Evidence of mimicry of gelatinous zooplankton by anguilliform leptocephali for predator avoidance

Abstract

Leptocephali are the transparent larvae of eels and their relatives, whose laterally compressed bodies contain gelatinous material. Although abundant throughout the world’s oceans, leptocephali are rarely observed in their natural environment. Video recordings of leptocephali in surface waters at night at Osprey Reef in the Coral Sea revealed that 6 of 21 larvae filmed displayed a distinct shape-change behavior of curling up into fully or partially coiled shapes. Their transparency and gelatinous consistency results in the coiled leptocephali resembling the typical body shapes and consistency of gelatinous zooplankton such as jellyfish, ctenophores, siphonophores, and salps. Due to either stinging defenses or low food value, many fishes avoid consuming gelatinous zooplankton, so the curling behavior in response to threatening situations may result in mimicry of these organisms. This could provide leptocephali with higher survival rates compared with flight from pelagic predators that are close enough to detect them.