RESUMO
La tilapia es un pez dulceacuícola originario del África que posee muchas características que la convierten en un excelente pez para acuicultura, pero también es considerada como una de las especies exóticas invasoras más peligrosas del mundo debido a su adaptabilidad y potencial reproductivo. En este ensayo se analiza el dilema entre las bondades de estos peces como alternativa para contribuir con la seguridad agroalimentaria y la amenaza que representa para la biodiversidad acuática de Ecuador. La ausencia de información oficial hace necesario investigar el efecto de las invasiones por tilapia en los ríos, lagunas y esteros colonizados por esta especie. El nivel de acción para prevenir, erradicar o controlar la tilapia en Ecuador ha sido muy limitado y por lo tanto se impone la necesidad de establecer estrategias para evitar su propagación hacia áreas aún no invadidas. Aunque el gobierno de Ecuador posee regulaciones que restringen la introducción de especies exóticas, la realidad es que, en el caso de la tilapia, lejos de establecer controles adecuados, el cultivo de estos peces es impulsado sin mayores objeciones. Se discute la posibilidad de adoptar estrategias de control biológico para erradicar y/o mitigar las consecuencias de la invasión por tilapias en el país y la necesidad de fomentar campañas educativas para crear un nuevo comportamiento ambiental, conciencia y responsabilidad en la sociedad.
Tilapia is a freshwater fish native to Africa that has many characteristics that make it an excellent fish for aquaculture, but it is also considered one of the most dangerous invasive exotic species in the world due to its adaptability and reproductive potential. This essay analyzes the dilemma between the benefits of these fish as an alternative to contribute to agrifood security and the threat it poses to Ecuador's aquatic biodiversity. The absence of official information makes it necessary to investigate the effect of the invasions by tilapia in the rivers, lagoons and estuaries colonized by this species. The level of action to prevent, eradicate or control the tilapia in Ecuador has been very limited and therefore the need to establish strategies to prevent its spread to areas not yet invaded is imposed. Although the government of Ecuador has regulations that restrict the introduction of exotic species, the reality is that, in the case of the tilapia, far from establishing adequate controls, the culture of these fish is promoted without major objections. The possibility of adopting biocontrol strategies to eradicate and / or mitigate the consequences of the invasion by tilapia in the country and the need to promote educational campaigns to create a new environmental behavior, conscience and responsibility in society is discussed.
RESUMO
Karyotypic features of Rhoadsiaaltipinna Fowler, 1911 from Ecuador were investigated by examining metaphase chromosomes through Giemsa staining, C-banding, Ag-NOR, and two-color-fluorescence in situ hybridization (FISH) for mapping of 18S and 5S ribosomal genes. The species exhibit a karyotype with 2n = 50, composed of 10 metacentric, 26 submetacentric and 14 subtelocentric elements, with a fundamental number FN=86 and is characterized by the presence of a larger metacentric pair (number 1), which is about 2/3 longer than the average length of the rest of the metacentric series. Sex chromosomes were not observed. Heterochromatin is identifiable on 44 chromosomes, distributed in paracentromeric position near the centromere. The first metacentric pair presents two well-defined heterochromatic blocks in paracentromeric position, near the centromere. Impregnation with silver nitrate showed a single pair of Ag-positive NORs localized at terminal regions of the short arms of the subtelocentric chromosome pair number 12. FISH assay confirmed these localization of NORs and revealed that minor rDNA clusters occur interstitially on the larger metacentric pair number 1. Comparison of results here reported with those available on other Characidae permit to hypothesize that the presence of a very large metacentric pair might represent a unique and derived condition that characterize one of four major lineages molecularly identified in this family.