. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ORGANISMAL TRANSPARENCY 309. Figure 3. Copepod (Labidocera) viewed under (A) unpolarized transmitted light, and (B) crossed polarizers. The copepod is more distinct in (B) due to the presence of birefringent muscle and connective tissue. Because the background underwater illumination is polarized, a viewer with polarization vision may be able to visualize the contrast increase from (A) to (B). Courtesv of Nadav Shashar. sured UV absorption was generally significantly greater in the UVB than in the UVA (where UV vision occurs
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ORGANISMAL TRANSPARENCY 309. Figure 3. Copepod (Labidocera) viewed under (A) unpolarized transmitted light, and (B) crossed polarizers. The copepod is more distinct in (B) due to the presence of birefringent muscle and connective tissue. Because the background underwater illumination is polarized, a viewer with polarization vision may be able to visualize the contrast increase from (A) to (B). Courtesv of Nadav Shashar. sured UV absorption was generally significantly greater in the UVB than in the UVA (where UV vision occurs), and because the highest UV absorption was often found in less transparent individuals. The conflict between UV protection and UV concealment may have important ecological implications in light of re- ports of decreasing ozone levels at polar, temperate, and tropical latitudes and concomitant increases in UVB radia- tion (measured at 10%-20% per decade at temperate lati- tudes) (Solomon. 1990; Smith et ui, 1992: Stolarski et <//.. 1992). A responsive increase in UV-protective pigmenta- tion (at either an individual or population level) increases visibility at UV and possibly visible wavelengths, poten- tially resulting in increased predation or decreased feeding success. A responsive increase in depth may decrease access to prey, phytoplankton, or warmer water. Given the impor- tance of transparent zooplankton to the trophic ecology of the pelagic realm (, Madin et til., 1997; Purcell, 1997), either response may have significant effects. A second visual adaptation that can increase the contrast of transparent predators or prey is polarization vision. Un- derwater light is polarized, particularly in the horizontal direction (Waterman, 1981). A transparent object can affect this polarization in two ways: it can depolarize it entirely or, if the object is birefringent, it can rotate the plane of polarization (Lythgoe and Hemmings. 1967; Fineran and Nicol, 1978). Either ch
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