THE ANIMAL FILES

Antarctic krill

Euphausia superba

A tiny feeding basket can work beneath the ice.

Antarctic krill are often introduced as whale food, but they have feeding machinery of their own. Front legs filter the water and scrape algae beneath ice; a rapid tail-flip offers escape. Following these actions makes a small crustacean an active participant in the Southern Ocean food web.[1]

Follow the evidence ↓
Antarctic krill
Image: Krill666.jpg: Uwe Kils I am willing to give the image in 1700 resolution to Wikipedia Uwe Kils · Commons · CC BY-SA 3.0
Water-column food
Minute phytoplankton[1]
Feeding gear
Thoracic legs form a basket[1]
Ice food
Algae on the underside of sea ice[1]

A basket made of legs

Several thoracic legs work together as a filtering basket. Fine bristles collect small food particles and move them toward the mouth. The arrangement turns appendages into a broad feeding surface rather than a set of walking legs.[1]

Grazing an upside-down lawn

Rake-like bristles at the appendage tips let krill scrape algae from beneath sea ice. The source describes zig-zag grazing across this surface. Food can therefore be attached overhead rather than floating freely.[1]

A sudden reverse

When escaping, krill rapidly flex the rear of the body and swim backward. This action is often called lobstering. It differs from the slower movements used to collect food.[1]

A COMMON MIX-UP

Do krill only wait to be eaten?

No. Filtering, scraping and escape are active behaviors. Being prey does not remove an animal’s own feeding strategies.[1]

TRY A LITTLE REASONING

Would clear water without many floating algae prove that no food is nearby?

Reveal the explanation

Not necessarily. Krill can also graze algae attached beneath sea ice. The location of food matters as well as what a water sample contains.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Euphausia superba (adapted and translated; exact revision)
  2. NCBI Taxonomy — Euphausia superba (identity and game lineage)

Last fact check:

One discovery leads to another

North Pacific krillA tiny Pacific animal makes a daily vertical journey.Euphausia pacifica ↗Giant tiger prawnA striped prawn whose address changes as it grows.Penaeus monodon ↗European lobsterTwo claws, two different kinds of work.Homarus gammarus ↗