Meeting Abstract
P1.26 Tuesday, Jan. 4 Hyperthermic stress-induced autophagy in the tropical anemone, Aiptasia pallida. HANES, S. D.*; KEMPF, S. C.; Auburn University; Auburn University hanessd@auburn.edu
Coral bleaching involves the physical loss of essential, photosynthetic endosymbionts from host tissues in response to elevated temperature/light stress. Little is known of the specific cellular events that occur during the cnidarian bleaching process, however, previous histological snapshots of bleaching tissues have implicated the involvement of several methods of cell death. In order to accurately determine the specific cellular events that occur during the bleaching process, a detailed ultrastructural examination at multiple stages of hyperthermic stress was conducted. In this study, both light and transmission electron microscopy (TEM) were utilized to examine anemone tentacle histology/ultrastructure in the common anemone, Aiptasia pallida, while undergoing progressive bleaching. Bleaching was induced by exposing specimens to hyperthermic stress conditions of ~32.5oC for 12 hours daily for 48 hours. Examination of heat stressed tissues revealed the presence of numerous residual bodies (RBs) throughout both host gastrodermis and epidermis after ~12 hours of thermal treatment. The abundance of RBs significantly increased with length of thermal treatment, and many host cells exhibited extensive degradation, suggesting that autophagic activity elevates during heat stress. Additionally, several individual symbionts were observed pinching off the apical region of degraded host cells. This study provides the first ultrastructural evidence of host autophagic activity during thermal stress in a cnidarian system and also supports earlier suggestions that autophagy is an active cellular mechanism during early stages of bleaching. In order to corroborate these ultrastructural findings, autophagy will be biochemically induced using rapamycin, and comparisons of cellular appearances will be made.
