INVESTIGADORES
DIEGUEZ Maria Del Carmen
congresos y reuniones científicas
Título:
Bioaccumulation of photoprotective compounds in copepods: environmental triggers and sources of intra-specific variability.
Autor/es:
29. ZAGARESE, HE., GARCÍA, PE, DIÉGUEZ, MC & FERRARO M A.
Lugar:
San Francisco
Reunión:
Simposio; AGU Fall Meeting; 2012
Institución organizadora:
AGU
Resumen:
Investigaciones Científicas y Técnicas (CONICET), Bariloche, Río
Negro, Argentina. ABSTRACT BODY: Ultraviolet radiation (UVR) and temperature are two
globally important abiotic factors affecting freshwater ecosystems. Planktonic
organisms have developed a battery of counteracting mechanisms to minimize the
risk of being damaged by UVR, which respond to three basic principles: avoid,
protect, repair. Copepods are among the most successful zooplankton groups.
They are highly adaptable animals, capable of displaying flexible behaviors, physiologies, and life
strategies. In particular, they are well equipped to cope with harmful UVR.
Their arsenal includes vertical migration, accumulation of photoprotective
compounds, and photorepair. The preference for a particular strategy is
affected by a plethora of environmental (extrinsic) parameters, such as the
existence of a depth refuge, the risk of visual predation, and temperature.
Temperature modifies the environment (e.g. the lake thermal structure), and
animal metabolism (e.g., swimming speed, bioaccumulation of photoprotective
compounds). In addition, the relative weight of UVR-coping strategies is also
influenced by the organism (intrinsic) characteristics (e.g., inter- and intraspecific
variability). The UV absorbing compounds, mycosporine-like amino acids (MAAs),
are widely distributed among freshwater copepods. Animals are unable to
synthesize MAAs, and therefore depend on external sources for accumulating
these compounds. Although copepods may acquire MAAs from their food, for the
few centropagic species investigated so far, the main source of MAAs are
microbial (most likely prokaryotic) organisms living in close association with
the copepods. Boeckella gracilipes is a common centropagic copepod in
Patagonian lakes. We suspected that its occurrence in different types of lakes,
hydrologically unconnected, but within close geographical proximity, could have
resulted in different microbial-copepod associations (i.e., different MAAs
sources) that could translate into intra-specific differences in the
accumulation of MAAs when experimentally exposed to different combinations of
radiation exposure and temperature. We exposed B. gracilipes individuals from
two lakes (Verde: high elevation, fishless; Morenito: piedmont, with fish) to
two radiation conditions (PAR+UVA vs. darkness) crossed with five temperatures
(5, 8, 12, 16 and 20 C) for periods of 10 days. DNA fingerprinting (DGGE)
revealed the existence of differences in microbial composition between the two
copepod populations. The two populations differed in initial total MAAs
concentration and composition. Exposure to PAR+UVR stimulated the accumulation
of MAAs in individuals from lake Morenito and to a lesser extent in those from
lake Verde. There were significant differences in the rates of MAAs
accumulation between the two populations. More specifically, individuals from
lake Morenito had a higher propensity to lose and gain MAAs that those from
Lake Verde, which maintain a more stable MAA concentration regardless of the
experimental conditions. Temperature affected the concentration of MAAs in
individuals maintained in darkness. As expected, the individuals tended to lose
MAAs at higher temperatures. Unexpectedly however, the lower temperatures
stimulated the accumulation of MAAs, even when the copepods were in the dark.
Thus, low temperature by itself may induce MAA accumulation.