A female deep-sea anglerfish from the genus Linophryne with a luminous lure and ‘beard’. Image: Danté Fenolio/DEEPEND Consortium
The mysterious bacteria that gives the anglerfish its distinctive glowing headlamp is now a little less mysterious.
Aside from a terrifying jaw, the anglerfish’s distinctive ‘lamp’ to guide it through the murky depths of the world’s oceans certainly makes it stand out. However, the bioluminescent bacteria responsible for this lamp has remained mostly a mystery to researchers.
Now, researchers from Cornell University have published a study revealing that the bacteria – which has a symbiotic relationship with the fish – most likely comes from the water. This contradicts previous studies which said that, based on their genomes, the bacteria appeared unable to live without their host.
“In previous work that I had done, we found for the symbionts of deep-sea anglerfish that the bacteria have undergone genomic reductions; they’ve lost a lot of genes, suggesting that they are probably obligately dependent on their host,” said Tory Hendry, the paper’s senior author.
Typically, a reduced genome indicates that bacteria have lived their whole lives inside a host. This is because it no longer needs to acquire ‘genetic software’ because it has ready access to the services and nutrients the host provides.
Bulb may spew bacteria
As part of this latest study published to eLife, the researchers obtained specimens of seven species of anglerfish across six families. They also studied the only two species of bioluminescent bacteria known to live within the bulbs of anglerfish.
This revealed that while one species of bacteria was found only in one fish, the other bacteria species were in the remaining six fish. The specimens were obtained from far and wide across the globe – both in terms of location and timeframe – with some caught almost 20 years apart.
Another related study showed that anglerfish only acquire bacteria later in life, once their distinctive light organ has developed. The researchers are now aiming to discover the reason for this organ containing a tiny pore.
They theorise the fish could use it to spew bacteria into the environment once microbe populations grow, potentially to ensure future anglerfish can obtain the luminous microbes through the water.
