Aerial exposure tolerance off zebra and quagga mussels (Bivalvia: Dreissenidae): implications for overland dispersal

Abstract

We examined the effects of ambient temperature (10, 20, and 30 °C) and relative humidity (10, 50, and 95% RH) on the aerial exposure tolerance of adult zebra mussel (Dreissena polymorpha) and quagga mussel (D. bugensis) collected from the St. Lawrence River. Survivorship of mussels in air significantly increased with increasing RH, decreasing temperature, and increasing mussel size. At 20 °C and 50% RH (early temperate summer conditions), large (21–28 mm) D. polymorpha survived more than 5 days exposure, whereas small (10–18 mm) D. polymorpha survived 1–3 days. Seventy-three percent of large D. polymorpha and 10% of small D. polymorpha survived 10 days exposure at conditions considered optimal for survivorship (10 °C and 95% RH). Survivorship of D. bugensis was tested at 20 °C and was 15–100% lower than that of D. polymorpha at all RH levels combined with exposures less than 5 days. Dreissena bugensis also suffered significantly higher percent weight losses because of desiccation than D. polymorpha. The differences in the desiccation tolerance of zebra and quagga mussels reflect their relative depth distribution in lakes. Our results suggest that, given temperate summer conditions, adult Dreissena may survive overland transport (e.g., on small trailered boats) to any location within 3–5 days' drive of infested waterbodies.