Effects of exposure to ambient UV-B on embryos of Anaxyrus canorus and Pseudacris regilla at various breeding sites near Tioga Pass, California, USA, in 1996 and 1998
Dates
Publication Date
2020-12-15
Start Date
1996-06-01
End Date
1998-07-30
Citation
Sadinski, W., 2020, Effects of exposure to ambient UV-B on embryos of Anaxyrus canorus and Pseudacris regilla at various breeding sites near Tioga Pass, California, USA, in 1996 and 1998: U.S. Geological Survey data release, https://doi.org/10.5066/P9BVZDOP.
Summary
We produced this data set as part of a larger, integrated study to assess the statuses of populations of Anaxyrus canorus and the causes of observed effects on fitness at field sites, primarily in Yosemite National Park near Tioga Pass, from 1996 to 2001. ENCLOSURES We used field enclosures to test the hypothesis that exposure to ambient UV-B caused embryo mortality in 1996 and 1998. We covered the top of each enclosure with one or two types of thin plastic sheeting. One type was transparent to the solar spectrum. The other type filtered UV-B below 314 nm (UV-B<314) but was otherwise transparent to solar radiation. Laying both types together over the top of an enclosure did not alter the transmission characteristics of either type [...]
Summary
We produced this data set as part of a larger, integrated study to assess the statuses of populations of Anaxyrus canorus and the causes of observed effects on fitness at field sites, primarily in Yosemite National Park near Tioga Pass, from 1996 to 2001. ENCLOSURES We used field enclosures to test the hypothesis that exposure to ambient UV-B caused embryo mortality in 1996 and 1998. We covered the top of each enclosure with one or two types of thin plastic sheeting. One type was transparent to the solar spectrum. The other type filtered UV-B below 314 nm (UV-B<314) but was otherwise transparent to solar radiation. Laying both types together over the top of an enclosure did not alter the transmission characteristics of either type when used alone. We installed enclosures in each study wetland near where egg masses had been deposited. Enclosed embryos rested on the flat surface of each enclosure’s bottom, near the water’s surface at depths similar to those of embryos that were positioned in the tops of nearby egg masses of A. canorus. HATCHING SUCCESS We used these enclosures to test whether exposure to ambient UV-B<314 reduced hatching success (1996 and 1998) or induced dipyrimidine dimers (1996) in embryos of A. canorus and Pseudacris regilla at select breeding sites. These sites typically were exposed to full sunlight from at least 0730 h to 1845 h daily. For tests of effects on hatching success, we enclosed embryos only from egg masses that had been laid earlier in the same day to ensure that we maximized their exposure to UV-B<314 throughout as much of pre-hatching development as possible, including the earliest stages. 1996 For embryos of A. canorus, we conducted experiments at three breeding wetlands (C3, C9, and Sub) very soon after breeding began. At each of these sites, we collected egg masses of A. canorus with embryos that were in early cleavage and distributed embryos to individual enclosures indiscriminately until we had 30 embryos in each enclosure. We replicated each treatment (enclosures with ultraviolet-B [UV-B] transparent plastic or enclosures with UV-B-transparent plus UV-B<314-opaque plastic) six times per site. Similarly, we collected egg masses of P. regilla and placed them in enclosures at Sub. Embryos were in early stages of cleavage. We replicated each treatment (enclosures with ultraviolet-B [UV-B] transparent plastic or enclosures with UV-B-transparent plus UV-B<314-opaque plastic) six times. 1998 In 1998, we tested for effects of exposure to ambient UV-B<314 on hatching success among A. canorus embryos at two sites (C3 and C9). We collected egg masses that were laid the day we collected them and distributed them to six replicate enclosures per treatment, which we then deployed at the embryos’ natal sites. In 1996 and 1998, we checked all enclosures daily across sites but did not assess hatching success until hatching was completed. We returned all hatchlings to their respective natal sites. DNA DAMAGE – 1996 During the spring of 1996, we also tested the hypothesis that exposure to ambient UV-B<314 induced the formation of dipyrimidine dimers in embryos of A. canorus and P. regilla at two sites (Sub and C9). We collected and placed embryos in enclosures and exposed them to, or shielded them from, UV-B<314 according to the procedures described in the sections above. We placed A. canorus embryos in each of six replicate enclosures per treatment (each species by UV-B-transparent plastic or by UV-B-transparent plus UV-B<314-opaque plastic) and deployed them during the late afternoon at Sub and C9. Similarly, we placed P. regilla embryos in each of five replicate enclosures at Sub. We then collected the embryos from these enclosures at midday the following day, placed them in cryogenic vials and held them briefly on ice, then froze and stored them in liquid nitrogen until we transferred them later to an ultra-cold freezer (-70˚C) at the University of California, San Francisco, for storage until analysis. At C9, we expanded the P. regilla experiment at C9 to test whether the quantity of any DNA damage varied over the course of the day and night and whether embryos potentially were repairing such damage over time. We added 120 embryos to each of 12 enclosures at C9 in one afternoon. Six enclosures transmitted UV-B<314 and six did not. We then collected one-third of the embryos in each of these enclosures at midday on the day after we had enclosed them, one-third at dusk on the day after we had enclosed them, and the remaining third at dawn of the second day after being enclosed. We collected, froze, and stored all P. regilla embryos at C9 as described above. We analyzed the DNA of all the embryos from the DNA-damage field experiment via an Enzyme-Linked Immunosorbent Assay (ELISA). We extracted and purified the DNA from embryos of each experimental unit via commercially available kits for extracting and purifying DNA according to the manufacturer’s instructions. We added the purified DNA to solutions that included monoclonal antibodies specific for dipyrimidine dimers. Such additions resulted in changes to the color of the solutions in proportion to the presence of dimers. To quantify relative color changes, we measured absorbance at 492 nm via a multiscan plate reader. As laboratory controls, we irradiated plasmid DNA with 0, 2, 4, 8, 16, or 32 J/m2 of UV-C via a germicidal lamp (254 nm). We similarly irradiated cells from human cell lines that were deficient in DNA repair genes, with 0 or 10 J/m2 of UV-C. We processed and analyzed the plasmid and human DNA via the same methods (as positive controls) when we processed and analyzed DNA samples from A. canorus and from P. regilla embryos we had exposed or not exposed to ambient UV-B<314 in the field.
Click on title to download individual files attached to this item.
Effects of exposure to ambient UV-B on embryos.xml Original FGDC Metadata
View
32.28 KB
application/fgdc+xml
UV-B experiments_96 and 98.csv
32.15 KB
text/csv
Purpose
We used these data to help us evaluate any effects of potential exposure to ambient UV-B on embryos of A. canorus relative to embryos of P. regilla in our study area. Other researchers could use them to address various ecological questions related to fitness, reproduction success, recruitment, and natural history, among other topics for A. canorus or P. regilla in our study area or elsewhere.
