Horizontal transmission of disseminated neoplasia in the widespread clam
Limecola balthica from the Southern Baltic Sea
Disseminated neoplasia (DN) is one of the most challenging and
unrecognised diseases occurring in aquatic fauna. It has been diagnosed
in four bivalve species from the Gulf of Gdańsk (Southern Baltic Sea)
with the highest frequency in Limecola balthica (formerly Macoma
balthica), reaching up to 94% in some populations. The aetiology of DN
in the Baltic Sea has not yet been identified, with earlier studies
trying to link its occurrence with environmental pollution. Taking into
account recent research providing evidence that DN is horizontally
transmitted as clonal cells between individuals in some bivalve species,
we aimed to test whether DN is a transmissible cancer in the population
of L. balthica from the Gulf of Gdańsk highly affected with cancer. We
examined mitochondrial cytochrome c oxidase I (mtCOI) and elongation
factor 1α (EF1α) sequences of genomes obtained from haemolymph and
tissues of neoplastic and healthy individuals. Sequence analysis
resulted in detection of an independent transmissible cancer lineage
occurring in 4 neoplastic clams that is not present in healthy animals.
This paper describes the first case of transmissible DN in the clam L.
balthica providing further insights for studies on this disease.