5 research outputs found
Antarctic marine chemical ecology: what is next?
71 pĂĄginas, 1 tabla, 3 figuras.Antarctic ecosystems are exposed to unique environmental characteristics
resulting in communities structured both by biotic interactions such as
predation and competition, as well as abiotic factors such as seasonality and
ice-scouring. It is important to understand how ecological factors may trigger
chemical mechanisms in marine Antarctic organisms as a response for survival.
However, very little is known yet about the evolution of chemical compounds
in Antarctic organisms. Investigations in chemical ecology have demonstrated
over the last several years that defensive metabolites have evolved in numerous
representative Antarctic species. This contradicts earlier theories concerning
biogeographic variation in predation and chemical defenses. As reviewed here,
a number of interesting natural products have been isolated from Antarctic
organisms. However, we believe many more are still to be discovered. Currently, many groups such as microorganisms, planktonic organisms and deepsea fauna remain almost totally unknown regarding their natural products.
Furthermore, for many described compounds, ecological roles have yet to be
evaluated. In fact, much of the research carried out to date has been conducted
in the laboratory, and only in a few cases in an ecologically relevant context.
Therefore, there is a need to extend the experiments to the ïŹeld, as done in
tropical and temperate marine ecosystems, or at least, to test the activity of the
chemicals in natural conditions and ecologically meaningful interactions.
Defense against predators is always one of the main topics when talking about
the roles of natural products in species interactions, but many other interesting
aspects, such as competition, chemoattraction, fouling avoidance and ultraviolet (UV) protection, also deserve further attention. In our opinion, challenging
future developments are to be expected for Antarctic marine chemical ecology
in the years to come.This work would not have been possible without the ïŹnancial support of the Ministry of
Science and Education of Spain through different
grants along recent years in the general frame of
our ECOQUIM projects (ANT97-1590-E, ANT97-0273,
REN2002-12006-E âANT, REN2003-00545 and CGL2004-
03356 âANT).Peer reviewe
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Deterrent activities in the crude lipophilic fractions of Antarctic benthic organisms: chemical defences against keystone predators
Generalist predation constitutes a driving force for the evolution of chemical defences. In the Antarctic benthos, asteroids and omnivore amphipods are keystone opportunistic predators. Sessile organisms are therefore expected to develop defensive mechanisms mainly against such consumers. However, the different habits characterizing each predator may promote variable responses in prey. Feeding-deterrence experiments were performed with the circumpolar asteroid macropredator Odontaster validus to evaluate the presence of defences within the apolar lipophilic fraction of Antarctic invertebrates and macroalgae. A total of 51% of the extracts were repellent, yielding a proportion of 17 defended species out of the 31 assessed. These results are compared with a previous study in which the same fractions were offered to the abundant circum-Antarctic amphipod Cheirimedon femoratus. Overall, less deterrence was reported towards asteroids (51%) than against amphipods (80.8%), principally in sponge and algal extracts. Generalist amphipods, which establish casual hostâprey sedentary associations with biosubstrata (preferentially sponges and macroalgae), may exert more localized predation pressure than sea stars on certain sessile prey, which would partly explain these results. The nutritional quality of prey may interact with feeding deterrents, whose production is presumed to be metabolically expensive. Although optimal defence theory posits that chemical defences are managed and distributed as to guarantee protection at the lowest cost, we found that only a few organisms localized feeding deterrents towards most exposed and/or valuable body regions. Lipophilic defensive metabolites are broadly produced in Antarctic communities to deter opportunistic predators, although several species combine different defensive traits