Meeting Abstract
The proteinaceous slime threads in hagfish slime feature one of the highest aspect ratios among biological fibers in nature and are essential to the mechanical property of the slime, which functions as a defense against gill- breathing predators. Prior to extracellular export, these slime threads are generated within the cytoplasm of gland thread cells and coiled as highly organized skeins. Both the developmental process and evolutionary origin of the slime threads remain unclear, but they are likely homologous to the epidermal threads generated by epidermal thread cells that are found near the basal region of epidermis. Here, we studied the morphology of epidermal threads in Pacific hagfish (Eptatretus stoutii) using confocal laser scanning microscopy and three-dimensional geometry reconstruction. Distributed along the inner periphery of the cell membrane, the epidermal threads are characterized by a loosely packed helical geometry and thus exhibit lower aspect ratio than gland threads. Examining the ontogenetic variation of the chiral helix of gland threads, we further show two levels of structural organization. These results offer the first detailed study on epidermal thread morphology in hagfishes and provide insights into the origins of threads produced in the slime glands.
