Lilliput
Toxolasma parvum
Species Description
A small, rare mussel, on average, Lilliput grow to a mere 25mm and have a thick, oval to egg-shaped shell. Juveniles are often a pale shade of yellow to gray, becoming darker as they age, adults are brown to black. The periostracum (skin-like outermost layer of the mussel shell) is smooth and dull, almost cloth-like in appearance. They live to a maximum age of 12 years.
Lifecycle
As with all mussels native to the Sydenham River, a host fish is required to complete their life cycle. Lilliput release white, club-shaped conglutinates (mucous packages filled with glochidia) that look like prey items to potential host fishes. Lilliput hosts are not well studied but there are four suspected host species known to frequent the Sydenham River’s waters: Bluegill, Green Sunfish, White Crappie, and Johnny Darter.
Habitat
They are known to occur in a variety of habitats including small to large rivers, ponds and wetlands and can be found in softer substrates such as mud, sand, and fine gravel.
Lilliput in the Sydenham
Despite targeted surveys over the last few decades, Lilliput has only been detected in the Sydenham watershed on three occasions since 1967, in 1991, 2011, and 2017. The 1991 record from the Sydenham was the first live Lilliput documented in Canada (the first shells in Canada were found in 1913). In 2011, seven individuals were detected at one site on the East Branch and the most recent observation, in 2017, was a live Lilliput surveyed on the North Branch of the Sydenham.
Threats to Lilliput
Many of the major threats Lilliput face are not unique to the species and are known to affect the greater mussel community. Sedimentation, pollution, nutrient loading and exposure to contaminants and toxins are among the most impactful. Turbid (cloudy) waters can decrease visibility, preventing potential host fish from locating the Lilliput and studies have shown that freshwater mussel glochidia and juveniles are very susceptible to fertilizer and pesticide run-off, road salts and heavy metals that enter the waters through industry and human activity.