By tracking the daily activities of an octopus dubbed "Super Star", divers in South Africa have discovered a new species of shrimp-like crustacean. These tiny mysid shrimp appear to shack up with cephalopods, an interspecies relationship that has never been observed before. 

'Super Star' (nicknamed by local divers) in the den she shares with the tiny mysid shrimp (Heteromysis octopodis). Image: Craig Foster

Documentary filmmaker Craig Foster has worked with countless researchers throughout his career, but Cape Town University marine biologist Charles Griffiths has become a mentor to his efforts as a citizen scientist. So when Foster happened upon these double den-dwellers, he knew exactly who to call. 

Along with a team of collaborators, Griffiths has been studying mysid (or "opossum") shrimp near Miller Point in False Bay, where Super Star's underwater abode also happens to be located. The region has produced several new species in recent years, so after hearing about Foster's find, Griffiths encouraged him to collect some samples on his next dive. With the help of Austrian crustacean expert Karl Wittman, the team was able to confirm that the tiny animals – which can perch comfortably on a fingertip – are new to science. 

Griffiths has described over 100 new species, but collaborating with local divers on this project has been especially rewarding. 

"It is a revelation to most biologists," Griffiths told National Geographic's Voices blog. "This discovery was made by amateurs with a butterfly net scooping around. [Citizen scientists] are making new observations because they are doing things in a different way to us scientists; they are actually going and observing every single day."

Amazingly, Foster also managed to locate a second new species of shrimp while scouring nearby coastal waters; Griffiths and his colleagues bagged a third. Together, the trio was recently described in the journal ZooKeys.

Finding three new species at a single study site is an impressive feat, but what makes this group of animals particularly interesting is that they belong to the same genus. What's more, Super Star and her crustacean roommate (Heteromysis octopodis) weren't the only "odd couple" on the roster. One of the other mysids – Heteromysis cancelli – was found inside the occupied shell of a hermit crab.

"You look at a hermit crab living in a shell and you don't imagine other animals living inside with them," says Foster. "Yet they allow that. 

The third species was seen inside empty urchin tests and gastropod shells. In a nod to the man who found it, that animal was named Heteromysis fosteri.

An adult female of Heteromysis fosteri (A) and adult male Heteromysis octopodis (B). Images: C.L. Griffiths, Craig Foster/ZooKeys

The naming honour isn't lost on Foster. "It's an amazing feeling to have that name connection," he says. "It's quite beautiful, and powerful. 

It's also a recognition of his efforts to become what he describes as a "marine tracker", which has been quite the learning experience. 

"In the first two years I found almost nothing," he explains. "It's noticing little signs and little tracks. Sometimes you watch incredible behaviour, but you don't know it's amazing because you don't know what it is! And then the different things start to speak to you. That happened with the octopus."

Gaining Super Star's trust wasn't easy: it took six months of swimming with the large female (a common octopus, Octopus vulgaris) before she tolerated the human presence near her den. But persistence paid off, and Foster was eventually able to monitor her daily activities, including hunting behaviour.

The team hopes their success in False Bay will inspire amateur naturalists elsewhere in the world to reach out to local researchers. Foster didn't know the commensal relationship in Super Star's den was unusual, and if he hadn't shared his observations with the experts, the invertebrates may have gone undiscovered. 

"When most people find something new, the first thing they assume is that scientists know its name," Griffiths said. "But that's often not the case."

A subadult female (Heteromysis octopodis) found in a nearby rock pool (A) Super Star sits in her den with a crab to the right. Upper white arrow points to a mysid school of what the team assumes to be H. octopodis (B). Images: Craig Foster/ZooKeys


Top header image: Craig Foster/ZooKeys