Rare Species Guide

  Synonyms

Lampsilis higginsi, Lampsilis higginsii

  Basis for Listing

The Higgins eye was the first freshwater mussel to receive federal protection, which took effect in 1972. Degradation of the Mississippi River in the form of navigation improvements and pollution severely restricted the range of this species. Today, the lower St. Croix River has one of the largest remaining Higgins eye populations throughout the species' range. It has been extirpated from the Minnesota River, and is rare in the Mississippi River. The Higgins eye was afforded state endangered status in 1984.

  Description

The shell of the Higgens eye is up to 15 cm (6 in.) long, and is inflated, with thick valves and a beak that is pointed forward. The outside of the shell is yellow, greenish, reddish, or brown, often with green rays. This species is sexually dimorphic, with the females having a shell that is rounded and truncate posteriorly, while the males have a shell that is oval. The beak sculpture in both sexes is obscure, and the pseudocardinal and lateral teeth are well developed. The inside of the shell is white, and sometimes pink or salmon in the beak cavity. The Higgens eye resembles the hickorynut (Obovaria olivaria), mucket (Actinonaias ligamentina), and plain pocketbook (Lampsilis cardium) mussels.

  Habitat

The Higgins eye occurs only in the Mississippi River and the lower portion of some of its large tributaries (Havlik 1980). It occupies stable substrates that vary from sand to boulders, but not firmly packed clay, flocculent silt, organic material, bedrock, concrete or unstable sand. Water velocities should be less than 1 m/s (3.3 ft./s) during periods of low discharge. The species is usually found in mussel beds that contain at least 15 other species at densities greater than 0.01 individual/m&sup2 (U.S. Fish and Wildlife Service 2004).

  Biology / Life History

Mussels are long-lived animals. Members of many species may live for several decades and in some instances a century or more. They spend most of their lives buried in the bottom sediments of permanent water bodies, and often live in multi-species communities called mussel beds (Sietman 2003).

Mussels are primarily sedentary, but they can move around with the use of their foot, which is a hatchet shaped muscle that can be extended out between the valves. A mussel will burrow its foot into the sediment and then contract it to pull itself slowly along the bottom of its aquatic habitat (Sietman 2003).

Mussels eat by filtering out bacteria, protozoans, algae, and other organic matter out of the water. They draw water into their body through their incurrent siphon, remove food and oxygen with their gills, and expel the water through their excurrent siphon. Food particles are carried to the mussel's mouth by tiny hairlike cilia located on the gills. Waste is expelled through the excurrent siphon (Sietman 2003).

Mussels have a complex and distinctive reproductive cycle. Males release sperm into the water, which are drawn in by females through their incurrent siphon. Fertilized eggs are brooded in the female's gills, where they develop into tiny larvae called glochidia. Baker (1928) reports that the Higgins eye is bradytictic, with females brooding their young long-term before they are released as glochidia . They are gravid in May and September. Once the glochidia are expelled from the female's gills, they attach to fish gills or fins by clamping onto them with their valves. The glochidia live as parasites on the host fish until they develop into juvenile mussels, at which point they detach from the fish and fall to the streambed as free-living mussels. The bluegill (Lepomis macrochirus), freshwater drum (Aplodinotus grunniens), green sunfish (Lepomis cyanellus), largemouth bass (Micropterus salmoides), northern pike (Esox lucius), sauger (Sander canadense), smallmouth bass (Micropterus dolomieu), walleye (Sander vitreus), and yellow perch (Perca flavescens) have been reported to be viable host fish species for the glochidia of the Higgins eye mussel (Waller and Holland-Bartels 1988; Watters 1994).

  Conservation / Management

The Higgins eye is rare or extirpated throughout most of its former range. The viability of remaining populations in the Mississippi River is jeopardized by the continuing decline in habitat conditions associated with management of the river as a navigation canal; with non-point and point source water and sediment pollution; and by the infestation of non-native zebra mussels (Dreissena polymorpha) in the Mississippi River and its tributaries. Zebra mussels can attach themselves in large numbers to the shells of native mussels, eventually causing death by suffocation.

  Conservation Efforts in Minnesota

In the early 1980s, a recovery team consisting of biologists from the U.S. Fish and Wildlife Service, Minnesota and Wisconsin DNRs, the U.S. Geological Survey, U.S. Army corps of Engineers, University of Minnesota, Macalaster College, and Western Wisconsin Technical College drafted the first Higgins Eye recovery plan. The plan identified actions necessary for the recovery of this rare mussel species (U. S. Fish and Wildlife Service 1983). The recovery team subsequently reconvened in the early 2000s to review all Higgins eye research conducted since 1980, and to review the status of the species. A revised recovery plan, taking into account new information and threats, such as the infestation of zebra mussels, was completed in 2004 (U. S. Fish and Wildlife Service 2004).

An intensive multi-state program is underway to propagate juvenile Higgins eye and reintroduce them into areas where the species occurred historically, with the hope of establishing new viable populations. As of 2004, 2 new populations of juveniles had been reintroduced into suitable habitat in Pools 3 and 4 of the Mississippi River. In addition, a population of adult Higgins eye were salvaged from a severely zebra mussel infested area of the Mississippi River and relocated to an area of the Mississippi River near the Twin Cities, where native mussels are recovering.

  References and Additional Information

Baker, F. C. 1928. The fresh water mollusca of Wisconsin: part II: Pelecypoda. Wisconsin Geological and Natural History Survey Bulletin No. 70, Part II. University of Wisconsin, Madison. 495 pp.

Dawley, C. 1947. Distribution of aquatic mollusks in Minnesota. American Midland Naturalist 38:671-697.

Havlik, M. E. 1980. The historic and present distribution of the endangered naiad mollusk Lamsilis higginsi. The Bulletin of the American Malacological Union 1980:19-22.

Kelner, D., M. Davis. 2002. Final report: mussel (Bivalvia:Unionidae) survey of the Mississippi National River and Recreation Area Corridor, 2000-01. Final report submitted by the Minnesota Department of Natural Resources. 44 pp. + appendices.

Sietman, B. E. 2003. Field guide to the freshwater mussels of Minnesota. Minnesota Department of Natural Resources, St. Paul, Minnesota. 144 pp.

United States Fish and Wildlife Service. 1983. Higgins Eye mussel recovery plan. United States Fish and Wildlife Service, Ft. Snelling, Minnesota. 98 pp.

United States Fish and Wildlife Service. 2004. Higgins Eye Pearlymussel (Lampsilis higginsii) Recovery Plan: First Revision. United States Fish and Wildlife Service, Ft. Snelling, Minnesota. 126 pp.

van der Schalie, H., and A. van der Schalie. 1950. The mussels of the Mississippi River. American Midland Naturalist 44:448-464.

Waller, D. L., and L. E. Holland-Bartels. 1988. Fish hosts for glochidia of the endangered freshwater mussel Lampsilis higginsi Lea (Bivalvia: Unionidae). Malacological Review 21:119-122.

Watters, G. T. 1994. An annotated bibliography of the reproduction and propagation of the Unionoidea (Primarily of North America). Ohio Biological Survey Miscellaneous Contributions No. 1, Columbus, Ohio. 158 pp.