Nutritional drivers of adult locomotion and asexual reproduction in a symbiont-hosting sea anemone Exaiptasia diaphana

Some sedentary marine invertebrates have the potential to modify the environments they experience by moving, even as adults. Of particular interest are sea anemones, which, despite appearing immobile, can move throughout their lives. Individual locomotion may mitigate changes in environment conditions and, therefore, play an important role in the natural history of sea anemones, especially in naturally variable and/or stochastic environments. Sea anemones that associate with algal endosymbionts may respond to changes in nutrition, both autotrophic (from algae) and heterotrophic (from prey). Here, we describe the adult movement behaviors and asexual reproduction of the sea anemone Exaiptasia diaphana in response to changes in food availability and photosymbiont density. Anemones were collected from mangrove roots in the Florida Keys USA (24° 49′ 21.91″ N, 80° 48′ 37.95″ W) during January 2016 and exposed to a factorial experiment in which food availability and exposure to temperature shock were manipulated. Sea anemones exhibited a variety of responses, including (1) increased crawling along the substrate in response to starvation, (2) increased detachment from the substrate and reattachment in a new location in response to starvation, and (3) increased production of motile asexual clones in response to both starvation and temperature-induced changes in symbiont density. These responses are shaped not only by the direct consequences to the sea anemone, but also by the effects on the symbiotic algae, which exchange sugars, lipids, and oxygen for nutrients within the host. Observed patterns of movement and reproduction are likely advantageous for life in the dynamic mangrove root fouling communities where this anemone species occurs. The ability to disperse as an adult may give this otherwise sedentary invertebrate an advantage in naturally stochastic conditions or in rapidly changing environments.