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| The
Peanut worm is a burrowing worm-like creature that is sometimes
seen above the ground on Chek Jawa. |
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'Siphunculus'
means 'little tube'. There are about 300 species of
peanut worms.
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When contracted, they look like peanut shells because of their ridged
skins. Most are only a few millimeters long. Some burrow in mud, while
others hide in crevices or abandoned snail shells and even in tubeworm
tubes.
Peanut worm parts: Peanut worms
are unsegmented. They belong to Phylum Sipuncula and not to Phylum
Annelida which includes the segmented bristleworms
and earthworms we are more familiar with. What is unique to peanut
worms is their introvert, a long tube on their front end. This is
attached to the rest of the body, called the trunk. Like the finger
of a glove, the introvert can be turned completely inside the trunk
or extend out of the trunk. The mouth is at the end of the introvert,
surrounded with tentacles. The tentacles are covered with cilia (tiny
beating hairs) and mucous. Food particles are gathered with the tentacles
and then either the entire introvert is withdrawn into the trunk and
the food particles eaten, or cilia on the tentacles transfer the particles
along tracts into the mouth.
Their introvert allows peanut worms to collect food while their soft
bodies remain safely hidden. Some also use their introvert to burrow.
One species even uses its introvert to swim!
Peanut food: Peanut worms eat
detritus, most of them mopping it up from the surface. Others eat
their way through the sand as they burrow, and process the edible
bits in it. They have a J-shaped digestive tract with the anus in
the middle of the body so that wastes are brought back up near the
entrance of the burrow.
Peanut babies: Peanut worms have
separate genders, releasing eggs and sperm simultaneously into the
water for external fertilisation. Some have a free-swimming larval
stage that can travel long distances, in others, the eggs develop
directly into little peanut worms.
Human uses: Peanut worms were
once so plentiful in Singapore that they were fed to ducks. |
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See
also...
Worms of Chek Jawa.
Links
Sipuncula
on the Canada's Aquatic Environments webpage on the University of Guelph
website: an easy introduction to the more technical aspects of their morphology,
metabolism, reproduction, ecology with an interesting section on their idiosyncracies
and photos.
Worms on Life
on Australian Seashores by Keith Davey on the Marine Education Society
of Australia website: an introduction to worms including sipunculids with
explanations of the major parts of their bodies and their lifestyles, and
fact sheet on a peanut worm found in Australia.
Peanut worms
on the Museum of Paleontology, University of California, Berkeley website:
fact sheet on the phylum with diagrams and photos.
Phylum
Sipuncula on
Biomedia of the Glasgow University Zoological Museum on the Biological
Sciences, University of Paisley, Scotland website: a brief introduction
with explanations of the major classes, a glossary of terms and diagrams
and photos.
Other references
- Barnes, Robert
D. & Ruppert, Edward E., 1996. Invertebrate Zoology. Harcourt
College Publishers. 6th Edition. pp. 1056, G-1-16, I-1-30.
- Pechenik, Jan
A., 2000. Biology of the Invertebrates. McGraw-Hill Book Co.,
Singapore. 578 pp.
- Ng,
Peter K. L. & N. Sivasothi, 1999. A Guide to the Mangroves of Singapore
II (Animal Diversity). Singapore Science Centre. 168 pp. online
version
- Tan, Leo W. H.
& Ng, Peter K. L., 1988. A Guide to Seashore Life. The Singapore
Science Centre, Singapore. 160 pp. online
version
- Davey, Keith,
1998. A Photographic Guide to Seashore Life of Australia. New
Holland, Australia.144 pp.
- Chuang, S. H.,
1961. On Malayan Shores. Muwu Shosa, Singapore.225 pp., plates
1-112.
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