Which invertebrates use hemerythrin as an oxygen-binding pigment?

Which invertebrates use hemerythrin as an oxygen-binding pigment?

• A. Mollusks and arthropods
• B. Sipunculida, Brachiopoda, Priapulida, and certain annelid worms
• C. Echinoderms and chordates
• D. Insects and arachnids

Answer: (B)

Hemerythrin is an iron-containing pigment used to bind and transport oxygen in the circulatory or coelomic fluids of certain invertebrates, and it is distinct from the more familiar hemoglobin (heme iron) and hemocyanin (copper-based). This pigment occurs in a relatively small, specific set of groups rather than across all invertebrates. The groups that use hemerythrin include sipunculans (peanut worms), brachiopods, priapulids, and some annelid worms. In these animals, hemerythrin functions in the oxygen transport system, residing in the circulating fluid or body fluids rather than in red blood cells as in vertebrates. Mollusks and arthropods typically rely on hemocyanin (a copper-containing pigment) for oxygen transport, or in some cases different arrangements, while many insects and arachnids rely on their tracheal systems for gas exchange rather than a circulating pigment. Echinoderms and chordates largely depend on other pigments or systems, with chordates famously using hemoglobin. So the best match is the group of organisms that includes sipunculids, brachiopods, priapulids, and certain annelids, which are known to use hemerythrin as their oxygen-binding pigment.

Hemerythrin is an iron-containing pigment used to bind and transport oxygen in the circulatory or coelomic fluids of certain invertebrates, and it is distinct from the more familiar hemoglobin (heme iron) and hemocyanin (copper-based). This pigment occurs in a relatively small, specific set of groups rather than across all invertebrates.

The groups that use hemerythrin include sipunculans (peanut worms), brachiopods, priapulids, and some annelid worms. In these animals, hemerythrin functions in the oxygen transport system, residing in the circulating fluid or body fluids rather than in red blood cells as in vertebrates.

Mollusks and arthropods typically rely on hemocyanin (a copper-containing pigment) for oxygen transport, or in some cases different arrangements, while many insects and arachnids rely on their tracheal systems for gas exchange rather than a circulating pigment. Echinoderms and chordates largely depend on other pigments or systems, with chordates famously using hemoglobin.

So the best match is the group of organisms that includes sipunculids, brachiopods, priapulids, and certain annelids, which are known to use hemerythrin as their oxygen-binding pigment.