Ribbon Worm
A worm that can stretch to 55 meters, shrink back to 20cm, and fire its entire throat at prey as a weapon
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Superpower
The ribbon worm has a proboscis — an eversible tube normally held inverted inside the body — that it fires outward faster than the eye can track to seize prey. In many species, the proboscis tip carries a sharp stylet coated with toxins that punctures and paralyzes prey on contact. After firing, the proboscis wraps around the prey and retracts it into the mouth. The body itself is so extensible that a 20cm individual can stretch to several meters with no internal skeleton to prevent collapse.
Overview
Ribbon worms (phylum Nemertea) are one of the least-known major animal phyla despite containing over 1,300 described species in marine, freshwater, and terrestrial environments worldwide. The largest species — Lineus longissimus — reaches over 30 meters, potentially making it the longest animal on Earth by linear measure. It is also typically as thick as a shoelace. Despite being largely unknown outside biology, ribbon worms are ancient (Cambrian fossil record), extremely widespread, and entirely harmless to humans.
Found in
Marine sediments, rocky shores, and coral reefs worldwide, plus freshwater streams and moist terrestrial soil. Most species live hidden in sand, mud, or algal mats. Found from the intertidal zone to depths over 7,000m.
Things worth knowing
- 1
The longest ribbon worm ever recorded — found washed ashore in Scotland in 1864 — measured approximately 55 meters (180 feet), potentially the longest animal ever documented. The same species normally lives coiled in a knot the size of a tennis ball inside rock crevices.
- 2
Ribbon worms have closed circulatory systems — one of the earliest animals in the fossil record to develop true blood vessels circulating blood throughout the body rather than relying on diffusion. Their vascular system predates that of any vertebrate ancestor.
- 3
Many ribbon worm species can autotomize — voluntarily shed fragments of their own body when threatened. Each fragment may survive independently, and the original animal regenerates what it lost. They treat self-dismemberment as a defensive option.
- 4
Fully terrestrial ribbon worm species exist — land-dwelling species live in moist tropical soil and leaf litter, hunting earthworms. They're almost invisible to naturalists because they live underground and are rarely seen.
- 5
Ribbon worm sperm is the largest known among invertebrates relative to body size — in some species individual spermatozoa are visible to the naked eye at over 1mm in length. The reason for this extreme size is not understood.