Colour-changing allows brittlestars to see

DIVING NEWS

Colour-changing allows brittlestars to see

Brittlestar
Red brittlestar Ophiocoma wendtii. (Picture: Lauren Sumner-Rooney)

Brittlestars have no eyes but one species has been shown for the first time to be able to see – thanks to its ability to change colour from day to night. It is only the second-known example of vision in any eyeless animal.

An international team led by Lauren Sumner-Rooney of Oxford University Museum of Natural History have established that the red brittlestar Ophiocoma wendtii is able to see its way around Caribbean coral reefs.

The species, which changes colour from bright red in daytime to beige at night, was known to be covered in light-sensitive cells and to appear averse to light.

The researchers ran hundreds of behavioural experiments on the brittlestars to show that during the day their coarse form of vision allowed them to distinguish areas of light contrast. This enabled them to shift to areas they believed would provide better protection from predators.

However, the team were surprised to find that the responses vanished at night, even though the light-sensitive cells still appeared active.

They traced this to the day/night colour change. A paler brittlestar, Ophiocoma pumila, that was also covered in light sensors didn’t change colour at night, and appeared unable to see.

4 January 2020

Using digital models of both species’ light-sensing cells, the scientists showed that during the day the pigment in O wendtii restricted light reaching the sensors to a narrow angle. Without this pigment, as in O pumila or at night in O wendtii, light could reach the sensors from a far wider angle, rendering vision impossible.

The scientists will now test whether a single species of sea-urchin – the only other animal known to see without eyes – also changes colour in response to light levels.

Also involved in the study were the Smithsonian Tropical Research Institute in Panama, Berlin's Museum für Naturkunde, Lund University and the Georgia Institute of Technology.

The study is published in the journal Current Biology.

biggest

LET’S KEEP IN TOUCH!

Get a weekly roundup of all Divernet news and articles 🤿

We don’t spam! Read our privacy policy for more info.

Leave a Reply

Your email address will not be published.

Related Divernet Posts

Diver Magazine Relaunch

Diver magazine needs YOU!

Are you still lamenting the demise of Diver magazine? Well now you can help resurrect an icon as we seek to bring back the magazine

manta ray and diver over reef in Komodo

Divers pitch into Komodo manta probe

Manta rays choose to stick around Indonesia’s Komodo National Park in unusually large numbers – and, according to a new diver-led study, this community could

female diver holding pair of Fourth Element Tech fins

Tech fins inspired by humpback whales

Whales provided the inspiration for optimising efficiency in Fourth Element’s latest fins, according to the Cornwall-based manufacturer. The “turbulence disruptors” on top of the blades

Last Breath portrait of Woody Harrelson

Woody dives into Last Breath remake

A new version of the British documentary-thriller that captured the imaginations of divers in 2019 is about to be previewed at the Cannes Film Festival.

Viagra tablet

Viagra and diving: Risk reduction

Awareness is everything in diving, and BOB COLE has advice for divers who, for whatever reason, take PDE5 inhibitors I recently met an old friend

Reefs of Raja Ampat

Reefs of Raja Ampat

Local Guide to Raja Ampat Reefs, #4 Neu Reef While Raja Ampat is home to an incredible number of dive sites, one area, in particular,

Follow Divernet on Social Media