Extracellular and Mixotrophic Symbiosis in the Whale-Fall Mussel Adipicola pacifica: A Trend in Evolution from Extra- to Intracellular Symbiosis
Figure 1
Adipicola mussels.
Transmission electron micrographs of transverse sections of ctenidial filaments. (A)–(C) Adipicola pacifica. (A) Epithelial cells of the ctenidial filament. Gram-negative bacterial symbionts (arrows) are visible on the surface of the cells. Arrowheads indicate pseudopodium-like structures. (B) Bacterial symbionts (arrows) contained in vacuoles accompanied by microvilli (arrowheads). (C) Intracellular degradation of symbionts. Relics of decomposed bacteria (arrows) located in vacuoles of host cells and accompanying host microvilli (arrowheads). (D) Adipicola crypta. Intracellular gram-negative symbiotic bacteria within epithelial cells of the ctenidial filament. Arrowheads indicate the symbionts in vacuoles and arrows indicate digested bacteria in lysosomes.