Qualitative distribution of neutral lipids and phospholipids in Hymenolepis microstoma from the cysticercoid to the egg producing adult.

The distribution of neutral lipids and phospholipids in Hymenolepis microstoma has been studied using Fettrot, Sudan Black B, Sudan IV and copper phthalocyanin staining techniques. In the cysticercoid, neutral lipids are found in the outer membrane, the lining of the cysticercoid cavity, the tegument of the larval worm and the calcareous corpuscles. A decreasing gradient of phospholipids is found starting from the acellular layer, through the circular fibrous layer, the longitudinal fibrous layer, the adjacent dense zone and ending with the lining of the cysticercoid cavity. Phospholipids are also found in the calcareous corpuscles and the tegument of the larval worm. In the young adult (3 days p.i.) fat globules are first seen to accumulate in the last 2-3 proglottids. Until the 6th day p.i. they are found in the posterior third of the worm, surrounding developing gonads, but mostly concentrated along the transverse line. The mature proglottids contain fat, (a) in both granular and globular forms: in the folds of the uterus, sperm ducts, cirrus pouch and tegument (proximal cytoplasm), (b) in a diffuse form: in the vitellaria, ovary, testes and the tegument (distal cytoplasm). Pre-gravid and gravid proglottids show the largest fat globules. From the cleaving embryo to the fully developed oncosphere the concentrations of neutral lipids and phospholipids vary in form, intensity and location. In all strobilar forms of the parasite neutral lipids and phospholipids are found in the tegument and calcareous corpuscles. Although in H. microstoma lipid droplets are found in the excretory canals, all lipids in the proglottids are not absolutely waste products. From the results it would appear that they play a role in the maturation of gonads and transformation of the fertilized ovum to the oncosphere.