FLORIDA'S AQUATIC TROGLOBITES

Florida lies over a limestone basement riddled with water-filled cavities. The voids in the rocks range from miniscule cracks to rooms that could swallow cathedrals. Some springs and sinkholes in the state offer glimpses into this world endless night. With no green plants beyond the twilight zones (areas where natural light from the surface enables human vision) in Florida's caves, you might expect them to be biological deserts. Yet a few amazing aquatic creatures, little known to humans, thrive there.

Biologists place cave animals into three distinct groups know as trogloxenes, troglophiles and troglobites. Most of us only associate trogloxenes (or cave visitors) with caves. Bats and extinct fauna such as the cave bear usually come to mind. The underwater denizens in this group include some salamanders, many crayfishes and cave divers. Pirate perch, sunfishes and minnows also haunt the twilight zones. While these guests spend much time in dark grottos, none live their entire lives there. They must return to the surface to feed or breed.

Troglophiles (or cave lovers) can reside either in caves or outside. Nothing limits them to living underground. Although no true cave fishes exist in Florida, the yellow bullhead, American eel and redeye or spring chub are troglophiles that inhabit the state's underwater caves.

During the 1987 Wakulla Springs Project, divers saw all three fishes as far back as 3,500 feet and as deep as 300 feet. After having dived in Florida springs and sinks for more than 20 years, catfishes and eels seem to me to be the most obvious occupants in caverns.

The yellow bullhead, or yellow catfish, probes far underground. These scavengers often feed on mud, rotting leaves, pieces of limestone, springtails (tiny wingless insects) and crayfishes. Reaching just over a foot long, with a squat body and square tail, they often develop abnormalities such as reduced or deformed fins. Of the three troglophiles noted here, yellow bullheads might be the best suited for subterranean life because of their small eyes and elaborate chemosensory systems.

The American eel may be the most intriguing troglophile. Only females live in freshwater, but they must return to the Sargasso Sea in the North Atlantic to spawn. Eels could be classed as trogloxenes since they don't breed in caves. The females, however, stay in freshwater from 7 to 20 years before returning to the ocean. These snake-like fishes range in length from one to four feet. Larval insects comprise about 90 percent of their diet. A cave diver in central Florida, though, claimed that an eel nipped his finger while he decompressed. Several years ago, one almost knocked off my mask when I brushed it with the beam of my light. Though Americans do not eat eels, they're considered a delicacy in much of Europe and Asia. A few years ago elvers (young eels) sold for between $400 and 500 a pound in Japan.

Redeye chubs, too, make their way into isolated sinkholes and caves far from surface openings. Also common in and near spring vents, these diminutive fishes rarely grow longer than two inches. They eat insects, crustaceans and smaller fishes.

Troglobites (cave life) comprise the final group of cave animals. The eminent French speleologists Norbert Casteret dubbed them "pariahs of creation." They are true cave dwellers who cannot survive on the surface. Sometimes "trogs" may accidently be flushed out of caves by local downpurs.

Many troglobites share traits that allow them to seach for food and mates in the seasonless reaches of caves. Their eyes are either poorly developed or lacking altogether. They have little or no pigment--often appearing sickly white. Cave animals do not need to see, to be camouflaged or protected from the sun. They usually grow longer, slimmer antennas and other parts than surface fauna so that they can better detect enemies or seek prey through odors, chemical changes and movements. Their antennas may even hold special hair-like growths that act as feelers.

Troglobites live much longer than their topside counterparts because of lower food intake and a slower pace of life. They excel in conserving energy. Some retain larval traits well into adulthood. Lastly, they lay fewer and larger eggs than their outside kin. These traits probably arose because the creatures had to adapt to a limited and erratic food supply.

In 1961, only ten species of aquatic troglobites were known in Floridaa. According to the Florida Natural Areas Inventory, 24 species are now known in the state, six of which are listed as threatened or species of special concern. Crustaceans make up most of this group. They include blind cave crayfishes (3 general and 15 species), a cave shrimp, isopods (2 genera and 4 species) and amphipods (2 species). A salamander and cave snail comprise the rest of the troglobitic clan. Most of these animals exist in a few sites in Florida and nowhere else. Each year explorerers venture into virgin passages leading to the discovery of new species.

Troglobites most often recognized by Florida divers are the blind cave crayfishes. Divers have seen them as far back as 4,220 feet from the cave mouth and at depths of 310 feet in Wakulla Springs. Noted for their long pincers, the crayfishes resemble dwarf Maine lobsters. Horton Hobbs, a biologist who studies them, thinks they represent old relicts. He belives they probably orginated from surface ancestors more than a millon years ago. With 15 know species, the blind cave crayfishes account for over half Florida's aquatic troglobites. Crayfishes seem much more prevalent near sinkhole openings where food periodiclally washes in as opposed to spring outputs. Flatworms, salamanders, amphipods, isopods and copepods make up their diet.

One aquatic troglobite, a cave shrimp, exists only in Squirrel Chimney, a sinkhole 11 miles west of Gainesville. Almost colorless and translucent, it grows to about 1.5 inches. According to Richard Franz, a biologist with the Florida Musuem of Natural History, "We know nothing about this animal. We know nothing about its distribution. We know nothing about its biology. The only thing we know is it occurs at Squirrel Chimney." We also know that other varieties of cave shrimp living farther north feed on the bottom. They screen silt, which harbors protozoans and other microbes, through their mouths.

Cave amphipods form an order of vertically flattened creatures shaped like giant fleas. They range from 3/16 to 7/16 inches long. These small crustaceans have long legs, some of which point backward and flex against the body. They either swim in the water column or crawl around on the bottom. Amphipods can walk, jump, swim and scull about on one side. Sometimes they scoot through the water by arching their backs. They eat protozoans, rotifers, bacteria and other organic matter in the silt. I saw my first cave amphipod in a sink near Woodville, Florida, only after many years of diving.

Cave isopods, tiny crustaceans less than 1/4 inch long, are realted to the roly-poly or sow bugs that live under logs in terrestrial habitats. They look somewhat like leveled rowboats Isopods prefer the safety of ceilings and floors as opposed to teasing predators in the water column. Cave divers often call them snowball or kamikaze shrimp because of their sudden free falls. They eat the same foods as amphipods.

Blue Springs Cave near Econfina Creek in the panhandle holds the state's only known cave snails. This cave wends through a series of small rooms and tunnels. The snails there feed on wood brought into the labyrinth by beavers. Like most other troglobites, they are colorless and lack eyes. The snails bear the name of Richard Franz whom discovered them while searching for unknown cave fauna in Florida.

The Georgia blind salamnder, the only vertebrate troglobite, inhaits several caves near Marianna and in nearby southwest Georgia. The small amphibian grows from one to two inches long. First described by Dr. Archie Carr in 1939, its sunken head houses minute dark eye spots buried under the skin. The creature propels itself with a laterally flattened tail, shaped like a fin. In partially submerged grottos, the salamander sometimes climbs out of the water. It feeds on troglobitic crustaceans. Blind cave crayfishes, eels and other salamanders.

Sporadic floods prevent aquatic caves from being lifeless. While green plants can't live in caves, bacteria and fungi flourish if organic matter from the surfvace such as wood, humus, feces and dead bodies reaches the underworld by way of sinks and swallow holes. Various iron and sulphur bacteria even make organic matter from non-living materials. Bacteria are eaten by protozoans and rotifers, who supply meals for trogs such as amphipods and isopods. Blind cave crayfishes, then, prey upon them. Finally, troglophilic fishes as the yellow bullhead sit atop the food chain in aquatic caves.

Some people might wonder, why be concerned with a few tiny lackluster animals that they'll probably never see? For starters, the state's many sinkholes and chimneys, some of which have been open a million or more years, have allowed animals to reach underground sanctuaries. Many scientists think that caves served as refuges for ancestors of troglobites during the dramatic climatic shifts of the Pleistocene or Ice Age (2,000,000 to 10,000 years ago).Thus, troglobites inhabiting these isolated, simple niches furnish us with natural labs in which to study evolution.

The specialized fauna living in underwater caaves also can be used to gauge the environmental health of the state's massive limestone aquifers. These aquifers hold about 90 percent of our potable water. Waste and storm water runoff as well as agricultural and industrial contaminants may seep into sponge-like rocks that house the aquifers. Unfortunately, tainted wsater does not magically cleanse itself after vanishing beneath the earth. It sometimes shows up in unexpected locales such as springs or wells. In some areas, water travels over a half mile underground in one day. Even slight changes in temperature, water quality or nutrient levels can annihilate the small populations of fragile creatures living in our aquifers. If the troglobites go, so too may our water supply.

After a recent dive in a sinkhole called Falcon's Nest in southeastern Leon County. I even began to wonder if divers might unknowlingly be harming creatures living in our aquifers. As my buddy and I slid down through a samll slot and entered a gigantic room, trogs began raining from the ceiling. Did our bubbles cause undue stress on the animals' limited reserves by prying them from the roof? I've also noticed that well-known dive sites seem to have fewer troglobites than more remote places.

Much work needs to be done to learn more about aquatic cave communities and how humans are affecting them. Unfortunately, troglobites usually get little, if any, mention in the popular press. It is unlikely they will ever grace license plates that would fund studies to conserve them. Still, these inconspicuous creatures must be accounted for if we are to protect our groundwwater--one of Florida's most vital natural resources.

FLORIDA'S AQUATIC TROGLOBITES

AMPHIBIA

Haideotriton wallacei--Georgia Blind Salamander (SSC)

AMPHIPODS

Crangonyx grandimanus--Florida Cave Amphipod (C2)

Crangonyx hobbsi--Hobb's Cave amphipod (C2)

DECAPODS

Cambarus cryptodytes--Apalachicola Cave Crayfish

Palaeomonetes cummingi--Squirrel Chimney Cave Shrimp (T)

Procambarus acherontis--Orlando Cave Crayfish (C2)

Procambarus delicatus--Big Cheeked Cave Crayfish

Procambarus erythrops--Red-eyed Cave Crayfish (SSC)

Procambarus franzi--Orange Lake Cave Crayfish

Procambarus hortsi--Big Blue Springs Cave Crayfish

Procambarus leitheuseri--Coastal Lowlands Cave Crayfish

Procambarus lucifugus lucifugus--Withlacoochee Light Fleeing Cave

Crayfish

Procambarus lucifugus alachua--Light Fleeing Cave Crayfish

Procambarus milleri--Miami Cave Crayfish

Procambarus morrisi--Devil's Sink Cave Crayfish

Procambarus orcinus--Woodville Karst Cave Crayfish

Procambarus pallidus--Pallid Cave Crayfish

Procambarus attiguus--Silver Glen Springs Cave Crayfish

Troglocambarus maclanei--Norther Spider Cave Crayfish

Troglocambarus baveri--Apopka Cave Crayfish

GASTROPODS

Dasyscias franzi--Shaggy Ghostsnail

ISOPODS

Caecidotea hobbsi--Hobb's Cave Isopod

Caecidotea sp. 1--Rock Springs Cave Isopod

Caecidotea sp. 2--Econfina Blue Springs Cave Isopod

Remasellus parvus--Swimming Florida Cave Isopod

C2 = Candidate Species, Category 2. Taxa for which information held by USFWS indicates that listing the species as endangered or threatened may be warranted, but lack enough conclusive data to support the rules at this time

SSC = Species of Special Concern

T = Threatened

AQUATIC TROGLOPHILES NOTED IN ARTCLE

FISHES

Ameiurus (formerly Ictalurus) natalis--Yellow Bullhead

Anguilla rostrata--American Eel

Apherdoderus sayanus--Pirate Perch

Notropis harperi--Redeye or Spring Chub

Florida's Aquatic Cave Animals