The metabolism of hypogean organisms is frequently molded by the cave environment traits, especially food scarcity. The aim of the present work was to evaluate the inf luence of such environment on lipid composition and hepatic lipogenesis in the f ish Ancistrus cryptophthalmus. For this, the species was compared to an epigean population of the species. A greater accumulation of total lipids was observed in the cave-dwelling f ish (18.36 g/100 g tissue) compared to the surface f ish (14.09 g/100 g tissue). The muscle fatty acid prof ile also varied between the populations. Arachidonic acid was only detected in the epigean f ish, while docosahexaenoic acid was present in the cave f ish. In the lipid prof ile of Ancistrus cryptophthalmus there was a higher proportion of saturated fatty acids, followed by monounsaturated and polyunsaturated fatty acids; Ancistrus sp. showed a predominance of monounsaturated fatty acids. Signif icant differences were also observed in the activities of the hepatic enzymes glucose-6-phosphate dehydrogenase and malic enzyme. The activities of these two enzymes were greater in the epigean animals. The differences could be related to different food availability observed in the two environments. An ecotone zone was observed, located next to the entrance of the Lapa do Angélica cave (Goiás State, Brazil), where the f ishes showed characteristics that were intermediate between those of hypogean f ishes from deeper within the cave, and the epigean population. It could be concluded that the characteristics of the cave environment signif icantly inf luenced the composition of muscle fatty acids and lipogenesis in the hypogean f ish Ancistrus cryptophthalmus.