Worms & Leeches

All images on this website have been taken in Leicestershire and Rutland by NatureSpot members. We welcome new contributions - just register and use the Submit Records form to post your photos. Click on any image below to visit the species page. The RED / AMBER / GREEN dots indicate how easy it is to identify the species - see our Identification Difficulty page for more information. A coloured rating followed by an exclamation mark denotes that different ID difficulties apply to either males and females or to the larvae - see the species page for more detail.

Worms & Leeches

'Worms' has no specific scientific meaning, but in common speech it covers the groups of animals that have no legs.  This includes species in several unrelated Phyla or major divisions of animal life.  Classification is complicated, and frequently revised or updated, and identification to species-level is usually very difficult.

Annelids or segmented worms - as the name suggests, these species have their body divided into segments.  Many are hermaphrodite, with both male and female sex organs.  It includes earthworms, blackworms, leeches and the marine ragworms. 

Nematodes have adapted to nearly every ecosystem in the planet and are abundant, but despite this are rarely recorded. Their bodies are not segmented. The Phylum includes internal parasites of vertebrates ('roundworms') and invertebrates, animal pathogens, plant gall-causers and plant pathogens ('eelworms'), but also many species that live in soil, the sea and fresh waters.  They are found from the poles to the tropics, and from mountain-tops to the deep ocean floor.  

Platyhelminthes or flatworms are simple organisms that lack specialised circulatory or respiratory systems.  Unlike other 'worms' their digestive system has only one opening.  Oxygen and nutrients pass into their flattened bodies by diffusion.  The Phylum include many parasites of vertebrates, such as tapeworms and flukes, but also free-living flatworms that are found in the soil, leaf litter and water. 

NOTE: The Earthworm Society will only accept records of earthworms that have been identified using an approved key. They do not approve of the OPAL earthworm key as this only includes around half the UK earthworm species and uses photographs for identification which isn't a reliable method. Visit their website linked below for more details.

Click on the headings below to expand/contract the text.

Earthworms (and blackworms)

Earthworms are Annelids - i.e. they have segmented bodies. They are often classed as Oligochaeta, but this is being reviewed as a result of DNA studies, and more recent sources class them as Clitellata.  They are terrestrial invertebrates, eating a variety of organic matter, and all 31 of the terrestrial species found in the British Isles are in the family Lumbricidae - apart from one North American species with two unverified records from south-east England.  

They have tiny claw like bristle or 'setae' along their length used in locomotion.  They are hermaphrodite, and in adult worms the clitellum or saddle can be seen - this is a ring covering several segments towards the front of the worm and is where egg cocoons are produced.   

It is not possible to identify the majority of species when alive; the standard key is based on preserved adult specimens (i.e. those with a clitellum).  The position of this and the location and structure of the markings and lumps underneath (the 'TP' or Tubercula pubertatis) are the main features used in identifying species. 

Blackworms are related, but are aquatic species in the family Lumbriculidae.  

Identification resources: 

The Earthworm Socity  https://www.earthwormsoc.org.uk/

https://www.earthwormsoc.org.uk/fullscreen/earthwormkey

Sherlock, E. (2018). Key to the earthworms of the UK and Ireland - 2nd edition.   FSC (Aidgap guide) 

The OPAL Earthworm Guide was produced as a resource for the OPAL Soil & Earthworm Survey and includes an identification key to the 12 most common species of British earthworm based on the observation of live earthworms, using colour and size as distinguishing features.  There are many more species of earthworm in the UK than those covered in the OPAL guide, and further research has shown that some of the features used in the field key are unreliable.  For this reason the Earthworm Society (and NatureSpot) cannot accept records based on this guide. 

Lumbricidae

Lumbriculidae

Leeches

Leeches are Annelids - i.e. they have segmented bodies. Recent sources class them as Clitellata, in the sub-class Hirudinea. 

Most live in freshwater and are parasitic species, with suckers at both ends of their bodies used to attach to a host before piercing the skin.  Hirudin is secreted to prevent blood clotting, and this has given rise to medicinal uses, past and present.  A few live in terrestrial or marine environments, and a few are predatory. 

Like earthworms, they are hermaphrodites with a clitellum or saddle in which egg capsules are produced.

Identification resources: 

Elliott, J.M. & Dobson, M. (2015).  Freshwater Leeches of Britain and Ireland. Freshwater Biological Association

Hirudinidae

Piscicolidae

Glossiphoniidae

Erpobdellidae

Flatworms

Flatworms are Platyhelminths, and are free-living in water or shaded humid terrestrial environments. 

Terminology is confusing.  They are usually classified as 'Turbellaria' to separate them from the parasitic species, but this is now considered incorrect following DNA studies; however the term is still used in many publications.  The larger freshwater flatworms are also referred to as 'triclads' or 'planarians', in the order Tricladida - which have a triple-branched intestine.  

Identification resources: 

Buglife: Non-native land Flatworms

UK Freshwater Flatworm Recording Scheme

A Key to the Freshwater Triclads of Britain and Ireland, with Notes on their Ecology (Reynoldson, T.B. & Young, J.O. 2000)  Freshwater Biological Association.

Dendrocoelidae

Geoplanidae

Planariidae

Rhynchodemidae

Nematoda (Nematodes)

Nematodes, or roundworms, are in the phylum Nematoda. This is a large and diverse group, probably best known for those species that are plant parasites so come to the attention of gardeners. Most live in the soil but they have adapted to nearly every habitat, including marine and freshwater. They are very difficult to tell apart so you won't see many species represented here!

Anguinidae (Roundworms)

Nematomorpha (Hairworms)

The phylum Nematomorpha are a type of long, thin worm found in damp habitats, including marshes, water troughs, streams and ponds. They are commonly referred to as hairworms. The adults are free-living whilst the larvae are parasitoids of various arthropods. Adult worms are wire-like and move very slowly. They get their alternative name of 'Gordion' worms from the legendary gordion knot, as they often form themselves into tight knots.

Nematomorpha (general)

Enchytraeidae

Enchytraeidae (general)