Penetration gland secretion by hexacanths of Hymenolepis diminuta

Publisher Website
Google Scholar
Abstract
The rate of expulsion of penetration gland material was determined from photomicrographs of Hymenolepis diminuta hexacanths stained with neutral red dye at intervals after hatching in vitro. Identical secretory rates were recorded for hexacanths incubated in either Tyrode's solution or Tyrode's solution plus an extract of the midgut of Tenebrio molitor. In both media the reduction in stained material observed in the glands after 135 min incubations was equivalent to that observed for hexacanths that had had opportunity to penetrate in vivo during the same time period. These results were interpreted as indicating that the in vivo secretory pattern was similar to that observed in vitro, and that chemical stimuli from the tissue extracts were not required to initiate secretion. Microdensitometric readings also demonstrated a quantitative decrease in dye within the glands as incubation time increased. Ultrastructural examination of the glands showed that their secretory inclusions were exported via ducts to the epithelial cytoplasm where they accumulated in discrete blebs enclosed by the surface membrane. These inclusion-filled, membrane-bounded blebs were apparently formed and released continuously until, after approximately 2 h, only a few inclusions remained in the penetration glands.