Gnathostomulids: Gnathostomulida

Physical characteristics: Red haplognathia are 0.1 inch (3.5 millimeters) long and 0.006 in (140 micrometers) in diameter. They are one of the largest gnathostomulids. Most of these worms are brick red, reddish brown, or pink. The head is pointed, and the rear is rounded. The jaws are solid and have large winglike structures and many sharp feelers. The bottom plate of the jaw is shieldlike and has thorns.

Geographic range: Red haplognathia live on the coasts of Australia, Fiji, Hawaii, eastern North America, western Europe, and countries surrounding the Mediterranean Sea.

Habitat: Red haplognathia live in waste-rich sand in shallow water near the shore.

Diet: Red haplognathia graze on fungus threads and bacteria among sand grains.

Red haplognathia graze on fungus threads and bacteria among sand grains. (Illustration by Amanda Smith. Reproduced by permission.)

Behavior and reproduction: Red haplognathia coil up by muscular action, then uncoil using their hairlike fibers, often from both ends at the same time, the head pulling forward and the rear pulling backward. Red haplognathia lay a single egg, which bursts through the worm's back. The egg then sticks to a sand grain until the young worm emerges.

Red haplognathia and people: Red haplognathia have no known importance to people.

Conservation status: Red haplognathia are not considered threatened or endangered. ∎