Animal Venoms: Origin, Diversity and Evolution


Venomous animals and their venoms have intrigued mankind for millennia. Venoms are complex cocktails of chemically diverse components that disrupt the physiological functioning of the victim to aid the venom‐producing animal in defence and/or feeding. Despite evolving independently on at least 30 occasions in the animal kingdom, venom exhibits remarkable evolutionary convergence, both in composition and biochemical activity. Various factors, including geography, diet, predator pressure, evolutionary arms race and phylogenetic history, underpin the diversification of venoms. Certain venomous animals, particularly snakes, are medically important and are responsible for tens of thousands of permanent loss‐of‐function injuries and deaths in humans every year. At the same time, as venom harbours many bioactive and highly specific components, it has tremendous potential applications in the development of novel lifesaving therapeutics and environment‐friendly agrochemicals. Several wonder drugs based on venom proteins have saved millions of lives worldwide, and many others are in development.

Key Concepts

  • Venom has evolved independently ∼30 times in the animal kingdom to assist the venom‐producing animal in self‐defence and/or prey capture.
  • A remarkable convergence can be observed in the composition and bioactivity of venoms.
  • While most animals modified their salivary glands into venom glands, the duck‐billed platypus and echidna evolved venom glands through the evolutionary tinkering of sweat glands.
  • Cnidarians evolved peculiar cell types to inject venom into their victims, while many hymenopterans have modified their ovipositors for venom injection.
  • The strong influence of positive Darwinian selection has driven the evolutionary diversification of venoms, while the structural integrity is conserved by purifying selection.

Keywords: venoms; poisons; toxins; evolution; venom delivery system; therapeutics

Figure 1. Parallel origins of animal venom. The tree of life, based on Casewell et al. (), is depicted here, indicating the multiple origins of venom in animals. Venoms used for defence, predation or intraspecific competition are indicated in blue‐, red‐ and orange‐coloured branches, respectively.
Figure 2. Diverse mechanisms of venom delivery in the animal kingdom. This figure portrays venom delivery in (a) Cnidaria – jellyfish with nematocytes; (b) Gastropoda – cone snail with a harpoon; (c) Echinodermata – starfish with dorsal spines; (d) Hirudinea – leech with the suctorial disc and (e) Polychaeta –Glycera worm with the mineralised jaw.
Figure 3. Diverse mechanisms of venom delivery in the animal kingdom. This figure portrays venom delivery in (a) Cephalopoda – octopus with beak; (b) Arachanida – scorpion with stinger; (c) Arachanida – tarantula with fangs; (d) Hymenoptera – wasp with stinger; (e) Chilopoda – Scolopendra centipede with forcipules and (f) Hemiptera – assassin bug with a proboscis.
Figure 4. Diverse mechanisms of venom delivery in the animal kingdom. This figure portrays venom delivery in (a) Blennoid – fangblenny with mandibular fangs; (b) Synanceia – stonefish with dorsal spines; (c) stingray with stinger; (d) Aparasphenodon and its forehead spines; (e) Pit viper with maxillary fangs and (f) Varanus lizard with mandibular fangs.
Figure 5. Diverse mechanisms of venom delivery in the animal kingdom. This figure portrays venom delivery in (a) duck‐billed platypus and its spur and (b) vampire bat with incisors and the tongue.
Figure 6. Molecular evolution of venom. This figure describes the homology model of elapid three‐finger toxins, where positively selected sites are indicated in red. A colour code is provided to depict selection pressures experienced by other residues. A sequence alignment has also been provided, where the signal and mature peptides are indicated, along with the sites that exhibit greater than 90% sequence identity (blue) and those that experience positive selection (red).


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Further Reading

Bücherl W , Buckley EE and Deulofeu V (eds) (2013) Venomous Animals and Their Venoms: Venomous Vertebrates. Amsterdam, Netherlands: Elsevier.

Fry BG , Koludarov I , Jackson TNW , et al. (2015) Seeing the woods for the trees: understanding venom evolution as a guide for biodiscovery. In: King GF (ed) Venoms to Drugs: Venom as a Source for the Development of Human Therapeutics, pp. 1–36. Cambridge, UK: The Royal Society of Chemistry.

Gopalakrishnakone P and Calvete JJ (eds) (2016) Venom Genomics and Proteomics. Dordrecht: Springer.

Jenner R and Undheim E (2017) The Secrets of Nature's Deadliest Weapon. CSIRO Publishing, ISBN: 9781486308378.

King G (ed) (2015) Venoms to Drugs: Venom as a Source for the Development of Human Therapeutics. London: Royal Society of Chemistry.

Mackessy SP (ed) (2016) Handbook of Venoms and Toxins of Reptiles. Florida, United States: CRC Press.

von Reumont BM , Campbell LI and Jenner RA (2014) Quo Vadis Venomics? A roadmap to neglected venomous invertebrates. Toxins 6 (12): 3488–3551.‐6651/6/12/3488.

Shiomi K , Midorikawa S , Ishida M , Nagashima Y and Nagai H (2004) Plancitoxins, lethal factors from the crown‐of‐thorns starfish Acanthaster planci, are deoxyribonucleases II. Toxicon 44 (5): 499–506.

Sues H‐D (1996) A reptilian tooth with apparent venom canals from the Chinle Group (Upper Triassic) of Arizona. Journal of Vertebrate Paleontology 16 (3): 571–572.

Undheim EAB and King GF (2011) On the venom system of centipedes (Chilopoda), a neglected group of venomous animals. Toxicon 57 (4): 512–524.

Williams BL (2010) Behavioral and chemical ecology of marine organisms with respect to tetrodotoxin. Marine Drugs 8 (3): 381–398.‐3397/8/3/381/htm.

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Suranse, Vivek, Srikanthan, Achyuthan, and Sunagar, Kartik(Mar 2018) Animal Venoms: Origin, Diversity and Evolution. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000939.pub2]