Galunggong that glows in the dark? Bioluminescent bacteria may be the cause, says marine biologist

A woman was surprised after discovering the galunggong she bought from a public market in Dasmariñas, Cavite, glowed in the dark. 

In Kuya Kim’s report on “24 Oras” on Thursday, Maricris Radam was shocked to see blue-green lights emitting from the fish.

“Noong nililinis ko na siya, napansin ko na para siyang umiilaw. Blue-green siya na parang spot, dot dot. Nagtaka ako. Ang ginawa ko pinatay ko ang ilaw, Ayun, maliwanag talaga siya,” Maricris shared.

Despite this, Maricris still cooked the galunggong but did not eat it.

“Hindi ko nga lang siya kinain. Siyempre natakot ako kasi first time kong makakita ng galunggong na ganoon,” she said.

According to marine biologist Glennville Castrence, the glow may have been caused by bioluminescent bacteria.

“Klase ng mga living organisms na may capability na mag-emit sila ng cold light. Sila is naturally occurring sa ating mga karagatan,” he explained.

The luminescence is due to a reaction between two chemicals in their bodies called luciferin and luciferase.

“Symbiotic sila or nag-a-attach sila doon sa mga isda at doon sila nag-mu-multiply lalo na sa skin, sa gills at sa katawan. Base doon sa footage, it is very strongly indicative na ‘yung nakikita natin doon is 'yung tinatawag natin na Photobacterium phosphoreum. Mas nakikita na natin sila lalo na sa dark na area,” Castrence added. 

While there are no reports that consuming fish with bioluminescent bacteria is harmful, Castrence reminded the public to check the fish for freshness. 

“Wala namang report na nagkakaroon ng harmful effect siya sa humans pag nakain. Sa rule of thumb lang, 'pag medyo doubtful na tayo dun sa freshness ng isda, pwede na natin huwag ipilit o i-discard na natin kaysa magkaroon pa tayo ng mga hindi magandang karanasan,” he said.

—Jade Veronique Yap/CDC, GMA Integrated News