Respiration

Pattern of circulation over (broken arrows) and within (solid arrows) a sea anemone, including flows in the pharynx. Arrows on the right and left illustrate a flow pattern on a mesentery and between mesenteries respectively. Adapted from Ruppert, Fox & Barnes (2004).

Sea anemones do not have oxygen-carrying respiratory pigments and rely on diffusion^1,2. Water is circulated over the body surface and the gastrodermis by ciliated epidermal cells to facilitate gas exchange between the tentacles and the general body wall². Although individuals may reach rather large sizes, having a primarily two-dimensional and laminar body plan minimizes diffusion distance and hence enhances oxygen delivery. As a result, oxygen consumption is almost directly proportional to body mass¹.