One of recurrent health problems that effect the culture of the Japanese oyster, Magallana gigas, which is one of the bivalve mollusks with the highest aquaculture production at a global scale. Is the infestation by burrowing worms of the family Spionidae that have the ability to settle on calcareous shells piercing them and forming tunnels where they take refuge. The hosts become affected when the infestation is high and the worms reach the inner face of the shell. This ultimately triggers a reaction from the host who expedites energy into depositing additional nacreous layers to isolate the polychaete to stop it from reaching the soft tissues forming blisters. In such cases that the worm reaches the soft tissues of the hosts, it becomes to be more susceptible to bacterial infections. Additionally, severe infestations result in a brittle and unpleasant aspect of the shell for marketing. In Mexico the production of M. gigas is concentrated in San Quintin Bay and since 1997, the presences of these burrowing worms and the damage that produces in the oyster has been documented: however, his identity has not been confirmed.
In this study we carry out a broad sampling of oysters from the Bay and found three different phenotypes of polydorids, which differ in the pigmentation of the palps. The Whole Genome Sequencing analysis of the most prevalent phenotypes shows that the 18S rRNA gene has a similarity of 99.5% whit Boccardiella hamata while mitochondrial genes show similarities of ranging from 83-89% (Table 1). Conventional taxonomy analysis and ultrastructural studies for describing discrete morphological features are underway in addition to further next generation sequencing and sanger sequencing studies. Similar analysis will be conducted to the other two phenotypes. This research will help clarify the taxonomic affiliation of these burrowing worms and their role in the effect on the shell. Additionally, will aid in the development of diagnostic tools to differentiate among possible different species and to provide base line element that contribute to mitigate their negative effect on Mexican oyster culture