Notes from underground

Karst regions occur around the world where carbonate rocks, primarily limestone and dolomite deposited on the beds of ancient seas, are dissolved by slightly acidic rainwater seeping into the ground. Over time this water can form vast subterranean drainage systems, changing the landscape by creating sinkholes and caves, some of the most intriguing natural regions in the world containing unique life-forms found nowhere else.

Southern Indiana is home to a major karst region- the south-central karst, formed in Mississippian rock (358.9 - 323.2 million years old) which includes some highly developed caves such as Binkley, near Corydon, which now has over 44 miles of passage mapped. Binkley is also believed to be the most biodiverse cave in the state, with 21 species of cave-restricted (troglobitic) organisms. Among these is the near-endemic millipede Scoterpes sollmani, the only member of its genus known in Indiana. Ice age bones have been found in this cave and others in the state, representing species such as the flat-nosed peccary (Platygonus compressus), a now-extinct relative of the Central and South American peccaries.

Another karst region exists in southeastern Indiana, less well-developed due to the thick sediments deposited by the Illinoian glaciation which occurred 191,000 to 130,000 years ago. These caves are formed in bedrock from the Silurian (443.8 - 419.2 million years ago) or Devonian (419.2 - 358.9 MYA). These caves are consistently shorter and less biodiverse than those in the south-central karst. Big Oaks contains over 30 known caves in this southeastern karst.

Although caves may seem inhospitable to life due to the lack of light, many small animals survive off the decaying matter washed in by streams or the feces of bats and raccoons. These organisms are classified based on their ecology: trogloxenes, which spend time in caves but leave to feed to reproduce; troglophiles, which can feed and reproduce in caves but are not restricted to them; troglobites, which are morphologically adapted and restricted to caves. The equivalent terms for aquatic organisms are sygoxenes, stygophiles, and stygobites.

Meta ovalis, a common troglophile. — *Meta ovalis*, a common troglophile.

Pseudanophthalmus, an eyeless, troglobitic predatory beetle with over 250 known species in eastern North America. Many are known from Southern Indiana, including species restricted to a single cave and still-undescribed species. — *Pseudanophthalmus*, an eyeless, troglobitic predatory beetle with over 250 known species in eastern North America. Many are known from Southern Indiana, including species restricted to a single cave and still-undescribed species.

Oronectes inermis, an eyeless, depigmented stygobitic crayfish found in Southern Indiana. — *Oronectes inermis*, an eyeless, depigmented stygobitic crayfish found in Southern Indiana.

A Ceuthophilus cave cricket, a common trogloxene. — A *Ceuthophilus* cave cricket, a common trogloxene.

Oxidus gracilis, and invasive exotic millipede in Indiana caves. — *Oxidus gracilis*, and invasive exotic millipede in Indiana caves.

The caves at Big Oaks, sitting on 50,000 acres of protected land, are biologically important. Three new species of copepod crustaceans have been described from type specimens collected at the Refuge: Diacyclops indianensis, D. salisae, and D. lewisi. A new species of spider, Oreonetides beattyi, was described after being found on the Refuge, though the holotype was collected elsewhere. Tricolored bats (Perimyotis subflavus), proposed for listing as a federally endangered species, have been found hibernating in the caves on the Refuge prior to the white-nose outbreak. We hope they are still here.