Taxonomy & naming
Parasphaerichthys ocellatus was described by Prashad and Mukerji in 1929 from a muddy stream along the Kamaing Jade Mines Road, Kamaing, Myitkyina District, Upper Myanmar — a type locality that situates the species firmly in the upper Ayeyarwady (Irrawaddy) drainage of Kachin State. The Catalog of Fishes records the valid combination as Parasphaerichthys ocellatus Prashad & Mukerji, 1929, with the authority unparenthesised because the species was originally described in this genus.
The genus Parasphaerichthys was erected to accommodate labyrinth fishes that resemble the chocolate gouramis of the genus Sphaerichthys without being fully assignable to them. P. ocellatus is one of only two species in the genus, the other being P. lineatus, which is distinguished by a continuous mid-lateral stripe and fewer anal-fin rays (8–10 versus 11–16 in P. ocellatus). The single documented Mandalay market specimen from 1983 adds a tentative southward data point but has not altered the genus or species diagnosis.
Morphology
Parasphaerichthys ocellatus is a small, somewhat laterally compressed fish reaching a maximum standard length of approximately 1.5 in (Seriously Fish records 1.5 in SL; FishBase lists 2 in SL for the largest recorded individual), with most aquarium specimens and hobbyist reports citing a practical size of 1 in. The body is stocky and broadly ovoid in profile, typical of the Sphaerichthys alliance, with a relatively large head and upturned mouth suited to surface-film feeding.
Colouration is cryptic: the overall ground colour is brown to greyish-brown with a faint iridescent sheen under direct light. The diagnostic feature is a prominent, dark-edged ocellus — a round spot resembling an eye — on each flank roughly behind the pectoral fin insertion. This ocellus, referenced in the specific epithet, distinguishes the species from P. lineatus, which carries a mid-lateral stripe instead. The dorsal and anal fins are soft-rayed and similarly muted. Females are reported to be larger and more thick-bodied than males, a reversal of the male-larger pattern seen in many anabantoids.
Habitat
The species inhabits small, shallow, muddy streams and marginal standing-water pools in Kachin State, northern Myanmar, within the upper Ayeyarwady basin. Known localities include streams near Kamaing in Myitkyina District and the littoral zone of Lake Indawgyi — a shallow, lowland lake protected as Indawgyi Lake Wildlife Sanctuary since 1999 and recognised as one of the largest inland lakes in Southeast Asia.
The characteristic habitat is slow-moving to standing water with heavy bankside and marginal vegetation, soft or muddy substrate, and naturally turbid conditions. As a labyrinth fish, P. ocellatus is a facultative air-breather capable of supplementing gill respiration at the surface — an adaptation well-matched to the oxygen-depleted, organically rich water of the muddy pools it frequents. A striking ecological feature is the large diel thermal swing of these shallow habitats: field and hobby sources report temperatures of roughly 59 °F at night rising to 77–82 °F during the day, a fluctuation far wider than the stable tropical baseline assumed for most equatorial labyrinth fishes. FishBase cites a thermal range of 75–79 °F for the species; Seriously Fish records 59–77 °F, reflecting the full seasonal sweep. Water chemistry is reported as mildly acidic to neutral (pH 6.5–7.5) with moderate hardness (90–179 ppm).
Feeding
Parasphaerichthys ocellatus is a micropredator in the wild, picking small aquatic invertebrates from the water column and substrate. Natural prey items include small crustaceans, worms, insect larvae, and zooplankton — the typical small-prey diet of a diminutive anabantoid hunting in still, vegetated water.
In the aquarium the species can be a finicky feeder and may refuse or be slow to accept dry prepared foods. Live and frozen micro-prey — baby brine shrimp, Daphnia, cyclops, micro-worms — are preferred and are generally necessary to bring fish into peak condition. The small mouth size restricts particle size; foods appropriate for nano-fish and small tetras are the correct reference point. A varied diet with a strong live-food component is the most reliable route to long-term health and breeding condition.
Mating
Parasphaerichthys ocellatus is a bubble-nest builder, and that fact places it in a minority among the Sphaerichthys-allied group that otherwise trends toward oral brooding. The confirmation came from aquarium observation by hobbyist breeder Frank Strozyk, whose experience is documented on Seriously Fish; the eggs are described as morphologically unusual for a bubble-nester — bearing spiralling surface ridges more typical of mouthbrooder eggs — a trait that Aquarium Glaser notes as unique and suggestive of a relatively recent evolutionary shift from mouthbrooding ancestry.
Male P. ocellatus construct a foam nest at or near the water surface, typically among floating vegetation or under a leaf. Courtship involves the male displaying to the female, and spawning takes place beneath the nest. Females are reported to be larger and more robust than males, an inversion of the typical anabantoid pattern and consistent with female-size advantage in mouthbrooding Sphaerichthys, though P. ocellatus does not itself mouthbrood. After spawning the male guards the nest and patrols territory while the female is reported to patrol the perimeter of the spawning area.
Breeding
Breeding P. ocellatus in captivity is rarely achieved and poorly documented in the mainstream literature, reflecting how infrequently the species is imported or held. From the accounts that exist, males build a bubble nest near the surface, the pair spawns beneath it, and the fertilised eggs are gathered into the foam structure. Incubation lasts approximately 3–5 days before the eggs hatch. The male guards the nest through this period.
Replicating the species' unusual thermal environment is likely important for conditioning and spawning: the wide day-to-night temperature swing (roughly 59 °F overnight to 77–82 °F by day) that Aquarium Glaser records for the natural habitat suggests the fish may require, or at least benefit from, a programmed temperature variation rather than the constant-temperature conditions assumed for most tropical aquarium fishes. A soft, slightly acidic, well-planted aquarium with floating cover, very gentle filtration, and live-food provisioning gives the best chance of spawning success. Fry are presumably very small and will need appropriately sized first foods such as infusoria or commercial nano-fry preparations.
In the aquarium
Parasphaerichthys ocellatus is extremely rarely available in the hobby — Aquarium Glaser describes it as one of the least-frequently imported anabantoids — and is primarily an interest for the dedicated specialist rather than the general aquarist. When obtainable, it suits a small, quiet species tank of 10–15 US gal or more, heavily planted and with floating vegetation at the surface to provide the cover this shy fish expects and to support bubble-nest building.
Water conditions should be soft and slightly acidic to neutral (pH 6.5–7.5), warm but subject to deliberate temperature fluctuation as described above. Filtration must be gentle enough not to disturb the surface or the nest; a sponge filter is ideal. The species should not be mixed with boisterous or nippy tankmates; smaller, calm fish or a single-species setup is safest. As a labyrinth fish, unobstructed surface access for air-breathing is non-negotiable — the space between the water surface and the tank lid must be warm and humid, not cold, as sudden temperature shock at the surface can damage the labyrinth organ. Given the species' sensitivity to disease when the thermal fluctuation of its natural habitat is not replicated, maintaining some degree of controlled temperature variation — or at minimum avoiding stable high temperatures — may improve long-term survival.
Conservation
Parasphaerichthys ocellatus is assessed as Least Concern (LC) on the IUCN Red List, with the assessment dated 24 January 2010. The Least Concern designation reflects that no range-wide decline or severe threat was identified at the time of assessment, though the restricted distribution in upper Myanmar — a region subject to varying degrees of environmental pressure and limited survey effort — means the data underpinning the assessment are not extensive.
The species benefits from at least one well-protected locality: Lake Indawgyi and its surroundings are designated as the Indawgyi Lake Wildlife Sanctuary, a Ramsar Wetland of International Importance, which affords a degree of habitat protection. The rarity of the species in the aquarium trade means commercial collection pressure is negligible. Ongoing monitoring of the upper Ayeyarwady basin streams and the Indawgyi watershed would strengthen confidence in the Least Concern assessment over time.