Krill Facts

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One of the most abundant animals in the entire food chain, krill is key to many of the world's marine ecosystems.

It provides food for hundreds of different species of animals, especially in harsh Arctic and Antarctic waters. The krill fish is also an interesting creature in its own right. These tiny animals radiate light from their transparent bodies and hard shells. The name krill is derived from Norwegian and means small fry, but it is actually a type of crustacean.

3 Unbelievable Krill Facts!

  • Krill are not a social species like many birds and mammals. Still, they travel together in groups for protection. These schools of fish often migrate between deeper waters during the day and shallower waters at night. Some swarms are so large that they can actually be seen on satellite imagery.
  • Krill move from place to place by floating along ocean currents. When they encounter a predator, krill can quickly escape by swimming backwards at a rate of about 10 body lengths per second. This is known as the lobster trick.
  • Krill excrement is an important part of the Earth's carbon cycle.

krill scientific name

The scientific name of these animals is Euphausiacea. This comes from the Latin and Greek term euphausia, meaning light or illumination. The name may be derived from the bioluminescence of krill. They belong to the class Malacostraca, which includes about 40,000 species of crustaceans. In general, a defining characteristic of Malacostraca and of all crustaceans is the presence of a hard shell consisting of a carbohydrate material called chitin.

krill species

The krills are a large order consisting of about 86 species divided into two major families. The family Euphausiidae contains almost all known krill species. The Bentheuphausia family contains only one species. Here's just a small sample:

  • Antarctic krill: Despite living in the inhospitable waters of the far south, this may be the most abundant animal species on Earth.
  • Ice krill: The ice krill or crystal krill that live off the coast of Antarctica is the southernmost of all krill species.
  • Northern krill: This species is endemic to the northern Atlantic region.
  • Arctic krill: Up to an inch long, they are important prey for seagulls, marine mammals, and some plankton-eating fish.
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krill appearance

This animal is covered with a hard shell, at its core is a crustacean. It has a long, three-part body (cranial, breastplate, and abdomen), a pair of antennae, 10 swimming legs, plus external gills for absorbing oxygen. It's also one of the smaller crustaceans, measuring no more than 2.4 inches long, about the size of a paper clip, and weighing less than an ounce. They have transparent bodies that give off a fairly bright glow. Light is a product of internal organs called luminophores. It's not clear what this light does, but it could have something to do with camouflage or social signaling.

Antarctic krill krill
Antarctic krill krill

© Krill666.jpg: Uwe Kils/Creative Commons – Licensed

Krill vs Shrimp

Krill are sometimes mistaken for shrimp because of the resemblance between their long, segmented bodies. But the main difference is that the shrimp has two segments, the body is colorful and opaque, and the body is slightly larger. The largest shrimp can even grow to a foot long.

Krill distribution, populations and habitats

These crustaceans are versatile and adaptable animals that inhabit nearly every major body of salty water on Earth between the Arctic and Antarctica. This includes coastal and deep water areas. The total number of global krill populations is truly staggering. The total biomass of Antarctic krill alone (the total mass of each member of the species) is estimated to be between 125 million and 6 billion tons, among the highest in the animal kingdom. It equates to trillions of individuals.

However, this impressive figure hides some worrying trends. Some scientists estimate that the species may have declined by about 80 percent since the 1970s due to climate change, disease and overfishing (though not yet threatened).

Krill Predator and Prey

These animals are an essential link in the marine food chain. It connects tiny sea creatures at the bottom of the chain with larger predators at the top. The vast majority of them are herbivorous or omnivorous in nature, feeding on small algae or microfauna that happen to pass by. Some species are completely carnivorous and feed on fish larvae. Krill feed by filtering edible material from their tiny appendages. They passively feed on large amounts of small food in the water.

Higher up the food chain, krill is probably the most widely eaten animal in the entire marine ecosystem. It is an important prey item for seals, birds (especially penguins), whales and various fish. Therefore, any disruption in the populations of these animals would have a greater impact on the food chain. Threats include ocean pollution, climate change, and changes in habitat or prey abundance. Krill is routinely caught in some fishery locations, which may also reduce numbers.

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Krill Reproduction and Lifespan

These crustaceans have a unique breeding season that varies by location and climate. After the male deposits the sperm pouch near the female's genitals, the female lays thousands of eggs throughout the breeding season, usually spaced into multiple clutches. The total weight of these eggs is equivalent to one-third of her body weight. Depending on the species, the female releases her eggs directly into the water or places them in specialized sacs during gestation.

After hatching from the egg, the hatchling will go through several larval stages. In the early stages, immature krill lack suitable feeding utensils and survive almost entirely on egg yolk. In later stages, they develop a mouth and digestive system to eat plankton. Each stage requires them to replace their entire exoskeleton through a series of molts. Life expectancy depends on where the species is located. Krill that live in warm tropical or subtropical waters live 6 to 8 months, while polar species can live for up to 6 years if they can successfully evade predators.

Krill in Fishing and Cooking

Worldwide, krill consumption remains a relatively niche phenomenon, at least compared to the closely related shrimp, but it is an important source of seafood in Russia, Spain, Japan and the Philippines. All of these countries developed large-scale fisheries in the mid-20th century to catch large numbers of these animals. The Antarctic krill fishery is the most favored because these species are abundant and easy to catch. Other uses for krill include aquarium food, pet or livestock food, fishing bait, and nutritional supplements.

Fish Oil vs. Krill Oil

Krill oil is a very nutritious supplement, containing high levels of protein and omega-3 fatty acids. These fatty acids are associated with a lower risk of cardiovascular disease. Not enough research has been done to tease out the difference between fish oil and krill oil, but the omega-3 fatty acids in both are essentially the same.

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Krill FAQs (Frequently Asked Questions)

What is krill?

Krill are small, transparent, three-segmented crustaceans that occupy most of the world's oceans.

What do krill eat?

The krill passively filter out plankton and fish larvae from the surrounding water.

Is krill a shrimp?

Krill and shrimp are very different from each other. While both belong to the class Malacostraca (along with lobsters and crabs), shrimp belong to a completely different order.

Can Humans Eat Krill?

Yes, despite its small size, krill is just as edible as shrimp, lobster, and crab.

Where do krill live?

Krill inhabit nearly every major saltwater body of water on Earth, including the Southern Ocean near Antarctica.

To which kingdom do krill belong?

Krill belongs to the animal kingdom.

What phylum do krill belong to?

Krill belong to the phylum Arthropoda.

Which category does krill belong to?

Krill belong to the class Malacostraca.

What order do krill belong to?

Krill belongs to the order Krillidae.

What type of mulch does krill have?

Krill are covered with a hard shell.

What type of habitat do krill live in?

Krill live in coastal and deep-sea areas.

Who are the natural enemies of krill?

Natural enemies of krill include whales, seals, birds, fish and humans.

What is the scientific name of krill?

The scientific name for krill is Euphausiacea.

How long do krill live?

Krill live up to six years.

What are the distinguishing features of krill?

Krill have a bioluminescent body.

What is the biggest threat to krill?

The biggest threats to krill are climate change and habitat change.

How much krill is left in the world?

There are trillions of krill left in the world.

What are some interesting facts about krill?

Krill may be the most important animal in the marine ecosystem!

How do krill give birth?

Krill spawn.

What is the Difference Between Krill and Shrimp?

The biggest differences between krill and shrimp include their size, shape, and body color. Krill are smaller than shrimp. The former's body is divided into three segments instead of the shrimp's two, and the exoskeleton is almost transparent with a pinkish hue rather than the shrimp's distinct pinkish-brown color.

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