‘Giant genes’ shed light on how ‘alien’ crustacean has adapted to the deep sea

Chinese scientists say they have discovered “giant genes” in a deep-sea crustacean that could shed light on how it grows so big in a hostile environment.

The giant isopod has a huge stomach and a lot of fat stored for energy, and it also has expanded gene families related to its body size evolution, according to a study by researchers from the Chinese Academy of Sciences’ Institute of Oceanology in Qingdao.

It can grow up to 50cm (19.7 inches) long and is a relative of the sea roach and the land-based pill bug – also known as a woodlouse – both of which are typically smaller than 3cm (1.2 inches).

The researchers said the crustacean had also been observed fasting for more than five years – the longest period any animal has been known to fast.

Larger animals usually need more energy, and the extreme deep-sea environment appears to be unsuitable for them given the cold temperature and limited food supply, the team wrote in a paper published in peer-reviewed journal BMC Biology last month.

“The enormous size of giant isopods is a classic example of a phenomenon known as deep-sea gigantism,” the scientists wrote, adding that “isopods from deep sea tend to be larger than their relatives in shallower waters”.

To find out how the giant isopod has adapted to the harsh deep-sea conditions, the team sequenced the genome of Bathynomus jamesi – a new species discovered in 2017 near Hainan Island in the South China Sea at a depth of about 900 metres (2,950 feet).