ABSTRACT
Fertilized eggs of the American horseshoe crab, Limulus polyphemus, are buried in shallow nests above the high tide line, where they are exposed to variations in abiotic conditions during early development. Using a multiple-stressors approach, we examined whether the rate of embryonic development is affected by exposure to combinations of three factors: temperature (25, 30 and 35°C), salinity (5, 15 and 34 ppt) and ambient O2 (5%, 13% and 21% O2). Newly fertilized eggs were incubated under 27 fully factorial stressor combinations for 14 days, then allowed to recover in control conditions (30°C, 34 ppt, 21% O2) for an additional 14 days. Growth rate was measured every 2 days throughout the experiment (N=1289). We found that the effect of isolated stressors (high temperature, low salinity or low O2) reduced developmental success by up to 72% (low salinity), and that stressor combinations showed stronger effects and evidence of complex interactions. For example, low O2 had little effect individually but was lethal in combination with high temperature, and low temperature in isolation slightly decreased the rate of development but reduced the negative effects of low salinity and low O2. Development was delayed under exposure to low O2 but resumed upon return to control conditions after a 10 day lag. These data demonstrate that complex, synergistic interactions among abiotic stressors can substantially alter the development of a coastal invertebrate in ways that may not be predicted from the effects of the stressors in isolation.
FOOTNOTES
↵* Present address: Biological Sciences Department, California Polytechnic State University, San Luis Obispo, CA 93407, USA.
↵‡ Present address: Department of Biology, University of Regina, Regina, SK, Canada S4S 0A2.
Competing interests
The authors declare no competing or financial interests.
Author contributions
M.C.V., H.J.B. and D.J. designed the experiment and analysis. The study was conducted by M.C.V. and A.M. M.C.V. analyzed the data and M.C.V. and D.J. wrote the manuscript. All authors approved the final manuscript.
Funding
This research was supported in part by the PADI Foundation [Req. No. 4030 to M.C.V.].
Supplementary material
Supplementary material available online at http://jeb.biologists.org/lookup/suppl/doi:10.1242/jeb.117184/-/DC1
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