Inertial Mass in the Balance Organ of Pomacea Diffusa: An Experiment on Biosatellite Bion-11

The inertial mass in the balance organ – the statocyst – of Pomacea diffusa was studied from the moment snails hatched from the eggs to completion of the life cycle. The effects of weightlessness on inertial mass were assessed during a 14-day orbital flight on the Bion-11 biosatellite. As snails matured, statocyst diameter increased from 150 to 650 μm and its inertial mass increased from 11–13 to 700 statoconia. The internal structure of statoconia consisted of layers with a central core. The main mineral element giving statoconia mass was calcium carbonate, in the form of aragonite crystals. Exposure to weightlessness for 14 days led to notable changes in the morphometric pattern of the inertial mass in the statocysts of snails on the flight as compared with control snails studied at the same time. Most statoconia showed increases in area, size, perimeter, form factor, length, and width, which may indicate that weightlessness has a stimulating effect on the inertial mass in the balance organ of Pomacea diffusa.