**William K. Fitt 1,\* and Dietrich K. Hofmann <sup>2</sup>**


Received: 7 July 2020; Accepted: 21 September 2020; Published: 24 September 2020

**Abstract:** Benzophenones are UV-blockers found in most common sunscreens. The ability of Scyphozoan planula larvae of *Cassiopea xamachana* and *C. frondosa* to swim and complete metamorphosis in concentrations 0–228 μg/L benzophenone-3 (oxybenzone) was tested. Planulae of both species swam in erratic patterns, 25–30% slower, and experienced significant death (*p* < 0.05) in the highest concentrations of oxybenzone tested, whereas the larvae exhibited normal swimming patterns and no death in ≤2.28 μg/L oxybenzone. In addition, metamorphosis decreased 10–30% over 3 days for both species maintained in 228 μg/L oxybenzone. These effects do not involve symbiotic dinoflagellates, as planulae larvae of *Cassiopea* sp. are aposymbiotic. It is concluded that oxybenzone can have a detrimental impact on these jellyfish.

**Keywords:** *Cassiopea xamachana*; *C. frondosa*; Scyphozoan; planulae; settlement; metamorphosis; oxybenzone
