Arctic Comb Jelly
The Arctic comb jelly or sea nut (Mertensia ovum) is commonly found in the surface (top 50 meters) in cold, northern waters. Like other cydippid ctenophores, it has two tentacles fringed with smaller tentacles, which are dappled with colloblasts. Colloblasts are specialized cells that, upon contact with other organisms, act as a glue, allowing the comb jelly to pull the food to its mouth with little resistance. This species has light bioluminescence in blues and greens, but the rainbow effect in this photo is caused by light refracting off of its comb-like rows of cilia, which propel it through the water.