Abstract
The ultrastructure of flame bulbs and epithelium of excretory canals in Bothrioplana semperi (Turbellaria, Seriata) have been studied. The flame bulbs consist of two cells, the terminal cell and the proximal canal cell. The weir is formed by two rows of longitudinal ribs. The ribs of the internal row originate from the flame cell, external ribs are formed by the proximal canal cell. Each external rib has a remarkable bundle of microfilaments, originating in the cytoplasm of the first canal cell distally to the bases of external ribs. Membrane of internal ribs is marked by small electrondense granules, separate or fused to an electron-dense layer, continuous to dense “membrane,” connecting both external and internal ribs. Sparse internal leptotrichs originate from the bottom of the flame bulb cavity. External leptotrichs are lacking. Septate junction is present only in proximal canal cell at the level of tips of cilia. The apical surface of the canal cell bears rare short microvilli. The basal membrane of canal cells forms long invaginations that may reach nearly the apical membrane. The epithelium of excretory canals lacks the cilia. The ultrastructure of flame bulbs and epithelium of the excretory canals in B. semperi shares representatives of suborder Proseriata (Seriata). The contradiction exists in interpretation of the structure of flame bulbs in Proseriata. Ehlers and Sopott-Ehlers assumed that the external ribs are derivatives of the proximal canal cell and internal ones are outgrowths of the terminal cell, while Rohde has found conversely: the external ribs are outgrowths of the terminal cell, the internal ones are outgrowths of the proximal canal cell. However, the illustrations provided by Rohde do not enable to ascertain what cells the internal and external ribs derive from, while illustrations provided by Ehlers justify his interpretation. The order of weir formation in B. semperi confirms the viewpoint of Ehlers. The implication of ultrastructure of flame bulbs in Proseriata, especially of the order of flame bulb formation, in the Platyhelminthes phylogeny has been discussed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Journal of Evolutionary Biochemistry and Physiology
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.