Effects of Salinity on Physa acuta, the Intermediate Host for the Parasite Posthodiplostomum minimum: Implications for the Translocation of the Protected White Sands Pupfish

Abstract

We report the salinity tolerance of snails to evaluate how parasite communities with complex life cycles have been altered by translocations of the White Sands pupfish Cyprinodon tularosa to habitats with altered salinity levels. Native and introduced pupfish populations co-occur with the gastropods Physa acuta and associated white grub parasite, Posthodiplostomum minimum, at two brackish springs (Malpais and Mound), but physids are absent from the two saline habitats occupied by White Sands pupfish. We conducted a salinity challenge experiment to test the hypothesis that environmental salinity limits the distribution of physid snails. A 22-d survival experiment with the Malpais Spring physid population indicated that exposure to elevated salinities significantly reduced survival. We also saw sequential declines in survival and reproduction that were proportional to salinity exposure. Salinity of 7‰ was the apparent threshold for these effects. These results have implications for the use of translocation as a conservation tool in the management of fish populations.

Received December 14, 2010; accepted March 27, 2011

ACKNOWLEDGMENTS

We thank S. Schaeffer for assistance in conducting these experiments. We thank H. Reiser and J. Dye (Holloman Air Force Base) for logistical support. We thank R. Myers for facilitating access to the White Sands Missile Range (WSMR). This work was funded by Department of Defense Legacy Resource Program Grant DACA87–00-H-0014 to C.A.S. administered by M. H. Reiser and J. Dye, 49 CES/CEV, Environmental Flight, Holloman Air Force Base. Thanks are extended to B. Lang, A. Wethington, and R. Dillon for their assistance in determining the identity of Physa acuta. J. Heilveil, S. Henkanaththegedara, D. Mushet, and three anonymous reviewers provided valuable comments on an earlier version of this manuscript. This article was approved for public release by White Sands Missile Range; distribution unlimited. The Operational Security review was completed on 16 February 2010.

Notes

^aThe White Sands pupfish comprises two evolutionarily significant units (ESUs), the Malpais Spring and Salt Creek ESUs. The latter includes the populations derived from Salt Creek at Lost River and Mound Spring (Stockwell et al. 1998).

^bStockwell and Mulvey (1998).

^cRogowski and Stockwell (2006).

^dHershler et al. (2002).

^eC. A. Stockwell, M. L. Collyer, and J. Janovy, unpublished data.

^fRogowski et al. (2006).

^gCollyer (2000).

^hCollyer and Stockwell (2004).

ⁱBrian Lang, New Mexico Department of Game and Fish, personal communication.