HIOMT activity in the pineal complex of Geotria australis ammocoetes was found to reach a peak, 4-5-fold that of the basal value, between 2 and 3 hr after the onset of darkness. This short burst of HIOMT activity was associated with aggregation of pigment in the melanophores causing pallor in the ammocoetes. 3H-Melatonin was taken up by all the tissues examined (pineal complex, pituitary, endostyle, brain, liver, gut and tail muscle). It is concluded from these results that the pineal complex in Geotria australis is a photoneuroendocrine transducer conveying diurnal information to other body tissues. © 1977.
Joss, J. M. P. (1977). Hydroxyindole-O-methyltransferase (HIOMT) activity and the uptake of 3H-melatonin in the lamprey, Geotria australis gray. General and Comparative Endocrinology, 31(3), 270–275. https://doi.org/10.1016/0016-6480(77)90090-9