Taxonomy & naming
Boleophthalmus dussumieri was described by Achille Valenciennes in 1837, and the Catalog of Fishes (Eschmeyer, CAS) — the authority for valid names — places it in the genus Boleophthalmus within the family Oxudercidae, the subfamily Oxudercinae that contains the mudskippers and their close allies. Earlier literature sometimes listed it under Gobius or placed the genus in the now-disused Periophthalmidae; the current family arrangement unites the mudskippers with the rest of the former Gobiidae sensu lato in a restructured scheme, but Boleophthalmus has always stood as a distinct and recognisable genus.
The species epithet honours Jean-Jacques Dussumier, a French merchant and naturalist who collected specimens along the coasts of the Indo-West Pacific in the early nineteenth century and whose material underpins many Valenciennes descriptions. Boleophthalmus dussumieri is closely related to B. boddarti (the blue-spotted mudskipper) and B. pectinirostris (the Chinese blue-spotted mudskipper), and the three species share the diagnostic character of the comb-like lower jaw dentition used in deposit-feeding — a feature that sets the Boleophthalmus mudskippers apart from the carnivorous Periophthalmus and Periophthalmodon genera.
Morphology
Like all members of its family, Boleophthalmus dussumieri is a true goby, and the clearest sign of that is the pelvic fins, which are fused into a cup-shaped sucker disc on the underside of the body — the character that distinguishes true gobies (Gobiidae, Gobionellidae, Oxudercidae) from the sleepers and gudgeons (Eleotridae), which keep their pelvic fins separate. The pectoral fins are thick-based and muscular, forming the stiff arm-like props the fish uses to prop itself upright and to crutch across the mud in the characteristic mudskipper gait.
Adults of this species reach approximately 8–8.5 in in total length, making them among the larger Boleophthalmus mudskippers. The dorsal fins are two: the first is a short, erect fan of spines that the fish raises in territorial display and courtship; the second is longer and runs back along the body. The body colouration is a dull brownish-olive, often with a bluish or greenish iridescent sheen on the flanks and scattered pale spots, providing camouflage against the grey-brown surface of tidal mudflats. The large, mobile eyes are set high on the head and can be rotated independently — a functional adaptation that lets the fish scan for predators while stationary.
Habitat
Boleophthalmus dussumieri inhabits the intertidal zone of estuaries, mangrove forests, and tidal mudflats along the coasts of the northern Indian Ocean and the western Pacific. Its range spans from the Persian Gulf and the coasts of India and Sri Lanka east through Myanmar, Thailand, Malaysia, and Indonesia, and into the South China Sea. It is an animal of the tidal edge: at low tide it emerges onto the exposed mud surface to feed and to engage in territorial and courtship behaviour; as the tide rises it retreats into the burrow it has excavated or rises to perch on mangrove roots.
The habitat is brackish rather than fresh: tidal mudflats receive a fluctuating mix of river water and seawater, and salinity varies with rainfall, tide, and season. Water temperatures across this range are warm to very warm, broadly 75–90 °F through most of the year, and the fish spends much of its active time in air rather than water — it breathes cutaneously through its moist skin and retains water in its enlarged gill chambers, which must stay damp. High humidity is essential; a fish confined to water without emersion access will deteriorate.
Feeding
The feeding ecology of Boleophthalmus dussumieri is one of its most distinctive features. Unlike the majority of mudskippers, which are active carnivores that hunt small crustaceans, worms, and other invertebrates on the mudflat surface, Boleophthalmus is a deposit-feeder and microalgae grazer. It moves slowly across the surface of the mud with a rhythmic side-to-side scooping movement of the lower jaw, scraping up the thin layer of diatoms, cyanobacteria, and microalgae that grow on the upper few millimetres of tidal sediment. This is why the lower jaw dentition is comb-like rather than pointed: it is designed to rake the sediment rather than seize prey.
In captivity, replicating this diet is one of the main challenges of keeping the species. A tank with a mature mudflat substrate that has developed a visible biofilm is more likely to sustain the fish than one where it is offered conventional fish foods. Some keepers supplement with finely crushed algae wafers or nori placed on the substrate surface; others cultivate diatom films on rocks or trays of mud. Carnivore feeds and pellets are generally ignored or poorly accepted.
Mating
Courtship in Boleophthalmus dussumieri centres on the burrow. Males excavate and defend territories that each include one or more J- or Y-shaped burrows dug into the mud, and it is in and around these burrows that breeding takes place. Rival males are challenged with erect dorsal fin displays, lateral posturing, and chasing; a sufficiently challenged male may be pushed out of his territory altogether. Courtship of a female involves similar dorsal-fin fanning and a series of jumps and skips — the leaping behaviour common to mudskippers and used in both territorial and courtship signalling.
The female is attracted into the burrow by the displaying male. Both sexes visit the burrow entrance repeatedly during pair formation, and the final descent into the tunnel for spawning follows prolonged courtship. Because breeding occurs inside the sealed burrow and is rarely observed directly, the exact sequence is inferred from burrow structure, egg observations, and analogy with the closely related B. boddarti and B. pectinirostris, for which there are more detailed accounts.
Breeding
Boleophthalmus dussumieri spawns inside its mud burrow in a specialised air-filled chamber. The female lays adhesive eggs on the wall of this chamber, and the male then takes sole charge of the clutch: he guards the entrance, repairs the burrow against tidal disturbance, and — critically — tops up the air supply in the breeding chamber by swallowing mouthfuls of air at the surface and expelling them underground, maintaining an oxygen-rich atmosphere around the eggs. The embryos develop in this aerial environment, not submerged, and the hatchlings are pelagic — they enter the water column and are dispersed by tidal currents, developing in the estuarine or coastal zone before eventually recruiting back to intertidal mudflat habitat.
The pelagic larval phase means that captive breeding of mudskippers of this type is rarely if ever achieved in the home aquarium. Even if spawning were to occur in a paludarium, the larvae would need conditions that replicate estuarine dispersal and development — effectively impossible to provide domestically. Boleophthalmus dussumieri should be considered a display and observation animal, not a breeding project, and specimens in the trade are wild-collected.
In the aquarium
Keeping Boleophthalmus dussumieri requires a paludarium — an enclosure that provides both a body of warm brackish water and an accessible land area of soft, fine-grained substrate, ideally a deep sand-mud mix that the fish can excavate. A salinity of around 1.005–1.015 specific gravity (roughly 7–20 ppt) suits the intertidal brackish habitat; the water portion of the tank need not be large, but it must be present for swimming and skin-moistening. A secure, tight-fitting lid is mandatory — mudskippers can and do climb, and escapes are fatal.
The land area must be humid at all times; a misting system or regular manual spraying keeps the emersed substrate moist and supports the fish's cutaneous respiration. Temperatures should be maintained at 75–86 °F. Decor of driftwood, mangrove root sections, or artificial rock replicates the mangrove-edge perching spots the fish uses in the wild. Feeding is the principal difficulty: a mature biofilm on the substrate surface is the closest approximation to the natural microalgae diet, and without it the fish is hard to sustain long-term. This is a specialist fish for a specialist keeper; it is not suitable for a community aquarium or for beginners, and its dietary requirements mean most hobbyists find it challenging to keep in good condition.
Conservation
Boleophthalmus dussumieri has not been formally assessed on the IUCN Red List, and it carries no conservation category here; we record it as Not Evaluated rather than assign a speculative status. Across much of its range it remains locally common on tidal mudflats, and it is a widespread species rather than a narrow endemic. However, the tidal mudflat and mangrove habitats it depends on are among the most threatened coastal ecosystems in South and Southeast Asia. Mangrove clearance for aquaculture ponds, coastal reclamation for industrial and urban development, and increased sedimentation from deforestation of inland catchments have reduced suitable intertidal habitat substantially across India, Thailand, Malaysia, and Indonesia over recent decades.
All specimens entering the aquarium trade are wild-collected, since captive breeding is not achievable. Collection pressure on this species specifically is thought to be low relative to habitat loss, but the trade should be noted when purchasing. Keepers in a position to support intertidal habitat conservation efforts — particularly those focused on mangrove restoration — contribute more to the long-term future of animals like this one than any captive-husbandry effort can.