Taxonomy & naming
Andreas F. Recknagel, Henrik Kusche, Kathryn R. Elmer and Axel Meyer described Amphilophus tolteca in 2013, in a paper — 'Two new endemic species in the Midas cichlid species complex from Nicaraguan crater lakes: Amphilophus tolteca and Amphilophus viridis' (aqua, International Journal of Ichthyology, volume 19) — that also named its sister endemic, Amphilophus viridis, from a different crater lake. The holotype was collected in Asososca Managua. The species sits in the Amphilophus citrinellus species complex — the 'Midas cichlid' radiation of Nicaragua's great lakes and their satellite crater lakes — among the heroine cichlids of subfamily Cichlinae, and both the Catalog of Fishes and FishBase list it as valid. The epithet honours the Toltecs, a pre-Columbian Mesoamerican culture: the describers took the name from a mural of the feathered serpent Quetzalcóatl near Lake Asososca Managua, tying the fish to the cultural landscape of its home lake. What sets Amphilophus tolteca apart is its youth. Asososca Managua is a maar estimated at a maximum of about 1,245 years old, so the fish evolved within roughly that span — one of the youngest vertebrate species ever described.
Morphology
Amphilophus tolteca is a small-to-medium Midas-group cichlid, reaching about 6 in standard length according to FishBase. It has the laterally compressed body of the complex, but in a slimmer, more streamlined form than the deep-bodied benthic Midas cichlids — a build the describers linked to a more open-water, limnetic life within the small crater lake. Colour is mostly dark: like the rest of the complex it can in principle show both a cryptic grey-to-dark 'normal' morph and a gold (amelanistic) morph, but the fish is noted especially for its dark colouration. The Asososca population is unusual for its continuous variation in ecologically relevant traits — body shape and lower pharyngeal-jaw morphology grade along a benthic-to-limnetic axis, so individuals are tuned to different feeding niches even within this one young species. The sexes differ in the genus pattern: males run larger and can develop a modest nuchal swelling, while ripe females are smaller and rounder.
Habitat
The tolteca cichlid is endemic to Asososca Managua (Laguna de Asososca), a small volcanic crater lake on the western edge of the city of Managua, and it occurs nowhere else. The lake is a maar — an explosion crater — of very recent geological origin, ringed by steep rocky cliffs and cut off from any other water body. It has long served as a drinking-water reservoir for Managua, which both shields it from some uses and ties it to the pressures of an urban setting. Its chemistry follows the volcanic Nicaraguan crater lakes: warm, clear, hard and alkaline, broadly in the high-20s Celsius with an alkaline pH. Shoreline is limited and the open-water volume is large relative to the lake's small area — the setting in which the fish's elongate, limnetic form makes ecological sense. This single-lake range falls within the San Juan freshwater ecoregion (FEOW 205).
Feeding
Amphilophus tolteca is an omnivore, and within its single lake it shows unusually fine-grained dietary specialisation. FishBase records it taking fish, snails, insects, plants, seeds and algae, and places it at a trophic level of about 3.3 — a broad diet by any measure. The more interesting finding is that individuals specialise along a benthic-limnetic axis: differences in body shape and in the lower pharyngeal jaw track differences in diet and niche, so some fish lean toward bottom-feeding on hard prey such as snails while others work the open water. That individual-level niche splitting inside one very young species is much of what makes the fish scientifically valuable — it is the raw material of the ecological divergence that, in older crater lakes, has built whole species flocks. The flexible Midas pharyngeal jaw is what makes such versatility possible.
Mating
Like all Midas-complex cichlids, Amphilophus tolteca is a biparental, pair-bonding substrate spawner. A male and female form a pair, stake out and defend a territory, and ready a nest site together, working through the genus-typical courtship of lateral displays, fin-spreading, quivering and shared substrate-cleaning while their colours intensify. Mate choice matters more here than in most cichlids, because of the fish's youth and its within-lake variation: how individuals pair — and whether assortative mating along the benthic-limnetic axis is starting — bears directly on whether the single Asososca population might one day split, the opening move of the sympatric speciation documented in older Nicaraguan crater lakes such as Apoyo. Around the nest, territorial aggression sharpens, as it does across the complex.
Breeding
Amphilophus tolteca breeds in the universal Midas pattern. The adhesive eggs are laid on a cleaned hard surface — a rock face, a cleared patch of substrate, or the wall of a sheltered cavity — and both parents share the work: the female fans and tends the clutch while the male defends the territory, and once the eggs hatch the free-swimming fry are herded and guarded as a school by both adults. Clutch counts specific to wild fish have not been published; Midas-complex cichlids of similar size typically lay a few hundred eggs, with prolonged biparental care of eggs, larvae and fry. Breeding is expected to be seasonal, picking up as conditions in the lake turn favourable. Because the species was described so recently and lives in a single, partly protected reservoir, in-situ breeding data stay thin, and aquarium accounts are essentially absent.
In the aquarium
Amphilophus tolteca is a fish of scientific interest that is effectively absent from the aquarium hobby. It lives in one drinking-water reservoir, is not commercially collected, and has no established husbandry — everything below is extrapolated from the broader Midas group and the lake's own conditions.
Tank: were it kept, it would need what a small-to-medium Midas cichlid needs — a good footprint and a fair volume of open water to suit its limnetic build, on the order of 55 US gal or more for a pair, with rockwork for cover and spawning sites and a substrate it can dig in.
Water: match Asososca's warm, hard, alkaline chemistry — around 79–86 °F and an alkaline pH of roughly 7.5–8.5, with strong filtration and regular water changes.
Feeding: straightforward for an omnivore — quality pellets rounded out with frozen and live invertebrates, some snails and vegetable matter, in keeping with its broad natural diet. Expect the heightened territoriality of any Amphilophus around spawning.
The honest verdict is that this is a conservation fish, not an ornamental one: its single-lake endemism and Vulnerable status make it far more important as a wild population and research subject than as anything for a display tank.
Conservation
The IUCN Red List assesses Amphilophus tolteca as Vulnerable (assessed 7 February 2020). The reason is its extreme range restriction: the entire global population lives in one small crater lake, Asososca Managua, with no refuge population anywhere else, so any lake-wide disturbance reaches the whole species at once. The lake's role as Managua's drinking-water reservoir cuts both ways — it deters direct exploitation, but it also exposes the water to an urban catchment, with the attendant risks of pollution, water-level management, and the perennial danger that a non-native fish could be introduced into a small closed system, as has already harmed native cichlids in other Nicaraguan crater lakes. The species' very recent origin and its value as a near-contemporary example of incipient ecological divergence only strengthen the case for protecting the lake. There is no CITES listing; safeguarding the water quality and native fish community of this one small lake is, in effect, the whole of its conservation.