Experimental evaluation of the pathogenicity of Perkinsusolseni in juvenile Manila clams Ruditapes philippinarum

We evaluated the pathogenicity of Perkinsus olseni towards the Manila clam, Ruditapes philippinarum, by an experimental challenge. For production of prezoosporangia of P. olseni, we injected uninfected Manila clams with cells of a pure strain of P. olseni and reared them for 7 d. Prezoosporangia were isolated from the soft tissue of the injected clams after culturing in Ray’s fluid thioglycollate medium. Hatchery-reared, uninfected juvenile clams (3–10 mm shell length) were challenged by immersion in one of two concentrations of a prezoosporangial suspension of P. olseni for 6 d. The challenged clams had significantly higher mortality at both the concentrations than the unchallenged clams. The mortality due to infection dose-dependently began approximately 4 weeks and 7 weeks after challenge in the higher and lower concentrations, respectively. This is the first experimental evidence that P. olseni causes direct mortality in Manila clams. The lethal level of infection was estimated at approximately 107 pathogen cells/g soft tissue weight.

Graphical abstractMortalities of juvenile Manila clams Ruditapes philippinarum challenged with Perkinsus olseni at two different doses.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► A challenge of juvenile Manila clams with Perkinsus olseni was successful. ► Prezoosporangia were produced from a pure culture of P. olseni for the challenge. ► Challenged juvenile clams showed significantly higher mortalities than controls. ► This is the first evidence that P. olseni can directly kill Manila clams.