Wavyrayed lampmussel (Lampsilis fasciola)

Wavy-rayed lampmussel
IUCN Red List species status – Least Concern LEAST

Top facts

  • The wavyrayed lampmussel is named for the wavy green rays seen on the outer surface of its shell.
  • Wavyrayed lampmussels are good indicators of healthy ecosystems as they are particularly sensitive to pollution.
  • The wavyrayed lampmussel is threatened by the introduced zebra mussel.
  • Like all mussels, wavyrayed lampmussels are filter feeders and they are capable of filtering up to 40 litres of water a day.
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Wavyrayed lampmussel fact file

Wavyrayed lampmussel description

GenusLampsilis (1)

The wavyrayed lampmussel (Lampsilis fasciola)is a medium sized freshwater mussel around of 75-100 millimetres in length (2) (3) (4) (5). The rounded shell is circular among males and oval-shaped and inflated in appearance among females (2) (3). The outside of the shell is shiny and yellow to yellow-green in colour, with many thin, green, wavy rays that vary in width (2) (4) (6) (7). The inside of the shell is white, sometimes with a blue tint, and can be iridescent towards the posterior end of the shell (2) (5) (6). There are two triangular-shaped teeth in each half of the shell, found at the front edge of the hinge (4) (6).

Unio multiradiatus.
Shell length: 75-100 mm (2)

Wavyrayed lampmussel biology

The wavyrayed lampmussel is a long-term brooder (2) (3). Spawning takes places in the autumn when the male mussels release sperm into the water column from where females siphon it to fertilise eggs (2) (5) (6). Mature glochidia (larval stage of the mussel) are then released by the females the following summer (2) (3) (5) (6). These glochidia are parasitic, and must attach to the gills or fins of an appropriate host fish in order to gain the appropriate nutrients to complete their development (2) (3) (6) (8).The parasitic glochidia cause no damage to the two known host fish species, the smallmouth bass (Micropterus dolomieuI) and the largemouth bass (Micropterus salmoides) (6). In order to maximise the chances of the glochidia attaching to a host fish successfully, the female wavyrayed lampmussel lures fish close to her using a mantle flap that mimics small fish such as minnows before releasing them (2) (3) (5) (6) (8).

Once the glochidia have developed into juvenile mussels on the host fish, they drop off the host into a suitable sandy or gravel substrate (2) (5). They are typically sessile throughout their adult life, usually partially buried into the substrate (2). The wavyrayed lampmussel is a filter feeder (2), feeding on suspended organic particles in the water (5).  Water is brought into its shell and over its gills, where food particles are extracted (2). In this way, an adult wavyrayed lampmussel can filter up to 40 litres of water a day (6).

Individuals are known to live for more than 10 years, but are not thought to live more than 20 years (3) (6) (8).


Wavyrayed lampmussel range

Populations of the wavyrayed lampmussel are declining, but it has historically been found in the Great Lakes region (2) (6) (8). Its range has been known to extend from Ontario south to Alabama, and from New York west to Illinois where it can still be found in disjunct populations (5).


Wavyrayed lampmussel habitat

The wavyrayed lampmussel is usually found in small or medium sized streams in shallow areas with a good, steady current. It prefers clean gravel or sand substrate (3) (5) (6) (7).


Wavyrayed lampmussel status

The wavy-rayed lampmussel is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern


Wavyrayed lampmussel threats

The most significant threat facing the remaining populations of the wavyrayed lampmussel is water pollution (2) (3) (6) (7) (8). This species is very sensitive to water quality, and is therefore one of the first organisms to disappear from a polluted aquatic ecosystem (6). They are also significantly threatened by the introduced zebra mussel (2) (6) (7) (8). Zebra mussels attach themselves to local mussel species, such as the wavyrayed lampmussel, and directly inhibit feeding and breeding (6) (7). The introduction of zebra mussels is thought to be the primary cause for the loss and decline of many lake populations of wavyrayed lampmussels (3) (8).

Juvenile wavyrayed lampmussels are eaten by predators such as worms and crustaceans (5). As mature mussels, they are predated upon primarily by muskrats (Ondatra zibethicus) (3) (5). Due to their parasitic lifestyle, threats facing the wavyrayed lampmussels host fish must be considered as threats to the mussels as well (7).


Wavyrayed lampmussel conservation

Conservation efforts appear to have led to an increase in some populations of the wavyrayed lampmussel (3) (6). In Canada, their status was down-listed from endangered to a species of special concern in 2010, thanks to increasing numbers (6). However, this is not the case everywhere, and numbers appear to be in decline particularly in the northern part of its range (7) (8). It is considered an endangered species in Illinois and a species of special concern in Indiana and Michigan (4).

The wavyrayed lampmussel is protected under the Species at Risk Act (SARA) in Canada, as well as the federal Fisheries Act, which offers shellfish the same protection as fin fish (3).


Find out more

Find out more about the wavyrayed lampmussel at the Illinois Natural History Survey -



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Diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
Describes an organism that derives its food from, and lives in or on, another living organism at the host’s expense.
Situated behind or at the rear.
Permanently attached; not freely moving.
The production or depositing of eggs in water.


  1. IUCN Red List (January, 2014)
  2. University of Georgia: Museum of Natural History (January, 2014)
  3. COSEWIC (2010) COSEWIC assessment and status report on the Wavy-rayed Lampmussel (Lampsilis fasciola) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa.
  4. Illinois Natural History Survey (January, 2014)
  5. Michigan Natural Features Inventory (2004) Species Abstract: Wavyrayed lampmussel
  6. Fisheries and Oceans Canada (January, 2014)
  7. Ontario Freshwater Mussel Recovery Team. Recovery Strategy for the Wavyrayed Lampmussel (Lampsilis fasciola) in Ontario (January, 2014)
  8. Royal Ontario Museum (January, 2014)

Image credit

Wavy-rayed lampmussel  
Wavy-rayed lampmussel

© Corey Raimond

Corey Raimond


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