Tracking the Pulse of the Dunes: Seasonal Metabolic Responses of <i>Liolaemus arambarensis</i> to Climatic Variability

Seasonal environmental fluctuations profoundly influence ectothermic vertebrates, regulating their physiology, metabolism, and life cycles. This study investigated the metabolic and morphometric seasonal dynamics of the subtropical sand lizard Liolaemus arambarensis, an endangered species endemic to the coastal dunes of southern Brazil. Over two annual cycles (July 2020 to May 2022), 133 individuals (43 males, 45 females, 45 juveniles) were sampled across all seasons. Through an ecophysiological and biochemical approach, we quantified intermediate metabolism biomarkers-including glucose, proteins, albumin, uric acid, lactate, triglycerides, cholesterol, glycogen, and total lipids-in plasma, liver, gonads, and skeletal muscles, alongside somatic and organ indices. Data were analyzed using generalized linear models (GLMs) with gamma distribution and log-link, followed by type III ANOVA and Tukey post hoc tests. Marked sex- and age-specific seasonal patterns were detected. Females exhibited strong reproductive investment in spring and summer, characterized by increased gonadal proteins and triglycerides, elevated plasma albumin and cholesterol, and depletion of hepatic and muscular reserves-consistent with vitellogenesis and egg production. Males initiated reproductive investment earlier, accumulating hepatic and muscular glycogen and lipids in autumn-winter and mobilizing these reserves during spring for spermatogenesis and reproductive behaviors. Juveniles displayed strategies oriented toward somatic growth and survival, with high tissue lipid content in summer (yolk-derived reserves), hyperglycemia and hepatic glycogen accumulation in winter (suggesting cryoprotective or osmotic roles), and metabolic depletion in autumn, likely due to intraspecific competition for limited resources. The results reveal a plastic physiological strategy combining temperate-like energy conservation during cold periods with tropical-like reproductive allocation in warm months. Such metabolic flexibility underlies the species' adaptation to subtropical thermal variability and provides valuable predictive indicators for ecological modeling and conservation planning in the context of ongoing climate change.