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Unlocking Coelacanth Secrets
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| 5. Unlocking Coelacanth Secrets By Professor Paulette Bloomer Since the launch of the African Coelacanth Ecosystem Programme (ACEP) in April 2002, a multidisciplinary research team from seven African countries has been inspired by this 'living fossil'. Their research efforts to date have not only enriched marine science in the region, but also enhanced public awareness of this enigmatic creature and of oceans as the last frontier for earth exploration. The geophysics team has made great strides in mapping the ocean floor and canyons that contain possible coelacanth habitats. Similarly, oceanographers have challenged previously held views regarding the flow patterns of the Mozambique and Agulhas currents. These researchers have laid a foundation that other scientific disciplines can now build upon, to further refine our understanding of coelacanth biology and the unique marine ecosystem of which they are a part of. Coelacanth genetic variation The ACEP genetics team will build on the research from the other teams, though this will not be the first time that genetics has been used in the study of coelacanths. The German research team that generated so much of our existing knowledge of coelacanths through their in-depth study of the Comoros. population, also developed a novel way to sample scales from living coelacanths. Sampling of biological materials from endangered species is very challenging, as one cannot use so-called invasive methods that may harm the animals. In the case of coelacanths, thin layers of cells can be scraped from the scales, to allow scientists access to DNA contained within each cell. |
 Coelacanth scale collection and analysis - to determine genetic and kinship relations. |
| The DNA in animal cells is contained in two compartments. The bulk
of the genetic material is found in the chromosomes of the nucleus. In
species that reproduce sexually, half of the material comes from each
parent. A small number of genes are found in the mitochondria, the
energy powerhouses of each cell. These genes, that are absolutely
crucial for the survival of all animals, are in most instances only
passed on from the female parent to the offspring. Studying
mitochondrial DNA thus allows us to trace back female lines through
time. The preliminary research done by the German scientists used mitochondrial DNA and showed little variation among coelacanths from the Comoros, Madagascar, Mozambique and Kenya. More data should be added as, up to two years ago, only small numbers of samples were available from outside the Comoros. One may be tempted to think that all these coelacanth populations have in the recent past been connected through female gene flow. Recent predictions based on the comparison of coelacanth genes to those of other animals (genome level research), caution us against this interpretation. It may be that coelacanth DNA changes very slowly over time due to their long, relatively slow lifestyles. The few changes in the DNA of Comoran and other Western Indian Ocean (WIO) populations may therefore translate into reasonable isolation between these populations. We should also study the DNA in the nucleus as this will give us an indication of the mixing of male and female lines in the past and present, and may help us get a handle on the rate at which coelacanth DNA changes. Comparing specific coelacanth genes to those of other animals provides a window to the deep past, and our genomics team will explore this further in collaboration with oversea sscientists. The ACEP genetics team in collaboration with international partners will focus on genetic variation between different coelacanths in the same population and among different populations. This will allow us to answer questions such as: How many males contribute sperm to the offspring of a single coelacanth female? How many coelacanths form part of a family group? Are all the coelacanths off Sodwana part of one population? How many other relatively 'closed' breeding populations inhabit the Western Indian Ocean? How have these populations been connected in the past and are they connected in the present? Can genetic data give us an indication of the number of coelacanths? |
 This diagram illustrates how variation in DNA sequences from different coelacanths can be used to determine whether the areas where they occur are isolated from each other or connected via gene flow. |
 Microsatellites are genetic markers that evolve very fast in most vertebrate species. This marker type is the standard method used in human forensics and paternity disputes. The diagram illustrates how microsatellites can be used to study coelacanth populations. |
| These questions are not only important for unravelling coelacanth
secrets, but for studying populations of species that are exploited for
human consumption, such as fish and prawns. Several countries share
some of thesepopulations and we should therefore guard against
over-exploitation by any country to ensure sustainable and equitable
sharing of these renewable, but not limitless resources. DNA can also
be used as identity tags in cases where marine resources are harvested
illegally. Western Indian Ocean phylogeography The WIO provides us with unique opportunities to contribute to another genetic sub-discipline, namely phylogeography. This research field combines information from population genetics, population dynamics, animal behaviour and ecology with information from geography and palaeontology. The genetic variation within a species is a balance of factors operating within each individual and its population, and the external environmental influences on them. The combined result of data from all these research fields affords a better understanding of why animals occur where they are found today, how different populations have interacted in the past and how they interact at present. Within ACEP, this discipline translates into exciting possibilities for geoscientists, oceanographers, marine ecologists and geneticists to work together in piecing together the history of this ocean ecosystem. If we understand the past and the current functioning of the ecosystem, we should be in a better position to react to any future environmental changes affecting the system and its species. Genetics offer enormous opportunities for capacity building in the WIO region and these methods are widely applicable not only in biodiversity conservation but in agriculture and medicine. Professor Paulette Bloomer, Molecular Ecology and Evolution Programme, Department of Genetics, University of Pretoria and genetics team member within ACEP. |
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