Dorvillea australiensis image logo image

This is Ophryotrocha adherens, from Hawai'i, squeezing some eggs out through tiny pores in its body wall.

Benthic Animals in General and Polychaetes in Particular

Eurythoe complanata, HawaiiWant to learn more about these fantabulous animals?  Excellent! Me too!  I've been very happy to hear of the classroom projects students and teachers have been doing that use polychaetes as learning tools and subjects.  Please let me know what YOU are doing with polychaetes!  If you have a question for the wormguy, just email it to me.  If I don't have the answer then I'll try to find the person or resource that does.  The most exciting thing about science is that surprisingly often NOBODY knows the answer. Then it's fun to think about what we can do to find out something entirely new and add our answer to the planet's central library, the internet! Science isn't about looking up answers, it's about thinking of new questions and carefully DOING something to find out what is true in the real world. 


When you start out learning about a new subject, you often run across LOTS of new words you've never heard before.  When I wrote my first paper my dad said that he tried to read it, but that he couldn't understand half of the words because they weren't even in the dictionary!  Scientists aren't trying to use a secret code, sometimes we just have to use exactly the right word to help avoid confusion.  Often it's shorter than the plain-language equivalent.  For example, once you know the words it's easier to say 'palp' than 'those particular head appendages used for sensing through touch and manipulating food.'  Two marvelous folks, Maggenti and Gardner, wrote a very useful and searchable dictiontionary to help define some words used to describe many invertebrates.  You can open it here (Note! big, 9.7 Mb, file opens in a new window).  




Polychaetes ('poly' = many, 'chaeta' = bristle)


Neanthes arenaceodentata, Hawaii

  Pictures of polychaetes
  Pictures of other benthic animals
   Some polychaete identification guides on the web

What are they?

A parapodium (foot) from a polychaete.Animals are categorised into about 40 phyla (singular = phylum). All vertebrates (including all fish, bird, reptile, amphibian, and mammal species) are only one part of a single phylum called Chordata.  Sponges are their own phylum.  Corals, anemones, and jellyfish are another (Cnidaria).  Sea urchins, sea cucumbers, sea stars, and brittle stars are another (Echinodermata).  Shrimp, lobsters, bumble bees, and cockroaches belong to a huge phylum (Arthropoda), and so on.  People commonly call many things without a backbone (most animals on the planet) that are somewhat sausage shaped a worm. A 'worm' can then be any animal from about 10 different phyla! 


Polychaetes belong to the phylum Annelida (ringed or segmented worms) along with oligochaetes (like earthworms) and leaches.  Polychaetes are annelids that have flappy extensions (parapodia or 'feet') on each segment that help them swim, crawl, breathe, etc.  These parapodia have chaetae, bristles, in a remarkable variety of shapes and functions.  Some are harpoon shaped and help defend the worm while others help them swim or burrow.  Tubeworms have chaetae that act like the emergency brakes on a runaway lift, locking them into their tubes when a hungry fish or crab tries to pull them out. There are over 50 polychaete families and thousands of species living everywhere in the ocean in beaches and tidepools, drifting in the plankton, all the way down to the deepest hydrothermal vents.


There are many species of polychaetes that have not been named or described yet so the world needs more worm guys and worm ladies!


What do they do?


Lumbrineridae, Otago, New ZealandLike all animals, polychaetes must breathe, eat, find (or make) shelter, and reproduce.  Polychaetes solve all these life problems in an amazing variety of ways.  Some hunt other animals using antennae to ‘sniff’ the water and seabed.  They use palps to feel out the prey right before their pharynx ('thoat') shoots out of their mouths and captures their dinner with multiple jaws!  Others graze algae along the surface of rocks, filter plankton out of the water, or swallow enormous quantities of sediment just to digest out the thin bacterial film coating each sand grain.  


Many polychaetes burrow into the ocean floor for protection.  While doing this they return buried nutrients to the surface, oxygenate the sediments (just like earthworms in your garden), and may bind sand grains together with mucous.  Others build tough tubes out of limestone or cement bits of rock and shell to themselves for armour. 

A polychaete is 'budding' its young! (Insert shows parapodia and chaetae)


In terms of reproduction, polychaetes offer a dizzying array of methods.  Most polychaetes are dioecious (have separate males and females), but some are hermaphrodites.  Some shed eggs and sperm into the water and hope they get lucky, others go through elaborate courtship rituals, building special structures for the purpose.  Some even sprout a bunch of babies from their bodies which drop off and grow into new worms!  Many worm parents never see their young while most species make special cocoons or otherwise tend the eggs, and protect the little ones until they’re big enough to leave on their own.


How are they important to people?

EarthHow aren’t they important!  Take a sample of the seafloor just about anywhere on the planet (remember, over 2/3 of the planet is ocean) and you will likely find polychaetes living there ranging in size from over four metres to individuals living between individual sand grains less than 0.1 mm long!  Most species have been found in the ocean, but they live in estuaries, lakes, and rivers too. They are incredibly diverse and often comprise over 50% of the animal species found in any sea bottom sample.  It's not unusual to find more than 20 000 polychaetes living in a square metre of sand!


Hoiho, yellow-eyed penguin, Otago, New ZealandBecause they are so numerous and active, they contribute a huge amount of food to important seafood species like flatfish, skates, really just about any demersal (fish living on or near the seafloor) or small benthic fish. They rapidly turn inedible seafloor materials into tasty bite-size morsels which can support much of the food web, including penguins and us!  All of that is only a tiny fraction of their job recycling nutrients between the sea floor and the water column.  They constantly rework the sea bottom and stabilise sediments with their tubes.  Some worms tubes are dense enough to form reefs which can shelter other animals and even offer protection from hurricanes!


Scientists are curious about the variety of ways worms which share the same basic body plan have evolved to live in so many different habitats and niches.  Some geneticists even use polychaetes to understand stages of HUMAN development! Like the famous lab fruit fly Drosophila melanogaster, several polychaete species are very important model animals for study.


In short, polychaetes are one of the most important groups of animals that keep aquatic ecosystems working! Indirectly, they provide a huge number of services to people worth billions of dollars. They feed us, recycle for us, they teach us about the world and ourselves, and they keep those beautiful coasts, estuaries, and rivers pretty and productive for us! Have you appreciated worms today?


"Worms have played a more important part in the history of the world than most persons would at first suppose." - Charles Darwin, 1898


What do I do with polychaetes?

Brian Paavo at a microscopeI like watching polychaetes (and other invertebrates) because they’re fascinating beasties that are absolutely everywhere in the ocean.  They are the stagehands behind the scenes of the world...the unsung heroes.  Think of all the fun thing that you like to do.  I bet you had to learn how to do them! Learning about stuff is fun, and learning about critters or how to do things that no one else knows about is even more fun. 


The actual process sounds very simple, but there are careful tricks and techniques a good wormperson uses every step along the way to do efficent and useful science.  I get samples of soft sediments from the seashore or the seabed, keeping them cool and disturbing them as little as possible.  Then I anesthetise (or relax) the animals in the sediments with chemicals so that they extend their chaetae and jaws.  Next I quickly kill them with a nasty chemical that also hardens their bodies.  Next I have to wash the animals and sediments many, many times to dilute the chemical so it doesn't harm the environment.  Then I carefully separate the animals from MOST of the sediment by  sieving or elutriating (floating animals away).  There's always leftover sediments so then I manually pick the worms out while looking at small dishes of the sieve residue under a microscope. I've picked hundreds of thousands of worms doing that!  Once separated from sediments, then comes the most fun part, looking at them closely under the microscope to try to identify what species I've found.  It's not as easy as it sounds.  Even today, a lot of species are unknown. I have several new species in my lab right now!  Just like it's hard to tell what kind of butterfly might come from a caterpillar, it can be difficult to identify small, young, or injured specimens.  The next step is also pretty cool.  I may have a few hundred worms in a project or many thousands, but after I'm done counting them I use statistics and mapping software to analyse the data.  After all that processing, this is the step where the worms that died teach us about the environment by showing where they lived. Sometimes that helps us protect the environment for the uncounted millions left on the seafloor.   


Worms can also tell us a lot about the environment they live in.  Humans have some impact on their environment wherever we live, catch food, or dispose of our waste. Impacts can be positive, negative, or neutral.  I believe that it is our responsibility to make sure that our impacts are as gentle as possible to ensure our own future. Some species of worms can live in polluted areas, while others are too sensitive to live there.  Some like one type of sediment while others are more general.  Some like certain temperature, chemical, or physical environments that others can’t tolerate.  By mapping out where different groups of worms exist near fish farms, sewage outfalls, harbour dredge spoil disposal sites, etc. we can see where humans have an impact and just how big it might be.  While expensive chemical and physical tests are possible, they provide only a ‘snapshot’ of the environment when those samples were taken and it's usually too expensive to take enough samples.  Worms are living, mostly in the same spot, all their lives (which can vary from a few days to many years in different species). They ‘average’ out the impact in a more realistic way over time.  Analysing worm communities helps us gauge the health of that particular part of the ocean!  Learn to listen to the worms and you’ll hear some amazing stories!

What's this? I have NO idea...we need more wormguys.


For these reasons I research where worms live and how they interact with their environment. Lots of coastal acitivities like outfalls, housing development, aquaculture, dredging and such need someone to find out what species are living on the bottom. I help people by identifying polychaetes the best that I can, but there's a lot more worm work than workers! THE WORLD NEEDS MORE WORMLADIES AND WORMGUYS! Besides identifying worms we need people to understand the development, ecology, chemistry, and physics of the worms' world in order to live in it well. It's not only useful science, it can be very exciting and satisfying as well.



Polychaete Pictures

Unless otherwise stated, all pictures in this gallery were taken by me, Brian Paavo, they are copyrighted and I retain all rights.  If you'd like to use one for your own non-commercial project, please contact me for permission.

Pictures of Other Benthic Animals

Unless otherwise stated, all pictures in this gallery were taken by me, Brian Paavo, they are copyrighted and I retain all rights.  If you'd like to use one for your own non-commercial project, please contact me for permission.

Polychaete Guides on the Web

Polychaete identification keys on the web:

Other useful links

Geoff Read's - A major central store of links and information related to annelids, especially those of New Zealand.  Useful information for professionals and noobies alike, but also the home of the list serve every polychaetologist should be on.


WoRMS - The most comprehensive and up-to-date register of accepted names of marine species, not just worms


Invertebrate Zoology Dictionary - A marvelously useful and searchable dictionary by  Maggenti and Gardner.  [9.7 Mb .pdf document, opens in a new window]

These publications provide general introductions to polychaete diversity and biology.  (from POLIKey, above)

Beesley, P.L., Ross, G.J.B. and Glasby, C.J. 2000. Polychaetes & Allies: The Southern Synthesis. CSIRO Publishing: Melbourne. xii + 465 pp.

A recent overview of Polychaetes, and related groups including myzostomes (Myzostomida), pogonophorans (Pogonophora), echiurans (Echiura) and sipunculans (Sipuncula)


Day, J.H. 1967. A Monograph on the Polychaeta of Southern Africa. Trustees of the British Museum (Natural History): London. 2 vols: Pt 1, Erranta pp. 1-458; Pt 2, Sedentaria pp. 459-878 pp.
Now badly outdated, especially in the recognition given to supposedly cosmopolitan species and in generic classification. Many currently-recognised families are treated as subfamilies. However the figures accompanying the key to families are still useful and much easier to use for beginners than more recent and comprehensive (but highly technical) family keys.


Fauchald, K. 1977. The polychaete worms. Definitions and keys to the orders, families and genera. Natural History Museum of Los Angeles County, Science Series 28, 1-188.
The "pink book". Has been the first port of call for generic diagnoses and keys to genera, but now out of date for many families. However, for other families there is still no more recent systematic summary.


Fauchald, K. and Rouse, G. 1997. Polychaete systematics: past and present. Zoologica Scripta 26, 71-138.


Hutchings, P.A. and Fauchald, K. 2000. Class Polychaeta: Definition and general description. pp. 1-3 in Beesley, P.L., Ross, G.J.B. and


Glasby, C.J. (eds), Polychaetes and Allies: the Southern Synthesis. . CSIRO Publishing: Melbourne.


Rouse, G.W. and Fauchald, K. 1995. The articulation of annelids. Zoologica Scripta 24, 269-301.


Rouse, G. and Fauchald, K. 1997. Cladistics and polychaetes. Zoologica Scripta 26, 139-204.


Rouse, G.W. and Pleijel, F. 2001. Polychaetes. Oxford University Press: Oxford.


International Polychaetology Conferences:

  • 11th, 2013, Australia
  • 10th, 2011, Lecce, Italy (Proceedings)
  • 9th, 2007, Portland, Maine, USA  (Proceedings)
  • 8th,2004, Madrid, Spaid (Proceedings)
  • 7th, 2001, Reykjavik, Iceland, Published as: Advances in Polychaete Research. (Developments in Hydrobiology 170) Kluwer Academic Publishers, 399 p. reprinted from Hydrobiologia, volume 496.Sigvaldadottir, E.; Mackie, A.S.; Helgason, G.V.; Reish, D.J.; Svarvarsson, J.; Steingrimmson, S.A.; Gudmundsson, G. (eds). (2003).
  • 6th,1998, Coritiba, Brazil, Published as: Sixth International Polychaete Conference (Eds: Reish, Donald J., Lana, Paulo) In: Bulletin of Marine Science 67(1, July, 2000.
  • 5th, 1995 Qingdao, China, Published as: Fifth International Polychaete Conference (Ed: Reish, Donald J. & Qian, Pei-Yuan)  In: Bulletin of Marine Science Volume 60(2), March 1997.
  • 4th, 1992, Angers, France, Published as:ACTES DE LA 4EME CONFERENCE INTERNATIONALE DES POLYCHETES [Proceedings of the Fourth International Polychaete Conference] (Ed: DAUVIN, Jean-Claude, Lucien LAUBIER, and Donald J. REISH) 1994 In: Memoires du Museum National d'Histoire Naturelle, Volume 162. pp. 642. ISBN 2-85653-214-4
  • 3rd,1989, Long Beach, California, USA, Published as: Third International Polychaete Conference (Ed: Reish, Donald J. ) 1991 In: Bulletin of Marine Science Volume 48(2) p.177-596
  • 2nd,1986, Copenhagen, Denmark, Published as: Systematics, Biology and Morphology of World Polychaeta (Ed: Petersen, Mary E. and J. B. Kirkegaard ) 1991 In: Ophelia Supplement 5, pp. 723. ISSN 0078-5326, ISBN 87 88757 24 2.
  • 1st, 1983, Sydney, Australia, Published as: Proceedings of the First International Polychaete Conference. (Ed: Hutchings, Patricia. A. ) 1984 The Linnean Society of New South Wales, Sydney, pp. 483, ISBN 0 9590535 0 6.