Bacterial composition in the toheroa (Paphies ventricosa), a threatened surf clam from Aotearoa (New Zealand)

Abstract

AbstractThe toheroa (Paphies ventricosa) is an Aotearoa (New Zealand) endemic surf clam that remains threatened following population collapse due to overfishing in the twentieth century. Despite protective measures being in place for more than 4 decades, toheroa populations have inexplicably failed to recover. As part of an investigation into the possible role of disease in preventing their recovery, an exploration of the bacterial composition in toheroa was conducted over their entire geographic range. The bacterial composition in toheroa tissues was dominated by Spirochaetaceae, Mycoplasmataceae, and Endozoicomonadaceae, and varied at both large (between geographically separated sites) and small spatial scales (beds < 10 km apart). At small scales, it was habitat, in this case the presence or absence of freshwater outflows, which appeared to be a major influence on bacterial composition. Given that the decline of toheroa has also coincided with changes in land use that have reduced the amount of freshwater reaching the toheroa beaches, it is possible that habitat-related shifts in the abundance of certain bacterial symbionts are affecting the health and impeding recovery of this iconic and culturally significant species.