In order to explore whether the temperature-regulated aflatoxin biosynthesis affects the morphology of Aspergillus flavus mycelia, comparative observation on the ultrastructure of mycelia in different developmental stages grown in various temperatures was carried out based on scanning and transmission electron microscopy. Scanning electron microscope observation showed that filamentous viscous particles appeared on the mycelium surface in 24 hour (h) and 44h after inoculation at 28°C, and the mycelium gradually appeared to be shrinked, and then collapsed and distorted in 48h and 72h, while the mycelia grown at 37°C remained thick and robust in 24-72h. Transmission electron microscope observation displayed that large vesicles appeared in hyphal cells cultured at 28°C in 24h after incubation, and the internal organelles were indistinct in 44-72h. The organelles at 37°C were clear, and the number of mitochondria and liposome increased obviously in 44-48h, and the septal structure was observed at 72h. The ultrastructure of Aspergillus flavus mycelia cultured at 30°C and 40°C also verified the above findings. Taken together, 28°C and 30°C promoted the aflatoxin biosynthesis, but accelerated senescence of mycelia. On the contrary, 37°C and 40°C were unfavorable to the biosynthesis of aflatoxin, but beneficial to the growth of mycelia, and the senescence process of mycelia was relatively slow. This study showed that the aflatoxin biosynthesis was closely related to the internal morphological changes of Aspergillus flavus mycelia.

Keywords： ultrastructure; transmission electron microscopy; scanning electron microscopy; aflatoxin