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MOLLUSCS - INFO

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The Rayed Bean (endangered) is a very small freshwater mussel is elliptical in shape, and has crowded wavy green rays. Its shell measures up to 38 mm long, 19 mm high and 13 mm wide. The nacre inside the shell is silvery white and iridescent. Females tend to be more inflated and more broadly rounded posteriorly than males. Habitat :The Rayed Bean prefers the headwaters and smaller tributaries of river systems, where it is found deeply buried in sand or gravel, in or near riffle areas. It is occasionally reported from shallow water areas of lakes and large rivers. The historical distribution of the species in Canada falls within a region that is heavily impacted by agriculture and urban development. Biology :The female mussels brood their young from the egg to the larval stage in their gills. They hold the larvae (glochidia) over winter and release them in the spring. Once expelled into the water, the glochidia must immediately attach to an appropriate fish host in order to complete their metamorphosis. The only known fish host of the Rayed Bean is the Tippecanoe Darter (Etheostoma tippecanoe), which is found in the U.S. but not in Canada. The host fish in Canadian waters is not known. The mussel probably feeds on suspended organic particles such as detritus, bacteria and algae.

The Wavy-Rayed Lampmussel (endangered) is readily distinguished by its yellow or yellowish-green rounded shell with numerous thin wavy green rays. The rays may be narrow and individual, or they may coalesce to form wide rays, but they are always wavy with multiple interruptions. The maximum shell length is 0.75-10 cm. Females can be distinguished from males by their more distended shell shape. Habitat :
The mussel inhabits clear rivers and streams of a variety of sizes, where the water flow is steady and the substrate is stable. It is typically found in gravel or sand substrates, often stabilized with cobble or boulders, in and around riffle areas up to 1 m in depth. It is most abundant in small to medium-sized streams. Even in optimal habitats, it accounts for only 2-4% of the abundance of the mussel community. Its presence at sites that invariably support a great diversity of other mussel species suggests that it cannot tolerate sub-optimal conditions. Habitats in Great Lakes waters are now heavily infested with zebra mussels and can no longer be utilized. Biology :This medium-sized, dimorphic mussel has a life span of 10-20 years. Spawning occurs in August, but the glochidia (larvae) are not released until the following summer (July or August in Ontario). The edge of the mantle of the female has evolved into a minnow-shaped "lure", which she waves to attract potential fish hosts just before the glochidia are released. Once expelled into the water by the female, the glochidia must attach to an appropriate fish host in order to complete their metamorphosis. Two known fish hosts for this species are the smallmouth bass (Micropterus dolomieu) and largemouth bass (Micropterus salmoides). The Wavy-rayed Lampmussel probably has a diet similar to that of other freshwater mussels, i.e., suspended organic particles such as detritus, bacteria and algae.

The shell of the Lake Winnipeg Physa Snail (endangered) is usually less than 11 mm long, globe-shaped, and fragile. The spire (whorls of a spiral shell, excluding the last) is flattened, making the snail appear relatively wide, and the surface of the shell is dull and often pitted. Fresh shells are bluish-grey, and the skin of living snails is light grey and sparsely peppered with black spots. Habitat :The Lake Winnipeg Physa Snail can be found on algae-coated rocks that are submerged just below the surface in open, wave-swept areas close to the shore of the lake. The lake bottom is usually a mixture of sand, gravel, and rocks, or occasionally limestone shingle. The Lake Winnipeg Physa Snail tends to occur only in sites with a higher number of other snail species. The average site where the Lake Winnipeg Physa Snail was found had 6.2 species of snails, while the overall average for sites with snails was 3.9 species. The Lake Winnipeg Physa Snail also is always found with at least one other species of Physa snail. The snail appears to be sensitive to metal contamination - the water at the sites where it was found had significantly lower levels of cadmium, copper, and lead than the sites where it was absent. Biology The Lake Winnipeg Physa Snail feeds on algae. Other species of Physa snail that occur in Lake Winnipeg spend the winter as adults and then reproduce in June and July of the following year. The shells of these snails are fragile and individuals typically do not survive for more than one year in Lake Winnipeg.

The Olympia oyster (special concern) is a small oyster species, whose maximum size is about 90 millimeters in diameter, and whose shape is roughly elliptical or circular. The valves of this oyster are different. Its lower (left) valve is deeply cupped and upper (right) valve is flat and fits inside the edges of its lower valve. The outside of the oyster ranges from white to purplish-black in colour and the insides of the valves range from white to iridescent green to purple in colour. Olympia oysters are often attached by the lower valve to hard substrate but can occur, either singly or in clusters, free on the substrate. Habitat :Olympia oysters are mainly found in the lower intertidal and shallow subtidal zones of saltwater lagoons and estuaries. They have also been found on tidal flats, tidal channels, bays and sounds, in splash pools, near freshwater seepage, or attached to pilings or the undersides of floats. On the outer coast, this oyster species is only found in protected locations. Within suitable habitat, Olympia oysters need hard substrate for settlement. Biology :Olympia oysters are sedentary and filter feed on a variety of plankton, including organisms such as diatoms and dinoflagellates. Outside of feeding, reproduction, and selection of settlement site, this species displays little specific behaviour. Reproduction in the Olympia oyster reproduction is closely tied to temperature. Oysters mature when the temperatures go up in the spring and spawn in the summer. Reproduction commonly occurs at ambient temperatures of 14-16*C. In Canada, Olympia oysters mature as males at about the age of one. They then alternate sexes between male and female for the rest of their lives (maximum life span is believed to be greater than ten years). Sperm is collected in the respiratory current and used to fertilize the 250 000 to 300 000 eggs produced by the female Olympia oyster. Fertilized eggs remain in the female mantle cavity for 14-17 days, after which the larvae are released into the water column. Here they drift and disperse for two to three weeks, and settle on hard substrate once the larvae have grown and developed.