The Adaptive Significance of Calanoid Copepod Pigmentation: A Comparative and Experimental Analysis

During summer 1980, dense swarms of the calanoid copepod Diaptomus tyrrelli formed during midday in several areas of the nearshore surface of Lake Tahoe, California‐Nevada. Swarms were most consistently found immediately adjacent to rocks in pools protected from wave action. Swarms were as dense as 11,354 copepods·liter−1 and composed primarily of adult males. They were not formed passively by currents. Swarming copepods have greater mating success than midlake copepods. Swarming may offer some protection from fish predation. The high densities and small size of swarms indicate that they could severely alter estimates of zooplankton density when they are included in integrated net tows.

Section: Observationsmentioning

confidence: 75%

Observations of copepod swarms in Lake Tahoe1

Byron

Whitman

Goldman

1983

“…Indeed, pigmented copepods suffer from higher predation mortality compared to nonpigmented specimens (Luecke and O'Brien 1981;Byron 1982). On the other hand, photoprotective compounds protect the organism from UVinduced damages, either by screening out radiation or by quenching photo-produced radicals (Hairston 1976;Sommaruga and Garcia-Pichel 1999;Tartarotti et al 2001), and zooplankton with lower levels of protective pigmentation suffer greater mortality when exposed to UV radiation (Ringelberg et al 1984).…”

Section: Discussionmentioning

confidence: 99%

Zooplankton vertical migration and plasticity of pigmentation arising from simultaneous UV and predation threats

Hylander

Larsson

Hansson

2009

We assessed how zooplankton (copepods) handle the simultaneous threats of predators and ultraviolet (UV) radiation and whether they respond with changes in pigmentation, vertical migration, or both. We found weak vertical migration among copepods in response to UV stress, and this response was not apparently influenced by predation risk. Exposure to high levels of UV radiation caused copepods to retain pigments in the absence of a predation threat. When exposed to predation threat, they reduced their pigmentation regardless of UV level. Thus, they ranked predation as a threat more severe than UV radiation. Reducing the protective pigment level in response to predation in a situation in which UV radiation is high may, however, lead to higher mortality.

“…A central focus of many earlier studies was the relationship between pigmentation, photoprotection, and the vertical distribution of zooplankton. Although variations in carotenoid concentrations in zooplankton were found to be related to dietary availability (Ringelberg 1980(Ringelberg , 1981Moeller et al 2005) and possibly temperature regulation (Byron 1981(Byron , 1982, extensive evidence accumulated on the important photoprotective function of carotenoids in copepods and melanin in cladocerans. In freshwater zooplankton, higher mortality of pale vs. pigmented individuals exposed to damaging wavelengths of light has been demonstrated for carotenoids in Diaptomus nevadensis (Hairston 1976), Heterocope septentrionalis (Luecke and O'Brien 1981), Acanthodiaptomus denticornis (Ringelberg et al 1984), and Leptodiaptomus minutus (Moeller et al 2005) as well as for melanin in Daphnia pulex obtusa (Siebeck 1978), Daphnia middendorffiana (Luecke and O'Brien 1983), Daphnia pulex (Hessen 1996), and the Daphnia pulex group (Hebert and Emery 1990).…”

mentioning

confidence: 99%

Toward a more comprehensive theory of zooplankton diel vertical migration: Integrating ultraviolet radiation and water transparency into the biotic paradigm

Williamson

Fischer

Bollens

et al. 2011

185

202

The current prevailing theory of diel vertical migration (DVM) of zooplankton is focused largely on two biotic drivers: food and predation. Yet recent evidence suggests that abiotic drivers such as damaging ultraviolet (UV) radiation and temperature are also important. Here we integrate current knowledge on the effects of abiotic factors on DVM with the current biologically based paradigm to develop a more comprehensive framework for understanding DVM in zooplankton. We focus on ''normal'' (down during the day, up at night) DVM of holoplanktonic, primarily herbivorous zooplankton. This new transparency-regulator hypothesis differentiates between structural drivers, such as temperature and food, that vary little over a 24-h period and dynamic drivers, such as damaging UV radiation and visual predation, that show strong variation over a 24-h period. This hypothesis emphasizes the central role of water transparency in regulating these major drivers of DVM. In less transparent systems, temperature and food are often optimal in the surface waters, visual predators are abundant, and UV radiation levels are low. In contrast, in more transparent systems, vertical thermal gradients tend to be more gradual, food quality and quantity are higher in deeper waters, and visual predator abundance is often lower and damaging UV radiation higher in the surface waters. This transparency-regulator hypothesis provides a more versatile theoretical framework to explain variation in DVM across waters of differing transparency. This hypothesis also enables clearer predictions of how the wide range of ongoing transparency-altering local, regional, and global environmental changes can be expected to influence DVM patterns in both inland and oceanic waters of the world.Diel vertical migrations (DVM) of zooplankton in the world's lakes and oceans comprise some of the most widespread and massive migrations of animals on Earth. These striking migrations across strong vertical habitat gradients have inspired numerous ecological and evolutionary studies addressing mechanisms of habitat selection and consequences for species interactions. These migrations also have important implications for water quality and fisheries production as well as biogeochemical cycling. Natural and anthropogenic environmental changes, such as shifting local land use patterns and regional to global climate change, are altering water transparency and have the potential to affect DVM in lakes and oceans worldwide. The purpose of this article is to provide a common theoretical framework for understanding variation in the drivers of DVM across transparency gradients with a particular emphasis on recent advances in our understanding of the role of ultraviolet radiation (UV).Many environmental factors are recognized as providing both important proximate cues as well as ultimate consequences of adaptive significance for DVM, including light, temperature, food availability, and predation pressures (Table 1; Lampert 1989;Ringelberg 1993;Hays 2003). In spite of the wides...