Shrimp Vs. Prawn-What's the Difference?

In this week's Ask Asta, we will explore Andrew's question;
"What's the difference between shrimp and prawns, and how can you tell them apart?"

Read on to find out!

In the infamous movie Forrest Gump, Bubba said it best;" Shrimp is the fruit of the sea!"  


But what about prawns? How do they compare?

Image taken from Crosby.com

This plate contains bite-sized, firm and tender morsels of undersea deliciousness.

Imagine this has just been delivered to your table at a nice restaurant.

I'll let you devour it, after you answer one simple question:

​ Are these shrimp, or prawns?
​

​Why, you say, does that matter? Also, you say, why is Asta torturing me with food?

Because we're imagining, silly. 

So, what's your answer?  

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Did you say that this was a lovely plate of Garlic grilled shrimp? Because if you did, you'd be wrong.

Or right.

Depending on which country you're standing in.

Have I confused you yet? 

Let me explain.
​

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SIMILARITIES
Shrimp and Prawns are both types of invertebrate, meaning they have no backbone and use a hard outer shell to protect them and keep their bodies enclosed. 

Shrimps and prawns are also both considered to be Crustaceans (from the Latin root crustaceus, "having a crust or shell,"). Crustaceans are a subgroup of invertebrates which share the characteristics of a hard outer shell, or exoskeleton, segmented bodies, and paired appendages (arms and legs).
​
 Both shrimp and prawns grow via a process known as molting, or ecdysis, in which the outer shell is removed and then replaced with a new one whenever the animal begins a growth cycle. 

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Decapoda imagery courtesy of Wikipedia Commons and Ernst Haekel.

Shrimp and prawns are also both considered to be decapods. The roots of the word are deca, meaning 10, and poda, which refers to appendages, (or more specifically, feet). Both shrimp and prawns exhibit pairs of swimming, walking and foraging appendages which give these animals bilateral symmetry (meaning when the body is cut in half along a vertical axis, the sides of the body appear as mirror images, much like our own bodies.)

Shrimp and Prawns can be found throughout the world, in both fresh and salt water conditions.  Both are opportunistic scavengers, meaning they generally eat what can be stirred up off the sea or pond bottom.Their early diet includes zooplankton, phytoplankton and algae, and dead organic materials. Later in life, both types of decapod scavenge some dead and some living organic material, such as decaying plants, fish, clams, and even other shrimp.

Both groups use special chemosensory antennae structures located on the tops of their heads to help them detect the chemical signature of food particles and to help them locate them.

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Image found on imgur at https://imgur.com/gallery/i4c3PC2

The reason that a lot of people have trouble differentiating between this organisms has to do with the prevalence of the use of the common names, "shrimp" and "prawn". The terms have been used interchangeably in many fishing communities, as the similarities between these organisms are very obvious, and to the common eye, the differences are pretty minor.

In the United Kingdom, Australia, and other primarily English speaking countries, "Prawn" is used to refer to either shrimp or prawns, whereas in the United States and Canada, the word "Shrimp" is used more commonly for both. 

This is why science nerds worldwide use latin names when communicating, to ensure they really are talking about the same organisms. 

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Australian prawn species. Image found at http://www.fish.wa.gov.au/PublishingImages/Swainston/prawn.jpg

PRAWNS

Prawns are defined as a group of similar species which make up the suborder Dendrobranchiata. In one way, you could categorize them as the larger shrimp. It is thought that perhaps the term "prawn" came from a need to differentiate larger species from smaller ones. Both terms originated in Great Britain, although if you asked a fisherman there, the definition of what a shrimp vs a prawn would be is often highly individual.
Biologically, Dendrobranchiata share a couple of key physiological differences. Prawns have a series of overlapping plates on their abdomen, each overlapping easily over a single other plate.Prawns also have three sets of feeding arms, or maxillipeds. ​ Although the tail, or telson, of a prawn often bends inwards towards the central carapace in a smooth, "C" shape, prawns lack the distinct Caridean angular bend in the plates of the abdomen. 
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Prawns also have unique gill structures. Instead of the platelike gill structures seen in shrimp, they have tree-like, branched gill structures. There are seven layered gills on each side of the prawn's head inside a specialized gill chamber. It isn't clear why this physiological difference exists between these groups, but it is thought that perhaps the difference has to do with the amount of oxygen the prawn requires, as well as what part of the ocean it is more commonly found in (meaning their environment may be more mid-water than bottom feeding.)

Some species of prawn are highly sensitive to light, an often bury themselves under the seafloor during the day, only to emerge and migrate to the surface to feed on microorganisms at night time.

Prawns can live 3-6 years. Each prawn spawning event creates up to 100,000 young, which is less impressive when compared with the number of young a shrimp can produce. Prawns also require that the female prawn has recently undergone a molting process in order to begin reproduction. The hard outer shell of the female prawn has to have been removed for the male to be able to properly transfer his sperm package to the female, and for her to properly fertilize the eggs. Once fertilized, the eggs are immediately released into the water column, and left to drift and settle on their own before continuing through the development cycle. 

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Prawn gill structure image taken from biologydiscussion.com

Taken from Arnold Zwicky's Blog https://arnoldzwicky.files.wordpress.com/2011/11/shrimp.jpg

 







SHRIMP

​Shrimp are a part of a suborder of crustaceans known as the Plyoceyemata, and an infraorder (smaller grouping) known as the Caridea. They have two pairs of feeding claws (also known as maxillipeds).  One set of their feeding claws has a pair of pincers on it for cutting and holding their prey.

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You can tell a shrimp from a prawn by looking at the second segment of their abdomen, which overlaps with the first and third segments of the central area of the body. Shrimp are generally small (0.25-5 centimetres in length), and have a distinct structural characteristic, known as the Caridean bend, in their abdomen, their lower digestive and reproductive area. 


If you're really looking at a specimen in detail, you could open up their respiratory system to look at their gills-the organ these animals use to remove oxygen from the water around them and use it to metabolize their food. Shrimp have what's known as lamellar gills. These gills are dinner plate-like in structure, and lie just inside the entrance of the cardiac section of the carapace.  Shrimp have specialized appendages that can actually fit perfectly between the lamellar gills and can be used to brush parasites and fouling organisms from the gills- just like your toothbrush removes plaque from your teeth!

Shrimp are known as broadcast spawners, meaning that when they reproduce, they make thousands of young at a time. For protection, the female shrimp will carry her fertilized eggs with her for the initial stages of their development by holding them to her body using a pair of legs known as pleopods. A female shrimp can have up to 1 million eggs in a single reproductive season!

Most shrimp live 8 months to 3 years, depending on the species and geographical distribution, but in confined conditions, shrimp have been known to live up to 20 years. 

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Gill cleaning image taken from asnailodyssey.com

So there you have it! If you're having a nice seafood dinner in Wales, UK, it might be prawns on your plate, but the same meal could be a shrimp dish in Vancouver, BC! 

Stay tuned to learn more about how shrimp and prawns are harvested, farmed and brought to your dinner table!

References:

Bauer, R.T. "Research on the Biology of Shrimps and Marine Habitats". Accessed online, November 4, 2017. http://www.ucs.louisiana.edu/~rtb6933/shrimp/index.html

Diffen.com. "Prawn vs. Shrimp". Accessed online November 2, 2017.  
http://www.diffen.com/difference/Prawn_vs_Shrimp

Shaikh, F. July 26, 2017. "Prawn vs Shrimp: Know the Difference between Shrimp and Prawn." Foodsforbetterhealth.com. Accessed November 5, 2017.

https://www.thespruce.com/difference-between-shrimp-and-prawns-2217280
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Haekel, E. Kunstformen der Natur (1904), plate 86: Decapoda.
https://en.wikipedia.org/wiki/Decapoda#/media/File:Haeckel_Decapoda.jpg​

Watson, M. October 23, 2017. "What's the Difference between Shrimp and Prawns?" The spruce.com. Accessed online November 7, 2017. 
https://www.thespruce.com/difference-between-shrimp-and-prawns-2217280
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Zwicky, A. November 11, 2011. "Rock Shrimp". Accessed online, November 17, 2017. 
https://arnoldzwicky.org/2011/11/11/rock-shrimp/