Gnathostomulida

Gnathostomulida is a phylum of microscopic, marine worms that belong to the superphylum Loricifera. They are characterized by their unique, segmented bodies and the presence of a proboscis, a specialized appendage used for feeding. Gnathostomulids are typically found in deep-sea environments, where they inhabit sediments and are often associated with organic matter.

The phylum Gnathostomulida was first described in 1902 by the German zoologist Carl Grünspan. It is currently divided into two classes: Micrognathozoa and Macrogathozoa. Micrognathozoa includes the smallest species, with body lengths ranging from 0.1 to 0.5 mm, while Macrogathozoa encompasses larger species, with body lengths up to 2 mm.

Gnathostomulids are hermaphroditic, meaning they possess both male and female reproductive organs. They reproduce sexually, with fertilization occurring internally. The larvae are planktonic, drifting in the water column before settling and metamorphosing into adults.

The biology and ecology of Gnathostomulida are not well understood, largely due to their small size and elusive nature. However, they are believed to play a role in nutrient cycling in deep-sea ecosystems. Their unique morphology and lifestyle make them an intriguing subject for further study.