Larvae of the threadsail filefish Stephanolepis cirrhifer feed on eggs and planulae of the jellyfish Aurelia sp. under laboratory conditions

Although population dynamics of the egg and planula stages of jellyfish are key factors that predict the abundance of polyps and subsequent jellyfish blooms, information about predation on these stages of jellyfish is lacking. We examined whether threadsail filefish Stephanolepis cirrhifer, an efficient predator of Aurelia sp. medusae in the wild, could feed on eggs or planulae of Aurelia under laboratory conditions. S. cirrhifer larvae at 17 days post hatching (dph) with 4.9 +/- 0.8 mm standard length fed on significantly more eggs or planulae (maximum value: 151 inds. per 15 min.) than other growth stages of S. cirrhifer larvae (0-18 inds. per 15 min.). Considering prey-size selectivity in fish larvae, the mouth size of S. cirrhifer at 17 dph matches well with consuming jellyfish eggs or planulae as prey. These results suggest that S. cirrhifer larvae, during their free-swimming stage or possibly at the beginning of their jellyfish-commensal stage, can be potential predators of eggs or planulae of jellyfish.