Deep ocean 'barrel shrimp' gives glimpse into how animals see the world

A research team, including biologists from The University of Western Australia, is addressing the age-old question of how animals see the world through a study into a four-eyed, deep-sea crustacean.

The semi-transparent Phronima, or ‘barrel shrimp’, lives throughout the world’s ocean and looks out for prey in its dark habitat through two sets of compound eyes, each made up of hundreds of eyelets.

Postdoctoral researcher Dr Zahra Bagheri, from UWA’s School of Biological Sciences and Oceans Institute, said researchers created a computer model based on a detailed reconstruction of the eyelets, physics of optics and how light travels through the water to find out what Phronima and other deep-sea animals see.

“Vision in the open ocean requires animals to perform visual tasks quite unlike those of any other environment,” Dr Bagheri said.

“What is unusual about Phronima is that as many as 60 eyelets in the larger eye look at the same point in space. 

“Our results show one of the benefits of the design of Phronima’s large eyes is that they allow it to see the types of deep-sea objects at longer distances and over a wider depth range. 

“The smaller eyes provide low resolution vision of nearly the entire sphere surrounding them, meaning they don’t miss anything close by.”

Postgraduate researcher Anna-Lee Jessop, from UWA’s School of Biological Sciences and Oceans Institute, said Phronima lived in a ‘barrel’ made out of the remains of gelatinous animals but this limited their field of view. 

“We suggest that the evolution of their unusual eyes is related to the restricted viewing field created by the narrow opening of the ‘barrel’ they live in,” Ms Jessop said.

“The pressure to see without being seen in a dim but completely open environment caused many unusual adaptions in deep-sea animals, including those seen in Phronima.”

The research was led by Associate Professor Jan Hemmi, from UWA’s School of Biological Sciences and Oceans Institute, and scientist Dr Karen Osborn, from the Smithsonian National Museum of Natural History, and Monterey Bay Aquarium Research Institute.