Segmented worms are a topic within invertebrate zoology encompassing organisms in the phylum Annelida, characterized by a metameric body plan in which serially repeated segments (metameres) contain reiterated organ systems, often separated internally by septa. This segmentation underlies specialized locomotion via segmentally arranged circular and longitudinal muscles acting against a fluid-filled coelom as a hydrostatic skeleton. Annelids exhibit a closed vascular system, well-developed nervous system with a ventral nerve cord and segmental ganglia, and diverse feeding and reproductive strategies. Research on segmented worms informs developmental patterning, regeneration, soil ecology, and comparative morphology of body plan evolution among bilaterian animals.
Scientists have uncovered the earliest fossil evidence of annelids (ringed worms) in Cambrian microfossils dating back approximately 535 million years ago. This discovery offers fresh insights into the origin and early evolution ...
Evolution
Apr 20, 2026
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Most polychaete species spend their lives in burrows in the seabed. However, adult individuals of two species, Alitta succinea and Platynereis dumerilii, leave their burrows to spawn during warm summer nights around the full ...
Plants & Animals
Apr 10, 2026
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A new study, led by the University of Vienna and the Alfred Wegener Institute in Bremerhaven, shows how the eyes of adult marine bristleworms continue to grow throughout life—driven by a ring of neural stem cells reminiscent ...
Evolution
Dec 1, 2025
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Earthworms don't stop shaping soil processes when they die. A new study shows they can still help store carbon in the soil, even after death. "This is quite surprising," says lead author Tullia Calogiuri. "Most of our knowledge ...
Earth Sciences
Nov 3, 2025
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In a scary movie, creatures that can't always be seen often provide the biggest frights for characters and viewers alike. In deep-ocean research, the absence of one particular creature—the so-called zombie worm, "the bone ...
Plants & Animals
Oct 28, 2025
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A Chinese submersible has discovered thousands of worms and mollusks nearly 10 kilometers (six miles) below sea level in the Mariana Trench, the deepest colony of creatures ever observed, a study revealed on Wednesday.
Plants & Animals
Jul 30, 2025
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