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Wavyrayed Lampmussel

I. Background

Species Information

Scientific Name: Lampsilis fasciola

Common Name:  Wavyrayed Lampmussel

Current COSEWIC Status & Year of Designation:  Endangered (1999)

Range in Canada (provinces and territories where found):  Ontario

Rationale for Status:  The Wavyrayed Lampmussel has declined significantly in recent years across its historical range.  Its numbers have been reduced in Great Lakes waters by the zebra mussel while populations in the Thames, Sydenham and Ausable Rivers are disappearing or have been lost primarily as a result of agricultural impacts.

Distribution

North American repartition of Wavyrayed Lampmussel

Text Box: Figure 2: North American distribution of the Wavyrayed Lampmussel (modified from Parmalee and Bogan 1998)

Global Range: In the United States, the Wavyrayed Lampmussel is considered nationally secure and currently occurs in Alabama, Indiana, Illinois, Kentucky, Michigan, New York, North Carolina, Pennsylvania, Tennessee, West Virginia and Virginia (Figure 2), however recent declines have been observed across its distribution (Parmalee and Bogan 1998). It historically occurred in Georgia and Ohio, but the status of the species in these states is currently unknown. In Canada the Wavyrayed Lampmussel is considered critically imperiled and occurs only in southwestern Ontario (Figure 3; Table 1) (Metcalfe-Smith et al. 1998).

Actual and historical Canadian repartion of Wavyrayed Lampmussels

Canadian Range: The current Canadian distribution of the Wavyrayed Lampmussel is restricted to the upper Grand River and its tributaries (Metcalfe-Smith and McGoldrick 2003), the upper Thames River (T. Morris, Fisheries and Oceans, Burlington, unpublished data), all four branches of the Maitland River (Janice Metcalfe-Smith, NWRI, Burlington, pers. comm. October 2003), a small section of the Ausable River (Metcalfe-Smith and McGoldrick 2003) and the Canadian waters of the Lake St. Clair delta (Zanatta et al. 2002)(Figure 3).

Percent of Global Range in Canada: Less than 5% of the species’ global distribution is found in Canada.

Distribution Trend: The range of the Wavyrayed Lampmussel has been significantly reduced as it has been extirpated from its historical range in the western basin of Lake Erie, the majority of Lake St. Clair, the Detroit River, and the Sydenham River.  Distributions in the Ausable and Grand rivers have been reduced while the full extent of the historic range appears to still be occupied in the Thames River. The trend in the Maitland River can not be assessed since no historical surveys exist. The largest populations of this species occupy a 60 km stretch of the upper Grand River, a 45 km stretch of the Maitland River, 65 km in the upper Thames watershed divided between the North, Middle and South Thames Rivers and an area of approximately 12 km2 in the Lake St. Clair Delta (Metcalfe-Smith and McGoldrick 2003). 

Table 1: Canadian and U.S. national and provincial/state heritage status ranks (NatureServe 2004).
  
Canada(N1)ON (S1)
United States (N4)AL (S1S2), GA (S2?), IL (S2), IN (S2), KY (S4S5), MI (S2), NY (S1), NC (S1), OH (S?), PA (S4), TN (S4), VA (S4), WV (S2)

Population Abundance

Global Range:The Wavyrayed Lampmussel is globally secure (G4) but is an uncommon species throughout its range usually comprising less than 2% of the mussel community where it is found (Metcalfe-Smith and McGoldrick 2003).

CanadianRange: The Maitland River, upper reaches of the Grand River and the upper Thames River support the largest populations of this species in Canada while a smaller population exists in the Lake St. Clair delta. The Wavyrayed Lampmussel also occurs in the Ausable River but is represented only by large individuals with no evidence of successful reproduction.  A single live specimen was found in a recent benthic survey at one location on the St. Clair River. 

Percent of Global Abundance in Canada:Less than 1%

Population Trend:The rate of population change for the Wavyrayed Lampmussel is unknown.  The only stable population of this species in Canada occurs in the Upper Grand River while the status of the second largest population (Maitland R.) is unknown due to a lack of historical information.  The Grand R. population appears to have recovered from the poor water quality conditions present in the 1970’s and early 1980’s.  Overall densities of all mussel species in the St. Clair delta appear to be declining over time although the small numbers of Wavyrayed Lampmussels make it difficult to interpret results for this species specifically (Metcalfe-Smith et al. 2004). All other Canadian populations have declined sharply to only a few individuals or have been extirpated.

Biologically Limiting Factors

Reproductive Attributes: The Wavyrayed Lampmussel, like all unionids, has a complicated reproductive cycle characterized by a period of obligate parasitism. This parasitic phase makes the Wavyrayed Lampmussel particularly sensitive to external factors that may indirectly affect them via their hosts (Bogan 1993).

The Wavyrayed Lampmussel is a medium sized, moderately long-lived, sexually dimorphic species.  During spawning season, males release sperm into the water column and females located downstream take in the sperm via their incurrent siphons. Females brood the young from egg to larval stage in the posterior portions of the outer gills. Distended shells which swell along the posterior-ventral margins to allow room for expanded gill pouches (Metcalfe-Smith et al. 2000) characterize mature female Wavyrayed Lampmussels.  Wavyrayed Lampmussels are long-term brooders (bradytictic) with spawning occurring in August and glochidial release occurring the following year (May through August in Virginia (Zale and Neves 1982), June through August in Canada (Woolnough 2002)).

Three lure of Wavyrayed Lampmussel

When the larvae are mature they are released by the female and must undergo a period of encystment on the gills of a suitable host. Two host species have been identified for the Wavyrayed Lampmussel in the U.S.. Zale and Neves (1982) reported successful laboratory infestations of smallmouth bass (Micropterus dolomieu) with Wavyrayed Lampmussel glochidia while G.T. Watters (Ohio State University, cited in Metcalfe-Smith et al. 2000) reported success with largemouth bass (M. salmoides). The largemouth and smallmouth bass have recently been confirmed as host for the Wavyrayed Lampmussel in Canada (McNichols et al. 2005). Researchers at the University of Guelph have also successfully infected mottled sculpin (Cottus bairdi) and brook stickleback (Culaea inconstans) with Wavyrayed Lampmussel glochidia although it is unclear whether these species functions as a host under natural conditions (K. McNichols, University of Guelph, pers. comm., September 2003).

To increase the likelihood of encountering an appropriate host and facilitate successful encystment, female Wavyrayed Lampmussels have developed

specialized mantle tissue to function as a lure (Strayer and Jirka 1997). Three co-occurring mantle lure morphologies have been observed on displaying female Wavyrayed Lampmussels during field surveys of the Grand, Thames, Ausable and Maitland Rivers.  The three morphologies consist of a black lure, a bright red lure, and a fish-like lure (Figure 4).  It is unknown if the three lure morphologies constitute sibling species or if they are ecomorphs.  Molecular phylogenetic analysis is required to resolve this knowledge gap.

When a suitable host fish touches the mantle lure the mantle flaps are retracted into the shell, placing pressure on the marsupia and causing the release of the mature larvae (glochidia). The structure of the lure (e.g., eyespots and pigmentation consistent with a small minnow-shaped fish in the fish-like lure morph) and the method of glochidial release are consistent with a host species which is a visual predator. This indicates that water clarity likely plays a critical role in the successful completion of the reproductive cycle of the Wavyrayed Lampmussel.

Dispersal: Adult Wavyrayed Lampmussels have very limited dispersal abilities. Although adult movement can be directed upstream or downstream, studies have found a net downstream movement through time (Balfour and Smock 1995; Villella et al. 2004). The primary means for large scale dispersal, upstream movement, and the invasion of new habitat or evasion of deteriorating habitat, is limited to the encysted glochidial stage on the host fish.