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Ultrastructure of cell types within the scolex and cephalic peduncle of the litobothriidean tapeworm, Litobothrium aenigmaticum
Author(s) -
Gallagher Kaitlin,
Caira Janine,
Cantino Marie
Publication year - 2017
Publication title -
invertebrate biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.486
H-Index - 42
eISSN - 1744-7410
pISSN - 1077-8306
DOI - 10.1111/ivb.12174
Subject(s) - biology , ultrastructure , anatomy , peduncle (anatomy) , electron microscope , cytoplasm , excretory system , vesicle , organelle , cell type , golgi apparatus , nucleus , transmission electron microscopy , cell , microbiology and biotechnology , endoplasmic reticulum , physics , genetics , engineering , chemical engineering , membrane , optics
Litobothrium aenigmaticum Caira , Jensen , Waeschenbach , & Littlewood 2014 is a cestode species that parasitizes pelagic thresher sharks in Taiwan and the Gulf of California. A previous study using light microscopy suggested the scolex contains four types of unusual tissues, one of which was considered to aid in adhesion of the worm to the mucosa of the spiral intestine. The function of the other tissues was unknown. Also unknown was the function of two laterally paired ducts found extending throughout the length of the worm. The goal of the present study was to use transmission electron microscopy ( TEM ) to examine the internal anatomy of the scolex and cephalic peduncle of this tapeworm in more detail. Three specimens from Taiwan were examined with TEM and two with light microscopy. Transmission electron microscopy revealed that the laterally paired ducts were excretory, since they were closely associated with numerous protonephridia. The number of cell types, previously referred to as tissues, in the scolex was expanded to 11 based on a combination of features including cell size, nucleus size, ratio of the maximum diameter of the nucleus to maximum diameter of the whole cell, and types of observed organelles, as well as the presence or absence of cytoplasmic electron‐dense and electron‐lucent vesicles. The cytoplasm of all 11 cell types was found to include electron‐dense vesicles, and all types were periodic acid‐Schiff ( PAS ) positive. This suggests that the electron‐dense vesicles may contain glycoproteins and/or mucoproteins. As all 11 cell types occurred within the region of the scolex that is surrounded by a papilla of host mucosa at the site of tapeworm attachment, we hypothesize that one or more of these cell types may produce a substance that induces this inflammatory reaction. The specific products in the secretory vesicles and how those products are released are still unclear, as are any relationships between or among the cell types in terms of products produced. Further research will be necessary to fully understand the complexity of this organism.