Integrated Histological and Transcriptomic Characterization of Prolonged Starvation Responses in the Cavefish Triplophysa rosa

Abstract

Simple Summary Caves are dark, isolated, and food-poor habitats. Animals living in caves must therefore make careful use of limited energy to survive. The cavefish Triplophysa rosa lives in such an environment, but little is known about how it copes when food is unavailable for a long time. In this study, we combined growth measurements, liver and spleen histology, transcriptomic analysis, quantitative reverse transcription PCR, and transmission electron microscopy to examine T. rosa responses to 30, 60, and 90 days of starvation. Prolonged starvation reduced growth and liver reserve indicators and was accompanied by coordinated changes in metabolic gene expression. In the spleen, early immune-related transcriptional changes were followed by greater prominence of melano-macrophage centers, suggesting increasing involvement of cellular clearance and tissue maintenance during prolonged starvation. Autophagy-related gene expression and ultrastructural observations were consistent with increased involvement of intracellular recycling, which may support basic cellular maintenance during prolonged food deprivation. In summary, prolonged starvation in T. rosa involved coordinated temporal changes in metabolism, splenic function, and cellular maintenance. By providing an integrated characterization of prolonged starvation responses in a cave-restricted fish, this study may provide useful physiological information for future conservation and management studies of cave-dwelling species. Abstract Food scarcity is a major ecological challenge for cavefish; however, their coordinated physiological and molecular responses to prolonged starvation remain poorly understood. Here, we characterized the responses of Triplophysa rosa to 30, 60, and 90 days of food deprivation under controlled laboratory conditions by integrating growth measurements, histology, transcriptomics, quantitative reverse transcription PCR, and transmission electron microscopy. Starvation inhibited growth, reduced the condition factor and hepatosomatic index, and induced hepatocyte shrinkage, consistent with mobilization of hepatic energy reserves. Liver genes with declining temporal expression were enriched mainly in lipid biosynthesis, cholesterol metabolism, ribosomal function, and cell-cycle pathways, consistent with reduced biosynthetic activity. In the spleen, immune-related transcription increased during early starvation and declined at later stages, while the greater prominence of melano-macrophage centers was consistent with greater involvement of cellular clearance and tissue maintenance during prolonged starvation. Prolonged starvation also increased the expression of autophagy-related genes in the liver and spleen, and autophagy-related structures became more prominent in representative transmission electron microscopy images, consistent with increased involvement of intracellular recycling. Together, these findings reveal a coordinated temporal response involving metabolic adjustment, stage-dependent reorganization of splenic immune-related processes, and autophagy-associated cellular maintenance in T. rosa. This integrated approach improves our understanding of physiological maintenance during sustained nutrient limitation in cave-restricted fish.