Over the next three years, the National Genome Network will be involved in the work of mapping the genome of the Pacific white shrimp, the Litopenaeus vannamei, a species that is cultivated in almost the totality of Brazilian hatcheries. There are 13 laboratories that are bettering the knowledge about the genetics of this crustacean, which is gaining importance every year, in particular because Brazil has seen an amazing growth in the exports of this product. They leaped from US$ 14.2 million in 1999 to US$ 155 million in 2002. This year, the forecast is to reach US$ 240 million. Total production should come to 90,000 tons, of which more than 90% will come from the Northeast of Brazil, where shrimp breeding occupies second place on the list of exports, behind only sugarcane byproducts. Accordingly, the more that is known about the animal and breeding it, the more assured are the productivity and expansion of this delicacy, appreciated in all the corners of the planet.
Some other goods news on this aquatic animal, bred in seaside terrain where advantage is taken of the water from the sea or the estuary, is that it can be grown in fresh water, according to studies by Professor Paulo de Paula Mendes, from the Fishing Department of the Federal Rural University of Pernambuco (UFRPE). “After three years of research, we have succeeded in acclimatizing the marine shrimp and breeding it in totally fresh water, just like drinking water”, says Mendes, who prepared the work to be made public at the 13th Brazilian Congress of Fishing Engineering, set for the end of September, in Porto Seguro (BA). The basis of the technique used consists of slowly reducing the saline concentration of the water, until the salt is eliminated. With this process, Mendes says that he has achieved a 95% survival rate. “Breeding this kind of shrimp in totally fresh water is unprecedented, even in other countries that breed crustaceans, like China, Thailand, Indonesia and Ecuador.”
Breeding shrimps in slightly fresh water is already a practice followed in some localities of the Brazilian northeast. In Rio Grande do Norte, the leading state in shrimp production, there are experiments for raising them in water with extremely low salinity. The activity is one way of taking the breeding inland and bringing them to regions with scant possibilities for generating employment and income. In the town of Tangará, in a region 300 kilometers from Natal, the Trairi reservoir holds 70 hectares of this kind of hatchery, financed by the Rio Grande do Norte Development Agency, with funds from the National Bank for Economic and Social Development (BNDES).
According to Professor Mendes, “breeding this shrimp in fresh water will foster one more opportunity for fixing people in the country, particularly the small farmer, and will even serve as a means of subsistence”. In some farms, gross earnings from this crop can reach US$ 10,000 per hectare in one year, with the kilo of shrimp sold to the processing plants at R$ 8.00. These figures result from the fact that Brazil enjoys the highest productivity in the world, with 5,400 kilos per hectare a year (kg/ha/year). In China, it is 1,158 kg/ha/year, and in Thailand, 3,421 kg/ha/year, the second best.
The excellent Brazilian performance is a result of the successful collaboration between producers and researchers from public institutions, which culminated this year in the beginning of the Shrimp Genome project. The first studies of this species started in 1998 at the Federal University of Rio Grande do Norte (UFRN). It was work to identify, by means of an analysis of the DNA, the variability of reproducers with different pedigrees from various hatcheries. The objective was to rule out the possibility of consanguinity, a factor that can generate deficiencies in resistance and in growth. For shrimp breeding, these studies are very important, because these crustaceans are extremely prolific. A single couple can sustain several hatcheries, facilitating the crossing of individuals from one same family. One of the problems faced by the researchers was how to select the different reproducers. The researchers then arrived at a diagnosis of genetic variation found in the various groups of reproducer Litopenaeus vannamei. This information made it possible to steer the crossbreeding in order to establish different strains in the laboratories that produce post-larvae – the first stage of growth of shrimps in hatcheries.
“In 2000, we started our program on the genomics of the Pacific shrimp by means of a project prospecting for microsatellites (sequences of short repetitions in the genome), extremely useful markers for studies in genetic variation, identification of strains, studies of pedigrees and genetic mapping. After two years of prospection of these microsatellites, it was natural for us to propose carrying out the Genome project, to acquire a knowledge of the expressed sequence tags (ESTs) – the fragments of the genetic code that help to identify the genes”, explains the coordinator of the project, Professor Pedro Manoel Galetti Júnior, from the Genetics and Evolution Department of the Federal University of São Carlos (UFScar). The research won’t be an easy job at all. One of the reasons is the size of the Litopenaeus vannamei’s genome, roughly two-thirds the size of the human genome, which means about 2 billion base pairs. In total, the project will be sequencing 300,000 ESTs from different tissues and stages of development of the shrimp.
Sifting the chromosomes
Other work that should shortly be generating practical results has been concluded by Professor Wagner Molina, the coordinator of the UFRN’s Program for Postgraduate Studies in Genetics and Molecular Biology, and one of those taking part in the Genome project. The researcher completed the study of the karyotype – or set of chromosomes that are the structures containing the genetic information – of the shrimp, and attested that the crustacean has 88 chromosomes, in two batches, one paternal and one maternal. Just as a comparison, humans have 46 chromosomes.
The next step will be the attempted genetic manipulation of the chromosomes, to make the shrimps sterile, which would prevent undesirable reproduction in the hatcheries where they are fattened up. “Reproduction, which is of no interest to the producer, requires energy of the animals. Sterile shrimps could use this energy for growth, favoring production. Another gain with sterility would be for the marine environment, because there is no control over the hatcheries, and we know that many Pacific white shrimps are now in the sea off the Northeast, because of leaks from the hatcheries. The consequences for the environment are unforeseeable, because the species is not a native one.
They may be competing with the shrimps that are native to our coastline”, warns Wagner Molina. The environmental problems also extend to the places where breeding takes placed. Many producers have set their hatcheries up in mangrove swamps, endangering these ecosystems. At the end of 2001, the Brazilian Institute for the Environment and Renewable Natural Resources (IBAMA) carried out a mega-operation that fined 180 mostly small-scale producers. Half of the fines were for clearing vegetation from the areas of the mangrove swamps. The demand for these environments has a few explanations. Besides providing water of a good quality, the mangrove swamps are rich in nutrients, which makes it possible to reduce the use of feeds.
The solution may lie in breeding shrimps in fresh water, thus avoiding the problems in areas of environmental preservation and guaranteeing good development for shrimp breeding. When this new path is being consolidated over the next few years, the first results of the Genome project will begin to be made available. This will benefit even more the expansion of shrimp breeding. Galetti Júnior wants to release part of the information on the Genome even before the final conclusion of the work. The objective is for research that leads to practical results to be started right away. “The information about genetic marks that accompany characteristics of economic importance will make possible a selection assisted by these markers. Information will come up about the function of the genes identified and the way that this knowledge can be potentialized, to the benefit of the breeding business”, says the researcher.
The Shrimp Genome project will have a total cost of R$ 3 million, financed by the Brazilian Shrimp Breeders’ Association (ABCC), the National Council for Scientific and Technological Development (CNPq), the Ministry of Agriculture and Supply, and the government of the State of Rio Grande do Norte. Taking part in the sequencing are the following universities: UFSCar, UFRPE, UFRN, University of São Paulo, São Paulo State University, Federal University of Maranhão, Federal University of Ceará, Pontifical Catholic University of Rio Grande do Sul, Federal University of Santa Catarina, State University of Santa Cruz (Ilhéus, Bahia) and Federal University of Pará.
Employment and cash
The interest of the northeasterners in these researches is great. Shrimp breeding is a sector that works with the prospect of producing 90,000 tons this year, 40,000 more than in 2002. The business generates 3.75 direct and indirect jobs per hectare, against the 2.14 in the fruit growing under irrigation of the São Francisco Valley, for example, according to a study by the Economics Department of the Federal University of Pernambuco (UFPE). In 2002, through the 11,000 hectares under cultivation, shrimp breeding produced cash for about 40,000 who work along with the 680 producers from all over the country.
Found naturally on the coast from Mexico to Chile, the Pacific white shrimp was brought to Brazil in the 80’s. It was a species bred successfully in countries like Ecuador, a great producer at the time. The technique for breeding the crustacean already existed, and was adopted by the producers who started the business in Brazil. One of the advantages over the Brazilian species of shrimp was that Litopenaeus vannamei needed less protein for growth, although it is less resistant to diseases.
Many Brazilian went to learn with the Ecuadorians the techniques for handling, which, in the end, proved not to be effective. At the end of 90’s, a virosis called white spot wiped out 90% of the country’s production, and the Brazilian government prohibited the import of the breeding stock, on sanitary grounds. The producers worked hard to develop the productive chain in captivity, and today the handling techniques are more advanced than those in the largest producing countries. While the Brazilians are fighting to achieve a disease resistant shrimp, investing in genetic research, Chinese and Thai producers are using large doses of antibiotics in the hatcheries. This is leading them to face sanitary barriers of the major importers, such as the United States, France and Spain.
“The Shrimp Genome can help us to have an even better product. We also invested in the project to awaken the interest of the Brazilian scientific community to researches on shrimps”, says Itamar Rocha, the president of the ABCC. Some laboratories, like Aquatec, from Rio Grande do Norte, have already been concerned with genetic improvement for some time. The result is a production of 250 million larvae, sold to five Brazilian states. “Six years ago, we started work on selecting families and forming high quality pedigrees. For us, the Genome project will be a powerful tool for an even more rigorous selection”, says Ana Carolina de Barros Guerrelhas, a biologist and a partner in the laboratory. She thinks that Brazil should not be concerned with being the biggest producer, but rather with being one of the best.