Anatolichthys, Kosswig & Sözer, 1945

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 713

Scale reduction in Anatolichthys and Kosswigichthys .

The presence of scales on fish is a protective mechanism that safeguards the integumentary system from injury. However, this adaptation comes at a cost in terms of energy expenditure. This is evidenced by the observation that many cavefish, which inhabit environments with reduced levels of light, have reduced scales. Similarly, pelagic Aphaniids that inhabit mineral-rich lakes appear relatively safe from predators and flooding hazards. Consequently, they have also reduced their scales. The reduction of scales in Anatolichthys and Kosswigichthys is not a genetic adaptation to the high concentration of sodium sulfate, magnesium sulfate, and magnesium carbonate in the lakes in which they live. There was no difference in the salt tolerance of scale-reduced fish and normally scaled fish observed in experiments. The reduction is a consequence of the absence of stabilizing selection. Mutants exhibiting all variations in squamation survive, increasing the variability of the squamation. This may lead to the complete loss of scales, potentially saving energy by not developing and maintaining scales.

Further reading. Grimm 1980 (scale reduction).