Taxonomy & naming
Mogurnda spilota was described by Gerald R. Allen and Douglass F. Hoese in 1991, in a paper on the eleotrid fishes of Lake Kutubu published through the Western Australian Museum. It was one of three new species they placed in Mogurnda allied to the then-existing species M. variegata, distinguished from the others by its colour pattern and snout profile. The Catalog of Fishes (Eschmeyer, CAS) — the authority for valid names — retains Mogurnda spilota as the accepted combination, placing the genus firmly in the family Eleotridae.
The family Eleotridae, the sleepers and gudgeons, is the sister lineage to the true gobies (Gobiidae and their close relatives the Gobionellidae and Oxudercidae). The simplest way to separate the two lineages in the hand is the pelvic fin: in a true goby the two pelvic fins are fused into a single cup-shaped sucker disc on the belly; in an eleotrid — including all Mogurnda — the pelvis fins remain separate. This character has nothing to do with size or color and holds regardless of age or sex. The trade uses 'goby' loosely, but Mogurnda spilota is correctly called a gudgeon or sleeper.
Old systematic literature may have encountered Mogurnda species under earlier generic placements — Eleotris and Vaimosa appear in early accounts of related species — but these are superseded synonyms and should not be applied here. The species epithet spilota is from the Greek spilotos (spotted or marked), referring to the row of white blotches that defines the colour pattern.
Morphology
Mogurnda spilota reaches a standard length of approximately 5 in SL, making it a medium-sized member of its genus. The body is elongate, as is typical for Mogurnda, with the head somewhat flattened dorsally. The snout is notably elongate with a concave dorsal profile, a character that distinguishes it from the closely related M. vitta and that was noted in the original description.
The most striking feature is the lateral colour pattern: approximately ten irregularly shaped white blotches, each roughly the size of the eye, arranged along the midline from the operculum to the caudal fin base. This row of pale spots is the immediate recognition mark for the species and the source of the epithet spilota. The pelvic fins remain separate — the defining eleotrid character — and are not fused into a disc.
Sexual dimorphism in Mogurnda generally follows the genus pattern: males tend to be larger and more brightly coloured, and in breeding condition may show extended fin filaments (reflected in the common name 'filamentous gudgeon') and intensified markings, while females are smaller and rounder-bodied when gravid. Specific dimorphism data for M. spilota are sparse in the available literature, but the pattern is consistent across the genus.
Habitat
Mogurnda spilota is endemic to Lake Kutubu in the Southern Highlands district of Papua New Guinea. Lake Kutubu is the second-largest lake in Papua New Guinea, lying at approximately 2625 ft elevation in the interior highlands and fed by clear, cool upland streams. It is a closed freshwater system with no marine connection, supporting a highly endemic fish fauna — thirteen species known from no other water body — of which M. spilota is one.
Within the lake, the available records place the species near shore in dense aquatic vegetation. The upland location and clear-water character of Lake Kutubu set it apart from the warm, lowland rivers that many Mogurnda inhabit: temperatures of 73–82 °F have been recorded, somewhat cooler than the tropical lowland norm. The lake is strictly freshwater; no salt is present and this species has no brackish tolerance.
Feeding
Mogurnda spilota is a micro-predator. FishBase records its natural prey as small aquatic invertebrates — chironomid larvae, copepods, decapods and diving beetles (dytiscids) — as well as small fishes, a diet typical for a mid-sized eleotrid hunting near vegetation and the lake bottom.
In the aquarium it should be offered a varied diet of small live and frozen foods: bloodworm (chironomid larvae), brine shrimp, daphnia, small crustaceans and insect larvae. Experience with related Mogurnda species (M. adspersa, M. mogurnda) confirms that these gudgeons respond poorly to dry flake and need meaty, moving food to remain in good condition. Larger specimens may take small feeder invertebrates or very small fish. A diet based primarily on good frozen and live foods is the safest approach.
Mating
Mogurnda spilota is a resident freshwater cave-spawner with genuine parental care — the reproductive strategy shared by most Mogurnda and one that makes the whole cycle achievable in a home aquarium without any marine larval phase. A conditioned male selects and defends a cavity — a crevice among rock, a hollow piece of wood, a ceramic cave or a coconut shell half — and courts females by intensifying his colour and displaying at the entrance.
Pairing in aquarium settings follows the genus norm: a dominant male will court multiple females but typically spawns with one at a time. The male's control of the spawning site is central to the reproductive sequence, and providing adequate cave structures, spaced to reduce line-of-sight conflict between males, is the most effective way to encourage breeding attempts.
Breeding
Spawning follows the cave-spawner pattern documented for the genus: the female deposits 20–40 adhesive eggs on the interior surface of the chosen cavity — the roof or wall — and then withdraws. The male takes sole charge from that point, guarding the entrance against disturbance and fanning the eggs with his fins to maintain oxygenation and prevent fungal growth. Hatching occurs in 3–8 days depending on temperature, after which the fry initially feed on zooplankton and fine live foods before progressing to larger items as they grow.
The whole cycle is completed in fresh water — there is no need for a marine or brackish larval phase — so M. spilota can in principle be bred in a properly managed aquarium. Attentive male care, a stable water temperature in the mid-twenties, clean water, and a diet of live or high-quality frozen food are the key conditions. Fry may be left with the male or moved to a separate rearing vessel; the male does not typically eat the eggs, and his guarding behaviour is reliable.
In the aquarium
Mogurnda spilota is rare in the trade — its restriction to a single highland lake means supply depends almost entirely on wild collection, and specimens are not commonly available outside specialist circles or Papua New Guinea. When it does appear, the aquarium requirements follow the genus closely: a well-filtered tank with plenty of rocky caves, crevices and hiding places, stable water quality, and a temperature in the 73–81 °F range appropriate for a highland lake endemic.
As a micro-predator that will take small fish, tankmates should be chosen with care — similarly sized or larger, robust species are preferable. Males are territorial toward one another and need clear spatial separation through tank furniture. A tight-fitting lid is advisable, as eleotrids can be jumpers. The tank does not require salt. The main care demands are live or frozen meaty foods, caves and sight-breaks, and clean, stable water; given those, the species is a hardy and visually distinctive subject, though its wild-collection status makes sourcing ethically fraught until captive breeding is established more widely.
Conservation
Mogurnda spilota has not been formally assessed by the IUCN — it carries no Red List category, and we record it here as Not Evaluated (NE) rather than assign a speculative status. The biology and distribution profile, however, give real grounds for concern: the species is known only from Lake Kutubu, a single lake of limited extent at 2625 ft elevation in interior Papua New Guinea. Any species with so small and isolated a range is inherently exposed to localised threats — watershed disturbance, pollution, introduced predators or competitors, or sedimentation — with no adjacent population to act as a refuge.
Lake Kutubu lies within a landscape that has experienced oil and gas development in the surrounding Southern Highlands, and the watershed's long-term health is relevant to all thirteen of its endemic fish species. Trade collection of M. spilota, where it occurs, is wild-sourced by definition; captive breeding remains sparse. Until a formal Red List assessment is conducted and captive stocks are established more securely, aquarists are encouraged to source specimens from verified captive breeders where possible and to avoid adding pressure to the wild population of what may be an inherently small-ranged and potentially threatened species.