Year: 1977
Type: article
Abstract: Nine species of midwater cephalopods, fish, and shrimp, examined ina shipboard aquarium, adjusted the intensity oftheir luminescence to match the intensity of the overhead light. Most animals tested could regulate this ventral countershading luminescence in response to a wide range oflight inten sities. A black anglerfish, Cryptopsaras couesi, also produced a faint later glow, indicating that bioluminescence may be important in lateral countershading in some species. Our observations indi cate that ventral countershading is effective to depths of 750-775 m during the day off Hawaii. We suggest that the concealment strategy of ventral bioluminescent countershading is limited to depths greater than 350-400 m, largely because of the high visual acuity of predators and the high cost of producing countershading luminescence at lesser depths. In a previous paper (Young and Roper 1976), we demonstrated that the midwater squid Abraliop sis sp. turned its photophores on in response to dim overhead illumination in a shipboard aquar ium and turned them off when the light was extinguished. In addition, we noted that the squid became invisible from below when the lumines cence ofthe squid had the same apparent intensity as the overhead illumination. In this paper we examine in more detail bio luminescent countershading in living midwater animals. Tests were conducted on seven species of squids (Abralia trigonura, Abraliopsis sp., Pterygioteuthis microlampas, Pyroteuthis addo lux, Enoploteuthissp., Octopoteuthis nielseni, Het eroteuthis hawaiiensis), one black anglerfish (Cryptopsaras couesi), and one half-red shrimp (Oplophorus gracilirostris). We will demon strate that these animals not only respond to on-off sequences ofoverheadillumination, but alter their luminosity (luminous intensity) in order to match comparable alterations in the overhead illumina tion. The implications of these and our other find ings concerningbioluminescentcountershading in the midwater environment are discussed. Rauther (1927) first suggested that biolumines cent light from the ventrally directed photophores of teleost fishes might diminish their silhouettes
Authors: Richard Edward, Clyde F. E. Roper
Language: English
Domain: Life Sciences
SDG: Life below water
Open Access status: green
OpenAlex ID: W2181542342