The venom secretions used by octopods to immobilise and kill prey have been studied for over a century. Until very recently however, the molecular composition of these venoms was almost entirely unknown. Recent studies have used high throughput molecular techniques such as transcriptome sequencing to propose a wide variety of proteins that may play a role in octopod venom. In this work we used a combination of transcriptomic sequencing and mass spectrometry based proteomics to directly identify proteins from the posterior salivary glands of two octopod species, H. maculosa and O. kaurna. While both species are thought to have similar dietary preferences, the venom of H. maculosa is unique in that it is known to contain a potent non-proteinaceous neurotoxin (Tetrodotoxin) produced by bacteria.
Our analysis showed that the salivary gland proteomes of the two species were dominated by a similar suite of molecules with serine proteases being particularly diverse and abundant. Many of the most abundant proteins were shared between both species (orthologs) while 12 of the top 20 proteins across both species were not homologous to any proteins on the NCBI nr database by BLAST search. Among less abundant proteins we also identified representatives from nine other families of proteins that have been recruited to toxic function in other taxa. We examined the relative abundance and diversity of these between the two species as well as the molecular evolution of expanded protein families such as serine proteases.