First venomous crustacean confirmed

Blind cave-dwelling creature found to use highly toxic venom to liquefy its prey.

A team of scientists led by the Natural History Museum has identified the world’s first venomous crustacean.

The venomous creature is a blind animal with many legs called a remipede. Museum zoologist Dr Bjoern von Reumont and the team analysed the venom glands of one remipede species and found a cocktail of chemicals including enzymes and a paralyzing neurotoxin.

Remipedes live in underwater caves in the Caribbean, Canary Islands and Western Australia, and feed on other crustaceans. They are thought to liquefy their prey with the highly toxic venom and then suck out the liquid meal from their prey’s exoskeleton.
Evolution of venom

This technique is similar to that of spiders, but the venom itself has more in common with rattlesnake venom.

Some snake venoms rely heavily on enzymes which break down proteins. Remipede venom is full of these enzymes as well, but spider venoms are dominated by neurotoxins. The neurotoxin in the remipede venom is very similar to some spider neurotoxins.

‘This venom is clearly a great adaptation for these blind cave-dwellers that live in nutrient-poor underwater caves,’ said senior author and Museum zoologist Dr Ronald Jenner.
How to be a predator

Both spiders and remipedes belong to the larger group of animals known as arthropods. Crustaceans, a group of animals that contains crabs, shrimp and barnacles, form one of four main groups of arthropods. Characteristic organisms in the other three groups are spiders, centipedes and insects, each of which have thousands of venomous species.

‘While they can be as varied as tiny waterfleas, krill, crabs and barnacles, not one of the approximately 70,000 described species of crustaceans was known, until now, to be venomous,’ said Jenner.

One reason crustaceans may not have many venomous members is that few evolved to be predators. According to Jenner there are two ways to be a successful at eating things your own size, to be strong or to be venomous.

One of the only other crustaceans known to have specialized as a predator is the mantis shrimp, which ‘literally bludgeons’ its prey to death.
The root of insects

Following the discovery of a venomous remipede, there are other candidates for venomous crustaceans. These include other species of remipede, and a fish parasite known to pierce the skin of fish and cause them to haemorrhage, feeding on the resulting blood flow.

Jenner and von Reumont first started investigating the remipede as a candidate for the closest living relative of insects. Jenner said the creature now appears to be ‘weirder than we thought’ and ‘how we use a blind cave-dweller to look at the evolution of insects is even more of a headache.’