A team of Brazilian researchers have described five new species of ascidians, commonly known as sea squirts. The team, affiliated with the Federal University of Paraná’s Zoology Department (DZ-UFPR), discovered the five new species off the coast of Bahia State, with four of the five species belonging to the genus Didemnum (D. aurantium, D. flammacolor, D. lambertae, and D. longigaster) and the other belonging to the genus Diplosoma (D. citrinum).
Sea squirts refer to any member of the invertebrate class Ascidiacea (subphylum Urochordata, also called Tunicata) and are marine animals that possess some primitive vertebrate features. Sea squirts are primarily sessile, potato-shaped organisms found in all seas, from the intertidal zone to extreme depths. There are currently around 3000 known species of ascidians worldwide, 20% of them belonging to the family Didemnidae. The appeal of researching these marine organisms (besides the opportunity to enhance taxonomic knowledge of the group) are the potential uses of the natural compounds ascidians synthesise, which can contribute to the development of new medicinal drugs and pesticides among other products. Members of Didemnidae are generally promising in terms of chemical compounds, which are their only defense against predators
The researchers’ taxonomic analysis of the samples was supported by FAPESP through the Thematic Project “Investigation of metabolic and biotechnological potential of marine organisms in bioremediation processes and for the production of substances with anti-viral, anti-inflammatory and anti-Leishmania activities,” coordinated by Roberto Gomes de Souza Berlinck, a professor at the University of São Paulo’s São Carlos Chemistry Institute (IQSC-USP).
Sea squirts are sources of diverse natural products that are of special interest for biomedicine and drug discovery. For example Ecteinascidia turbinata, a colonial sea squirt, produces a substance known as trabectedin (ET-743) which has anticancer properties and is used in the treatment of soft tissue sarcomas. In 1969, the National Cancer Institue carried out a number of tests on marine organism material and found that E.turbinata exhibited anticancer activity. Recently, the biosynthetic pathway responsible for producing the drug has been determined to come from Candidatus Endoecteinascidia frumentensis, a microbial symbiont of the tunicate.
“Exotic molecules obtained from research on ascidians have been explored worldwide for use in combating cancer,” explains Rosana Moreira da Rocha, a researcher at DZ-UFPR. “However, preclinical trials are often aborted because of these animals’ high toxicity. The substances they produce can eliminate cancer cells, but they also destroy healthy cells. Nowadays there are different, more diversified targets, such as Parkinson’s, Alzheimer’s, leishmaniasis and malaria,”
The taxonomic classification of these 5 new species took a number of years. Samples of the individuals were then deposited at the University of São Paulo’s Zoology Museum, which holds one of Brazil’s main collections of ascidians, and with the Federal University of Paraná’s Zoology Department.
“We also shared the material with Professor Berlinck’s research group,” Moreira da Rocha said. “They’re working on extraction of chemicals, which will be tested to evaluate potential industrial applications.” If interest arises in specific substances, they will not be obtained directly from ascidians. “We’re looking for models,” she said. “Once the biochemists understand the structure of a specific molecule, the next step will be to synthesize it by imitating its chemistry and hence its physiological effects.”
The team believes there is still much to discover, regarding ascidians in the Brazilian territory. Although much of the coastal waters are naturally oligotrophic and deficient in nutrients compared with the Pacific coast, Moreira da Rocha expects to continue finding new species. The researchers’ findings were published in the January issue of the journal Zootaxa, the paper is available here.
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