The Carolina heelsplitter (Lasmigona decorata ) is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae.
It is named the "Carolina heelsplitter" because in life the sharp edge of the valves protrudes from the substrate and could cut the foot of someone walking on the river or stream bed.
This species is endemic to the United States and is found in only North Carolina and South Carolina.
This species current status is classified as "critically endangered". The IUCN Red List website states that to be considered critically endangered means that the species is facing an extremely high risk of becoming extinct in the wild in the immediate future.
The first recorded encounter with the Carolina heelsplitter was in 1852 by Isaac Lea. He described this new creature as Unio decoratus. The largest recorded specimen was about five inches long.
This freshwater mussel has a shell which is greenish-brown to dark brown on the outside. The inside of the shell usually has nacre that is pearly white or bluish-white, although the nacre can be pale orange in older specimens. The younger individuals tend to have faint black or greenish-brown rays on the outer surface of the shell.
This medium-sized mussel has well-developed, but thin, lateral teeth that are somewhat delicate. The Carolina heelsplitter also has two blade-like pseudocardinal teeth in the left valve, and one in the right valve.
With an “ovate, trapezoid-shaped, unsculptured shell“, the size of the largest Carolina heelsplitter currently is about 4.6 inches in length and 1.56 inches in width, with a height of 2.7 inches.
The reproductive cycle begins when the male Carolina heelsplitter releases its sperm into the stream. Soon afterwards the sperm is taken in by the females, a process which is called siphoning. The female's eggs, which will be carried in the females gills, are then fertilized. When the glochidia (larvae) are fully developed, the female mussel releases them into the water. The larvae must attach themselves quickly to a body part of their host fish, which is not harmed in the process. The host fish species for this mussel is still unknown.
Attached to the fish, the heelsplitters receive oxygen and other needs from the host for several weeks. When they have grown into fully developed juvenile mussels, they release themselves from the fish and settle into the stream or river.
A fish host is very important to all mussels, not only because it provides the young with food and oxygen, but also because it serves as a mode of transportation. The transportation of the mussels is key when attempting to create new populations in streams and river banks. Thus this creature can see the fresh waters and have more larvae.
