According to Julien Claes, a researcher at the Marine Biology Laboratory, there are about 50 different kinds of sharks, or more than 10% of all known shark species can emit light. This means that light can be generated and emitted from sharks. Crass and his colleagues chose a specific luminous shark as the key research object, which is a lantern shark with a velvet belly. The researchers named it "the death hunter in the Gulf". According to Crass, this shark can emit light because it has a luminous organ called visceral luminophor at the bottom of its body. In this study, Crass and his colleagues also collected male and female velvet belly lantern sharks found in Norway.

It is understood that scientists also measured the luminous intensity of each shark, and a few days later, a second measurement was made to test the shark's response to light. The results show that most sharks can spontaneously emit some light that lasts for a long time, occasionally lasting for more than an hour. The spectrum of light emitted by sharks matches their living conditions in the deep sea very well. At the same time, sharks can slightly adjust their own light according to the changes of external light. This ability to regulate light shows that they use small glands in the eyes and brain to monitor the information of light scattered from the ocean. Like many sharks, this shark's mouth is on their lower side. Camouflage system can help sharks catch their prey. For example, they can use their "invisibility" ability to catch animals such as krill and fish.