Difference Between Krill and Shrimp

The main difference between krill and shrimp is that the krill is a shrimp-like crustacean, whose body is segmented into three: Cephalon, thorax, and abdomen, whereas the shrimp is a crustacean, whose body is segmented into two; cephalothorax and abdomen. Furthermore, krill is smaller than a shrimp. 

Krill and shrimp are two types of crustaceans with a tough exoskeleton. They are food sources for many animals including humans. 

Key Areas Covered 

1. Krill
     – Classification, Anatomy, Behavior
2. Shrimp
     – Calssification, Anatomy, Behavior
3. What are the Similarities Between Krill and Shrimp
     – Outline of Common Features
4. What is the Difference Between Krill and Shrimp
     – Comparison of Key Differences

Key Terms 

Antennae, Appendages, Eyes, Head, Krill, Shrimp, Thorax

What is Krill

Krill is a crustacean that forms huge masses in the sea called swarms. The outer shell of the chitinous exoskeleton of most krill is transparent. The body of a krill has three segments: Cephalon or the head, cephalothorax, and thorax.  

Figure 1: Krill Anatomy

Krills have compound eyes in their head, along with a pair of antennae. The paired thoracic legs are called pereiopods or thoracopods. The number of leg pairs depends on the species. All species have additional five pairs of legs called swimmerets or pleopods used for swimming. A krill can grow up to 6 inches. 

Figure 2: A Northern Krill (Meganyctiphanes norvegica)

Krill are primary food sources of most marine animals such as baleen whales, dolphins, penguins, sea birds, etc. krill is rich in omega 3 fatty acids. They harvest enzymes required for wound cleaning and cleaning contact lenses.  

What is Shrimp

Shrimp is a crustacean with long feelers and a double tail, which is fish-like. It can grow up to 12 inches. The body of a shrimp has two segments: cephalothorax and abdomen. It bears two pairs of antennae. Also, a shrimp has a pair of jaws and five pairs of accessory jaws. Shrimps have a long abdomen.  

Figure 3: Shrimp Anatomy

One of the main characteristic features of shrimps is their picking off of parasites and fungi from fish. Therefore, shrimps are especially known as cleaner shrimps. In addition, some commensal shrimps live with sea urchins and on starfish. 

Figure 4: Lysmata amboinensis

The type of shrimp mostly consumed by humans is opossum shrimp. Many opossum shrimps are pale or translucent while some are red in color. Pistol shrimps are another important type of shrimps, which dislocate their claws to make a loud cracking noise. King shrimps live with dead sea plants, mud or fine sand. The most colorful shrimps are the mantis shrimps. Therefore, they are also called peacock shrimps. Also, mantis shrimps have the most complex eyes in nature, which can be rotated 180 degrees.  

Similarities Between Krill and Shrimp  

• Krill and shrimp are two types of crustaceans that belong to phylum Arthropoda, with a body covered by an exoskeleton made up of chitin. 
• They breathe through gills. 
• Generally, they are scavengers; they feed on detritus. 
• They have pairs of jointed legs. 
• Since they have an open circulatory system, the organs of both krill and shrimp are bathed in the hemolymph. 
• Their nervous system contains paired nerve cords. 

Difference Between Krill and Shrimp  

Definition 

Krill refers to a small crustacean that belongs to the order Euphausiacea while shrimp refers to a decapod with long antennae, slender legs, and a laterally compressed, muscular abdomen that is highly adapted for both forward swimming and a backward (retrograde) escape response.  

Size 

A krill is small while a shrimp is always bigger than a krill. 

Body Segments 

Also, a krill has three body segments called cephalon, thorax, and abdomen while a shrimp has two body segments called cephalothorax and abdomen. 

Number of antennae 

Furthermore, a krill has a pair of antennae and a shrimp has two pairs of antennae. 

Color 

Moreover, krills are mostly transparent while shrimps are colorful. 

Mode of Nutrition 

Additionally, krill is a herbivore while shrimp is an omnivore. 

Number of Eggs 

Besides, a krill may lay thousands of eggs per year while a shrimp may lay a million of eggs per session. 

Lifespan 

Considering their lifespan, a krill can live up to ten years while a shrimp can live up to two years. 

Conclusion 

Krill is a small transparent crustacean while shrimp is a comparatively large crustacean with a colorful body. The body of a krill possesses three segments; Cephalon, thorax, and abdomen. On the other hand, the body of the shrimp possesses two segments; cephalothorax and abdomen. The main difference between krill and shrimp is the anatomy and the size. 

Reference:

1. Hays, Jeffrey. “LOBSTERS, SHRIMP AND KRILL.” Facts and Details, Available Here

Image Courtesy:

1. “Krillanatomykils” By Uwe Kils – english wikipedia, original upload 15 June 2005 by en:User:Kils (CC BY-SA 3.0) via Commons Wikimedia
2. “Meganyctiphanes norvegica2” By Øystein Paulsen – MAR-ECO (CC BY-SA 3.0) via Commons Wikimedia 
3. “Crangon crangon” By Marc.hufnagl (CC0) via Commons Wikimedia
4. “Lysmata amboinensis in Tropicarium-Oceanarium Budapest” By Хомелка – Own work (CC BY-SA 3.0) via Commons Wikimedia