Do Starfish Have Hearts? 5 Amazing Facts About Blood starfish Biology

There are about 2,000 species of starfish, each varying in color, size, and shape. Unlike most creatures, they lack true brains and traditional organs for walking or seeing. Yet, they can still hunt and consume prey with their fascinating anatomy.

Do starfish have blood? Unlike humans, their circulatory system works in a completely different way. The truth might surprise you!

In this detailed post, we will explore that, but let’s start with a quick answer:

Starfish don’t have blood or hearts like many other animals. Instead, they use a system called the seawater vascular system to move nutrients, wastes, and gases around their bodies. This system also helps them get rid of waste through water currents.

However, it doesn’t end here,  Below, I’ll explain the biology of Starfish’s circulatory system and how their water vascular system works. And much more, read on!

Starfish Circulatory System: How They Survive Without Blood or a Heart

Starfish have one of the most unusual circulatory systems in the animal kingdom. Unlike humans and many other creatures, they don’t have blood or a heart to pump fluids through their bodies. Instead, they rely on a unique water vascular system that moves seawater to help them breathe, transport nutrients, and even move. This incredible adaptation allows them to thrive without a traditional circulatory system.

Let’s break it down into key facts for easy understanding:

1. Starfish, belonging to the phylum Echinodermata, do not have an open circulatory system, which means they do not have blood. 
2. Instead, the sea star circulatory system is a unique hydraulic system called the water vascular system.
3. This system doesn’t use blood; it uses seawater to move around the body. Its main job is to help how the starfish move, breathe and carry nutrients.
4. It does not directly transport wastes.
5. The water vascular system operates without a centralized pump, like a heart.
6. Instead, muscle contractions in small sacs called ampullae create pressure changes that push the seawater around.
7. Key nutrients, such as sugars and amino acids, dissolved in the seawater are absorbed through the tube feet and body wall.
8. Oxygen (O2) and carbon dioxide (CO2) move straight through the body wall and tube feet into the water system for exchange . Starfish don’t have gills. Instead, they use a fascinating method to take in oxygen.
9. Wastes, like ammonia and nitrogenous waste, are removed from the body through special cells called coelomocytes and gills.
10. Unlike humans and other vertebrates, soft-bodied invertebrates often lack a closed circulatory system with blood.

 Examples of these invertebrates include flatworms, roundworms, cnidarians (like jellyfish), annelids (like earthworms), and mollusks (like snails and clams)

Do Starfish Have Hearts?

No, Starfish don’t have hearts like humans and other animals. They have a unique system called the water vascular system, which uses seawater instead of blood to circulate throughout their bodies. 

The Starfish’s water vascular system is very important for transporting nutrients and gases in the starfish body, but it doesn’t work exactly like a heart. How starfish Heart pumps, while the water vascular system relies on muscle contractions in structures called ampullae to create pressure changes that move the seawater.

Our blood carries oxygen and nutrients directly to cells, while the water vascular system mainly transports these substances to the tube feet and body wall, where they diffuse into the cells. Starfish waste removal primarily happens through specialized cells called coelomocytes and gills, not directly through the water vascular system. 

Also Read: Top 10 Scary Sea Creatures You’d Never Want to Encounter

Do Starfish Have Veins & Blood?

Sea stars (or starfish) don’t have veins blood. Instead, they rely on a fascinating system called the water vascular system. This system enables them to circulate nutrients, oxygen, and waste throughout their bodies by using seawater instead of blood. Through this specialized system, sea stars can breathe, move, and even power their tube feet without the need for a typical circulatory system.

Starfish Circulation: How Their System Works Without Blood

Circulation in Starfish involves three main organs:

1. Perivisceral Coelom

 Inside a starfish, there’s a space filled with liquid around its organs.

 This space helps starfish respiration (breathing) move food, and waste removal around the Starfish’s body.

2. Water Vascular System

 Starfish have a special system called the water vascular system. It’s like a set of tubes that help the starfish move and eat by moving water around.

3. Hemal System

 The hemal system in a starfish is like its blood circulation system. It’s a bunch of tubes that carry food and oxygen to different parts of the Starfish, keeping it healthy. Let’s delve deeper into each part of the sea star’s circulatory system.

How Starfish Water Vascular System Works

Now, let’s examine the structure of the starfish water vascular system.

1.  Starfish tube feet, or podia, function as “secondary gills” and aid in gas exchange.
2.  They are connected to a network of canals inside the sea star’s body called the water vascular system.
3. Seawater enters through a pore called the madreporite on the upper side of the sea star’s body, slightly off-center during water circulation.
4.  It then flows into a tube called the stone canal.
5. The stone canal connects with the ring canal, which circulates the center of the sea star’s body and connects with radial canals.
6.   Each radial canal extends throughout an arm’s length, terminating at the tip.
7. Each radial canal branches into two short and narrow branches called lateral canals. 
8. Each lateral canal has a valve preventing water from flowing back into the radial canal.
9.  They connect with the base of the tube feet, which each have a sucker or adhesive disc at the end.
10. The ampullae, located near the base of the tube feet, contract by squeezing water into the tube feet, causing them to extend.
11.  When relaxed, the elastic tissue of the tube feet pulls them back, creating suction. 

This allows the Starfish to move, adhere to surfaces, capture prey, and perform other important functions. While they can be found in coral reefs, Starfish exist in diverse marine environments with suitable rocky or hard surfaces.

What is the function of the water vascular system of a starfish. The water vascular system in a starfish functions like a hydraulic system, aiding

•  Locomotion
• Feeding
• Gas exchange
• Sensory perception

Video Courtesy of Amy Hall Wildlife YouTube Channel

 It consists of several structures, including the

1. Madreporite
2. Stone canal 
3. Circular ring canal 
4. Radial canals 
5. Lateral canals
6. Tube feet
7. Cilia

1. Madreporite

This sieve-like plate on the Starfish’s upper surface filters seawater and allows it to enter the system.

2. Stone Canal

 This muscular tube regulates water flow and pressure within the system.

3. Ring Canal

This circular canal encircles the Starfish’s mouth and distributes water to the radial canals. Radial canals run along each arm, supplying water to the tube feet.

4. Lateral Canals

These smaller canals branch off the radial canals and connect to the ampullae.

5. Ampullae

These sac-like structures act as muscular pumps, forcing water into the tube feet.

6. Tube feet

These numerous, flexible appendages are the Starfish’s “feet,” powered by the water vascular system.

7. Cilia

Tiny hairs lining the canals help move water through the system.

Water Vascular Mechanism Of Sea Star

• The water vascular system functions like a hydraulic system, using changes in water pressure to power movement. 
• Seawater enters through the madreporite and is distributed throughout the system.
•  Muscles in the ampullae contract, forcing water into the tube feet, causing them to extend and stiffen.
•  The tube feet contract and become flexible by relaxing these muscles and allowing water to flow out. 
• This coordinated movement allows the Starfish to move and interact with its environment.

Sea Star Vascular System: Its Other Vital Functions

1. Attachment

The water vascular system in Starfish serves another function is attachment. Sea stars use their tube feet to attach themselves to rocks and substrates like coral and algae. Learn more about coral ecosystems in 11 Outrageous Coral Reef Facts That Will Change How You See the Ocean.

This attachment can help some starfish resist predation by certain predators, offering additional protection alongside other adaptations like spines. However, it’s not foolproof, as some predators have evolved techniques to overcome it.

Starfish have calcified skin, primarily composed of calcium carbonate, which offers some protection against certain predators. Some species, such as the crown-of-thorns starfish (Acanthaster planci), have poisonous spines for further defense. They firmly adhere to rocks, making it more difficult for the force of water waves and currents to dislodge them. This attachment can play a vital role in specific behaviors depending on the species (e.g., camouflage, hiding in crevices). Read exactly What Do Crown of Thorns Starfish Eat? 10 Surprising Facts

2. Food Capture

Starfish’s unique hydraulic system, also known as the water vascular system, uses water pressure to power various functions, including locomotion, gas exchange, and food capture. The tube feet, equipped with suction cups, are used to grip and manipulate prey, such as attaching to the shells of mollusks like clams, mussels, oysters, scallops, snails, and chitons. Tiny mouth  Starfish have a small mouth on the underside of their body. If you did not read how lobster can bite you, read my interesting blog Does Lobster Bite? 5 Amazing Facts You Need to Know

3. Stomach Eversion

This is where things get interesting. Starfish have a special ability to push their stomach, called the cardiac stomach, out through their mouth.  This everted stomach engulfs the prey, and enzymes are secreted to break it down externally.

4. Digestion & Absorption

Once the food is partially digested outside the body, the Starfish retracts its stomach and absorbs the nutrients through the stomach wall.

Suggested Read:

• Decomposers of the Ocean? 06 Types Scientifically Explained
• Florida Starfish Types: Expert Tips & Guides for Top 8 Species Identification

Pacific Blood Star: Exploring The Unique Henricia leviuscula

The Pacific Blood Star (Henricia leviuscula) is a striking sea star among 10 kinds of starfish you can find in california waters known for its rich red or orange hues, which give it the “blood star” name.

Found along the Pacific coastline of North America, this sea star’s vivid coloring adds a dramatic touch to rocky underwater habitats, drawing the interest of marine enthusiasts and researchers alike.

Through its distinct physiology and role in marine ecosystems, Henricia leviuscula provides valuable insight into the diversity and adaptability of life beneath the waves.

Frequently Asked Questions

Conclusion

Do starfish have blood? No, these amazing creatures survive without blood or a heart. Instead, they use seawater in a special system called the water vascular system, which helps them move, breathe, and obtain food. Their unique way of living highlights the fascinating and diverse adaptations found in ocean life.