“I love the excitement of turning over rocks and seeing what beasties are hiding underneath,” says Emily Roberts, a Marine Ecologist for the Taranaki Regional Council in New Zealand. “It stems from when my mum used to take us exploring rock pools of the north coast of Scotland when we were wee nippers.”
And while she’s found plenty of cool things in her explorations over the years, she’d never come across the “alien looking commensal beast” pictured above. “I’d never seen anything like it before. It looked more like something out of a science fiction film than a crab in an ID guide. On closer inspection it became obvious that it was a blue green chiton that had attached itself to the carapace of a New Zealand Half Crab.”
Most of us who’ve explored intertidal zones are familiar with chitons, an ancient mollusk class whose distinctive shells consists of eight overlapping plates surrounded by a softer fleshy girdle. Chitons are found in marine areas throughout the world, mostly in tidal zones, although a few species live in deep water. They stick onto hard substrates with their muscular foot and use their magnetite (the only animals to have this compound) teeth to scrape off algae, bryozoans, and other tiny organisms. Blue Green chitons are the most commonly found chitons in New Zealand, although it’s safe to say finding one attached to a crab is rare occurrence. “After taking a few photos, it tried to scuttle up my work colleague’s sleeve (see above),” says Emily. “As you can see from the photo, the crab’s eyes were totally covered. I wonder how long it had been attached to the crab like that for?”
Emily is involved in several New Zealand citizen science projects which use iNaturalist and its sister site, NatureWatchNZ, including CoastBlitz Waitara, which is a project that records biodiversity off of Waitara, Taranaki, and Project Hotspot, which focuses on four key marine species in the same area - Orca, Reef Herons, Little Blue Penguins, and New Zealand Fur Seals. “The extensive reefs off this special New Zealand town are of great cultural and historical significance to local iwi and hapu [Maori social groups],” she says. Local schoolchildren have even named several individual Reef herons, like Kelpie (below), which can be distinguished by their leg markings.
“iNaturalist has absolutely changed the way I see the natural world to the extent that it is now rare for me to leave the house at the weekend without a pair of binoculars, camera and smartphone in hand,” says Emily. “Collecting and recording what’s out there is essential to enable better protection of species and their habitats. From a selfish perspective it’s also awesome to feel better connected to the natural world and watch wild and wonderful creatures doing crazy things: long live the chiton crab!”
- by Tony Iwane
- Stefan Bienart shot this sweet footage of a male Orca surfing the waves off of Taranaki and shared it with Project Hotspot.
- Check out this chiton on the move!