A North Sea plankton sample in which some hyperiid amhipods Hyperia galba can be seen. They can swim very fast!
Most amphipods live on or in the seabed. They can often swim and some species can be found in the plankton from time to time. Flake amphipods of the family Hyperiidae live mainly in the plankton. They are often parasites of jellyfish,comb jellies and other gelatinous animals. Along the Dutch coast the amphipod Hyperia galba is commonly found in all kinds of jellyfish. You often see them near jellyfish washed ashore on the beach. They eat the food of the jellyfish, but can also eat the jellyfish itself. Many species of amphipods in the plankton are also predators, eating copepods and other zooplankton.
Hyperiid amphipods can adapt their colour to the jellyfish they are sitting on by making themselves transparent when sitting on a transparent jellyfish.
Hyperiidae look bizarre with their huge eyes, they look like aliens. The variation in eyes of different species within this family is enormous, especially deep-sea species can have enormous eyes with advanced retinas.
Two jellyfish parasites Hyperia galba. You can see clearly the difference between the female on the left that is rounder and has bigger eyes, and the male on the right that is somewhat narrower, has smaller eyes and also has two long antennae.
The big eyes of a female Hyperia galba.