Horizontal transmission of disseminated neoplasia in the widespread clam Macoma balthica from the Southern Baltic Sea

Abstract

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 Macoma balthica (formerly Limecola 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 bivalve transmissible neoplasia (BTN) in the population of M. 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 four neoplastic clams that is not present in healthy animals. This study describes the first case of BTN in the clam M. balthica (MbaBTN), providing further insights for studies on this disease.

Marine transmissible cancer navigates urbanised waters, threatening to spillover

“…Transmissible cancers are malignant cell lineages that have acquired the ability to infect new hosts through the transmission of living cancer cells. Eleven transmissible cancer lineages have been described to date: one in dogs (canine transmissible venereal tumour, CTVT [1,2]), two in Tasmanian devils (devil facial tumour, DFT1 and DFT2 [3,4]), and eight in different marine bivalve species (bivalve transmissible neoplasia, BTNs [5][6][7][8][9]).…”

The evolution of two transmissible leukaemias colonizing the coasts of Europe

“…Despite several BTN clones having been newly described in recent years (9)(10)(11)(12)(13)(14), no analyses of whole BTN genomes have yet been reported. Combining a range of approaches, our study provides a first outlook into the genomes of these singular marine leukaemias in European common cockles, complementing the work of Hart et al (30) on American soft-shell clams.…”

“…Transmissible cancers are clonal somatic cell lineages that spread between individuals via direct transfer of living tumour cells, in a process analogous to cancer metastasis (1,2). Naturally occurring transmissible cancers have been identified in dogs (3)(4)(5), Tasmanian devils (6)(7)(8) and, more recently, several species of marine bivalve molluscs (9)(10)(11)(12)(13)(14). To date, eight transmissible cancer lineages, collectively known as bivalve transmissible neoplasia (BTN), have been described in bivalves, probably spreading via transfer of free-floating cells in seawater.…”

Molecular diversity of bivalve transmissible neoplasia of blue mussels in the Kola Bay (Barents Sea) indicates a recent migration of the cancer lineages between the North Pacific and Northern Europe

“…Discovered in the past decade (Metzger et al, 2015, 2016), BTN lineages, the unicellular parasitic species of Bivalvia, are an unchartered component of marine diversity. Eight independent BTN lineages affecting nine different species are known (Garcia-Souto et al, 2021; Hammel et al, 2021; Metzger et al, 2015, 2016; Michnowska et al, 2022; Skazina et al, 2021; Yonemitsu et al, 2019). As an infectious disease, BTN is a threat to natural and commercial shellfish populations (Metzger et al, 2015, 2016 and references therein).…”