Non-indigenous upside-down jellyfish Cassiopea andromeda in shrimp farms (Brazil).
Invasive species are one of the biggest threats to coastal areas. Jellyfish, when found in aquaculture systems, may cause major economic damage; they are already present in many aquaculture facilities in the Mediterranean, Yellow Sea, and Bohai Sea. Herein, for the first time, we describe the occurrence of the upside-down jellyfish (genus Cassiopea) in shrimp (Litopenaeus vannamei) farms. The observed specimens were collected on the equatorial Southwestern Atlantic coast (Northeast Brazil) for identification by genetic sequence data (COI). The results indicate that the jellyfish in aquaculture systems are similar in terms of morphology and genetics to those found in natural environments in Bermuda, Egypt, Hawaii, Florida, and elsewhere in Brazil (Rio de Janeiro) and are related to specimens originally inhabiting the Red Sea (Cassiopea andromeda). In addition, we report the northward expansion of C. andromeda along the Brazilian equatorial margin. Only female jellyfish were observed, which suggests that the maintenance and spread of the non-indigenous population occur by asexual reproduction. The high abundance and presence of juvenile and adult animals may have major economic impacts on a high-value industry, given the potential of the population to spread to shrimp farms located in tropical mangroves.