Aggregation and Defence

Cassiopea sp., the Upside-Down Jellyfish, are considered to be sedentary epibenthic organisms which exhibit little to no movement on the seafloor. In this study, we use time-lapse videography of a Cassiopea population in the Florida Keys to demonstrate that Cassiopea sp. exhibit a greater degree of benthic locomotion than previously understood, with animals covering distances up to 178 cm per day. In addition, Cassiopea seem to aggregate on the bottom, with average number of neighbours consistently higher than would be expected for random distributions. Given the ability of Cassiopea to release nematocysts directly into the water column, we present this aggregation as a potential defensive behaviour in this species.