Experimental studies on the light sense in the hagfish, Eptatretus burgeri and Paramyxine atami (Cyclostomata)

Abstract

Photo-reception and sensitivity to light were studied in two Japanese hagfishes, Eptatretus burgeri living in shallow water and Paramyxine atami living in water of about 100m depth. Both species responded to general illumination by first moving the tail or head and then by swimming. Local illumination revealed that regions most sensitive to light were the skin of the tail in both species and a line of unpigmented skin running down the back of E. burgeri. The light sensitivity of the lensless eyes, which are situated below the skin, was very weak in both species. P. atami showed shorter reaction time to light than E. burgeri. No change in skin colour was induced either by almost complete hypophysectomy or by continuous illumination against a white background. Under-water observations with SCUBA revealed that free moving E. burgeri responded well to illumination uncovered during the night, but the ones buried in mud, with only the heads uncovered did not. © 1978 Biologischen Anstalt Helgoland.