Tube anemones, or cerianthids, are a phylogenetically informative group of cnidarians 14 with complex life histories, including a pelagic larval stage and tube-dwelling adult stage, both 15 known to utilize venom in stinging-cell rich tentacles. Cnidarians are an entirely venomous group 16 that utilize their proteinaceous-dominated toxins to capture prey and defend against predators, in 17 addition to several other ecological functions, including intraspecific interactions. At present there 18are no studies describing the venom for any species within cerianthids. Given their unique 19 development, ecology, and distinct phylogenetic-placement within Cnidaria, our objective is to 20 evaluate the venom-like gene diversity of four species of cerianthids from newly collected 21 transcriptomic data. We identified 525 venom-like genes between all four species. The venom-gene 22 profile for each species was dominated by enzymatic protein and peptide families, which is 23 consistent with previous findings in other cnidarian venoms. However, we found few toxins that 24 are typical of sea anemones and corals, and furthermore, three of the four species express toxin-like 25 genes closely related to potent pore-forming toxins in box jellyfish. Our study is the first to provide 26 a survey of the putative venom composition of cerianthids, and contributes to our general 27 understanding of the diversity of cnidarian toxins. 28 29 30 1. Introduction
31The phylum Cnidaria (sea anemones, corals, jellyfish, box jellies, hydroids/hydromedusae, 32 etc.) is the earliest diverging venomous lineage (~ 600 million years) [1,2]. Cnidaria deliver their 33 proteinaceous-dominant venom through organelles called nematocysts (a type of cnidae), housed in 34 cells called nematocytes [3,4]. Venom from discharged nematocysts is used in prey capture and 35 defense against predation, but cnidarians also use venom for a variety of other behaviors, such as 36 intraspecific competition [5][6][7] and maternal care [8] (see review by [9]). This ecological diversity is 37 complemented by the functional diversity of cnidarian venoms, which can include neurotoxic, 38 cytotoxic, and enzymatic (e.g. phospholipase and metalloprotease) proteins and peptides, in 39 addition to non-peptidic components [10,11]. For humans, stings from certain species can cause 40 intense localized pain, scarring, induced anaphylaxis, and in the worst cases, cardiac and 41 respiratory failure leading to death [12][13][14][15]. The venom of medically relevant species, such as the 42 Portuguese Man-o-War (Physalia physalis) [16][17][18] and several species of box jellyfish ([19-22], 43 reviewed in [23]), or easy to collect species, such as sea anemones [24,25], have been explored more 44 extensively at a biochemical and pharmacological level [26]. However, these species represent a 45 small fraction of the species diversity within the group, and only recently has the exploration the 46 2 venom composition for a wider number of cnidarians increased in an effort to characterize the 4...