A hydra with many heads: Protein and polypeptide toxins from hydra and their biological roles

Daniel Sher, Eliahu Zlotkin

Research output: Contribution to journalArticlepeer-review


Hydra have been classical model organisms for over 250 years, yet little is known about the toxins they produce, and how they utilize these toxins to catch prey, protect themselves from predators and fulfill other biological roles necessary for survival. Unlike typical venomous organisms the hydra allomonal system is complex and "holistic", produced by various stinging cells (in the hunting tentacles and body ectoderm) as well as by non-nematocytic tissue. Toxic proteins also fulfill novel, non-allomonal roles in hydra. This review described the toxins produced by hydra within the context of their biology and natural history. Hydra nematocyst venom contains a high-molecular weight (>100 kDa) hemolytic and paralytic protein and a protein of ∼30 kDa which induces a long-lasting flaccid paralysis. No low-molecular weight toxicity is observed, suggesting the lack of "classical" 4-7 kDa neurotoxins. The occurrence of a potent phospholipase activity in the venom is supported by the detection of several venom-like phospholipase A2 genes expressed by hydra. Hydra also produce toxins which are not part of the nematocyst venom. In the green hydra, Hydralysins, a novel family of Pore-Forming Proteins, are secreted into the gastrovascular cavity during feeding, probably helping in disintegration of the prey. Other putative non-nematocystic "toxins" may be involved in immunity, development or regulation of behavior. As the first venomous organism for which modern molecular tools are available, hydra provide a useful model to answer many outstanding questions on the way venomous organisms utilize their toxins to survive.

Original languageEnglish
Pages (from-to)1148-1161
Number of pages14
Issue number8
StatePublished - 15 Dec 2009
Externally publishedYes

Bibliographical note

Funding Information:
We thank the many students and collaborators who took part in our study of cnidarian chemical ecology and toxinology. This work was supported by grants 476/01 and 750/04 from the Israel Science Foundation.


  • Hydra
  • Nematocyst
  • Nematocyte
  • Pore-forming
  • Toxin

ASJC Scopus subject areas

  • Toxicology


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