Food for thought: Venom composition of Vipera ammodytes from the island and mainland population is likely related with diet

Abstract

Snake venom is a complex secretion of proteins, peptides and small compounds. Being closely related to feeding, this important ecological trait is highly variable. The resulting variations are notably characterised by the abundance of different toxins, both at inter-and intraspecific levels. Here we addressed variation in venom composition of two populations of Vipera ammodytes from North Macedonia. One population inhabits Golem Grad Island (Prespa Lake) where vipers feed mainly on ectotherms, and the other is from the nearby mainland (Konjsko village) where endotherms are included in the diet. Using the bottom-up protocol for venom proteome analysis, five pools (insular juveniles, subadults, adult males and adult females, and adults from the mainland) were analysed, from a total of 50 individuals (46 from the island and four from the mainland). The venom profiles of the insular and mainland population differed, likely reflecting prey divergence between the sites. At the population level, in Golem Grad, venom composition showed an ontogenetic shift in the relative occurrence of different toxin families. This change is probably due to the shift in the diet; juveniles feed mainly on centipedes and small lizards, while adults essentially consume lizards. On the contrary, there was negligible variation in venom profiles of island adult males and females, likely due to their similar diet. Our results reveal fine-tuned and rapid (ontogenetic) parallel shifts in diet and venom composition and highlight the need to consider species' ecology in any causal model of venom variability.