Caves and Swallets - Gower - page 288

The water beetles include Helophorus laticollis , which is usually found in shallow, exposed, grassy pools
on heathland. Many of these animals have obviously been carried into the caves by the various streams.
Fish may also enter the underground stretches of streams and the common brown trout is the species
mostoftenseen.Someanimalsappearpaleandareoftenrecordedas'whitefish',butalthoughtheyarein
a remarkably blanched condition they darken rapidly if brought into daylight The dark spots, that in any
casetendtobevariableintrout,arereducedtoalmostnothingalthoughtherowoforange-redspotsalong
the lateral line is often retained. The fish feed on invertebrates carried underground by the cave streams.
CAVE FLORA
In general caves are not known for their flora and the Gower caves are no exception. Plants in the cave
threshold, however, show a marked zonation controlled by light intensity and the nature of the substrate.
Floweringplantsnearthecaveentrancearesucceededbyferns,thenmosses,thenliverwortsandfinallyin
thedimlightgreenandblue-greenalgae.Inthedarkzoneonlyfungiandmouldsoccur,althoughthereare
no species that are confined to underground habitats. There have been no studies of the Gower cave flora,
but typical plants of cave entrances include herb Robert, dog's mercury and common nettle Urtica dioica
(Fig.163).Fernsrecordedelsewherefromthislocationincludehart's-tonguefern,maidenhairspleenwort
Aspleniumtrichomanes ,wall-rueandrustybackfern Ceterach officinarum .Oneofthecommonestmosses
is Gymnostomum aerinosum , which forms dense cushions in the damp areas and may become encrusted
with calcite deposits. The liverwort Conocephalum conicum is also a very common species in cave en-
trances. These areas often accumulate deep layers of soil and organic material that can produce acid con-
ditions.