Skip to Content

7 Animals with No Blood

A stunning bioluminescence photo of group of jellyfish.

The vast majority of animals that inhabit the earth have a circulatory system much like we do, complete with a heart and blood. Most of us have red blood, though some animals have blue, black, or even green blood. Then, strangest of all, are the animals that have no blood at all.

Here are a few animals that live without blood in their body!

1. Jellyfish

Spectacular bioluminescent jellyfish heading in left direction.

It seems pretty obvious that a jellyfish has no circulatory system when we look at it. These transparent, gelatinous masses don’t have any obvious muscles or organs and are usually transparent, floating aimlessly around the ocean. Jellyfish belong to a class of animals called cnidarians, which include coral and sea anemones.

Instead of using blood to transport nutrients throughout their body, cnidarians absorb them directly from the water into their cells.

According to the UCSB Science Line: “When the cells on the outside of their body come into contact with water, oxygen and nutrients can diffuse into their body to provide them with everything they need.” Jellyfish are the largest animals without a heart.

2. Flatworms

A flatworm hanging around the seabed.

Flatworms, as the name implies, are flat, worm-like invertebrates. Their extremely flat bodies mean that they have no room for organs. Not only do they have no blood, but they also have no heart, circulatory system, or respiratory system.

They gather nutrients and oxygen through a process called diffusion. Unlike in humans, this process doesn’t involve any kind of pump; instead, the nutrients simply flow through the flatworm’s body without direction. Some flatworms are parasites, such as the tapeworm. Other types include the fluke and the planarian.

3. Nematodes

A high magnification view of a nematode.

Nematodes, also known as roundworms, are an incredibly common parasite, living in other animal species of all kinds as well as in food, soil, vinegar, malt, and deep within the earth. There are a huge number of nematodes — as many as 20,000 distinct types have been identified — but scientists think that these might only be a small percentage of the true number. The internal organs and other systems vary among different types of nematodes, but in general, they have a nervous system, digestive system, reproductive system, and excretory system.

While they don’t have blood, they do have a special fluid in their body that carries nutrients to their organs. Unlike in most animals, however, this fluid doesn’t circulate. Many common parasites are nematodes, including hookworms, ringworms, lungworms, and pinworms.

4. Starfish

A closeup photo of group of starfish.

Starfish have some of the strangest anatomies in the animal kingdom. Not only do they not have blood, but they also don’t have a brain or heart. Most of their organs are on the outside of their body.

This lets them absorb nutrients through their external cells, even digesting food through their body. Because of these outside organs, some starfish can even regenerate their whole body from a single arm. Fascinatingly, while they don’t have a circulatory system, they do have a system that pumps seawater through their body to absorb more nutrients — which the National Ocean Service calls a “water vascular system”.

5. Mollusks

Portrait shot of a mollusks.

Mollusks are a common sight both in and out of the water, including animals such as snails, slugs, oysters, mussels, cockles, and scallops. But you might not know that these creatures are completely bloodless! Instead of blood, they have an open circulatory system that moves a fluid called hemolymph throughout their body walls.

This fluid helps transport nutrients and oxygen throughout their body. This system does include a rudimentary pump to force the fluid through the mollusk’s body; but unlike in most animals, the hemolymph passes mostly through open cavities rather than from organ to organ.

6. Sponges

A complex shape of sponges under the sea.

Sponges are some of the oldest multicellular creatures on the planet, having evolved about 600 million years ago. Their anatomy is extremely simple, and they have no distinct body systems whatsoever. They have no muscles, nervous system, or circulatory system; they can’t move independently or feel pain and do not have blood.

Instead, they simply absorb nutrients from microorganisms in their environment, straining seawater through their body to extract tiny nutritional particles.

7. Coral Polyps

A beautiful soft-bodied coral polyps.

Most of us think of coral as a plant that just happens to grow in the sea. But it is a living animal — albeit an unusual one. Coral is alive and has physical needs just like other animals, but its anatomy and the way it gets nutrients are unique. Fascinatingly, coral does indeed have certain body systems, including a nervous and digestive system! But it does not have blood or a circulatory system.

Instead, it absorbs nutrients both through prey (which it can hunt for and catch without even moving) and through photosynthesis, absorbing oxygen and other important substances through light and water.

Learning About Animals With No Blood

While most animals with no blood live in the ocean, some are on land, as well! Some have rudimentary circulatory systems, some have alternate fluid that transports nutrients, and some simply absorb and process substances from their environment. Despite their simpler anatomy, one thing is certain: these creatures are as complex and fascinating as any creatures on our planet.

  • It’s Not Water: Pooph is totally fragrance free because it eliminates odor instead of covering it up! Pooph contains no harsh chemicals—it’s a proprietary mineral-based formula so clean and pure you could actually mistake it for pure natural spring water until you actually use it and see for yourself how miraculously it works!
  • Risk-Free Guarantee: Try POOPH for 30 days and if you aren’t happy, simply return it for a 100% no-hassle refund. Just send us a message via your Amazon order page and we’ll take care of the rest!
  • Instant & Safe: Instantly and safely freshens and dismantles puppy, dog, cat, pet, and litter urine and feces odors on a molecular basis – so they never return! Safe for people, pets, plants, and the planet!
  • Eliminates: Safely eliminates (doesn’t just cover up) urine, feces, vomit, and other pet odors that may invite your pets to defecate in the same spot over and over
  • No stains & Fragrance Free: Contains a clear, odorless, and non-staining formula that freshens and eliminates odors and will not stain carpets, clothing, toys, and more - use in every room in your house
  • PREMIUM QUALITY: A combination of premium texture and granule size made with 100% bentonite clay for maximum clumping creates litter particles that are just the right size.
  • LOW DUST: Ideal for cats and owners who suffer from allergies with a 99.9% dust-free and hypoallergenic litter formulation.
  • HARD CLUMPING: Hard clumping medium grain clay helps prevent moisture from reaching the bottom of the tray and forms hard clumps that won't break down, making it easier to scoop.
  • SUPERIOR ODOR CONTROL: Formulated for single or multi-cat households with natural ingredients to keep your home smelling clean and fresh between litter box cleanings.
  • LOW TRACKING: A unique formulation of medium grain clay helps keep litter in the box where it belongs.
  • FOUNDED IN 1987: Dr. Elsey’s is a veterinarian-owned cat product brand dedicated to creating products that solve the complex needs of pet owners. Founded in 1987 with the first all-natural clumping cat litter, Dr. Elsey’s line of products has since grown to include a variety of premium litters that address the health and behavioral needs of cats in every stage of life.
  • Open four-arm frame design protects the blade and does not trap dirt in the case
  • Lightweight case for easy handling and transport
  • Dual-material grip elevated above the reel prevents contact between reel and knuckles
  • Versatile folding end hook for use in multiple applications
  • Rewind reel tucks away for protection during storage
  • Gift Cards never expire and carry no fees.
  • Multiple gift card designs and denominations to choose from.
  • Redeemable towards millions of items store-wide at or certain affiliated websites.
  • Available for immediate delivery. Gift cards sent by email can be scheduled up to a year in advance.
  • No returns and no refunds on Gift Cards.
  • Gift Cards can only be used to purchase eligible goods and services on and certain related sites as provided in the Gift Card Terms and Conditions. To purchase a gift card for use on an Amazon website in another country, please visit:,,,,,,,,, or
  • ROLL ON: Our compact and convenient dog poop bag refill rolls help you keep poop bags where you need them–everywhere.
  • DURABLE & LEAKPROOF: Extra long, extra strong and 100% leak-proof guaranteed to keep hands clean on the go.
  • BETTER BAGS : A new generation of high quality & durable dog poop bags made from 65% certified post-consumer recycled plastic. Giving a second life to over 5 million pounds of landfill-bound plastic a year recycled plastic.
  • OUR MISSION: At Earth Rated, We are on a mission to make life with dogs simpler and better. We are also proudly B Corp Certified.
  • WHAT'S INCLUDED: This pack includes 270 lavender scented Earth Rated dog poop bags that measure 9"x13" on 18 refill rolls.
  • NO MORE HAIR EVERYWHERE: The ultimate pet hair roller for effective dog and cat hair removal. Far superior to traditional lint rollers for pet hair or sticky rollers, the ChomChom ensures deep cleaning.
  • CONVENIENT: Take the ‘fur’ out of ‘furniture’ once and for all! Ideal for cleaning couches, pillows, rugs, and more. Whether it's furniture, your car, or a carpet, this pet lint roller is an essential tool for all pet owners.
  • VERSATILE: Not just a dog lint roller, it's adept at cat hair removal too. The lint roller for pet hair extra sticky capability ensures every strand is picked up, leaving your spaces hair-free.
  • EASY TO USE: Just roll back and forth along any surface to trap fur and lint into the built-in receptacle. When you’re all done, just press down on the release button to open the pet fur remover and empty it out completely. Purr-fectly simple!
  • SUSTAINABLE - This reusable lint roller requires no adhesives or sticky tape, and can be used again and again.
  • Super High Bounce: Better than standard tennis balls, the Ultra Ball is made of durable rubber yielding an ultra bouncy, exciting fetch experience on land or on water thanks to lightweight, bouyant design. Compatible with size Medium Chuckit Launchers
  • Tough and Durable: This rugged dog fetch toy has a textured surface and a thick rubber core that can stand up to rough play yet is soft on dog's mouths. Not intended as a pure chew toy, always supervise your dog when playing with this toy
  • Sizing matters: Size medium measures 2.5" in diameter and is best suited for dogs weighing 20-60lbs. Dog balls should be small enough for your dog to carry, but large enough that the ball can't completely fit in their mouth. When in doubt, buy a size up
  • Make Fetch Happen: Chuckit Performance toys are designed with you and your dog in mind; Try our full range of indoor and outdoor interactive dog toys including tumblers, flyers, fetch toys, other balls for dogs and more
  • ChuckIt Fetch Pet Toys: Chuckit makes indoor and outdoor dog toys that enrich the human-animal bond and helps dogs and puppies stay engaged. Try our full line of ball launchers, puppy toys, flying discs, tennis balls for dogs, dog chew toys, and more
  • Contains one (1) 40 ounce package of small dog treats with real bone marrow (packaging may vary)
  • The dog biscuit shell encases a real bone marrow center, delicious treats that you can feel good about giving
  • Crunchy on the outside and meaty on the inside, our MaroSnacks dog snacks are a satisfying combo of texture and mouthwatering flavor
  • Savory treats with calcium, perfect for dogs of all sizes
  • Baked with love in Buffalo, New York, USA, with colors from natural ingredients only

The Black Friday Deals