Crustaceans and Mollusks

 

A freshwater mussel opening its shell.

NPS Photo

Crustacean and mollusk species in the park provide essential ecosystem services that are integral to the health of freshwater environments. Of these aquatic species, some common crustaceans include crayfish and shrimp, and some common mollusks include mussels, clams, and snails.

 

The tiny Kentucky cave shrimp is almost completely translucent.

USFWS Photo

Crustaceans

The many species of crustaceans that call Mammoth Cave National Park their home are truly one of a kind. The Kentucky cave shrimp, and the Mammoth Cave crayfish can be found inhabiting the watery depths of the cave system. The most widespread crayfish species in Kentucky (Cambarus tenebrosus) calls the Green River its home.

Kentucky cave shrimp Palaemonias ganteri

The endangered Kentucky cave shrimp is found nowhere on Earth except for in the large, base level cave streams that flow through Mammoth Cave. They prefer streams with a slow flow, plenty of organic material, and with coarse, sandy bottoms. These tiny crustaceans will eat algal cells, fungi, and protozoans that are washed in by floodwaters. They are troglobites, spending their entire life cycle in the cave.

Cave shrimp are specially adapted for this subterranean life, as they have no eyes, and are able to use their two pairs of antennules to taste, touch, and smell their food. They also have no pigment in their shell, making them transparent and incredibly hard to spot. They grow to about 1.25 inches long and are estimated to live for about 10-15 years.

Learn more about the endangered status of the Kentucky cave shrimp and continued efforts to conserve this rare species.

 

A cave crayfish (Orconectes pellucidus) moves through a shallow pool of water in a cave river passage.

NPS Photo/ Anya Gupta

Mammoth Cave crayfish Orconectes pellucidus

This crayfish is a troglophile, meaning they prefer to spend their time in the cave but will travel aboveground if necessary. They are able to move over land to different pools and streams in order to find food, mates, or to avoid predators. Normally found in cave streams, these crayfish typically hide under rocks or in sediment and can be seen scurrying across the rocky and sandy bottoms of stream beds. They have no eyes and no pigmentation, which is an evolutionary adaptation that allows them to conserve energy and survive in an environment with total darkness. They depend on the surface water runoff for food and nutrients, while bat guano and cricket droppings also provide sustenance for subterranean life. They lay eggs and are sensitive to environmental changes on the surface, like pollution, which may alter groundwater quality.

Freshwater crayfish Cambarus tenebrosus

The most widespread crayfish species in Kentucky, they live in areas with permanent surface streams, preferring muddy river bottoms They can grow to be about 2-6 inches, and have a largely plant-based diet. They are essential to maintaining freshwater food webs and water quality by eating algae.

 

Mollusks

Mostly buried deep in the mud or hidden amongst the rocks, mussels, a type of mollusk, are a rare sight here at Mammoth Cave National Park. As filter feeding powerhouses, they constantly filter sediments and nutrients from the water, help sequester heavy metals, and remove pharmaceutical waste and bacteria like E. coli. This helps to keep the visibility of the water high, making it easier for other organisms to find food. Mussel beds also help create habitat for other species, while empty mussel shells provide shelter for fish, snails, and crayfish.

 

Historical Importance of Freshwater Mussels 

The prehistoric people who lived in the region 3000-5000 years ago consumed mussels from the Green River and utilized their shells as tools. Mussel shells and fragments dating back centuries have been found within the depths of the Mammoth Cave system. These mussel shells may have been used to scrape off minerals from the cave walls.

 

A park scientist examines an endangered sheepnose mussel (Plethobasus cyphyus).

NPS Photo

Sheepnose mussel Plethobasus cyphyus

These mussels can grow to be about 5 inches in length, they are usually found in the shallows of wide rivers such as the Mississippi River or the Ohio River. Like many freshwater mussels, sheepnose mussels have a complex reproduction cycle in which at the larvae stage they must attach to a fish’s gills or fins. Within a few weeks the larvae become juveniles and detach to sink to the river bottom, having used the fish as a host to transport them up or downstream. For this reason, these federally endangered mussels are especially vulnerable to the effects of dams.

Rayed bean mussel Villosa fabalis

Previously found in the area, the rayed bean mussel is now locally extinct in Virginia, Illinois, and Kentucky. These small mussels are often brown or a yellowish-green in color and grow to around 1.5 inches in length. They usually prefer smaller streams and headwaters and are still present in several Midwest and North-Eastern states as well as Ontario, Canada. Rayed bean mussels have been successfully reintroduced to streams in Tennessee and West Virginia.

 

 

A snail (Mesodon sp.) clinging to the cave wall inside of the Frozen Niagara entrance of Mammoth Cave.

NPS Photo/ Anya Gupta

Snails

Snails are gastropods, which literally translates to “stomach foot”. Thousands of gastropod shells are preserved in the limestone that contains Mammoth Cave, dating back to the Ordovician Era over 480 million years ago, when ancient aquatic snails inhabited the region.

Today there are many species if snails present in the park, some of those species are specially adapted to survive in a subterranean environment. These species prefer wet or moist areas of caves and their diet typically consists of cricket guano and very fine organic matter and bacteria. Of these cave-dwelling snails, three species were first discovered and described from springs and caves at Mammoth Cave National Park.

With copious amounts of cricket guano and moisture, the Frozen Niagara entrance of the Mammoth Cave is for a common place to find cave snails.

 

Park Species List

Explore a sortable database of species found in the park.

NPSpecies