P2.118 Friday, Jan. 4 Behavioral Effects of Light on the Tropical Holothurian Pearsonothuria graeffei MAGI, J.T.*; PATTEN, S.B.; NESTLER, J.R.; Walla Walla University; Walla Walla University; Walla Walla University email@example.com
Sea cucumbers (Holothuroidea) influence ocean communities by affecting physical and chemical characteristics of water and sediment through their deposit feeding and excretion activities. Pearsonothuria graeffei inhabits coral reefs in the Philippines, exhibiting active behaviors during the day and resting at night. Daily cycles of behavior may be triggered by environmental cues such as food supply, tides, predation, temperature, and light. To investigate the role of light in determining the behavioral patterns of this species, movement, feeding status, and body posture were observed in situ during dawn and dusk as well as during light manipulation experiments. Data were collected at depths of 10-20 m using scuba from April to June 2007. During dawn, Pearsonothuria graeffei transitioned to an active state within 6.9 ± 10.3 min (mean ± sd, n= 17) after sunrise. Individuals adopted an active body posture (complete contact with substrate), began feeding (characterized by extension of feeding tentacles), and moved on the ocean floor. At dusk, these organisms became inactive within 46.3 ± 13.8 min (n=18) after sunset. They ceased moving, adopted an inactive body posture (anus extended up into water column), and retracted feeding tentacles into the oral cavity. During the night, shining light on these organisms caused a significant increase in activity (p<0.001, n=8). During the day, blocking light from these organisms did not significantly alter their activity state (p>0.05, n=6). Inhibiting light from reaching Pearsonothuria graeffei during dawn significantly extended the period of inactivity in the test subjects compared to surrounding individuals (30.6 min, p=0.032, n=5). Shining light on experimental subjects during dusk significantly extended their active period compared to surrounding individuals (35.2 min, p=0.015, n=5). These results indicate that light is an important cue in determining daily activity cycles of Pearsonothuria graeffei.