Why is insect blood green

Hemoglobin contains an atom of iron to bind to oxygen. Patients with sulfhemoglobinemia exhibit cyanosis , or a blueish tinge to their skin.

Sulfhemoglobinemia is caused by excessive exposure to sulphur-containing compounds, like medications that contain sulfonamides such as sumatriptan or furosemide , nitrate fertilizer, or the overconsumption of nitrogenous vegetables like spinach usually only in infants. The treatment for sulfhemoglobinemia is a simple one: just wait it out.

So, after about 3 months, any red blood cells that contain sulfhemoglobin will have been recycled into proper red blood cells, and any non-red tint to the blood will have disappeared. Want to comment on this article? The pigments, however, are usually rather bland, and thus insect blood is clear or tinged with yellow or green. The red color that you see upon squashing a housefly or fruit fly is actually pigment from the animal's eyes.

Unlike the closed circulatory system found in vertebrates, insects have an open system lacking arteries and veins. The hemolymph thus flows freely throughout their bodies, lubricating tissues and transporting nutrients and wastes. Whereas the vertebrate circulatory system serves primarily to carry oxygen throughout the body, insects respire an entirely different waynamely, through tracheal tubes.

In the case of the fruit fly Drosophila, for example, a series of tiny openings called spiracles line the impermeable outer skin of the fly, and these convey air directly to tracheal tubes that, in turn, convey air to the internal tissues.

Insects do have hearts that pump the hemolymph throughout their circulatory systems. Though these hearts are quite different from vertebrate hearts, some of the genes that direct heart development in the two groups are in fact very similar.

The development and evolution of the vertebrate heart is currently the subject of much research. Horseshoe crabs are bled in the PBS documentary Crash. These arthropods' blood uses a different protein, called hemocyanin , to bind oxygen.

Because that binding process involves an atom of copper, rather than iron, the blood has a blue appearance when it's oxygenated, and little or no color when it's not.

Entirely separate from the color, horseshoe crab blood also has a chemical called coagulogen that can detect bacterial contamination at extremely low concentrations. It's very useful for testing pharmaceuticals, which is why companies collect horseshoe crabs and bleed them alive, as shown in the PBS documentary Crash.

A number of other marine species also have hemocyanin in their blood, and depending on the surrounding tissue, it can sometimes appear purplish, like in this red rock crab :. A cut-open red rock crab. Jerry Kirkhart. Meanwhile, some marine worms such as peanut worms , have purple blood for a different reason: an oxygen-binding protein called hemerythrin. Like hemocyanin, it only turns color when oxygenated, and in some species — like the peanut worm — you can see this purple color without cutting them open, thanks to somewhat translucent skin:.

Finally, there are other marine worms called polychaetes that have blood with yet another oxygen-binding protein, called chlorocruonin. Chemically, it's similar to hemoglobin, and uses iron to bind oxygen. And though it looks red when concentrated, when it's more diluted, it can appear bright green and, as with peanut worms, can be seen through the skin :. Read more : Andy Brunning takes on another interesting chemistry question: Why does old book smell have hints of vanilla? Our mission has never been more vital than it is in this moment: to empower through understanding.

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