A man's evening of enjoying a supper of fish meal was completely ruined after he shockingly discovered a tongue-eating parasite dwelling around a portion of the fish he had purchased from Morrisons, the fourth largest chain of supermarkets in the United Kingdom, on Sunday.

Paul Poli, a 62-year-old retired headmaster, spotted the yellow unpleasant creature as he was about to start eating a meal of tasty sea bass, the South Wales Evening Post reported.

"It was about 3cm long and 8mm wide, luckily just big enough for me to see it before I put it in my mouth," he said.

Promptly taking the fish back to the store in Swansea, South Wales, the bug was identified as cymothoa exigua, commonly referred to as the tongue-eating louse.

The parasite is known to enter a fish through the gills and attach itself to its tongue. Then, it proceeds to destroy the tongue by eating it before replacing it as a new host tongue. Horrifying as it sounds, this doesn't actually harm the fish, according to The Independent.

Following the incident, Morrisons gave a bottle of wine and a $31 (£20) voucher after making an apology to Poli. "Certain fishes often pick up parasites naturally from their eco system," a spokesperson said.

"Although we make every effort to screen these out during the skinning or packaging processes, they may be present on very rare occasions."

"Our skilled fishmongers will also identify them as they fillet a fish - Mr. Poli's fish was sold un-filleted at his request," the spokesperson added.

Unfortunately for Poli, the gross experience has put him off eating fish for life, he said, accoding to UK Metro.

Back in September, doctors were left horrified after a Chinese man's body was discovered to be riddled with tapeworms when he came in complaining of stomach ache and itchy skin, UK MailOnline reported.

Scans revealed that after eating too much sashimi, a delicacy containing raw slices of fish, his body had become infested with worms. Some of the uncooked Japanese delicacy of raw meat or fish must have become contaminated, doctors said.

Once a human is infected, a tapeworm will grow inside the intestine to a length of up to about 50 feet over a period of weeks. It can survive for years and go undetected for weeks or months, in turn releasing its own eggs that infect other parts of the body,

The unidentified man, whose love of sashimi nearly killed him, was treated at the Guangzhou No. 8 People's Hospital in Guangdong Province, in eastern China.