Dietary Carotenoids Regulate Astaxanthin Content of Copepods and Modulate Their Susceptibility to UV Light and Copper Toxicity

Abstract

High irradiation and the presence of xenobiotics favor the formation of reactive oxygen species in marine environments. Organisms have developed antioxidant defenses, including the accumulation of carotenoids that must be obtained from the diet. Astaxanthin is the main carotenoid in marine crustaceans where, among other functions, it scavenges free radicals thus protecting cell compounds against oxidation. Four diets with different carotenoid composition were used to culture the meiobenthic copepod Amphiascoides atopus to assess how its astaxanthin content modulates the response to prooxidant stressors. A. atopus had the highest astaxanthin content when the carotenoid was supplied as astaxanthin esters (i.e., Haematococcus meal). Exposure to short wavelength UV light elicited a 77% to 92% decrease of the astaxanthin content of the copepod depending on the culture diet. The LC50 values of A. atopus exposed to copper were directly related to the initial astaxanthin content. The accumulation of carotenoids may ascribe competitive advantages to certain species in areas subjected to pollution events by attenuating the detrimental effects of metals on survival, and possibly development and fecundity. Conversely, the loss of certain dietary items rich in carotenoids may be responsible for the amplification of the effects of metal exposure in consumers.

Selective Feeding of Bdelloid Rotifers in River Biofilms

“…It has been previously hypothesized that the photoprotection of microalgae, assured by the accumulation of photoprotector carotenoids in their cells, could be transferred to grazers in the form of pigments. In addition, the survival of certain species of meiobenthic copepods is directly related to their carotenoid content when exposed to copper [70]. In this context, our results suggest that the potential link between the accumulation of echinenone and a possible improvement of resistance to metal toxicity and UV light exposures deserves to be tested for bdelloid rotifers.…”

Carotenoid accumulation in copepods is related to lipid metabolism and reproduction rather than to UV‐protection

“…As astaxanthin must be accumulated or biologically converted from carotenoids in the diet, copepod pigmentation may be subject to seasonal shifts in the availability of an appropriate algal diet. Phytoplankton carotenoids that may serve as precursors for the synthesis of astaxanthin in copepods include b,b-carotene, lutein and zeaxanthin (Andersson et al 2003;Rhodes 2006;Caramujo et al 2012).Carotenoid pigmentation may also be disadvantageous to copepods, as pigmented animals are generally more likely to be targeted by visual predators than unpigmented ones (Hairston 1979a;Gorokhova et al 2013). Hence, copepods reduce their carotenoid content when exposed to predator cues (Hansson 2004;Hylander et al 2012), and predation and UV radiation, acting in concert, are likely environmental factors affecting zooplankton pigmentation.…”

“…UV-exposed copepods at low water temperatures have especially been suggested to profit from increased carotenoid content to counteract the reduced efficiency of enzymatic UVR responses such as photoenzymatic repair at low water temperatures (Williamson et al 2002;Hansson and Hylander 2009). Apart from UVR, carotenoids may protect copepods from other sources of oxidative stress, such as metal toxicants (Caramujo et al 2012), and may also improve the immune defense (van Der Veen 2005) and reproductive output (Gorokhova et al 2013) of the animals. Astaxanthin has also been shown to positively affect metabolic activity as well as egg production in copepods, supposedly due to its antioxidant properties (Gorokhova et al 2013).…”

Plastids of Marine Phytoplankton Produce Bioactive Pigments and Lipids

“…It selectively accumulates in the macula of the human retina, protects the eyes from oxidative stress, and acts as a filter of the blue light involved in macular degeneration and age-related cataract [131,132,133]. Asta protects against UV light; it is true for microalgae, animals and human beings [38,105]. Fuco inhibits tyrosinase activity, melanogenesis in melanoma and UVB-induced skin pigmentation by topical or oral application [130].…”