Brachiopods and octopuses are animals with blood that can appear dark.
While many animals have red blood due to the presence of hemoglobin, some have evolved different blood pigments that result in other colors. Here's a breakdown of animals with what is commonly perceived as dark blood, based on the provided reference:
Dark Blood in Animals
It's important to note that what we perceive as "dark blood" can vary depending on the pigment involved and the amount of oxygen it carries. Here's an overview:
Brachiopods
- According to the reference, brachiopods have black blood.
- Brachiopods are marine animals that resemble clams.
Octopuses
- Octopuses have a copper-based blood called hemocyanin.
- Hemocyanin absorbs most colors except blue, which it reflects, resulting in a bluish appearance. However, in certain lighting or when deoxygenated, hemocyanin can appear quite dark.
- This isn’t technically "dark" as in black, but it is very distinct from the red seen in mammals.
Other Considerations:
The color of blood can be influenced by several factors, including:
- The type of respiratory pigment present (e.g., hemoglobin, hemocyanin).
- The oxidation state of the pigment (oxygenated vs. deoxygenated).
- Concentration of the pigment within the blood.
Therefore, while certain animals have blood that appears dark, the specific pigment and conditions can cause variation in the observed color. The reference highlights the distinct black blood of brachiopods and the bluish, potentially dark-appearing, blood of octopuses.
