Meeting Abstract
Aggregate formation and clustering are common behaviors observed across taxa and can facilitate the survival of the collective (Allee, 1978). Here we study the aggregation of blackworms ( Lumbriculus variegatus ) into large ensembles of entangled, living “blobs” composed of thousands of worms knotted together. To understand the mechanism and advantages of aggregation in these worm blobs, we systematically expose them to different environmental stresses including evaporation, light, temperature and starvation. The diameter of the worm blob can be controlled by both light stimulus history and light intensity. At low light intensity the blob dilates; conversely, increasing the light intensity contracts the blob and leads to more entangled and tightly packed state. This behavior also affects the collective movement under thermal stress. Under high light intensity (>1500 Lux) we find that a 5 g (∼600 hundreds) worm blob placed under a linear temperature gradient between 15 to 50°C stay as a blob and move collectively to the cold side at speeds of 0.35 ± 0.001 cm/min. In contrast, if the light intensity is reduced to 400 lux, the worm blob dissipates and individual worms crawl to the cold side with a speed of 0.38± 0.01 cm/min. We find that the number of surviving worms increases as they move as a blob. Finally, we show that this worm blob can also navigate structured environments (mazes) to survive from starving. Individual worms search the maze and the worm blob finds the shortest path to the food source. We hypothesis that the exchange of information between individuals and the perception of nutrient concentration released from a food source determines the direction of migration.
