VULNERABILITY OF BRANCHIOPOD CYSTS TO CRUSHING

Abstract

Ephemeral wetlands, such as vernal pools and playas, have become increasingly threatened by a variety of destructive human practices, including off-highway vehicle (OHV) activity. Among the resident animals that may be adversely affected are the branchiopod crustaceans which produce desiccation resistant cysts to withstand the pools' dry periods. We report a quantitative investigation of the force required to crush individual branchiopod cysts of 8 species: Branchinecta lynchi, B. sandiegonensis, B. mackini, Streptocephalus woottoni, Thamnocephalus platyurus, Linderiella occidentalis, Lepidurus lemmoni, and Triops longicaudata. Very small forces of less than 1 newton crushed dry cysts. Wet cysts were even more fragile; many were crushed under less than 7 X 10-2 newtons. Differences in vulnerability were found within and between taxa and may be related to cyst morphology. Knowledge of these effects should be taken into consideration when developing management strategies for ephemeral wetlands.