Maternal care and juvenile feeding in a hyperiid amphipod (Oxycephalus clausi Bovallius, 1887) in association with gelatinous zooplankton

The manner of maternal care of the hyperiid amphipod, Oxycephalus clausi, was investigated at Senzaki, Nagato, Yamaguchi Prefecture, Japan. In situ observation underwater over a period of seven years as well as in vitro observation under laboratory conditions were conducted. Most of the amphipods (90.1%) were associated with gelatinous zooplankton. At least 13 species, including cnidarians, ctenophores, and salps hosted O. clausi amphipods. However, females presumably caring for demarsupiated juveniles were found only on the ctenophore Ocyropsis fusca, suggesting that O. clausi is selective in its choice of host species for reproduction. We also confirmed for the first time that O. clausi juveniles consume the surface tissue of the host ctenophore under laboratory conditions, indicating that they most likely prey on host tissue before leaving maternal care and then disperse from the host.