Dwarf Shrimp External Anatomy

In this article, I am going to talk about the external anatomy of the shrimp. However, I would like to start off by saying that, there are so many types of shrimp that it is absolutely not possible to mention all the differences between them. Actually, anybody who will be able to do that will leave their names and legacies in the science. That is why I will describe the dwarf shrimp anatomy in general.

In short, shrimp external anatomy comprises a rostrum, carapace, abdomen segments, telson, pleopods, pereiopods (legs), maxilliped, and antennule. 

Quite often in my articles, I have to refer to different parts of the shrimp’s body. Although in most cases, I usually provide additional pictures for that, it is still not enough, in my opinion. Sometimes people need to see the full picture for better understanding.

Dwarf Shrimp Body Structure.

Dwarf shrimp belong to the class of invertebrates. They do not have bones (spine) or any internal skeleton. Their body is covered with an exoskeleton (shell), which is divided into two main parts:

• The cephalothorax.

The cephalothorax is the result of the merger of the rostrum (“Beak-head”) and the carapace bearing all the appendages except the pleopods, and uropods. This part of the shrimp body protects their vital organs (brain, heart, stomach, bladder, testicular or ovarian).

• The abdomen.

The abdomen of dwarf shrimp includes 6 abdominal segments, pleopods, and the tail (consists of telson, uropods, endopod, and exopod). It is the main muscle which allows shrimp to swim.

 Quick Notes about Shrimp Body Structure

Scientific names	Customary name	Function
Cephalothorax consists of
Carapace	Upper body	Protection of inner organs
Antennae	Whiskers	The sensor of orientation and coordination
Antennule		The sensor of chemical information
Maxillipeds	Jawfoot	For eating
Pereiopods	Legs	Movement
Chela	Claws (or Fans)	Holding and picking food
Scaphocerit	Fang	Equilibrium and orientation for swimming
Eyes	Eyes	Vision
Rostrum	Beak or Nose	Protection of eyes, stabilizer
Abdomen consists of
6 Abdomen segments	Stomach	Swimming
Pleuron	–	Protection of abdominal segments
Telson	Tail	Swimming
Uropods
Endopod
Exopod
Pleopods	Swimmerets	Adaptation for swimming, holding and fanning eggs
Petasma	Male organ	Insemination

Carapace:

The carapace is heavily calcified upper part of the shrimp body, which protects the cephlathorax. It is thicker than the shell elsewhere on the shrimp. The carapace connects to main legs (pereiopods), maxillipeds, whiskers (antennae and antennule) and eyes of the shrimp.

I highly recommend to read my article “How to Supplement Shrimp and Snails with Calcium”.

Rostrum

Rostrum (from the Latin rōstrum meaning “Beak”) is a hard extension of the shrimp’s carapace that prolongs forward of the eyes. It does not have any sensors. However, rostrum has 2 important functions:

1. The protection of the shrimp’s eyes.
2. The stabilizer of the shrimp when it swims backwards.

Note: When it comes to taxonomy (the species identification of shrimp), the shape of the rostrum plays a very significant role.

Stalked Eyes

The eyes of the shrimp sit either side of the rostrum. They are located on the short, independently movable and adjustable eyestalks. Shrimp have compound eyes, which give them panoramic vision. Their eyes are very good at detecting movement. Which is especially important for shrimp because they are at the bottom of the food chain.

Interesting fact:  The eye stems are also responsible for production of the hormones, which regulate metabolism, molting process, the location of the pigment in the cells, and the accumulation of calcium in the body.

Shrimp can regenerate their lost limbs with every molting process. However, unlike other body parts, shrimp cannot regenerate the eyes.

Antennae and Antennule

Antennae and Antennule are paired, usually, flagellate appendages projecting from the front end of the cephalothorax. Dwarf shrimp have:

• Two sets of short antennules (first antennae).
• One set of long antennae (second antennae).

They use long antennae to gather tactile information from the environment. Antennae can easily catch water vibrations around the shrimp. Thus, it allows shrimp to feel where (what) they touch and helps them to orientate and coordinate their positioning.

The short ones also help assess the suitability of food and provide chemical information (“taste” and “smell”) about what they are touching.

Scaphocerit

Scaphocerit is flattened plate, which is located at the base of antennae and antennule. It looks like a “Fang”, but it is not. Actually, this is an organ of equilibrium. Scaphocerit contains sensitive bristles that orient the shrimp in relation to the earth’s gravity.

Abdomen

The dwarf shrimp abdomen is made up of 6 abdominal segments and contains most of the musculature. The first segment is just behind the carapace and the sixth segment is in front of the tail. The shell of the abdomen segments is significantly thinner than the carapace. Each segment has a separate overlapping shell, which can be transparent. Each abdominal section also has a pair of pleopods, except the last one (near the tail). Shrimp can swim backward by a rapid contraction of its abdominal muscles, powerfully flexing the abdomen.

Note: When shrimp molt, they have a breaking point at the junction of the first abdominal segment and the carapace.

Interesting fact: There are some species of shrimp in the ocean, which can hold the world record for darting speeds. By squeezing their abdominal muscle, they have been clocked at over 200 meters per second. It is close to the bullet’s speed!  

Uropod

This is a paired, biramous appendage which is attached to the sixth abdominal segment. Uropods flank telson from both sides. Because of their shape, people also call it a “tail fan” which usually functions as locomotion when swimming backwards, and function like rudders, steering the shrimp when it swims forward.  

Telson

The 6^th abdominal segment ends in the telson. It is not a real segment because it never has any pleopods. Shrimp actively use it when swimming.  

 

 

Pleopods (swimmerets)

Pleopods are shaped like paddles and are used for carrying eggs and swimming forward. In addition, in the male, the first pair of pleopods is modified for insemination (see Petasma). There are 5 pairs of pleopods (swimmerets) on the underside of the abdomen. They are tucked under the abdomen of the shrimp.  Each abdominal segments has one pair of pleopods.  

Pleuron (Pleura)

Pleuron is one of the lateral flaps on each of the anterior five abdominal segments. Basically, it is what overlaps the nearby abdominal segments. The main purpose is the protection of the junction between different abdominal segments.

Petasma (Petasmata or Appendix masculina)

This is the male genital organ (Appendix masculina). It consists of the much enlarged and coupled endopods of the first pair of pleopods. The shape of a petasma is the easiest way of distinguishing between Neocaridia and Caridina shrimp.

You can read more about “The Difference between Neocaridina and Caridina Shrimp” right here. 

Pereiopods (Legs) and Chela

Dwarf shrimp have 5 pairs of jointed legs. However, they have a different function:

• the first 2 pairs of pereiopods have tiny claws / pincers / fans (Chela). Shrimp use them for feeding and fighting between themselves for food. However, because the claws are too small, they usually cannot harm each over.
• the next 3 pairs of pereiopods are used for walking as well as for “sensing” the environment.  

Maxilliped

Maxilliped (jawfoot, and foot jaw Origin: [Maxilla + L. pes, pedis, foot.]) is one of a pair of 3 sets of the mouth appendages on the heads of the shrimp modified to rummage and bring food to the mouth.

Note: Actually only two pairs of maxillipeds take part in the feeding process. The third pair (the longest) is usually used as a “semy-leg”. Maxillipeds are almost in constant movement as shrimp find and manipulate tiny morsels of food to its mouth.

Related articles:

Crayfish Internal Anatomy
Crayfish External Anatomy
Crab External Anatomy
Crab Internal Anatomy