Histamine-like immunoreactivity in the putative pacemaker of two Cambarellus montezumae generations at different times of day, between females and males

In different organisms, histamine (HA) is related to biological rhythms, moderating the circadian rhythm of the neuroendocrine system. Nevertheless, no work has been done on the putative pacemaker of the endemic crayfish, Cambarellus montezumae, wich threatened by anthropocentric modifications of its habitat. The aims of the present work were to evaluate the daily presence and localization of HA in two structures proposed as putative pacemakers of the crayfish, the eyestalk and the brain in females and males. We also evaluated whether there are changes in the F0 generation with respect to the F1 generation. Adult crayfish were used, euthanized at different times of day, to excise the eyestalk and brain and process them through immunohistochemical techniques. The results obtained showed that the immunopositivity to HA in the eyestalk and brain of the crayfish undergoes daily variations in both females and males, as well as between the F0 and F1 generations.