The effects of heavy metals on the asexual reproduction of the annelid Aeolosoma headleyi Beddard (1888)
Chronic bioassays were conducted on the annelid Aeolosoma headleyi Beddard (l888) to determine the effects of heavy metals on asexual reproduction. Bioassays were conducted with the chloride and sulfate salts of zinc, copper, cadmium, cobalt, and nickel. Additionally, chromium, as potassium dichromate, was tested. Of these metals, only two, zinc chloride and copper sulfate, significantly stimulated reproduction at or below 0.01 ppm of the metal. All metals inhibited reproduction at high concentrations and none, except the two above, had any significant effect on reproduction at the sublethal concentrations tested. Hydrogen ion concentrations between 6 and 10 units had no effect on reproduction. The effects of the metals were not due to pH or osmotic effects.
Subsequent studies were conducted with zinc chloride to determine its effect on zooid scissiparity. As zinc concentrations increase, the time for first zooid scissiparity decreased. Second bud formation was inhibited by zinc levels greater than 0.1 ppm. Normally the worm exhibits paratomy (release of zooid with a developed cephalic region). Above 7.0 ppm zinc, the worms also exhibit architomy where the cephalic region is not developed prior to scissiparity.