Taxonomy & naming
Mogurnda magna was described by Gerald R. Allen and J. D. Renyaan in 1996 from specimens collected in Irian Jaya, Indonesian New Guinea. The species epithet is Latin for 'large' and refers to its exceptional size among the purple-spotted gudgeons: it consistently outgrows all other Mogurnda species, a fact that immediately distinguished it from its congeners in the original description.
The Catalog of Fishes (Eschmeyer, CAS) places the genus Mogurnda in the family Eleotridae, the sleepers and gudgeons — not in Gobiidae. This distinction matters: the sleepers are a sister lineage to the true gobies, recognisable in the hand by their pelvic fins, which remain separate rather than fusing into the cup-shaped sucker disc that characterises true gobies. Older literature placed several Mogurnda species under Gobiomorphus or Eleotris before these genera were reorganised; M. magna itself has not carried a different generic placement since its original description, but the family-level reassignment of eleotrids relative to gobiids has occurred more than once in the modern literature. The Catalog of Fishes is the governing authority for the valid name and family placement used here.
The genus Mogurnda is centred on Australasia and New Guinea, with a small number of species known from northern Australia and a larger number from the island of New Guinea; M. magna stands out among them for its size and its extreme endemism to just two lakes.
Morphology
Mogurnda magna is the largest member of its genus, documented to a maximum of 7.5 in standard length (SL) for females; males are expected to reach similar or somewhat smaller sizes, as is typical in the genus. The body follows the typical gudgeon plan: stocky, slightly compressed, with two dorsal fins (the first spiny, the second soft-rayed), a large mouth, and robust caudal and pectoral fins suited to life near the bottom.
Like other purple-spotted gudgeons, M. magna shows a pattern of reddish-brown to olive body colouration overlaid with rows of orange, red or purple spots, with the exact patterning varying among individuals and populations. The head is large and slightly flattened, the jaws broad enough to accommodate small fish and large invertebrates. The pelvic fins are unremarkable and clearly separate from one another — the key character separating eleotrids from true gobies.
Sexual dimorphism within M. magna is not exhaustively documented in the published literature, but male Mogurnda generally develop more intense colour and, in at least some species, a slightly more elongated body profile relative to females. The large size and solitary, territorial disposition of M. magna suggest that sexing adults in an aquarium context would rely on colour intensity and abdominal fullness in ripe females rather than gross body-plan differences.
Habitat
Mogurnda magna is known only from lakes Laamora and Aiwaso in the Irian Jaya (now Papua province) region of western New Guinea, Indonesia. This two-lake endemic range is among the most restricted of any Mogurnda species. FishBase records it as benthopelagic and common among aquatic plants and rocky substrate along the shoreline — the typical Mogurnda microhabitat of structured, nearshore zones rather than open deep water.
These are freshwater tropical lakes at low elevation, with water temperatures typical of lowland Indonesian New Guinea: warm, stable, and without marked seasonal swings. The species is associated with areas where macrophyte growth and rocky bottom meet, providing both hunting territory for an ambush predator and refuge for shelter. No detailed water-chemistry data for the specific lakes has been published in the accessible literature, but the broader context of lowland New Guinea freshwater — soft to moderate hardness, near-neutral pH — is the expected baseline.
The restriction to two lakes means that M. magna is ecologically dependent on the integrity of both water bodies. Any event that degrades shoreline vegetation, water clarity, or the prey base of those lakes affects the entire global range of the species.
Feeding
Mogurnda magna is a micro-predator and ambush hunter, a feeding strategy consistent across the genus. Congeners such as M. adspersa and M. mogurnda take small fish, aquatic invertebrates, worms, tadpoles and similar prey, ambushing from cover among plants and rocks rather than actively chasing prey in open water. The large body size of M. magna relative to other Mogurnda species likely means it can take correspondingly larger prey items, including small fish of meaningful size.
In the aquarium, Mogurnda species are well documented as refusing dry flake, particularly when first introduced. They require live and frozen meaty foods — bloodworm, earthworm, river shrimp, brine shrimp, feeder fish of appropriate size, prawns, and similar invertebrate and vertebrate prey. A large specimen of M. magna would be expected to consume small fish readily. Conditioning for breeding calls for generous live and frozen feeding; a fish maintained on dry foods alone will deteriorate in condition. Hobbyists keeping large Mogurnda describe them as ambush hunters that wait motionless before striking, and diet accordingly.
Mating
Mogurnda species are resident freshwater cave/substrate spawners, and M. magna is expected to follow the same reproductive strategy documented across the genus, including in the closely related M. adspersa and M. mogurnda. A conditioned male establishes and defends a territory centred on a cave, overhang, crevice, or hard substrate surface. He courts a ripe female with flared fins and intensified colour, leading her to the chosen spawning site.
Pairs in Mogurnda can be aggressive to one another outside of the spawning context — large-bodied sleepers are territorial and may injure each other — so conditioning in a sufficiently large tank with visual barriers, and only introducing the female to the male's territory when she is clearly ripe, reduces the risk of the male attacking the female. The scale of M. magna, the largest member of its genus, means this inter-individual aggression needs more space to manage than would be required for the smaller Australian congeners.
Breeding
In common with its congeners, M. magna is expected to be a cave/substrate spawner in which the female deposits a clutch of adhesive eggs on the roof or wall of a chosen cave, crevice, or hard surface. After spawning the female's role ends and the male takes over, guarding the clutch and fanning the eggs with his fins to maintain oxygenation and deter fungal growth until they hatch. Parental care is solely paternal. The entire cycle takes place in fresh water, so — unlike amphidromous stream gobies — captive breeding is biologically possible.
No detailed aquarium breeding account for M. magna has been located in the accessible literature; the accounts available draw on parallel data from M. adspersa and M. mogurnda. The large adult size of M. magna means a meaningful tank volume (well in excess of 55 US gal for a breeding pair) is required before successful spawning should be expected. Providing multiple caves or sheltered surfaces, warm water, and a conditioning regimen of live and frozen foods is the starting point. Fry, once they hatch, will initially require very fine live foods — infusoria or similar micro-prey — before graduating to freshly hatched brine shrimp nauplii and small chopped invertebrates as they grow.
In the aquarium
Mogurnda magna is a specialist fish that demands more space, more attention to diet, and more care in housing than most aquarium gudgeons. At nearly 8 in SL it is among the larger eleotrids in the hobby, and it will need a large, well-filtered aquarium — 80 US gal or more for a single specimen, substantially more for a pair, given the territorial nature of large Mogurnda. A covered tank is prudent, as eleotrids are capable of launching themselves from the water surface.
The tank should be set up to replicate the shoreline habitat of lakes Laamora and Aiwaso: a mix of rocky structure, bogwood or driftwood caves, and robust or fine-leaved plants that can withstand the attentions of a large benthic fish. Substrate should support digging and bottom-resting. Water should be clean, warm (around 75–82 °F), and freshwater — no salt is required or appropriate. Strong biological filtration is essential given the heavy feeding regime.
Compatibility is limited by the species' predatory nature and large adult size: any fish small enough to be swallowed will be. M. magna should be kept only with similarly sized, robust species or as a specimen fish. Feeding must rely on live and frozen foods; dry flake is generally refused. Hobbyists outside the Indonesian region are unlikely to encounter this species; where it does appear in the trade it is as a rare wild-caught import, and buyers should confirm provenance to avoid contributing pressure to the restricted wild population.
Conservation
The IUCN Red List assessed Mogurnda magna as Near Threatened (NT) in December 2019. The basis of that assessment is its extreme range restriction: the species is known only from lakes Laamora and Aiwaso in the Papua province of Indonesia, two isolated lake systems whose combined area represents the entire global extent of occurrence for the species. A localised pollution event, an introduced competitor or predator, or physical alteration of the lake shoreline could have outsized effects on the entire population.
No evidence of active population decline was available to the assessors at the time of evaluation, and the species was recorded as common within its habitat by FishBase. It therefore sits in the Near Threatened rather than Threatened categories, but the precautionary logic of that placement is straightforward: a species with this narrow a range has very little buffer against stochastic events. Pressures typical of lowland Indonesian New Guinea — forest clearance, agricultural runoff, artisanal fishing pressure, and the risk of invasive species introductions — are all plausible threats.
The species is not currently the subject of any documented captive-breeding conservation programme; any hobbyist who obtains and successfully breeds specimens is contributing to ex-situ knowledge about the species that could, in principle, support future conservation management. Wild collection for the trade should be considered carefully against the restricted population size.