Up until now, scientists thought an animal’s venom remains consistent throughout their lifetime. A scorpion emits venom from the barb on its tail, a spitting cobra sprays venom in its spit, and this behavior remains fairly constant from birth to death. But a new study recently published in eLife Sciences suggests this is not the case. At least, it’s not the case for every animal on the planet.
Meet Nematostella vectensis, commonly known as the starlet sea anemone. This stunning sea creature is tiny in size, translucent in color, and can be found lurking in the shallow waters of the lagoons and salt marshes of the eastern US and the south-eastern UK.
It turns out that the venom of the starlet sea anemone undergoes several adaptions throughout its lifetime in response to changes in its environments, diet, and predators. This is the first time scientists have detected variations in the recipe and potency of a single animal’s venom.
"Until now, venom research focused mainly on toxins produced by adult animals. However, by studying sea anemones from birth to death, we discovered that animals have a much wider toxin arsenal than previously thought,” said lead author Yehu Moran, a senior lecturer at Hebrew University's Alexander Silberman Institute of Life Science, in a statement. “Their venom evolves to best meet threats from predators and to cope with changing aquatic environments."
The researchers monitored the venom-producing cells from cradle to grave, labeling them with fluorescent markers, and noted any important interactions the sea anemones had, either as prey or predator.
During its larval stage, the sea anemones are vulnerable to attack from larger fish and, in response, the team found they produce a very potent type of venom. This results in prey spitting them out as soon as they attempt to swallow them.
An Atlantic killifish (Fundulus) attempts to eat a Nematostella larva. Jason Macrander, UNC Charlotte.
The sea anemones grow up and become predators themselves, using tentacles laced with venom to snatch shrimp and small fish. Meanwhile, their venom adapts, turning into a different type of toxin that is more appropriate for the job. Their venom continues to change as the sea anemone ages and moves to new environments.
“This evolutionary plasticity might be one of the factors that made sea anemones such a successful group that inhabits all the world’s oceans for the last 600 million years,” the scientists write in the study.
As well as being extremely interesting from an evolutionary perspective, these results could have important practical uses. Venoms are frequently used for medical purposes and this study suggests that there are several venoms out there that we still do not know about.
More research will have to confirm if this venom adaptation is unique to the sea anemone or widespread among the animal kingdom.