Antarctic Krill - Food

Food

The gut of E. superba can often be seen shining green through the animal's transparent skin, an indication that this species feeds predominantly on phytoplankton – especially very small diatoms (20 μm), which it filters from the water with a feeding basket. The glass-like shells of the diatoms are cracked in the "gastric mill" and then digested in the hepatopancreas. The krill can also catch and eat copepods, amphipods and other small zooplankton. The gut forms a straight tube; its digestive efficiency is not very high and therefore a lot of carbon is still present in the feces.

In aquaria, krill have been observed to eat each other. When they are not fed in aquaria, they shrink in size after moulting, which is exceptional for animals the size of krill. It is likely that this is an adaptation to the seasonality of their food supply, which is limited in the dark winter months under the ice. However, the animal's compound eyes do not shrink, and so the ratio between eye size and body length has thus been found to be a reliable indicator of starvation.