Field Meeting to Flitwick Moor, Bedfordshire 12th June 2010

Flitwick Moor, Bedfordshire's most important wetland, left behind when peat was cut from the site as recently as the 1960s, is a blend of fen, meadow, wet woodland and fragile peaty soil with naturally iron-rich acidic groundwater bubbling up to the surface from springs. Alder carr has developed in wetter places (figure 1) and there are areas of open water as well as cattle-grazed meadow with ancient ant mounds. This Wildlife Trust reserve and Site of Special Scientific Interest (SSSI) supports a wide variety of species including rare bryophytes, fungi and grasses as well as insects. The last Conchological Society field trip here was in the late 1960s, with records being submitted occasionally since then including records of Vertigo substriata and V. antivertigo by Bernard Verdcourt and Beryl Rands and an unconfirmed record of Phenacolimax major.

Four of us met on a very warm day after a wet week and visited as many of the different habitats as possible during the time available. Various sampling techniques were used to look for molluscs in both land and freshwater habitats. These included examining under logs and the grass of ant hills (whilst trying to avoid the ants!), vacuuming at the base of plants in marshy meadows (Ron Boyce), sieving soil samples, and sampling the sediment of streams and open water with pond nets and sieves. As was the case on the Sherwood Forest field trip (see Mollusc World 23), due to the shortage of calcium, very thin shelled Cepaea were present in the woodland areas. Although several possible habitats for Vertigo species were investigated, none were found on this occasion, but Rosemary Hill found Columella aspera, a first confirmed record from the site (figure 2). Also, both species of Euconulus (alderi and fulvus) were found in the same open wet marsh of mosses and reeds (with their complement of Succinea putris and Oxyloma elegans). Arion subfuscus (figure 4) was also observed in this area.

Tom Walker sampled a small, more alkaline stream at the east end of the reserve where species included Pisidium amnicum and P. subtruncatum (figure 3) as well as the planorbids Bathyomphalus contortus and Hippeutis complanatus. Two of us took home for examination some mud from the base of recently dredged plants by an area of open water. However this yielded only a single 2.5mm juvenile Ancylus fluviatilis (figure 5). When you look closely, this specimen shows the remains of a “septum”. Adrian Norris comments: “I have always presumed that the very young of Ancylus possess a tissue-like structure resembling a septum which is lost as they grow. I am however, unaware of any mention of this in the literature. A. fluviatilis is related to the Planorbidae and I presume that this structure in very young specimens must be a relict of these origins.”

With thirty species recorded, we felt that the day had been a successful one, updating some of the old records for this important wildlife site. We left, already planning a return early season trip (see Diary of meetings, page 31) to look for that elusive Phenocolimax major!

figure 1: Searching at edge of alder carr, Flitwick Moor.

figure 2: Columella aspera

figure 3: Pisidium subtruncatum

figure 4: Arion subfuscus

figure 5: Juvenile Ancylus fluviatilis with “septum”