The world of the Upside-down Jellyfish

Upside-down jellyfish, Cassiopea xamachana

Rachel Mellas, Masters candidate at SUNY Buffalo with Dr. Mary Alice Coffroth, spent 2 months at KML. She is studying the fitness effects and symbiont type in the upside-down jellyfish, Cassiopea xamachana.

Upside-down jellyfish right side-up!

In Cassiopea, establishment of the symbiosis occurs in the scyphistomae (polyp) stage of development where multiple strains of Symbiodinium can be acquired. Upon infection, the scyphistomae produce ephyra (young medusa) through a process termed strobilation. Once they reach the adult medusa form, they typically harbor one specific type of symbiont (Symbiodinium A1).

Cassiopea scyphistomae (polyp) stage

To understand the potential fitness advantages to the host of harboring different symbiont types, Rachel has set up laboratory experiments which look at the how different symbionts affect the growth rate, survivorship, and timing of strobilation of scyphistomae, and if strobilation occurs with only certain symbionts (A1). (photos by R Mellas)