Isolated ventral photophores of Argyropelecus hemigymnus and abdominal photophores of Maurolicus muelleri, respond to adrenaline 10-4M by a light emission which magnitude is proportional to the weight of photophores. The amplitude of the light response is four times as high in Maurolicus with regard to Argyropelecus photophores. According to the counter-lighting hypothesis, this difference suggests that those fishes might live in waters of a different ambiant light level
