Cutaneous water loss and epidermal lipid content in lanceheads (Crotalinae: Bothrops)

Cutaneous evaporation is the primary route of water loss in snakes. Species from arid environments typically show lower cutaneous water loss (CWL) rates due in part to higher epidermal lipid content. However, past comparative studies have used distantly related taxa or lacked phylogenetic comparative methods, limiting their conclusions. We measured CWL and lipid content (LC) in shed skins of eight lancehead species (Bothrops) from habitats with varying canopy coverage. Using phylogenetic comparative methods, we examined the effects of canopy coverage, snout-vent length (SVL), sex, and species on CWL and assessed its correlation with LC. Our results show that canopy coverage significantly influences CWL, independent of phylogeny. Snakes from open habitats exhibited lower CWL rates than those restricted to forests, which showed greater individual variation. Species from the most xeric habitat (Caatinga) displayed the lowest CWL. Neither sex nor SVL affected CWL, and phylogenetic signal was negligible (λ ≈ 0), suggesting weak phylogenetic constraints. CWL and LC were inversely correlated, with LC higher in open-habitat species. These findings indicate that habitat type, particularly canopy coverage, drives interspecific variation in CWL among closely related species, while phylogenetic effects are more relevant at higher taxonomic levels. Lipid content in the epidermis plays a critical role in regulating CWL, though differences in lipid composition may also contribute.