Krill vs Shrimp for Kids
Krill and shrimp look like tiny transparent cousins, but the names cover different crustacean branches. This page uses Antarctic krill, Euphausia superba, and northern shrimp, Pandalus borealis, so every measurement and drawing has a clear benchmark. Krill are euphausiids with externally visible gills, similar feeding legs, glowing photophores, and an open-ocean swarming life. Northern shrimp are decapods with gills protected beneath the carapace, specialised walking limbs, a long rostrum, bottom-associated habits, and eggs carried under the female’s abdomen. A northern shrimp can be more than twice the length of an Antarctic krill. Krill are still not baby shrimp, and neither name means every small prawn-shaped crustacean.
Antarctic Krill
- Type: Open-Ocean Euphausiid Crustacean
- Group: Living species Euphausia superba, a malacostracan crustacean in order Euphausiacea rather than a true shrimp in decapod order Decapoda
- Known for: Mostly transparent red-speckled body, large black compound eyes, externally visible branching gills, plankton-filtering leg basket, five pairs of abdominal swimming limbs, blue-light photophores, vast swarms, winter shrinking, and a central place in the Southern Ocean food web
- Diet: Flexible omnivore and suspension feeder eating mainly phytoplankton and ice algae, plus detritus and small zooplankton when plant food is scarce
- Special skill: Continuing to moult throughout life and shrinking during dark food-poor winters, then regrowing and regaining mature features as light and food return
Northern Shrimp
- Type: Cold-Water Caridean Shrimp
- Group: Living species Pandalus borealis, a true caridean shrimp in decapod order Decapoda and family Pandalidae
- Known for: Slender pink-red body, long toothed rostrum, carapace-covered gills, five pairs of walking legs, abdominal swimmerets, powerful tail fan, muddy deep-water habitat, nightly upward migration, egg carrying, and male-to-female sex change
- Diet: Omnivore, predator, and scavenger eating zooplankton, small crustaceans, worms, algae, detritus, and other organic material near the bottom or in nighttime water layers
- Special skill: Beginning reproductive life as a male and later changing permanently into a larger female that carries developing eggs beneath the abdomen for months
Quick Answer
Quick answer: Antarctic krill are roughly 6-centimetre euphausiids that form huge Southern Ocean swarms, filter microscopic food with a leg basket, show exposed gills, and release sinking eggs. Northern shrimp are true decapod shrimp that may reach about 16.5 centimetres as females, shelter their gills beneath the carapace, forage near cold muddy bottoms, carry eggs on abdominal swimmerets, and usually change from male to female. Both are swimming, moulting crustaceans, but krill are not baby shrimp.
Antarctic Krill vs Northern Shrimp: Quick Comparison
| Feature | Antarctic Krill | Northern Shrimp |
|---|---|---|
| Scientific identity | Euphausia superba; order Euphausiacea | Pandalus borealis; order Decapoda |
| Adult length | Usually about 5-6.5 cm | Up to about 12 cm in males and 16.5 cm in females |
| Main water zone | Pelagic open water, with daily and seasonal depth changes | Mostly on or near cold muddy bottoms by day, with many moving upward at night |
| Gills | Branching gills are visible outside and below the carapace | Gills are enclosed in chambers beneath the side of the carapace |
| Front limbs | Thoracic limbs form a fine feeding basket and remain fairly similar | Five walking-leg pairs are more specialised for bottom movement and food handling |
| Main food | Mostly phytoplankton and ice algae, plus detritus and small animals | Zooplankton, small animals, worms, algae, and detritus |
| Group pattern | Vast swarms may reach tens of thousands per cubic metre | Dense patches or schools often sort partly by size and life stage |
| Egg strategy | Females release broods of tiny eggs that sink before larvae swim upward | Females carry eggs attached beneath the abdomen until hatching |
| Adult sex pattern | Separate males and females, with seasonal regression of mature features | Usually matures first as male and later changes permanently to female |
| Unusual body trick | Blue photophores plus the ability to shrink across moults | A tail-flip escape and a life-stage sex change |
How Are Antarctic Krill and Northern Shrimp Alike?
- Both are living malacostracan crustaceans with segmented bodies, jointed appendages, antennae, compound eyes, gills, chitinous outer skeletons, and open circulatory systems.
- Both grow by moulting, hatch as very small planktonic larvae, pass through several larval stages, and become independent without parental teaching.
- Both use paired abdominal appendages and a tail fan for swimming and can make rapid backward escape movements when disturbed.
- Both eat a mixture of tiny living food and detritus, migrate vertically through the water, and connect small plankton or seabed particles to larger predators.
- Both gather in patches or schools and are major prey for fish, seabirds, and marine mammals in cold-ocean food webs.
How Are Antarctic Krill and Northern Shrimp Different?
- Antarctic krill belong to order Euphausiacea, while northern shrimp are true caridean shrimp in decapod order Decapoda.
- Krill keep conspicuous branching gills exposed below the carapace, while a shrimp’s carapace covers and protects its gill chambers.
- Krill are smaller open-water swarmers with a basket of similar filtering legs, while northern shrimp are larger bottom-associated animals with more specialised walking and food-handling limbs.
- A krill female releases many free eggs that sink through deep water, while a northern-shrimp female fastens a smaller brood under her abdomen and carries it for months.
- Krill males and females remain separate but adults can shrink and regress seasonally, while northern shrimp usually reproduce first as males and later become females.
Krill vs Shrimp Showdown
Adaptation showdown: Shrimp wins size because the FAO gives northern-shrimp maxima of about 12 centimetres for males and 16.5 centimetres for females, compared with roughly 5-6.5 centimetres for Antarctic krill. Speed is a Tie because both use tail flips and swimmerets, but no fair same-temperature race measures the two benchmarks. Strength is a Tie because krill filter and migrate while shrimp walk, forage, and tail-flip; there is no matched force test and this is not a fight prediction. Stealth is a Tie because both are partly transparent or pink-red and use depth or dim water, without evidence that one is consistently harder to detect. Krill wins social behaviour because Antarctic swarms can reach tens of thousands per cubic metre and move as immense coordinated layers, even though their exact social rules remain under study. Swimming is a Tie because both are capable swimmers with daily vertical migrations and different pelagic-versus-bottom schedules rather than comparable performance scores. Krill wins weirdest for carrying blue-light photophores and repeatedly moulting smaller during winter, losing mature features, then growing and maturing again in spring.
Fun Krill vs Shrimp Facts
Krill Are Not Baby Shrimp
Krill and shrimp share the familiar crustacean outline because both belong to Malacostraca, but their lineages separated before their modern orders evolved. A krill remains a euphausiid throughout life; it never grows into a prawn, shrimp, or lobster.
A Winter Moult Can Make Krill Smaller
Most moulting crustaceans replace a tight shell with a larger one. Antarctic krill can reverse that pattern when winter food is scarce. Across later moults they shrink, use body reserves, and lose mature reproductive features, then grow and mature again when spring light returns.
Northern Shrimp Change Reproductive Role
Most northern shrimp mature and mate first as males. After one or more seasons, they transform permanently into larger females. The timing varies with temperature, growth, location, and population, so the change does not happen at one universal birthday.
One Drops Eggs and One Carries Them
Antarctic-krill eggs are released near the surface and sink hundreds of metres while developing; newly hatched larvae must climb back toward food and light. Northern-shrimp females hold fertilised eggs on small abdominal swimmerets through winter until spring hatching.
Tiny Krill Hold Up a Giant Food Web
Antarctic krill turn phytoplankton and ice algae into bite-sized animal food. Fish, squid, penguins, seabirds, seals, and baleen whales then eat krill directly or depend on animals that do. Their ecological importance comes from enormous combined abundance, not individual size.
Krill vs Shrimp Quiz
- Are krill baby shrimp? Answer: No. Krill are euphausiids and shrimp are decapods.
- Which benchmark grows longer? Answer: The northern shrimp.
- Where are Antarctic-krill gills visible? Answer: Outside and below the carapace.
- What unusual reproductive change occurs in northern shrimp? Answer: They usually mature first as males and later become females.
- How can Antarctic krill save energy in winter? Answer: They can shrink across moults and regress mature features.
Krill vs Shrimp FAQ
What is the main difference between krill and shrimp?
Krill are euphausiid crustaceans with visible external gills and open-water swarms, while true shrimp are decapods with covered gills and more specialised limbs.
Which is bigger, krill or shrimp?
The northern-shrimp benchmark wins. Females can reach about 16.5 centimetres, while Antarctic krill are usually around 5-6.5 centimetres.
Do krill glow?
Antarctic krill have photophores that produce blue light. Scientists continue to study how the light helps with signalling, concealment, or other functions.
Do northern shrimp really change sex?
Yes. Most reproduce first as males and later become females, but the age and size of transition vary among populations and conditions.
Why are krill so important?
Their huge swarms transfer energy from microscopic algae to fish, seabirds, seals, penguins, squid, and whales across the Southern Ocean.
Animal Words to Know
- Euphausiid: A krill in crustacean order Euphausiacea.
- Decapod: A crustacean in the order whose name means ten-footed, including shrimp, crabs, and lobsters.
- Photophore: A specialised organ that produces light.
- Protandrous: Maturing first as male and later changing to female.
- Diel migration: A regular movement linked to day and night, often up at night and down by day.
Build Two Cold-Ocean Crustacean Models
Build Two Cold-Ocean Crustacean Models
Draw one 6-centimetre Antarctic krill and one 16-centimetre female northern shrimp on the same scale strip. Give the krill a mostly transparent red-speckled body, large black eyes, short rostrum, exposed branching gills, a fine front-leg feeding basket, five pairs of swimming pleopods, blue photophore dots, and a dense Southern Ocean swarm. Give the shrimp a longer pink-red body, long toothed rostrum, gills hidden beneath the carapace, specialised walking legs, abdominal swimmerets carrying eggs, broad tail fan, and a muddy North Atlantic bottom with a nighttime upward path. Add separate life-cycle cards for sinking krill eggs, rising nauplii, winter shrinkage, male shrimp, female shrimp, and carried eggs.
Meet Each Animal
Want the full fact file? Here are quick highlights from each animal’s own facts page.
Antarctic Krill Fact Highlight
From the full animal facts pageNorthern Shrimp Fact Highlight
From the full animal facts pageMore Animal Comparisons
Pick another animal matchup and keep exploring. Tiny facts, big questions, very serious animal business.
Make an Animal Story
Turn a glowing krill swarm, a shrinking winter survivor, and a sex-changing northern shrimp into an ocean adventure with our free Animal Story Generator.