Taxonomy & naming
Anatolichthys splendens was described by the German ichthyologist Curt Kosswig and his colleague Vedat Nuri Sözer in 1945 from material collected at Lake Salda, southwestern Anatolia. The authority is conventionally rendered with parentheses — (Kosswig & Sözer, 1945) — indicating that the species has since been moved from the genus in which it was originally placed. For a period it was assigned to the disused genus Anatolichthys, a grouping that subsumed several Turkish endemic toothcarps before molecular and morphological work consolidated them back into Aphanius. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) lists the valid combination as Anatolichthys splendens (Kosswig & Sözer, 1945), in the family Aphaniidae — the Old-World toothcarps, formerly treated as a subfamily of Cyprinodontidae but now elevated to family level.
The specific epithet splendens is Latin for 'shining' or 'brilliant', an allusion to the iridescent, reflective quality of the males in breeding dress. The common names in English — Gölçük toothcarp or Splendid toothcarp — are rarely encountered in the hobby literature; the species was rarely exported and never established itself as a trade fish.
Within Aphanius the closest relatives are the other Turkish endemic toothcarps, including Aphanius transgrediens from the now-dry Eber Lake basin, Aphanius anatoliae from various Anatolian drainages, and the more widely distributed Aphanius fasciatus of the Mediterranean coast. Lake Salda is hydrologically isolated — it drains to no river system — which means that splendens evolved in complete geographic seclusion, with no gene flow to or from any neighbouring toothcarp population.
This fish was long listed as Aphanius splendens; Eschmeyer's Catalog of Fishes places the species in Anatolichthys, and the current combination Anatolichthys splendens is followed here.
Morphology
Anatolichthys splendens reached a maximum total length of approximately 2.4 in (FishBase), making it a typical-sized member of its genus. As in all Aphanius, the sexes are strongly dimorphic. Males are the showier sex: the flanks carry 8–11 dark grey to black vertical bars on a pale or silvery-blue ground, the anal fin is white to yellow with a sharp black distal edge, and the dorsal fin has a dark border that grades to a pale base. Under good light the scales on the flanks have a metallic, reflective sheen — the quality implied by the epithet splendens. In breeding condition the colouration intensifies. Eggs are attached by short filaments to substrate or vegetation, a feature shared with other Aphanius.
Females are larger than males, as is typical for the genus, and are cryptically coloured: the body is pale brown to grey-green, the flanks show variable dark blotches rather than the males' regular barring, and the fins are largely hyaline. This reverse size dimorphism — females outgrowing males — is common in Aphanius and thought to be linked to egg production demands in hard, productive waters. The Gölçük toothcarp can apparently interbreed freely with other Turkish Aphanius in captivity, which has complicated efforts to maintain genetically pure captive lines.
Habitat
Lake Salda is one of the most chemically extreme freshwater bodies in Turkey. Situated at approximately 1,328 ft elevation in the Burdur Basin of southwestern Anatolia, it is a closed-basin soda lake fed by groundwater springs and concentrated by evaporation. The water chemistry is remarkable: pH values recorded by Seriously Fish range from 8.0 to 10.0 — strongly to extremely alkaline — with dissolved mineral loads far above normal freshwater; magnesium concentrations of 365 mg/L, calcium at 120 mg/L, and chloride at 1,277 mg/L have been documented. Total hardness reaches 274 ppm. The lake never freezes despite cold winters, with dense winter fog and water temperatures ranging from approximately 44 °F in winter to 72 °F at summer peak (Seriously Fish). FishBase records the species' thermal range as 61–75 °F, likely reflecting the temperatures at which it was most commonly active and collected.
The fish occupied the littoral zone among macroalgae and submerged vegetation in the shallower margins of the lake. Lake Salda is also notable for its white, magnesite-sand beaches — the result of hydrothermal mineral precipitation — which have become a popular tourist destination and brought additional pressure to the shoreline. Anatolichthys splendens was adapted to conditions that virtually no other vertebrate could tolerate: the combination of high pH, high mineral concentration, and temperature fluctuation that characterise terminal soda lakes. That specialisation was its evolutionary achievement and its fatal vulnerability.
Feeding
Anatolichthys splendens was a micropredator typical of its genus — feeding on small crustaceans, worms, insect larvae, and zooplankton, supplemented by algae. This broadly omnivorous diet is consistent with the resource base available in alkaline, productive soda lakes, where algal mats and the invertebrate communities they support provide dense, accessible food.
In the captive setting, wild-caught and aquarium-bred individuals accepted small live and frozen foods — Artemia nauplii, Daphnia, bloodworm — alongside fine dried foods. The species had no unusual dietary requirements by killifish standards, and feeding was never identified as a challenge in maintaining the fish. The lake's high productivity, driven by the mineral richness and alkalinity that supports dense algal growth, presumably provided abundant food year-round in the wild.
Mating
Anatolichthys splendens was a non-annual killifish — it lived in the permanent waters of Lake Salda and did not require the soil-burial diapause that defines the life cycle of annual killifish from seasonal pools and savanna streams. Instead, it was a fractional spawner in the plant-spawning tradition shared by most Aphaniidae and many non-annual killifish families: pairs spawned repeatedly over an extended season, depositing small numbers of adhesive eggs at a time rather than a single mass clutch.
Males established temporary territories and displayed to females using the bold barring and reflective flanks for which the species is named. Courtship involved lateral displays and chasing consistent with other Aphanius. Spawning was documented from April through September — approximately six months of continuous reproductive activity. Eggs were attached by short filaments to fine algae, submerged plant material, or artificial spawning mops in captivity; eggs do not require burial in peat or a dry incubation period. Incubation in water at ambient lake temperature took approximately 15–17 days (Seriously Fish).
Breeding
Under aquarium conditions, Anatolichthys splendens was maintained and bred in hard, highly alkaline water to match its soda-lake origin — an unusual requirement by killifish standards. Seriously Fish recommends recreating the water chemistry of Lake Salda as closely as practicable: very high pH (8.0–10.0), very hard water, and a temperature regime that allows a cooler winter period (down toward 50–54 °F) to replicate the natural seasonal cycle and condition the fish for the spring spawning season. The species could be kept and spawned in standard hard tap water if it was sufficiently alkaline, but the extreme mineral concentrations of Salda are difficult to replicate outside the lake itself.
Spawning mops of fine synthetic fibres or bunches of Java moss placed near the surface or mid-water were used to collect eggs. Females deposited eggs intermittently across the long spawning season; clutches were small by killifish standards. Eggs were removed to a separate container of the same water and incubated in the dark at moderate temperature. Hatching occurred after approximately 15–17 days. Fry required infusoria or very fine commercial fry food in the first days, graduating to Artemia nauplii as they grew. Growth was relatively slow compared to annual species. The risk of introgression with other captive Aphanius — the species can cross freely with related Turkish toothcarps — meant that pure-line maintenance required strict isolation. Whether any genetically uncontaminated captive population survived into the 2010s is uncertain.
In the aquarium
Anatolichthys splendens occupied a narrow niche in the specialist killifish hobby: a demanding, locality-sensitive species for keepers who could provide and maintain strongly alkaline, hard, mineral-rich water. Standard community-fish tap water was insufficient; the species did best in water deliberately prepared to approach the chemistry of Lake Salda, which is extraordinary by any freshwater standard. This requirement placed it outside the reach of most killifish hobbyists, and it was never widely distributed in the trade.
Those who kept it found a fish of modest size but striking male colouration: the barred flanks and reflective sheen were well displayed in clear, hard water under good lighting. The fish were active swimmers, somewhat territorial between males, and best kept in a species tank or with other alkaline-tolerant species of similar size. They were not regarded as difficult to maintain once water chemistry was correct; feeding was unproblematic, and the species spawned willingly on mops over the long summer season.
By the time the IUCN declared it Extinct in 2013, the species had effectively vanished from organised killifish collections. European aquarists had maintained small groups through the 1990s and into the early 2000s, but the risk of hybridisation with other Aphanius, the difficulty of the water requirements, and the gradual attrition of specialist collections meant that no confirmed pure captive colony was documented after that period. The Gölçük toothcarp is now effectively a museum species — known from specimens, photographs, and the occasional captive-bred descendant of uncertain genetic purity.
Conservation
The extinction of Anatolichthys splendens is among the most thoroughly documented freshwater fish losses of the twentieth century. The species was already classified as Critically Endangered by the IUCN in 1996, at which point wild populations were in severe decline. The cause was the introduction of common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) into Lake Salda — non-native predators and competitors for which the isolated endemic toothcarp had no evolved defence. Carp disturb littoral sediments and uproot vegetation; trout prey directly on small fish. The combination was lethal in a closed basin from which there was no escape route. By at least the 1980s the wild population was functionally extinct, and successive surveys since have found no individuals.
The IUCN formally listed Anatolichthys splendens as Extinct in an assessment published on 12 March 2013 — one of a small and sobering cohort of freshwater fish to achieve that status in the modern era. Additional pressures documented on the lake include water abstraction from the springs that feed it, agricultural runoff affecting water chemistry, and the growth of tourism around the lake's scenic white beaches. These factors compound the collapse already caused by the fish introductions.
Research by Güçlü and Küçük (2012) documented the species alongside Aphanius transgrediens — another extinct Turkish endemic — as emblematic of the vulnerability of single-locality Anatolian toothcarps to even minor perturbations of their habitat. Lake Salda has since been designated a protected area and Special Environmental Protection Zone in Turkey, but the protection came too late for splendens. The case is now widely cited in conservation biology as an example of the irreversible consequences of introducing non-native fish into isolated closed-basin systems.