Venom evolution in glycerid polychaetes (Annelida, Glyceridae) with special emphasis on alpha-glycerotoxin

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Venom systems evolved in a broad phylogenetic range of animals and are used for defence or predation. Venomous animals are found across most major metazoan taxa and prominent and wellstudied examples are snakes, cone snails, and spiders. Even though venoms evolved independently in these taxa, it is obvious that throughout evolution, many protein families have been recruited convergently. Within annelids, venomous species can be found within aphroditiform and glycerid polychaetes. Although there are more than 1000 potential venomous annelid species their venom characteristics are largely unknown and not a single study at DNA level is available. The pharynx of all members of the Glyceridae is equipped with large chitinous teeth which are connected to prominent venom glands. We will conduct a detailed morphological investigation of the glycerid venom gland system. A highly interesting toxin (glycerotoxin) has been found in these glands which is unique in specifically stimulating voltage gated calcium channels (N-type), giving this protein a potential medical importance. We aim to characterise the venom gland transcriptome of five glycerid species to give a first characterisation of glycerid venom composition. Using phylogenetic methods, we will analyse convergent recruitment of venom proteins in this group. Moreover, using an experimental approach we aim to identify domains of the glycerotoxin which specifically bind to the calcium channels. Signs of selection on these domains will be inferred across glycerids using ML based tests. Finally, we use a established molecular phylogeny of Glyceridae to trace venom evolution within this group. This analysis will allow us to compare venom protein gene trees with glycerid species trees and will provide the first detailed investigation into venom evolution in annelids.