Cerca i optimització de marcadors genètics per a la diferenciació de les dues espècies de sonso

Martínez Guillem, Àlex
The fish known as sand eel includes two species known as Gymnammodytes cicerelus and Gymnammodytes semisquamatus. Both are present in the Mediterranean Sea although it’s practically impossible to differentiate them morphologically due to their high similarity, leading to an indiscriminate fishing of both. This is the reason why it’s necessary to be able to differentiate them at molecular level with the aim of determine how many populations of each specie exist in order to avoid the loss of viability of any of them. The Genetics Ichthyology Laboratory of the University of Girona (LIG-UdG) has designed a mitochondrial marker for this purpose, which has allowed to differentiate the two species and determine that there is only one population for each of them. Following this objective, this paper proposes confirming the molecular differentiation of the two species using nuclear markers. To perform this, an exhaustive bibliographic search has been carried out in order to find nuclear markers that have been used in previous studies to establish the phylogeny of species genetically related to those of this study. Subsequently, the search of primers of the selected markers has been proceeded and the corresponding DNA extraction of individuals from both species, previously differentiated mitochondrially, has been performed. The optimal PCR conditions have been designed and the amplicons replication delimited by the pairs of selected primers has been performed, in addition, the quality of the PCR products has been verified by agarose gel electrophoresis. Next, the cleaning and purification of the resulting amplicons has been carried out with an ExoSAP protocol and has been followed by a BigDye sequencing protocol to sequence them for subsequent bioinformatic analyses. With the results obtained it can be concluded, through the construction of phylogenetic trees using the neighbour joining method, that Gymnammodytes cicerelus and Gymnammodytes semisquamatus are two different species within the same genus. At the same time, the distance between these two species has been calculated, along with an outgroup conformed by genetically close species, which has allowed to corroborate the final conclusion of this study ​
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