Toxicon 56 (2010) 897–913 Contents lists available at ScienceDirect Toxicon journal homepage: www.elsevier.com/locate/toxicon Venom on ice: First insights into Antarctic octopus venoms E.A.B. Undheim a,b, D.N. Georgieva c, H.H. Thoen a,b, J.A. Norman b, J. Mork a, C. Betzel c, B.G. Fry b,* a Norwegian University of Technology and Science, Department of Biology, Trondheim Biological Station, N-7491, Trondheim, Norway b Department of Biochemistry & Molecular Biology, Bio21 Institute, University of Melbourne, Melbourne, Victoria 3000, Australia c Laboratory of Structural Biology of Infection and Inflammation, Institute of Biochemistry and Molecular Biology, University of Hamburg, Germany article info abstract Article history: The venom of Antarctic octopus remains completely unstudied. Here, a preliminary Received 26 November 2009 investigation was conducted into the properties of posterior salivary gland (PSG) extracts Received in revised form 12 June 2010 from four Antarctica eledonine (Incirrata; Octopodidae) species (Adelieledone polymorpha, Accepted 16 June 2010 Megaleledone setebos, Pareledone aequipapillae, and Pareledone turqueti) collected from the Available online 25 June 2010 coast off George V’s Land, Antarctica. Specimens were assayed for alkaline phosphatase (ALP), acetylcholinesterase (AChE), proteolytic, phospholipase A2 (PLA2), and haemolytic Keywords: activities. For comparison, stomach tissue from Cirroctopus sp. (Cirrata; Cirroctopodidae) Octopoda Antarctic was also assayed for ALP, AChE, proteolytic and haemolytic activities. Dietary and Venom morphological data were collected from the literature to explore the ecological importance Adaptation of venom, taking an adaptive evolutionary approach. Enzyme Of the incirrate species, three showed activities in all assays, while P. turqueti did not exhibit any haemolytic activity. There was evidence for cold-adaptation of ALP in all incirrates, while proteolytic activity in all except P. turqueti. Cirroctopus sp. stomach tissue extract showed ALP, AChE and some proteolytic activity. It was concluded that the AChE activity seen in the PSG extracts was possibly due to a release of household proteins, and not one of the secreted salivary toxins. Although venom undoubtedly plays an important part in prey capture and processing by Antarctica eledonines, no obvious adaptations to differences in diet or morphology were apparent from the enzymatic and haemolytic assays. However, several morphological features including enlarged PSG, small buccal mass, and small beak suggest such adaptations are present. Future studies should be conducted on several levels: Venomic, providing more detailed information on the venom compositions as well as the venom components themselves; ecological, for example application of serological or genetic methods in identifying stomach contents; and behavioural, including observations on capture of different types of prey. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction cirrate (Octopoda: Cirrata) and incirrate (Octopoda: Incir- rata) genera currently recognized, of which five genera are 1.1. Antarctic octopuses endemic (Adelieledone, Bathypurpurata, Megaleledone, Par- eledone, and Praealtus (Collins and Rodhouse, 2006)). The octopod (Cephalopoda: Octopoda) fauna of the However, although several major clades are represented, Southern Ocean is both rich and highly endemic, with 12 the Antarctic octopod fauna is dominated by a single ele- donine (Incirrata: Octopodidae) lineage which contains 27 of the 36 octopod species currently recognized as part of * Corresponding author. the Southern Ocean fauna (Allcock et al., 2007; Collins and E-mail address: [email protected] (B.G. Fry). Rodhouse, 2006). The main radiation is thought to have 0041-0101/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.toxicon.2010.06.013 898 E.A.B. Undheim et al. / Toxicon 56 (2010) 897–913 occurred after the separation of the Antarctic continent and can result in a secondary loss of the venom system e.g. eggs formation of the Antarctic circumpolar current approxi- (A. eydouxii (Li et al., 2005b), Dasypeltis sp. (Fry et al., 2008)) mately 34 million years ago (Strugnell et al., 2008). or slugs (Pareas sp. (Fry et al. 2008)). However, the venom The members of the unique Antarctic octopod clade that apparatus is not the only other structure that influences or are not restricted to the deep sea can be found throughout is influenced by the evolution of venom; the general ability the Antarctic shelf and continental slope where they have to catch and process the preferred prey by physical force is undergone extensive radiation, particularly in the case of often an important factor. This may ultimately determine Pareledone, with each species usually having a fairly limited the degree of reliance upon toxins for prey capture, and geographic, and often bathyal, range (Collins and Rodhouse, consequently the strength of the positive selection which 2006). While the species radiation has been contributed to drives the recruitment of toxins and evolution of venom in the effect of the shelf of isolated island groups combined an animal. with glaciation cycles (Allcock et al., 1997, 2001), there are large overlaps in species distributions, with often several 1.3. Venom in the Octopoda species appearing sympatrically in an area (Allcock, 2005). As sympatry is often associated with trophic niche parti- One group that uses venom in the capture of otherwise tioning, this may again lead to a range of adaptations, tricky or potentially dangerous prey is members of the including venom diversification. Octopodidae, which are known to prey on a range of taxa, including molluscs, crustaceans, fish, and even birds 1.2. Venom apparatus and diet (Grubert et al., 1999; Sazima and Bastos-de-Almeida, 2006). Although small prey is often handled without the use of Venoms play a range of adaptive roles in the animal venom, many octopods switch to the use of venom once the kingdom; killing, paralyzing, immobilizing or pre-digesting use of physical force becomes inefficient (Fiorito and prey, as well as defence against predators and deterring Gherardi, 1999; Grisley et al., 1999). In large, shelled prey, competitors (Kordis and Gubensek, 2000). In animals for example, small holes are often drilled through which relying on toxins for prey capture and handling, the the octopus injects its toxic saliva, which then acts by evolution of the molecular components of venom is often paralyzing and/or killing the prey as well as aiding in the tightly linked to diet and trophic ecology through an detachment of tissue from the exoskeleton (Grisley and evolutionary arms race between predator and prey (e.g. Boyle, 1987; Nixon, 1984; Pilson and Taylor, 1961). Chetty et al., 2004; Fry et al., 2003; Heatwole and Poran, The production of toxic saliva in octopod posterior 1995). Due to the strong selection pressure that results salivary glands (PSG) was first recognized at the end of the from this arms race, and because toxin genes are members 1800s (Ghiretti, 1960). Despite findings as early as 1906 that of multigene families (Kordis and Gubensek, 2000), toxins the toxin was a protein particularly potent against crusta- often show very rapid evolutionary rates (e.g. Ohno et al., ceans (Songdahl and Shapiro, 1974), it was long thought 2002). The accelerated evolution may be in a diversifying that the paralysis and death observed in envenomated prey manner, such as conotoxins (Duda and Palumbi, 1999), or was due to the actions of various amines isolated from convergent, like the fish-specialised venoms of sea kraits octopod PSG, such as tyramine, histamine, acetylcholine, (Elapidae; Elapinae) and sea snakes (Elapidae; Hydro- octopamine and serotonin (Erspamer and Asero, 1953; phiinae) (Chetty et al., 2004). However, the redundancy in Ghiretti, 1960; Henze, 1913). However, the findings that genetic material also means that a niche shift causing these amines at realistic concentrations only caused the a relaxed or loss of selection pressure usually leads to initial symptoms of “overexcitability” in envenomated a rapid loss of venom, such as in obligate egg-eating elapid crabs, and were unable to reproduce the irreversible snakes like Aipysurus eydouxii (Li et al., 2005b) and Bra- paralyzation achieved by injection of crude saliva, sug- chyurophis sp. (Fry et al., 2008). gested a more complex venom composition (Ghiretti, Unlike poisonous animals such as toads, “true” 1959). This resulted in the description of Cephalotoxin venomous animals (Goyffon, 2002) possess a venom (Ctx), a protein mixture consisting of four proteins, apparatus (glands, secretory tissues, etc.) that includes including at least one glycoprotein, originally extracted specialised venom delivery structures. As venom is from the PSG of the cuttlefish Sepia officinalis, and later a widespread feature in the animal kingdom, with every Octopus vulgaris (Ghiretti, 1959, 1960). Ctx was reported to major bilaterian metazoan clade having independently have a number of activities, including inhibition of respi- evolved venomous representatives (Fry et al., 2009), the ration in crabs, inhibition of blood coagulation in both crabs array of structures adapted for envenomation of prey are and humans, and paralyzation of crabs and cockroaches vast; with examples including teeth (snakes, varanid and (Ghiretti, 1960). helodermatid lizards (Fry et al., 2006)), walking legs (chi- Since then, several proteinaceous toxins have been lopods (Lewis, 1981)),