There is no true heart and the blood often lacks any respiratory pigment.

The blood itself may be colourless, or have any of three different respiratory pigments.

Hemocyanin is present in the hemolymph as the respiratory pigment.

Respiratory pigment is also dissolved in the blood plasma.

The wires were looking for the copper-based respiratory pigment, haemocyanin.

The blood contains the respiratory pigment hemocyanin as an oxygen-carrier.

The majority of gastropods have haemolymph containing the respiratory pigment haemocyanin.

Some gastropods, such as the sea hare Aplysia, appear to lack respiratory pigments altogether.

A respiratory pigment is a molecule, such as hemoglobin in humans, that increases the oxygen-carrying capacity of the blood.

All vertebrates use the hemoglobin respiratory pigment.

The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.

Many crustaceans, but few chelicerates and tracheates, use respiratory pigments to assist oxygen transport.

A few crustaceans and insects use iron-based hemoglobin, the respiratory pigment used by vertebrates.

The blood may appear pale green but this is not due to any respiratory pigments and oxygen is transported dissolved in the plasma.

The four most common invertebrate respiratory pigments are hemoglobin, haemocyanin, haemerythrin and chlorocruorin.

Cetacean muscle is usually very dark because of the presence of the respiratory pigment myoglobin, which acts as an oxygen reservoir.

The blood of oligochaetes contains haemoglobin in all but the smallest of species, which have no need of respiratory pigments.

Cytochromes were initially described in 1884 by MacMunn as respiratory pigments (myohematin or histohematin).

Lobsters use copper in their respiratory pigment hemocyanin, despite the proportion of this metal in seawater being minute.

Fluid transport and gas exchange are instead accomplished by the coelom which contains the respiratory pigment haemerythrin, and the tentacular system.

The most common respiratory pigment in arthropods is copper-based hemocyanin; this is used by many crustaceans and a few centipedes.

The iron-containing respiratory pigment in red blood cells of vertebrates, consisting of about 6 percent heme and 94 percent globin.

There are no vascular or respiratory systems, but the body cavity does contain phagocytic amoebocytes and cells containing the respiratory pigment haemerythrin.

The hemolymph usually lacks any respiratory pigment, although members of the families Arcidae and Limidae are known to possess haemoglobin dissolved directly into the serum.

The oxygen-binding respiratory pigment of harvestmen is hemocyanin, which is typically found in arachnids with book lungs, which harvestmen do not possess.