Taxonomy & naming
Mogurnda lineata was formally described by Gerald Allen and D.F. Hoese in 1991 as part of a review of the genus Mogurnda. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) — the authoritative register of valid names — places it in the family Eleotridae, the sleeper gobies or gudgeons. It is not a true goby. True gobies (families Gobiidae, Gobionellidae and Oxudercidae) carry their pelvic fins fused into a cup-shaped sucker disc that helps them cling to rocks in fast current; eleotrids like Mogurnda retain separate pelvic fins, the ancestral condition for the group. The hobby name 'goby' is applied loosely across both families, but the distinction matters for understanding behaviour and care.
Within Eleotridae, Mogurnda is an Australasian genus centred on Australia and New Guinea, and is most closely allied to other purple-spotted gudgeons of that region. No older combination under Eleotris or another genus has been found in the literature for this species; Allen & Hoese's 1991 description established the name that remains valid today. The species epithet lineata is Latin for 'striped' or 'lined', almost certainly referring to a pattern element on the body or fins visible in the type material.
Morphology
FishBase records a maximum standard length of 3.5 in — making this a small, stream-adapted gudgeon. Standard length (SL) excludes the tail, so total length in life is somewhat greater, though the fish would still be considered a compact species within the Mogurnda genus. The body plan is that of a typical sleeper: elongate and slightly cylindrical toward the head, tapering to the tail, with two separate dorsal fins and the diagnostic separate (not fused) pelvic fins.
Detailed colour pattern data for M. lineata are sparse in the accessible literature; the species epithet lineata points to a lined or striped pattern, and Mogurnda species typically display rich lateral markings — bands, spots, or streaks — used in species recognition and courtship. Sexual dimorphism follows the general Mogurnda pattern: males of related species are more intensely coloured and somewhat larger than females, and males may develop brighter fin colouration during breeding readiness. Without a published colour description in the available sources, fine details of patterning cannot be confirmed here.
Habitat
The Kokoda mogurnda lives in clear, fast-flowing rainforest streams in the foothills of the Owen Stanley Range, at elevations of approximately 919–1148 ft above sea level. The three known localities — Kali Creek, Ejava Creek, and Oivi Creek — lie within about 7–9 mi east of Kokoda. These are small, cool-to-warm, well-oxygenated freshwater streams over rocky and gravelly substrates, shaded by dense overhanging forest. The benthopelagic habit noted by FishBase indicates it lives and forages close to the stream bed rather than in the water column.
This is a strictly freshwater species: no evidence of estuarine or brackish tolerance has been reported, and the foothill stream environment is entirely freshwater. The altitude and latitude of the Kokoda track region mean water temperatures are somewhat moderated compared with lowland PNG streams; a range of roughly 64–82 °F is consistent with the climate of the region and the documented ranges of related Mogurnda species from comparable elevations, though direct temperature measurements from these specific creeks are not recorded in the accessible literature.
Feeding
Mogurnda lineata is a micro-predator, as is every member of the genus. In its stream habitat it would forage along the rocky benthos for small aquatic invertebrates — insect larvae, small crustaceans, worms and similar prey items that drift or cling to the substrate. Eleotrid gudgeons at this size class are visual hunters that wait and strike rather than active open-water chasers.
No aquarium-specific feeding data exist for this species in the available literature, but experience with closely related Mogurnda species indicates that small live and frozen foods — bloodworm, brine shrimp, daphnia, cyclops, tubifex and small crustaceans — will be accepted readily, while dry flake is typically refused or taken only poorly. Any keeper who acquires a specimen should prioritise live and frozen meaty foods and treat dry food as a supplement at best; a diet of flake alone risks condition loss and shortened lifespan.
Mating
Mogurnda species are resident freshwater cave-spawners with genuine male parental care — the same spawning strategy used across much of the Eleotridae in Australasia, and fundamentally different from the egg-scattering of cyprinids or the mouthbrooding of cichlids. A gravid female is typically rounder in the belly; males of Mogurnda species become more intensely coloured and display actively at cave entrances to attract females.
No direct observations of courtship in M. lineata have been published in the accessible literature. The species is not known to be amphidromous — unlike the stream gobies of the Sicydiinae, whose larvae must travel to the sea to develop, Mogurnda complete their entire life cycle in fresh water. This means that, in principle, a captive pair housed in appropriate conditions could attempt to spawn without any marine or brackish component.
Breeding
In the Mogurnda genus, breeding follows a consistent pattern: a pair selects a crevice, cave, undercut rock or sheltered surface; the female deposits a clutch of adhesive eggs on the roof or wall of the site; and the male then takes over, guarding the eggs and fanning them with his fins to maintain oxygen flow until they hatch. The female plays no further role. This is the same cave-guarding mode seen in the peacock gudgeon (Tateurndina ocellicauda) and other resident eleotrids.
For M. lineata specifically, no confirmed captive-breeding accounts appear in the available literature — the species is essentially unknown in the aquarium hobby, and the combination of its Endangered status and extreme range restriction means very few specimens are likely in private collections. Care notes based on its Mogurnda relatives suggest that a cave or pipe, clean, well-oxygenated water, and a well-fed pair in a species tank would be the conditions most likely to encourage spawning if the fish were ever kept. Fry from related species are small at hatching and require micro-foods in the first days.
In the aquarium
Mogurnda lineata is effectively absent from the aquarium trade. It is an Endangered endemic known from three creeks in a remote foothill catchment of Papua New Guinea, and there is no indication of any established captive population or commercial supply. Keeping this species is a realistic prospect only for a specialist working with PNG fauna, and any acquisition should be accompanied by careful documentation of provenance.
For reference, care would follow general Mogurnda principles: a covered aquarium (eleotrids can jump), well-oxygenated and filtered, with rocky substrate, cave-forming structures and adequate line-of-sight breaks between any male individuals. Water should be fresh — no salt — and maintained at temperatures consistent with the foothill-stream climate of the type locality (roughly 64–79 °F). Diet should consist exclusively of small live and frozen foods. Males of Mogurnda species are territorial and should not be kept in cramped conditions with other males. Given the species' Endangered conservation status, any hobbyist interest in this fish should prioritise captive-bred stock over wild collection.
Conservation
Mogurnda lineata is assessed as Endangered (EN) on the IUCN Red List, with the most recent assessment dated May 2020. The grounds for this listing are straightforward: the species has one of the most restricted natural ranges of any fish in this atlas, confined to three named creeks within a catchment of perhaps a few square kilometres near Kokoda, Papua New Guinea. A species with so small an area of occupancy is inherently vulnerable — a single pollution event, an agricultural expansion, water extraction, or a severe drought affecting those three streams could eliminate the entire wild population.
The Kokoda Track region is subject to ongoing pressures from subsistence agriculture, logging activities in surrounding forest, and the general development pressures affecting PNG's lowland and foothill zones. No evidence of trade-driven pressure on this species has been documented — it is not in the aquarium trade — but habitat degradation and water quality changes in its stream habitat remain the primary threats. Its continued survival depends on the integrity of the rainforest catchment in which those three creeks flow.