Troglobitic Cave Fauna
An Introduction to the Troglobitic Cave Fauna of the Woodville Karst Plain
by Brett Dodson
The subterranean systems of the Woodville Karst Plain (WKP) are covered by a ceiling of limestone and come in contact with the atmosphere by way of springs, and sinks, pools of permanent water resulting from partial structural collapse of underground systems. Unlike conventional open water systems, the main environmental parameters dominating these aquatic caves are the absence of light, relatively constant temperatures, low levels of dissolved oxygen, and a limited primary food supply.
These caves are host to a select group of animals that live out their entire life cycles in this perpetual darkness and are easily recognized by certain anatomical adaptations such as eyes ranging from small to non-existent, lack of pigmentation, and appendages that have undergone considerable elongation. Although it is not uncommon to see other animals within these systems such as fishes, frogs, turtles, alligators and snakes, they are not obliged to remain, they can and usually do spend all or part of their lives outside. So how do we recognize true cave animals from the visitors?
First, one must differentiate between zonation and stratification when looking at the residence of cave animals. Stratification results from the gathering of individual species in a localized area such as the floor, ceiling, or walls. When observing animals within an underwater cave one may also be inclined to add mid-water column to the list. Zonation on the other hand is derived by the preference individuals show toward a given area of the cave. Three areas are recognized when referring to zonation and are based on light availability, these are; the entrance zone which receives direct sunlight, the twilight zone or area of ambient light, and the dark zone which receives no light at all and is an area of total darkness. For example, crayfish may occupy the same strata, preferring the floor, but depending on species they may inhabit either the entrance or dark zone of the cave.
There are three terms commonly used to delineate the degree to which a species is dependent on a particular zone within a subterranean habitat, wet or dry. Troglobites, from the Greek troglos meaning cave and bios meaning life, are animals found exclusively in caves and are so adapted that they are unable to exist outside of the dark zone. A list of these types of animals would include the blind cave fishes and some crayfish. It is believed that all troglobites have evolved from troglophiles. Troglophiles, from troglos plus phileo, meaning to love, are animals frequently found in caves, reproduce there and complete their life cycles there, but are capable of surviving in other non-cave environments which closely mimic a hypogean (underground) habitat. Earthworms are a good example, as are select species of salamanders and crustaceans. Trogloxenes , from troglos and xenos, meaning guest, are animals often encountered in caves but never complete their whole life cycle underground. Examples of such would include bats, catfishes, eels, and even marine species such as corals, sponges, and lobsters.
Of the known troglobitic faunas of the Florida and South Georgia area, 27 are invertebrates (animals lacking backbones) and one vertebrate (an animal possessing a backbone). Furthermore, except for the existence of one insect and one spider, all of the rest are aquatic species (Franz et. al., 1994). The WKP is a limestone platform extending below the Cody Scarp, along southern Leon and Jefferson counties, across Wakulla county and to the Gulf of Mexico (Franz et. al., 1994). The unconfined aquifers of the WKP, possess some of the largest and deepest caves in the world. This plain is home to miles of underwater passage but is known to play host to only five of the 27 reported species of troglobites in the Florida and South Georgia fauna (Franz et. al., 1994). In addition, of the 267 caves in which biological materials have been collected (a mere 42% of those listed by the Florida Speleological Society in 1994), only 11 are located in Leon County and eight in Wakulla (Franz et. al., 1994). Finally, any determination of species range within the WKP is speculative at best. For example, the SWIMMING FLORIDA CAVE ISOPOD, Remasellus parvus, is known from only one cave in Wakulla County and none in Leon county, while the WOODVILLE KARST CAVE CRAYFISH, Procambarus orcinus, is reported from eight caves in Leon County and six in Wakulla (Franz et. al., 1994). These observations lend themselves to a limited understanding of the relationships between the faunas and their extended ranges.
It is evident there is allot of work to be done to advance our present knowledge and understanding of the Florida troglobitic cave faunas. With the advent of new technologies, while adhering to a strict set of standards, members of Woodville Karst Plain Project (WKPP) have refined their diving techniques to allow regular exploration of the plain to considerable depths and penetration distances with an outstanding record of safety. It is the adoption and implementation of these principals by cave biologists that will allow the advancement of our present knowledge and understanding of the WKP cave biology, subsequently the Florida troglobitic cave faunas, and no doubt result in the discovery of new and unknown troglobitic species.
NOTE: For a complete overview on the Florida and South Georgia Cave Faunas please see Franz et. al. in Brimleyana, 20: 1-109, June 1994.
WOODVILLE KARST PLAIN TROGLOBITIC SUMMARY
The five species as reported from the WKP and the sites they are identified from are as follows (Franz et. al., 1994);
SWIMMING FLORIDA CAVE ISOPOD
Jefferson County: none
Leon County: none
Wakulla County: Split Sink
FLORIDA CAVE AMPHIPOD
Jefferson County: none
Leon County: Little Dismal Sink
Wakulla County: Emerald Sink, McBride Slough, River Sinks, Sally Ward Spring, Shepard Blue Springs
HOBBS CAVE AMPHIPOD
Jefferson County: none
Leon County: Sullivans Tunnel
Wakulla County: McBride Slough, River Sinks, Sally Ward Spring, Shepard Blue Springs
BIG BLUE SPRINGS CAVE CRAYFISH
Jefferson County: Big Blue Spring
Leon County: collected from a well 7.5 km east of Tallahassee
Wakulla County: Shepard Blue Spring and a questionable sighting is also recorded from Wakulla Spring
WOODVILLE KARST CAVE CRAYFISH
Jefferson County: none
Leon County: Bird Sink Swallet, Clay Sink, Culleys Cave, Falcons Nest, Gopher Sink, Little Dismal Sink, Osgood Sink, Sullivans Tunnel
Wakulla County: Emerald Sink, Indian Springs, McBride Spring, Sally Ward Spring, River Sinks, Wakulla Springs