Over time, some cave- dwelling species adapt specifically for the cave
environment. Since caves are dark, there is little advantage for these
animals to exert energy on pigmentation or eye development; so evolution
of such species eliminates these unnecessary attributes. Such species are
known as troglobites. Unlike the troglophiles we've been discussing
so far, most troglobites would have a difficult time surviving outside
of the cave.
Troglobitic invertebrate species are not uncommon, but individual species usually aren't very widespread. The sightless cave crayfish pictured (Orconectes inermis inermis) is one example. Although abundant in one cave managed by the IKC, this species is listed as threatened in Indiana. Its population is closely monitored for any affects of human visitation.
Another
example of a threatened cave invertebrate is the brightly- colored beetle
Pseudanophthalmus shilohensis pictured at left. While beetles of very similar appearance
can be found in many Indiana caves, this particular species is known to
inhabit only three caves in Owen, Monroe and Lawrence Counties.
Beetle image courtesy of The Nature Conservancy of Indiana.