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Natural Product Reports Natural Products Mediating Ecological Interactions in Antarctic Benthic Communities: A Mini-Review of the Known Molecules Journal: Natural Product Reports Manuscript ID: NP-REV-11-2014-000150.R1 Article Type: Review Article Date Submitted by the Author: 17-Jan-2015 Complete List of Authors: Nunez Pons, Laura; University of Hawai'i, HIMB; Universitat de Barcelona, Biologia Animal Avila, Conxita; Universitat de Barcelona, Biologia Animal (Invertebrats) Page 1 of 18 Natural Product Reports Journal Name RSC Publishing REVIEW Natural Products Mediating Ecological Interactions in Antarctic Benthic Communities: A Mini-Review of the Cite this: DOI: 10.1039/x0xx00000x Known Molecules L. Núñez-Pons a,b and C. Avila a Received 18th November 2014, Accepted 13th January 2015 Out of the many bioactive compounds described from the oceans, only a small fraction has been studied for its ecological significance. Similarly, most chemically mediated interactions DOI: 10.1039/x0xx00000x are not well understood, because the molecules involved remain unrevealed. In Antarctica, this www.rsc.org/ gap in knowledge is even more acute in comparison to tropical or temperate regions, even if polar organisms are also prolific producers of chemical defenses, and pharmacologically relevant products are being reported from the Southern Ocean. The extreme and unique marine environments surrounding Antarctica along with the numerous unusual interactions taking place in benthic communities are expected to select for novel functional secondary metabolites. There is an urgent need to comprehend the evolutionary role of marine derived substances in general, and particularly in the Poles, since molecules of keystone significance are vital in species survival, and therefore, in structuring the communities. Here we provide a mini-review on the identified marine natural products proven to have an ecological function in Antarctic ecosystems. This report recapitulates some of the bibliography from original Antarctic revisions, and updates the new literature in the field since 2009 to our days . 1. Introduction of the ~24 000 marine reported compounds originates from higher latitudes, despite the fact that a huge portion of global shallow-water The sea is a rich source of bioactive molecules with great habitat is found around the Antarctic Continent. The reasons for this potentialities, including a range of applications from the asymmetry are probably related to the difficult accessibility, harsh development of drugs to fight cancer or inflammatory diseases, climate, and the prevailing theory that Polar systems should be less cosmetics, to ecologically friendly antifouling paints for boats and biochemically productive. 9,10 underwater machinery (see 1 and previous reviews of the series). Benthic organisms are under constant demand for space, light and Such products, however, did not originate in nature to serve humans food, and have developed a wide range of defensive mechanisms. in the first place. These substances most likely appeared as products Early geographical comparisons proposed a latitudinal hypothesis of secondary metabolic pathways and assisted organisms under with an inverse gradient between latitude and defensive chemistry in ecological constrains, regulating biology, co-existence and co- marine ecosystems, suggesting highest production of bioactive evolution, and enhancing survival. Subsequently the particular products near the Equator and lowest in the Poles. These studies natural compounds have been maintained during evolution to focused on fish predation, which is intense in the Tropics and mediate ecological interactions (allelopathy). 2–5 Fruit of the diminishes with latitude. 11 Soon this theory was refuted, after collaboration of chemists and biologists, aiming to examine the observing that in Polar zones fishes had been replaced by ecological functions of natural products obtained from marine invertebrate predators (e.g., sea stars and nemertine worms) exerting organisms, marine chemical ecology became known as a equivalent ecological pressures, and that the incidence of chemically multidisciplinary scientific branch, somewhat younger than its defended species was also extremely elevated. 12,13,4,14 Other than terrestrial counterpart. Methodologies have been refined, and with predation, fouling, competition for space/resources, or ultraviolet that the validity of the experiments attempting to explain the original radiation also promote challenges to Antarctic biota. Diatom blooms bioactivities of natural products in the ecosystem. For all intents and in high latitudes during the Austral summer promote produce intense purposes, full understanding about the functionality of most fouling events in exposed organisms. This is different from any other metabolites in the communities is still far from being disentangled. places, where prokaryotic microbes are normally the initiators of The research effort to comprehend chemical ecology is also notably epibiosis all year around. 15 Despite the slow growth characterizing asymmetric, and much more work has been published from tropical much of Southern Ocean’s biota, there are also certain opportunistic and temperate waters than from the Poles. 3,6–8 To date, less than 3% This journal is © The Royal Society of Chemistry 2013 J. Name ., 2013, 00 , 1-3 | 1 Natural Product Reports Page 2 of 18 REVIEW NPR species able to rapidly colonize space and overgrow displacing have been as well excluded. Our current report compiles the others. 13 In addition to all these competing interactions, the Southern literature published up to date about the ecological significance of Pole is the most affected area by ozone (O 3) depletion due to the identified Antarctic marine natural products, intending to Polar vortex, which consequently increases surface UV-B levels, and disseminate a quite unknown information from this isolated leads to biological damage. 16 Therefore, shallow water inhabitants geographic area. here require some sort of chemical photoprotection.17 Antarctic benthic ecosystems are antique, long evolved and diverse. They are 2. Methods dominated by sessile filter-feeding assemblages composed of sponges, cnidarian hydroids, gorgonians and soft corals, ascidians The information in this mini-review was selected from the and bryozoans, accompanied by macroalgae and other motile literature available on this specific area up to September 2014. invertebrate groups like echinoderms, molluscs, nemertines and The results are summarized throughout the text and in Table 1. polychaetes. 18,19,12,20–22 Below the zone influenced by ice dynamics, MarinLit, 10 as well as other databases were used to complete physical environment is fairly stable, and communities are exposed the information. Molecular formulae were drawn with to marked seasonal nutrient fluctuations (winter limitation vs MarvinSketch software (ChemDraw format). Taxonomy summer primary production explosion due to the ice melting and databases have been used to check current names for all the phytoplankton liberation), and intense ecological interactions. species (e.g., WoRMS, Encyclopedia of Life (EOL), World Bioactive compounds are, under these circumstances, of major Porifera, Algae Base), and species which name had changed relevance for species survival, and in mediating avoidance of since the original description have been corrected, maintaining opportunistic predators, fouling and competing organisms. 12,3 The the previous name in brackets. This review is organized by the interest in Southern Ocean regions, regarding ecological interactions type of ecological activity of natural products, with two involving chemistry, is growing, as is reflected by the increased introductory sub-sections; the first exposing several energy publication rate, and the number of characteristic natural products saving theories to counteract the expenses of defense, and the discovered in the past years, some with ecological functions (current second explaining some of the experimental limitations when review and 9,4,1,14 ). dealing with isolated marine compounds. A last miscellaneous Research proceeds at a rapid pace, with significant progress made in sub-section addresses additional relevant insights of Antarctic almost every area of marine chemical ecology: predator–prey and chemical ecology. seaweed–herbivore interactions, defenses against fouling organisms and infection by microorganisms, competitive interactions, and 3. Results and discussion settlement cues. Most advances however, refer to non Polar regions, Among the types of molecules found from Antarctic organisms are since ecological and field experimentation is very difficult in terpenoids, alkaloids, peptides, steroids, polyketides, organic acids, isolated areas like Antarctica. Several comprehensive reviews have and many derivatives. Some of these compounds have proved to been published that relate to the discovery of new natural products possess functions as antipredatory deterrents, competition mediators, with bioactivities in applied fields like pharmacology or industry antifouling, antibiotic, toxic, photoprotective agents and (e.g., 1 and previous revisions of the series), or to global marine reproduction promoters/inhibitors. Similar to other zones, the most chemical ecology (see 5, and previous reviews from Paul and co- studied taxa are sponges and algae, followed by molluscs, authors 7,6,23 ). Among these last ones, most of the bibliography refers cnidarians, ascidians and echinoderms,