housed in the suprabranchial chamber — the structure allowing direct atmospheric air-breathing that defines the anabantoids — as well as the elongated fin rays and laterally compressed body typical of the genus. The specific epithet lineatus (Latin: lined or striped) suggests a patterned appearance, likely involving longitudinal or lateral striping, but detailed colour descriptions from the original Vietnamese description have not been widely reproduced in English-language sources, and data on this species remain sparse.
Habitat
Macropodus lineatus is endemic to central Vietnam, with the type locality in Phong Nha-Ke Bang National Park, Quang Binh Province — a UNESCO World Heritage site renowned for its extensive limestone karst formations and cave systems. The species inhabits streams in this karst environment, where water chemistry is likely influenced by the calcium-rich geology of the surrounding limestone.
As a labyrinth fish in a stream habitat, M. lineatus presumably inhabits slower-flowing reaches, side pools, or marginal zones where the still or low-flow conditions suit its air-breathing physiology. Labyrinth fishes generally favour warm, often oxygen-poor water where their ability to take air at the surface confers an advantage; even in faster-flowing habitats, individuals tend to seek sheltered pockets. The precise water parameter range for the Phong Nha-Ke Bang stream system is not documented in the available cache sources, but the limestone geology suggests neutral to mildly alkaline conditions and moderate hardness.
Feeding
No dietary studies specific to Macropodus lineatus have been located in the available literature. By analogy with better-known members of Macropodus and the broader anabantoid literature, the species is most likely a generalist predator at the invertebrate scale — taking small aquatic insects, insect larvae, crustaceans, worms, and other invertebrates opportunistically from the water column and surface.
In the aquarium, if specimens were ever kept and studied, a diet of live and frozen foods such as Daphnia, bloodworm, and mosquito larvae — standard fare for small anabantoids — would be appropriate. Macropodus species are generally willing feeders in captivity and accept prepared dry foods alongside live or frozen items. Data on wild feeding ecology for this species remain absent from English-language sources.
Mating
Macropodus lineatus has not been documented in the aquarium hobby literature at the time of writing, and no breeding observations have been published in accessible English-language sources. However, as a member of Macropodus — a genus characterised uniformly by bubble-nest construction — it is fully expected to share the reproductive strategy of its congeners.
In Macropodus, males build and defend a floating raft of mucus-bound bubbles at the water surface, usually anchored beneath overhanging vegetation or a floating leaf. Courtship involves the male displaying to the female with erect, spread fins and lateral posturing. Once a receptive female is drawn in, spawning occurs beneath the nest in a characteristic embrace, with the male coiling around the female while eggs and milt are released simultaneously. The male takes sole responsibility for collecting eggs, placing them in the bubble nest, and guarding the nest site throughout incubation.
Breeding
No captive breeding of Macropodus lineatus has been documented in accessible English-language sources, and the species appears to be essentially unknown in the international aquarium hobby. Based on the genus-level biology of Macropodus, eggs deposited in the bubble nest would be expected to be buoyant and hatch within approximately 24–48 hours at typical tropical temperatures, with the male actively tending the nest and retrieving any eggs that fall. Free-swimming fry would initially require very fine first foods.
The species' endemism to a single national park in central Vietnam means wild populations are unlikely to be commercially collected, and any captive specimens would be rare research or specialist acquisitions. No clutch-size, incubation period, or rearing data are available for this species specifically. The bubble-nest mode and male-guarded parental care that define Macropodus breeding biology remain the best available framework until captive observations are published.
In the aquarium
Macropodus lineatus is not represented in the English-language aquarium hobby literature and appears to be absent from the international ornamental fish trade. No care guides, husbandry notes, or keeper experiences have been located in available sources. The species is known only from wild collections in a protected national park and from the primary scientific description.
For any aquarist who might encounter this species in a specialist context, the general framework for small Macropodus would apply: a planted aquarium with slow flow or still areas, surface access for air-breathing, temperatures in the tropical range appropriate to central Vietnamese upland streams, and the expectation of bubble-nest construction by the male. As with all paradisefishes, males may be territorial toward one another, and males can be aggressive toward females outside of spawning readiness. Data on specific care requirements remain absent.
Conservation
Macropodus lineatus has not been formally evaluated by the IUCN Red List; its status is Not Evaluated (NE). The species is a narrowly endemic fish restricted to the Phong Nha-Ke Bang National Park area of Quang Binh Province, central Vietnam — a protected area, which offers some baseline habitat security. However, endemism to a small geographic area is inherently a vulnerability.
The limestone karst streams of Phong Nha-Ke Bang are subject to ongoing pressures from tourism development, agricultural runoff from surrounding areas, and the general impacts of economic activity in the broader province. The species' status outside the park boundaries, if it occurs there at all, is unknown. A formal IUCN assessment would clarify whether the national park's protection is sufficient to safeguard the population or whether additional survey work and conservation measures are warranted. Until such an assessment is undertaken, the species' conservation situation remains unquantified.