Recording schemes

The hypogean (subterranean) Crustacea recording scheme is a small scheme dealing with the subterranean macro-Crustacea found in the groundwater and aquatic cave habitats of the British Isles, including Ireland. The scheme only encompasses the larger Crustacea specifically evolved to exist in underground aquatic habitats (stygobites). Adaptations to the underground aquatic environment typically involve a lack of pigment (i.e. specimens are white in colour), a lack of eyes and over-development of antennae and legs. Most species are also very small and have a thin body shape for squeezing between small water-filled crevices in underground rock strata and water-logged gravels.

Specimens of the ubiquitous epigean (surface-dwelling) freshwater shrimp Gammarus pulex are often recorded in caves but are usually washed in from the surface, although some isolated stygophilic populations have been recorded. In Ireland a similar case exists with Gammarus duebeni celticus. Both of these species are not included in the scheme.

The scheme also does not cover the micro-Crustacea (Copepoda, Ostracoda, Cladocera etc.) Amongst the micro-crustaceans there are several species that have been recorded from cave and groundwater habitats but it is thought that the copepod Acanthocyclops sensitivus is the only true sygobitic copepod in Britain. Proudlove et. al. (2003) lists the various micro-Crustacea and discusses their distribution and hypogean status. This same publication also discusses the occurrence of Gammarus species underground.

The eleven larger stygobitic Crustacea recorded from Britain and Ireland and covered by the recording scheme are listed below.