Fish are fascinating creatures that live in diverse aquatic environments ranging from freshwater streams to deep-sea trenches. Despite their ecological significance, there are many misconceptions about fish biology and physiology. Some people even have doubts about whether fish have blood.
Blood is an essential component of the circulatory system of all animals, including humans. It is the medium through which oxygen and nutrients are carried to various organs and tissues while simultaneously removing waste products such as carbon dioxide.
But what about fish? Do they have this vital fluid as well? In this article, we will examine the anatomy of fish to answer this intriguing query.
Do Fish Have Blood?
Fish are cold-blooded vertebrates with a closed circulatory system. Their body is designed so that blood and nutrients are passed through the blood vessels and into the body. But some fish, like Antarctic Ice fish, do not have hemoglobin, so they have colorless blood.
If you cut a freshly caught fish near its blood vessels, you would notice blood oozes from it, but when you buy a stored fish from a store, you may not see it because the blood would coagulate with time, or the store would remove it while process the fish.
Interesting Fact: The blood in a fish accounts for around 6-8% of its total body weight.
Fish, like humans, are Poikilothermic, which means they can regulate their internal body temperature depending on the temperature outside. So, their body temperature fluctuates depending on the temperature of their surrounding area.
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Are Fish Warm or Cold-blooded?
As fish are aquatic animals, most of them are cold-blooded vertebrates. There are some exceptions like, Opah, which is warm-blooded. Although they aren’t as warm-blooded as animals, they are comparatively warmer when compared to other fish.
Also, fishes like tuna and mackerel are warm-blooded too.
Fish breathe through the gills, absorb oxygen in the water, and then use hemoglobin in their erythrocytes to transport oxygen from their gills or lungs into their tissues and organs through their circulatory system.
What Is The Color Of Fish Blood?
Fish are also vascular, which means their circulatory system consists of a heart that pumps blood that flows through arteries and veins, just like humans.
Because of the presence of hemoglobin (a protein that contains iron and helps carry oxygen through the blood) in fish blood, it is red in color.
Why Do Some Fish Have Colorless Blood?
Antarctic Ice fish have colorless blood due to the absence of red blood cells and hemoglobin (the pigment that helps carry oxygen). So, as they don’t have any hemoglobin, their blood carries 90% less oxygen than normal (red) blood, but they still survive because antarctic waters are rich in oxygen.
These Icefish have massive hearts that pump blood in huge volumes around their body to ensure they get enough oxygen.
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Do Fish Have A Heart?
Yes, fish have a heart. But the structure of their heart is much simpler when compared to other animals. The heart of a fish is located behind its gills and consists of two chambers; ventricle and atrium.
However, some fish species, like eel and catfish, don’t have hearts.
Most fish do have blood, which is red, like human blood.
But some species of Antarctican fish have anti-freeze mechanism to cope up with colder temperatures. So, they don’t have hemoglobin in their blood, which is responsible for their red color. Instead, they have colorless blood.
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