5 minutes with Dr Marissa McNamara

Crabs, shrimps, lobsters, barnacles and more – spend five minutes with Dr Marissa McNamara, Collection Manager (Crustacea) and learn some fascinating facts about crustaceans and some of the reasons she loves her job so much.

What is your favourite species in the collection and why?

Mantis shrimp! Mantis shrimp are deadly predators that strike with the speed of a bullet. They have specialised hunting limbs called raptorial claws that are shaped either as clubs or as spears. Species with clubs smash their prey, while species with spears impale their prey.

Mantis shrimp also have the most complex vision in the animal kingdom—while humans have three cones in their eyes, mantis shrimp have 12, and can see UV light and polarised light.

Why do mantis shrimps have such complicated vision? Researchers are still trying to figure out the answer!

Do you have any interesting facts about crustaceans?

Crustaceans are incredibly diverse, they include animals like crabs, shrimps, lobsters, and barnacles, and come in a variety of shapes and sizes.

For example, the Swamp Crayfish (Tenuibranchiurus glypticus) is the smallest crayfish in the world. This diminutive species reaches 25mm in length and is only found across southeast Queensland.

In contrast, one of the largest crab species in the world, the Tasmanian Giant Crab (Pseudocarcinus gigas), is only found off southern Australia. This crab lives in deep waters and its carapace can reach up to half a metre across!

Another large, and weird, crustacean is the Giant Isopod (Bathynomus giganteus). The species is a giant relative of much more common small isopods such as pill bugs and woodlice, but instead of being found under logs in the garden, giant isopods are found in the pitch darkness of the ocean, where they are known to scavenge on whale carcasses. They can reach 50 centimetres in length, and are a prime example of deep-sea gigantism.

Finally, there is a group of crustaceans that don’t look like crustaceans at all: parasitic barnacles such as Sacculina carcini. Instead of having legs, or even a recognisable body, Sacculina carcini grows in a network of filaments throughout its host crab. Lack of a body doesn’t get in the way of this parasite, however; Sacculina can actually control the crab’s behaviour, and turn it into a ‘zombie’ that looks after the parasite’s eggs as if they were its own.

Tell us a little bit about your area and why do you love working with crustaceans?

I love the diversity of crustaceans! One day I could be working with giant crabs from Tasmania, the next I could be checking on tiny amphipods that live on whales. Seeing the variety of forms in Crustacea—which is only one subphylum—reminds me of the incredible biodiversity on the planet, and the beauty of life around us.

What is one of the most interesting facts you have discovered through working at the museum?

Many different crab species can be poisonous. One toxic crab species found in Queensland waters, the devil crab Zosimus aeneus, contains so much poison, just one specimen could potentially kill about 40,000 people!