Abstract
Abstract
The accumulation of neutral lipids in the cells predetermined to evolve into the cyst cavity lining in Hymenolepis diminuta cysticercoids is presented. The differentiation of these cells from the mesenchyma cells and the accompanying systhesis of lipids began in very young, blastula-shaped larvae. Both the number of the cells and the amount of their lipids increased gradually during further development of the parasites. In the pre-encystment stage of the cysticercoids the cells concentrated around the cavity of the prospective cyst. Following encystment, the scolex and the inverted neck became surrounded by a compact mass of the cells, which started using the stored lipids as a source of energy indispensable for the formation of the cyst tissues and of the definitive multilayer lining of the cyst cavity. No neutral lipids were detected in the mature 23-day-old cysticercoids as well as in the experimentally excysted scoleces. Beside a low level of uniformly distributed phospholipids apparently associated with cell membranes, no local accumulations of these substances were observed at any step of the development of the larvae. The utilization of neutral lipids proves both the presence of a lipase-type enzyme(s) and an operative β-oxidation pathway in the cells of the cysticercoids, the latter feature being highly indicative of oxidative metabolism of these larvae.