Ligumia recta
black sandshell

The black sandshell is found throughout the Mississippi drainage from Pennsylvania to Minnesota and south to Oklahoma and Alabama. It also occurs in the Alabama River and St. Lawrence River drainage. In Canada, it is found in the Canadian Interior basin in Lake Winnipeg and the Winnipeg and Red River systems.

In Michigan this species is found in the mainstem and/or lower stretches of rivers in the lower peninsula, generally from the Muskegon River and south, including the Detroit River. Ligumia recta has been recorded from the Menominee and Sturgeon Rivers in the upper peninsula. (Burch, 1975; van der Schalie, 1938)

The black sandshell is found in rivers, lakes, and large streams, usually in riffles or raceways with good current. Substrates it inhabits include sandy mud, firm sand, or gravel.

In the Huron River it was common in large and medium-sized river conditions with sand and gravel bottom in the current. Younger individuals were also found at one site on a fine sand-mud bottom in a backwater area. (Cummings and Mayer, 1992; van der Schalie, 1938; Watters, 1995)

The black sandshell is up to 25 cm (10 inches) long , and is elongate and quadrate in shape. The shell is usually fairly thick, heavy, somewhat inflated and cylindrical. The anterior end is rounded, the posterior end pointed in males, saber-shaped in females. The dorsal margin is straight and the ventral margin is straight to gently curved.

Umbos are low, being raised only slightly above the hinge line. Beaks are situated nearer to the anterior margin than the posterior margin. The beak sculpture has two to three indistinct, double-looped bars.

The periostracum (outer shell layer) is smooth, shiny, dark green or brown. Older specimens tend to be more black. The valves sometimes have visible green rays.

On the inner shell, the left valve has two pseudocardinal teeth, which are long, triangular, serrated and divergent. The two lateral teeth are straight, rough, thin and long. The right valve has one high, notched,triangular pseudocardinal tooth. Anterior to this tooth is occasionally a smaller (lamellar) tooth. The right lateral tooth is also straight, rough, thin and long.

The beak cavity is shallow. The nacre varies, from white, pink, and salmon, and occasionally is purple. At the posterior end it is iridescent.

In Michigan, this species can be confused with the spike. The spike is generally smaller and more compressed. The black sandshell also tends to be shiny and more distinctly rayed. (Cummings and Mayer, 1992; Oesch, 1984; Watters, 1995)

Fertilized eggs are brooded in the marsupia (water tubes) up to 11 months, where they develop into larvae, called glochidia. The glochidia are then released into the water where they must attach to the gill filaments and/or general body surface of the host fish. After attachment, epithelial tissue from the host fish grows over and encapsulates a glochidium, usually within a few hours. The glochidia then metamorphoses into a juvenile mussel within a few days or weeks. After metamorphosis, the juvenile is sloughed off as a free-living organism. Juveniles are found in the substrate where they develop into adults. (Arey, 1921; Lefevre and Curtis, 1910)

The age of mussels can be determined by looking at annual rings on the shell. However, no demographic data on this species has been recorded.

Mussels in general are rather sedentary, although they may move in response to changing water levels and conditions. Although not thoroughly documented, the mussels may vertically migrate to release glochidia and spawn. (Oesch, 1984)

The middle lobe of the mantle edge has most of a bivalve's sensory organs. Paired statocysts, which are fluid filled chambers with a solid granule or pellet (a statolity) are in the mussel's foot. The statocysts help the mussel with georeception, or orientation.

Mussels are heterothermic, and therefore are sensitive and responsive to temperature.

Unionids in general may have some form of chemical reception to recognize fish hosts. Mantle flaps in the lampsilines are modified to attract potential fish hosts. How the black sandshell attracts and/or recognizes a fish host is unknown.

Glochidia respond to touch, light and some chemical cues. In general, when touched or a fluid is introduced, they will respond by clamping shut. (Arey, 1921; Brusca and Brusca, 2003; Watters, 1995)

In general, unionids are filter feeders. The mussels use cilia to pump water into the incurrent siphon where food is caught in a mucus lining in the demibranchs. Particles are sorted by the labial palps and then directed to the mouth. Mussels have been cultured on algae, but they may also ingest bacteria, protozoans and other organic particles.

The parasitic glochidial stage absorbs blood and nutrients from hosts after attachment. Mantle cells within the glochidia feed off of the host’s tissue through phagocytocis. (Arey, 1921; Meglitsch and Schram, 1991; Watters, 1995)

Unionids in general are preyed upon by muskrats, raccoons, minks, otters, and some birds. Juveniles are probably also fed upon by freshwater drum, sheepshead, lake sturgeon, spotted suckers, redhorses, and pumpkinseeds.

Unionid mortality and reproduction is affected by unionicolid mites and monogenic trematodes feeding on gill and mantle tissue. Parasitic chironomid larvae may destroy up to half the mussel gill. (Cummings and Mayer, 1992; Watters, 1995)

Fish hosts are determined by looking at both lab metamorphosis and natural infestations. Looking at both is necessary, as lab transformations from glochidia to juvenile may occur, but the mussel may not actually infect a particular species in a natural situation. Natural infestations may also be found, but glochidia will attach to almost any fish, including those that are not suitable hosts. Lab transformations involve isolating one particular fish species and introducing glochidia either into the fish tank or directly inoculating the fish gills with glochidia. Tanks are monitored and if juveniles are later found the fish species is considered a suitable host.

Metamorphosis of glochidia and natural glochidial infestations of Ligumia recta have been observed for bluegill and white crappie.

In lab trials, glochidia have metamorphosed on several other fish, including the banded killifish, white perch, central stoneroller, redfin shiner, rosyface shiner, redbreast sunfish, green sunfish, longear sunfish, orangespotted sunfish, pumpkinseed, rock bass, largemouth bass, walleye and yellow perch. (Coker et al., 1921; Cummings and Watters, 2004; Hove, M.C., J.E. Kurth et al., 1998; Lefevre and Curtis, 1912; Steg and Neves, 1997; Watters et al., 1999; Young, 1911)

There are no significant negative impacts of mussels on humans.

Mussels are ecological indicators. Their presence in a water body usually indicates good water quality.

Ligumia recta is listed as Endangered in Vermont, Threatened in Illinois and Virginia, and Special Concern in Minnesota. The IUCN Red List considers this species Lower Risk, Nearly Threatened. (Hove, 2004)