VINICIUS PADULATambja stegosauriformis mollusk: isolated substances with potential for drug developmentVINICIUS PADULA
From the coastal region of Cape Orange in the Brazilian state of Amapá, to Arroio Chuí, a simple stream on the southern tip of the state of Rio Grande do Sul, including the archipelagos of Fernando de Noronha and Saint Peter and Saint Paul and the islands of Trindade and Martim Vaz, the coast of Brazil is famous for the beauty and diversity of its landscapes of beaches, rocky coasts, dunes, sea cliffs, and other environments. But the least-known part of the country’s coastal area is what can be found underwater and partially hidden by the shoreline, in a subsurface world that hosts extremely rich, complex ecosystems. “Of the world’s 2.2 million known marine species, only 9% have been described. This means we have no knowledge of over 90% of the biodiversity of our coastal environments,” commented biologist Mariana Cabral de Oliveira of the Biosciences Institute at the University of São Paulo (IB-USP), in a lecture she delivered on October 24 in São Paulo at the second-to-last meeting of the BIOTA-FAPESP Education Conference Cycle.
At the same time, she said, the high rates of extinction brought about by human activities such as overfishing, pollution, urbanization and the transfer of organisms that can become invasive have further complicated the work of identifying marine species. To get an idea of the scope, studies estimate that today’s international scientific community would require about 360 years and $263 million just to identify these animals. “We’re facing an enormous challenge,” Oliveira cautions. “Much of the marine biodiversity remains unknown, while degradation and overexploitation of the natural resources provided by these environments remain on the rise. In addition, we don’t have enough human and financial resources to conduct a thorough study of such a large variety of organisms.”
LÉO RAMOSFrom left, Maria Gasalla, Roberto Berlinck and Mariana Cabral de OliveiraLÉO RAMOS
One approach that would facilitate the process, in the biologist’s opinion, is DNA barcoding (see Pesquisa FAPESP Issue No. 167). The idea is simple: create a molecular tag based on a small sequence of DNA for each species to facilitate identification. “It would be a uniform, practical system for species identification on a global scale,” she said. This approach would also require a carefully-structured database.
Such a database already exists in The Barcode of Life Data Systems. “As it is fed collected information such as photographs, taxonomic data, etc., new tags are created, and they can be compared with other sequences,” she explained. According to Oliveira, this system can be used even when traditional taxonomic methods are not viable. “To identify a species, taxonomists generally need the complete organism. With DNA barcoding, it is possible to work with fragments of these organisms, provided that their genetic material can be extracted.” Projects developed under the BIOTA-FAPESP program are already using this approach. One such project, implemented through a partnership between the USP Biosciences Institute, the Botanic Institute and the Universidade Estadual Paulista in São José do Rio Preto, has studied the diversity, morphology and geographic distribution of red microalgae in the state of São Paulo.
Ana Paula CamposMany marine species also have considerable socioenvironmental importance, as in the case of algae. “Up to 50% of the available oxygen on the planet is produced by algae,” Oliveira noted. Planktonic microalgae are essential to global geochemical cycles, and multicellular microalgae can be a food source for a wide variety of marine organisms as well as for humans. According to a 2012 study published in the journal PLoS One, Brazil has the world’s largest, most continuous banks of calcareous algae, which play a role in the formation of natural reefs. They are equivalent in size to Australia’s Great Barrier Reef. The Abrolhos Bank alone stretches over an area of about 20,900 square kilometers (km2).
Algae, in fact, are a natural resource that has been increasingly exploited by man. The cultivation of nori (Pyropia spp.)—the algae used as a wrapper for sushi—drives a $3 billion industry in Japan alone. Other very important industries based on the cultivation of these organisms include the production of hydrocolloids, a type of gelatin extracted from some species of algae, and the production of biomass for biofuel or as a source of molecules for a wide range of applications. “Used as biofactories, algae also have a positive differential: they are able to utilize solar energy and remove carbon dioxide (CO2) from the atmosphere, while they create economically important bioproducts,” Oliveira emphasized. All told, about 2,000 species of algae have been described in Brazil. The groups with the largest number of identified species are diatoms, Rhodophyta (red algae) and Dynophyceae.
The diversity of species living in Brazilian coastal environments is not limited solely to marine flora. Surveys by Brazilian researchers estimate that coastal fauna account for over 10,000 species. “It is a curious thing to observe the contrast between the two South American coasts when it comes to species diversity and abundance,” said biologist Maria de los Angeles Gasalla of the Oceanographic Institute of USP (IO-USP). She pointed out that the Atlantic coast has more fish species than the Pacific coast. On the Brazilian coast, 10.5% of the fish species that inhabit the coral reefs are endemic. In the southern and southeastern regions, many fish have significant commercial value, such as King weakfish (Macrodon ancylodon), Brazilian sardines (Sardinella brasiliensis) and skipjack tuna (Katsuwonus pelamis).
Despite its greater abundance of species, the eastern coast of South America accommodates smaller numbers of each species of fish than does the western coast. “Against this backdrop, Brazil also stands out for its large diversity of mollusks, which number over 1,800,” Gasalla pointed out. The Brazilian coast is also home to an enormous diversity of crustaceans, fish, jellyfish and sponges, among other species.
Brazil’s marine and coastal region, including the exclusive economic zone and the extension of the continental shelf, encompasses 4.5 million km², 34% of which is deemed by the Ministry of the Environment as high-priority conservation areas. “But at least in bureaucratic terms, only 1.8% is under the protection of Marine Conservation Units. This does not mean that these units function properly, have been scientifically demarcated, or are actually protected from anthropic impacts,” Gasalla noted.
E. C. OLIVEIRASpecie of marine algae, essential for oxygen productionE. C. OLIVEIRA
This figure is well below Aichi Target 11 proposed by the United Nations Convention on Biological Diversity, which envisions protection of at least 10% of marine or coastal areas. The areas under concession for oil and gas exploration have been increasing, and now exceed 12%. “The objectives of the conservation units should be very clear in terms of what is actually being protected. Otherwise, we’ll go nowhere,” the IO biologist commented. In order to meet people’s need for income, jobs and food, she believes it is crucial to properly manage and regulate fishing. According to Carlos Joly, coordinator of the BIOTA-FAPESP program in São Paulo, since 2008, 90% of the coastline has been protected by a mosaic of Environmental Protection Areas and Areas of Relevant Ecological Interest.
The potential of the little-known marine universe can also be utilized from an application standpoint. Over the years, many marine organisms have been or were used as sources of new substances for the pharmaceutical and cosmetics industries. For example, a pigment known as Tyrian purple, obtained from the glands of Murex groschi and Murex recurvirostris mollusks, was used as a garment dye for centuries, from antiquity to the late Middle Ages. “That was one of the first chemical industries based on substances extracted from marine organisms,” said Roberto Berlinck of the USP Chemistry Institute in São Carlos. These mollusks were overexploited, and they became extinct in the mid-15th century. The structure of Tyrian purple was only discovered much later, in 1909, long after its commercial use was abandoned.
Anti-tumor agents
More recently, several isolated molecules of marine organisms have been tested as candidates for anti-tumor agents. For example, squalamine, a substance isolated from the viscera of the Squalus acanthus shark, is currently in the clinical trial phase. “It may be an inhibiting agent for angiogenesis, the mechanism through which new blood vessels grow from existing ones and thereby promote the proliferation of tumor cells,” Berlinck said.
VINICIUS PADULANudibranquio Tambja mollusk (above): high concentration of chemical compounds in its outer mantle.VINICIUS PADULA
Another example of a substance potentially useful for fighting cancer is ecteinascidin 743, isolated from Ecteinascidia turbinata, an invertebrate organism with a spongy appearance that lives attached to rocks. The researchers observed that this substance can be used in chemotherapy to damage the genetic material of tumor cells. This substance is currently in clinical trials.
Berlinck and other researchers have devoted their time to studying the chemical defenses of nudibranchs, a group of shell-less mollusks, found frequently in Brazil, that includes sea slugs. In a study on a mollusk of the genus Doris, they isolated a substance known as xylosil-MTA, a nucleoside modified with a sulfur atom. It was the first report of this substance, whose pharmacological potential will also be investigated in a specimen of that genus in Brazil. Other mollusks, such as those of the genus Tambja, have garnered attention for their small size and the fact that many chemical compounds concentrated in their outer mantle are used as a defense mechanism. According to Berlinck, several substances with pharmacological potential have already been isolated from these animals.
The BIOTA-FAPESP Education Conference Cycle is an initiative of the BIOTA-FAPESP program in partnership with Pesquisa FAPESP, focused on discussing the challenges involved in preserving Brazil’s principal ecosystems. The lectures, which conclude in November, are intended to present state-of-the-art knowledge created by researchers throughout Brazil, aimed at improving the quality of environmental and science education for high school teachers and students in Brazil.
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