Strange feeding habits, and even stranger reproductive strategies are found among the annelids.
Three peculiar polychaete worms illustrate the diversity found in the phylum Annelida.
Annelid Biology
There are over 15,000 known species of True Worms (Phylum Annelida) are all segmented – they have body units repeated along their length.
- In most members of the phylum (the polychaetes, with over 10,000 species) the majority of the body segments bear a pair of paddle-like appendages that are used for swimming or producing feeding currents, and as ‘gills’. Some wander the seabed, while others live permanently inside tubes that they construct for protection.
- Some of the other annelids (the earthworms and leeches) have lost their fleshy ‘legs’, but the segmentation is equally clear. The earthworms (as the name would imply!) live in soil and sediment, feeding largely on organic matter. The leeches famously suck blood.
- The ‘Zombie Worms’ (another name is ‘Bone-eaters’) are all members of the same genus (Osedax), and they were first discovered in 2002 living on the carcass of a Grey Whale. In 2005 Osedax mucofloris was discovered feeding on a dead Minke Whale – its common name is ‘The Bone Eating Snot Flower’!
- Palolo Worms are strange in a very different way. Once a year the back half of their body swells up with eggs or sperm and develops eyespots. When all members of the population are ready (around the seventh night after the full moon that follows the autumnal equinox) these rear ends break free from the head and swim to the surface (the head end survives on the sea-bed). At the surface the eggs and sperm are shed in a luminous cloud covering vast areas. In some parts of the South Pacific (notably Samoa) these ‘half-worms’ are caught annually and eaten boiled, fried, or raw on toast.
- Seep Tube Worms (Lamellibrachia luymesi) are among the longest-lived animals known – more than 250 years – and they are enormous, attaining over 3 metres in length. Their food (if it can be called food) comes from oil and methane leaking from ‘cold seeps’ deep in the ocean.
Molecular Studies and Annelid Classification
Annelids are thought to be closely related to the molluscs, since both phyla have a similar larval form (the ‘trochophore’ larva). They were also thought to be close to the arthropods at one time, but DNA and RNA studies suggest that this is very unlikely – similarities of body structure (notably segmentation and paired appendages) are now thought to have arisen independently in both groups.
The copyright of the article Worms Feeding on Dead Whales in Zoology is owned by John Blatchford. Permission to republish Worms Feeding on Dead Whales in print or online must be granted by the author in writing.
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