Taxonomy & naming
Sphaerophysa dianchiensis was described by Cao and Zhu in 1988, based on material from Dian Lake in Yunnan Province, China. It sits in the family Nemacheilidae, the stone and brook loaches — by far the largest loach family, with several hundred species spread across streams from the Balkans to East Asia — placed in the small genus Sphaerophysa alongside a handful of other Yunnan lake- and stream-dwelling nemacheilids.
The epithet dianchiensis refers directly to its only known home, Dian Lake (also romanised Dianchi), and the Catalog of Fishes lists the species under this combination. Beyond the original description, taxonomic literature on the species is sparse — a common situation for narrow-range Chinese lake endemics that were named once, in a regional survey, and then largely fell out of scientific attention as the lake itself declined.
Morphology
As a member of Nemacheilidae, Sphaerophysa dianchiensis would be expected to share the family's general body plan: a small, elongate, cylindrical body, a flattened underside suited to life on the bottom, and the small or absent scales typical of the group. Detailed morphometric data, colour pattern and precise maximum size for this particular species are not available from the sources consulted here, and this article does not invent them.
What can be said with confidence is genus and family placement — Sphaerophysa, Nemacheilidae — which places it among the true stone loaches rather than the spined botiids or the hillstream Balitoridae/Gastromyzontidae. Any suborbital-spine or fine-scale detail specific to this species is not confirmed in the available record and is left unstated rather than assumed from relatives.
Habitat
This species is endemic to Dian Lake (Dianchi), a large lake on the Yunnan-Guizhou Plateau near Kunming, sitting at an elevation of roughly 1,2920 ft. That makes it unusual for a nemacheilid: the family is overwhelmingly one of flowing streams, and a true lake-dwelling species like this is an exception worth noting rather than glossing over. The lake's elevation and Yunnan's subtropical highland climate imply cool-to-moderate water rather than lowland-tropical warmth, though no measured temperature range for the species itself is available in the sources consulted.
Dian Lake has suffered severe ecological decline over the past several decades, driven by urban and agricultural pollution, eutrophication and habitat alteration around greater Kunming — pressures widely documented for the lake's fish fauna as a whole. Sphaerophysa dianchiensis is one of roughly ten fish species considered endemic to the Dian Lake basin, several of which are now feared extinct or gone from the lake alongside it.
Feeding
No species-specific dietary data for Sphaerophysa dianchiensis were found in the sources consulted. By family, Nemacheilidae are typically bottom-foraging micro-predators, sifting fine substrate for small invertebrates, insect larvae and other benthic prey, and a similar diet is plausible for this species — but this is an inference from its relatives, not a confirmed fact, and should be read as such.
Given that the species has not been recorded alive in decades and has never entered the aquarium trade, there is no hobbyist feeding experience to draw on either. Any care-level feeding guidance would be pure speculation, so none is offered here.
Mating
No information on courtship, sexing or spawning behaviour for Sphaerophysa dianchiensis was found in the sources consulted. Nothing is known to have been documented about how or when this species reproduced in Dian Lake, and with no living population confirmed and no aquarium history, there is no observational basis — wild or captive — to describe here.
Breeding
There is no record of Sphaerophysa dianchiensis ever being bred, or even kept, in captivity. Like the great majority of small nemacheilid stone and brook loaches, it would be expected — by family pattern — to be an egg-scatterer over gravel or fine substrate with no parental care, but this is inferred from relatives rather than observed in this species, and no confirmed breeding mode is on record.
With the species missing from its only known locality since roughly the 1990s, the practical breeding picture is stark: there is no wild population known to be reproducing, and no aquarium population exists from which to attempt propagation. Any future conservation breeding would first require rediscovery of a living population.
In the aquarium
Sphaerophysa dianchiensis is not, and has never been, an aquarium fish. It does not appear in the ornamental trade, there is no hobbyist husbandry literature, and — given its likely extirpation from its only known habitat — there is no legitimate source of live specimens. No tank size, water parameters, tankmate or feeding recommendations can honestly be given for a species with no aquarium history and no confirmed living population.
Its inclusion here is documentary rather than practical: it stands as a record of a narrow-range lake endemic that was described, then lost, within a few decades — a cautionary case for what disappears when a single small lake degrades.
Conservation
Sphaerophysa dianchiensis is listed as Critically Endangered on the IUCN Red List. It has not been confirmed in the wild since approximately the 1990s despite its restriction to a single, well-studied lake near a major city, and there is a real possibility that it is already extinct — a status that field surveys have not been able to rule in or out in recent decades.
The threats are well documented for Dian Lake generally, even where species-specific data are thin: decades of pollution, eutrophication, and habitat alteration from urban and agricultural development around Kunming have driven a broader collapse of the lake's endemic fish fauna, of which this species is one of roughly ten affected members. There is no aquarium trade pressure on this species — its jeopardy is entirely a story of habitat loss at its one known site, and any future for it depends on the ecological recovery of Dian Lake and renewed field surveys to determine whether it survives at all.