Ocean life
Giant sea spiders produce blue light in the deep ocean
Researchers have confirmed that two species of deep-sea spiders off the Australian coast generate their own blue glow using leg tissue.
Reported by Phys.org · · 2 min read
Scientists exploring the deep waters off the eastern coast of Australia have confirmed bioluminescence in two species of giant sea spiders, Colossendeis tasmanica and Colossendeis minor. The findings mark the first formal visual documentation of self-generated luminescence in these marine invertebrates, solving a long-standing question about whether such creatures produce their own illumination.
Historic accounts dating back to the late nineteenth century described glowing markings on sea spiders taken from the Indian Ocean. Nevertheless, scientists had remained uncertain whether the animals were truly bioluminescent or simply coated in luminous secretions rubbed off from neighboring coral colonies.
To investigate the source of the glow, researchers gathered nine individuals during a 2017 expedition at depths ranging from 1,006 meters down to nearly 5,000 meters. A research team directed by Dr. Jerome Mallefet of UCLouvain examined the specimens aboard their survey vessel.
Inside a darkened workspace, investigators applied light mechanical pressure and chemical compounds to the limbs, causing the appendages to radiate a deep-blue light. Measurements revealed that the luminescence centered at 449 nanometers, originating exclusively from the legs and reaching its peak brightness near the leg tips. Manual stimulation triggered glows lasting up to a couple of minutes, while chemical exposure prolonged the emission for ten minutes.
Insights from laboratory analysis
Back in their home laboratory, the team examined preserved tissue slices to identify where the reaction occurred. Microscopic screening revealed that light generation takes place inside gut-related cells situated inside the legs, indicating the spiders might acquire necessary luminous compounds through their prey.
Standard assays for common light-producing enzymes yielded little activity. Instead, the team triggered luminescence using hydrogen peroxide alongside other compounds, noting that higher calcium concentrations amplified the effect. This behavior resembles photoprotein mechanisms present in jellyfish, though scientists emphasized that molecular validation of the system is still required.
The ecological purpose behind the display also remains unsolved. Researchers noted that further investigations will be necessary to determine why these deep-sea pycnogonids glow in their lightless habitat.
