title: Aging changes in the optic tectum of the guppy Poecilia (Lebistes) reticulatus.
abstract: Histological surveys of the brains of guppies throughout their lifespan showed no overall loss of tissue with advancing age. Brain and body increased in size at a similar rate throughout adult life in male fish. In old females after the age of two years, brain growth apparently ceased, although body growth continued at a low rate. In both sexes there was a loss of neurones from the stratum griseum periventriculare in the midbrain roof in old age; the decrease in size was significant. The midbrain is a major correlative center concerned with spatial orientation. How far neuronal loss may contribute to functional behavioral disorder in old age is unknown, but a loss of orientation could render the older fish more susceptible to predation.
mesh_terms: D000375:Aging; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000254:growth & development; D005399:Fishes; D013477:Superior Colliculi / Q000033:anatomy & histology / Q000166:cytology / Q000254:growth & development*