Zoologia

Exposure of organisms to ultraviolet radiation (UVR) is characterized by the climatology (annual cycle) and the variance (anomalies) of biologically-weighted irradiances at eight geographical locations in austral South America, from 1995-2002. Net 10 effect of UVR on biological systems is a result of the balance of damage and repair which depends on intensity and duration of irradiance and is modulated by its variability. The emphasis in this study is on day-to-day variability, a time scale of importance to adaptive strategies that counteract UVR damage. The irradiances were weighted with DNA-and phytoplankton photosynthesisaction spectra. Low latitude sites show high average UVR. For all sites, the frequency of days with above average irradiances is higher than below average irradiances. Persistence in anomalies is generally low (< 0.36 autocorrelation coefficient), but higher 15 for DNA-than phytoplankton photosynthesis-weighted irradiances due to their higher correspondence to stratospheric ozone. Cloudiness and other factors with small wavelength dependence (i.e., aerosols and albedo) are highly correlated with UVR anomalies at low latitudes (24°-33° S); ozone correlates higher at high latitudes (42°-54.5° S). Our results show that organisms in this region deal with several days of excess radiation and fewer, shorter and more intense periods of lower than average radiation. Relief from UVR stress (or higher frequency of days below the climatology) is more prevalent at high latitudes (54.5° S). Thus, 20 lower latitudes are more stressful to organisms not only because of higher average UVR irradiance but also for the higher frequency of days above the climatology. irradiance, UVR stress, UVR relief 65 constant. 6,24 UVA (315 to 400 nm) is more affected by atmospheric processes other than ozone. In South America, both UVA and UVB present a gradient with latitude. 2,4,14 Furthermore, a higher cross correlation between 305 nm and 340 nm at lower latitudes and higher cross-correlation 70 between 305 nm irradiance and ozone at higher latitudes indicated the importance of cloud cover and other factors with relative small wavelength dependence (i.e., aerosols and albedo) in explaining UVR variability at lower latitudes (24º S) and the importance of ozone at higher latitudes (54.5º 75 S). 14 Although UVB radiation represents less than 0.8% of the total energy reaching the Earth's surface, it is responsible for almost half the photochemical reactions in aquatic environments. 25 UVB is known to affect a variety of cellular 80

The error in irradiance measured with Sun-calibrated multichannel radiometers may be large when the solar zenith angle (SZA) increases. This could be particularly detrimental in radiometers installed at mid and high latitudes, where SZAs at noon are larger than 50°during part of the year. When a multiregressive methodology, including the total ozone column and SZA, was applied in the calculation of the calibration constant, an important improvement was observed. By combining two different equations, an improvement was obtained at almost all the SZAs in the calibration. An independent test that compared the irradiance of a multichannel instrument and a spectroradiometer installed in Ushuaia, Argentina, was used to confirm the results.

... 2002). De las 10 especies de mamíferos nativas solo una es endémica: el roedor cavícola Ctenomys magellanicus o &amp;amp;quot;tucu-tuco&amp;amp;quot;, que vive en colonias y construye redes de túneles en zonas abiertas con buen drenaje (Lizarralde et al. 2001). ...

In the last two decades as a consequence of ozone depletion there has been an increasing interest in the study of biological effects of ultraviolet radiation (UV). Spectral instruments, which provide detailed information on UV environmental conditions, have been in use systematically only for little more than a decade. These time series are still relatively short and information on spectral historical irradiance levels is not available. Many efforts have been carried out in inferring this information from other available data sets. One of them has been the use of statistical models. Spectral irradiances are available at South Pole (90 • 00 S 0) and Barrow (71 • 18 N, 156 • 47 W) from the NSF UV Radiation Monitoring Program since 1991. In the present paper, daily-integrated biologically weighted irradiances for these sites are inferred back to 1979 using a multi-regressive model, obtaining time series that extend near the beginning of the Antarctic ozone depletion. These datasets are unique since the daily-integrated irradiances were calculated from irradiance measured hourly at the earth's surface. The biologically weighted irradiances are estimated from irradiance measured with broadband instruments, ozone, and solar zenith angles. From daily-integrated irradiance, monthly means were also calculated. The RMS errors between the estimated and measured daily-integrated irradiances range from 4.69 to 7.49% at South Pole and from 9.57 to 15.20% at Barrow, while the monthly mean errors vary from 2.07 to 3% and 2.95 to 3.91%, respectively. Completing the databases with spectral measurements, the resulting time series extend from 1979 to 2000. Analyzing monthly values an increase relative to 1979-1981 during all years is observed at South Pole. Largest increases are observed for DNA and plant-chromosphere weighted irradiances during October. Although at a lower rate, an increase is also observed at Barrow during the spring. Maximum monthly increase at South Pole during October is near 1200% relative to 1979-1981, while the increase at Barrow is near one tenth of that percentage. Daily-integrated irradiance shows that a slight increase was present during the spring at South Pole for the period 1979-

The host response to 3 different larval digeneans affecting Southwestern Atlantic and Magellanic populations of the bivalve Gaimardia trapesina (Lamarck, 1819) (Gaimardiidae) is described. Unencysted metacercariae of 2 species of Gymnophallidae and 1 species of Lepocreadiidae co-exist in the peripheral and general extrapallial spaces. Differences in host responses to stimuli generated by each parasite are described. Infections by Gymnophallidae gen. sp. 1 metacercariae elicit a mantle-shell complex reaction involving both alteration of the mantle epithelium (hyperplasia and metaplasia) and calcium carbonate deposition to form an incomplete calcareous covering of single larvae, comprising individual crystallites in an organic matrix. The calcareous covering covers only the posterior two-thirds of the larval body, having its anterior end free in the extrapallial space, which ensures survival of the larvae. The peculiar features of the host response result from a successful process of adjustment to the parasite's life cycle. Metacercariae of Gymnophallidae gen. sp. 2 occur in one or more small groups of up to 30 individuals, either in the general or in the peripheral extrapallial spaces. The outer mantle reaction includes hyperplasia and metaplasia of the epithelium adjacent to the larvae. Deposition of calcium carbonate did not occur. Lepocreadiidae gen. sp. metacercariae were observed exclusively in the general extrapallial space lodged in single shallow pits whose shape fit the parasite's body shape and size. In simultaneous infections, metacercariae of Gymnophallidae and Lepocreadiidae elicited different responses in an individual, which suggests that each parasitic entity involves a different stimulus to the host.

1] Measurements of spectral and multichannel UV radiation became more common in the middle and late eighties after the discovery of the ''ozone hole,'' but time series for these measurements are still relatively short for the determination of trends to be applied in geophysical and biological studies. However, systematic measurements of total column ozone have been performed since the late 1950s at several stations, and global coverage has been available since the late 1970s. Also, long-term time series of broadband instruments (Pyranometers, UV and erythemally weighted) are available from many sites around the world. In this paper a multiregressive model that enables the inference of spectral or narrow band UV irradiances from total ozone column and broadband irradiance, in places where relatively short time series of UV spectral irradiances are available, is proposed. To test the model, measurements of irradiances performed at three of the stations in the NSF UV Radiation Monitoring Network, under all weather, solar zenith angle and surface conditions, were used. The model generated very good results over a wide variety of situations. Pyranometer data from the NOAA/CMDL surface radiation budget database for South Pole and Barrow Stations were used to estimate daily integrated narrow band irradiances. A time series of monthly means for the narrowband (303.030-307.692 nm) were then computed, dating back to the late 1970s.

Ozone and UV radiation were analyzed at eight stations from tropical to sub-Antarctic regions in South America. Ground UV irradiances were measured by multichannel radiometers as part of the Inter American Institute for Global Change Radiation network. The irradiance channels used for this study were centered at 305 nm (for UV-B measurements) and 340 nm (for UV-A measurements). Results were presented as daily maximum irradiances, as monthly averaged, daily integrated irradiances and as the ratio of 305 nm to 340 nm. These findings are the first to be based on a long time series of semispectral data from the southern region of South America. As expected, the UV-B channel and total column ozone varied with latitude. The pattern of the UV-A channel was more complex because of local atmospheric conditions. Total column ozone levels of <220 Dobson Units were observed at all sites. Analysis of autocorrelations showed a larger persistence of total column ozone level than irradiance. A decreasing cross-correlation coefficient between 305 and 340 nm and an increasing cross-correlation coefficient between 305 nm and ozone were observed at higher latitudes, indicating that factors such as cloud cover tend to dominate at northern sites and that ozone levels tend to dominate at southern sites. These results highlight the value of long-term monitoring of radiation with multichannel radio-meters to determine climatological data and evaluate the combination of factors affecting ground UV radiation.

After the discovery of ozone depletion, the study of the variability of the UV-B radiation at the earth&#39;s surface became a topic of interest for the atmospheric community. Also, biologists, physicians and epidemiologists, working in this field, require values of UV irradiance and dose in their studies. The variation of UV radiation at the earth&#39;s surface is not easily derived

On June 4th, 2011, the Puyehue-Cordon Caulle volcanic complex (40135 0 25″S 72107 0 02″W, Chile) started eruption, sending ash 45,000 feet into the atmosphere. After the initial period, the eruption continued for several months, with less intensity. Changes in global irradiance in the UV-B and UV-A, and direct irradiance and AOD in the UV-A, as consequence of the eruption, were studied. Global irradiance has been permanently measured at the Laboratory of Photobiology (LPh) (41.13S, 71.42W, 804 msl) since 1998. In addition, in the frame of a project to study altitude effect on direct and global irradiance, field campaigns were performed during September 17th to 23rd, 2010 and September 14th to 18th, 2011, in the region of the Nahuel Huapi National Park, near 100 km from the eruption. In those periods, simultaneous measurements of direct and global irradiance and aerosol optical depth (AOD) were carried out at three sites: Laboratory of Photobiology (LPh), Mt Otto (41.15S, 71.38W, 1386 msl) and Mt Catedral (41.17S, 71.48W, 1930 msl). The analysis of aerosols in 2011, three to four month after the eruption started, showed the presence of larger particles and more variability than in 2010, at all sites. Global irradiance, at LPh, also exhibited larger variability, compared to 1999, when no eruption or any other event that could have produced major changes in aerosols occurred. The mean decrease, as consequence of the volcano activity, at LPh, was around 20%, at 305 nm and closed to 10%, at 320 nm. At 380 nm, the decrease was very small and not statistically significant, although in particular days, with large aerosol load, a significant decrease was observed. Direct irradiance, in the UV-A, showed larger decrease than global irradiance. The effect of the eruption was more pronounced at the low altitude site.

El objetivo fundamental del IPY es el estudio del papel del Ártico y la Antártida en el contexto planetario, permitiendo el desarrollo de nuestra comprensión de los procesos polares y de nuevos sistemas de observación o la mejora de los sistemas ya existentes.