This event was an earthworm sampling day at Grove Farm, in North Greenford/Sudbury Hill, Ealing. This was led by Keiron Derek-Brown of the Biological Recording Company (and the Earthworm Society of Britain) , with Anna from Friends of Grove Farm, a volunteer group, who manage the site for wildlife.

The Biological Recording Company

Earthworm sampling day

06 April 2024

The site is comprised of meadows, some broadleaf woodland and a stream. The Friends of Grove Farm have received funding from the Mayor of London for conservation work, surveying and education/engagement activities. The sampling day itself has been funded by Defra and the UK Centre for Ecology & Hydrology (CEH) as part of the Earthworm Image Recognition Project. This project aims to determine the feasibility of developing an earthworm image recognition system that could be used in an app by the public. To do this, multiple images of individual earthworms are required that can be used as training data. The earthworms sampled during this event were to be photographed by volunteers and submitted as training data. They will be identified by an expert at a later date, as earthworm identification often relies on characters that are best viewed under magnification. See Taxonomic groups – Earthworms for some further information about earthworms.

Overview

Standard surveying protocols for soil pit sampling for earthworms was followed (Brown, no date) in 3 different sites. This entailed digging 5 pits 25cm x 25cm x 50cm deep at each site. This soil is then inverted and placed onto a tray. We worked in groups, each group digging a pit and hand-sorting to find earthworms. The earthworms were placed into a plastic container whilst sorting continued. Once the soil had been sorted the earthworms were counted. If there were partial remains of a worm, each part is counted as an individual – as you can’t know if it belongs to a different worm or the same one! Any juveniles, which are worms without a clitellum (‘saddle’), were counted and then returned without identifying the species. The positioning of the clitellum is an important character in worm identification. The adults were taken and put individually into a container. I, along with the other volunteers, took multiple photos of each container/worm which I submitted after the event to Keiron who was then to identify the species and submit the photos and identification to be used as training data.

Activity

Pit, with soil ready to sample and earthworm in a pot

'Photoshoot' line-up of individual earthworms.

This was on a nice area of meadow, with yellow meadow ant hills around (we made sure the pits weren't dug in one of them!). In the pit I sampled there were 14 juveniles that were returned. I also saw a worm egg which was interesting. Some of the specimens without a saddle were just showing a TP (Tubercula pubertatis, which are markings on the lateral underside of the clitellum and are also used in identification). This may be that they were on the cusp of becoming an adult, or it could be post-mating and the saddle had reduced in size. 22 adults photographed.

Site 1

Site 1: Note yellow meadow ant hills.

Adult worm from site 1. Note the visible saddle (highlighted).

As earthworms live in substrates other than soil e.g. deadwood, leaf litter, under stones it is a good idea to search in these other habitats (Brown, 2019, p. 11). The next part of the day saw us walk through the woodland area of the site and stop to look under logs and in the leaf litter to find earthworms. Again, any juveniles were counted and returned whilst adults were placed into containers to be photographed. These were then placed into separate tubes of preservative so that they could be identified under a microscope at a later date. 16 adults were photographed.

As a side note, the walk through the wood was very pleasant and it was great to see the amount of wood anemones Anemonoides nemorosa that the Friends of Grove Farm were very happy with. It was interesting to learn that they apparently spread at a pace of approximately 2m per 100 years; with the amount present indicating that they had been in this area for approximately 2000 years!

Microhabitat search

Log for turning over to look for earthworms. Note the slime mould, possibly wolf’s milk Lycogala epidendrum.

Wood anemones Anemonoides nemorosa

This site was owned by the local fitness club but wasn’t used. Each year the area is mown before a charity sports day, but the pits were dug in an area that wasn’t mown. In the pit that I, and my group, dug, we found 6 adults and returned 35 juveniles.

Site 2

Site 2. Note area in foreground was not mown the previous year, this is where the pits were dug.

Tray of earthworms (adult and juvenile) from pit at site 2.

Me holding a tube of preservative.

At the soil that was overturned from this pit, I was really interested to see that there were some yellow meadow ants and eggs (which I’d not seen before). Also, on the walk between the woodland and site 2 we looked under a refuge that had been placed out for slow worms Anguis fragilis – and saw some! Note that slow worms are most definitely not earthworms! They are in fact legless lizards.

Yellow meadow ants and eggs.

Slow worm found under a refuge.

The final set of 5 pits dug, were in the same area as Site 2, just that it was on an area that had been mown the previous year. It was also considerably wetter, which made the sorting even messier! In my group’s pit there were 25 juveniles put back and 5 adults taken.

Site 3

Tray with earthworms, pit backfilled after sampling.

Image submitted for use in the project.

In the image(s) submitted to Keiron for the image recognition project, note how there is a paper label below the tray. Each specimen was labelled this way. The protocol was to take a photo of the label, then a few photos of the worm in the tray before moving onto the next specimen and repeating. This was so that all images were sorted correctly for uploading.

Reflection

It was great to visit a different site and talk to people within the industry. I enjoyed the sampling, and it was great that as well as providing ecological records, the images I took were contributing to the Earthworm Image Recognition Project. I learnt some more about earthworms e.g. being able to distinguish between adult and juvenile, as well as the effort involved in sampling earthworms. After the event I got in touch with Keiron who said that he would send out a species list to all the volunteers, as well as acknowledging volunteers' contributions to the project. I hope to find more about earthworms, perhaps with a lab-based session to practice identification under microscope.

References

Brown, K. D. (2019) NERS Earthworm Recorder's Handbook v8. Earthworm Society of Britain Available at: https://www.earthwormsoc.org.uk/node/6 (Accessed: 09 June 2024).

Brown, K. D. (no date) The Earthworm Society of Britain: Sampling earthworms. Available at: https://www.earthwormsoc.org.uk/sampling (Accessed: 3 February 2024).