Ultraviolet Radiation Tolerance in High Elevation Copepods from the Rocky Mountains of Colorado, USA Page: 11
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warming of important metabolic processes, imparting an advantage to pigmented copepods in
cold waters (Byron 1981).
Carotenoids are concentrated in copepod eggs and nauplii, and can be seen in the
gonads of ovigenerous females (Fig. 1.2) (Pennak 1978, Hairston 1979a). Pennak suggests that
carotenoids are accumulated for use as food reserves (1978). While AX is an important
component of copepod diet and may be essential in several biological processes, increased
accumulation of AX when exposed to UVR (Luecke and O'Brien 1981, Stutzman 1999) and
enhanced survivability of copepods exposed to UVR strongly suggests that AX plays an
important role as a photoprotectant.
Copepods also accumulate mycosporine-like amino acids (MAAs) which are invisible in
visible light and function as sunscreens thereby assisting in mitigation of UVR stress (Hansson
and Hylander 2009). It is unlikely that MAAs also enhance predation in the same way that
carotenoids do by increasing visibility (Hansson et al. 2007) and MAAs are thus accumulated
preferentially in the presence of fish (Hylander et al. 2009).
Predation by sight hunting predators often counter-balances pigment accumulation in
zooplankton (Hansson 2000, Boeing et al. 2004). In a study of Heterocope septentrionalis in 37
lakes in the Toolik Lake region of Alaska, pale green copepods were found in lakes with fish,
while fishless lakes contained bright red copepods. The red copepods had greater UV
survivorship but were preferentially preyed upon by arctic grayling fish (Luecke and O'Brien
1981). Likewise, red copepods were preferentially preyed on, and periods of pigmentation
maxima were constricted in the presence of fish in central Washington (Hairston 1979a).11
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Hudelson, Karista. Ultraviolet Radiation Tolerance in High Elevation Copepods from the Rocky Mountains of Colorado, USA, thesis, December 2011; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc103331/m1/18/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .