Distribution of tetrodotoxin in the ribbon worm Lineus alborostratus (Takakura, 1898) (nemertea): Immunoelectron and immunofluorescence studies

• ТТХ in animals was first detected via CLSM and immunoelectron microscopy.
• Subepidermal bacillary gland cells type I of the body wall contain TTX.
• Pseudocnide-containing and mucoid gland cells of the proboscis contain TTX.
• TTX migrates through the protein secretion organoids into secretory granules.
• A hypothesis of the intracellular migration and excretion pathways is proposed.

Transmission electron and confocal laser scanning (CLSM) microscopies with monoclonal anti-tetrodotoxin antibodies were used to locate tetrodotoxin (TTX) in tissues and gland cells of the ribbon worm Lineus alborostratus. CLSM studies have shown that the toxin is primarily localized in the cutis (special subepidermal layer) of the body wall and in the glandular epithelium of the proboscis. Immunoelectron micrographs have shown that only subepidermal bacillary gland cells type I in cutis and pseudocnidae-containing and mucoid gland cells manifested TTX-gold labeling. TTX was associated with the nuclear envelope, endoplasmic reticulum membrane, and secretory granules of TTX-positive gland cells. These studies indicate that ТТХ is brought into the cytoplasm of the glandular cells of the cutis and proboscis epithelium, where it is associated with membrane-enclosed organelles involved in protein secretion and then concentrated in glandular granules.