DAO 110:71-79 (2014)  -  DOI: https://doi.org/10.3354/dao02737

Contribution to the DAO Special: 'Microcell parasites of molluscs'

Infection of Manila clams Ruditapes philippinarum from Galicia (NW Spain) with a Mikrocytos-like parasite

Andrea Ramilo1, David Iglesias1,2, Elvira Abollo3, Mar González1, Susana Darriba2, Antonio Villalba1,* 

1Centro de Investigacións Mariñas, Consellería do Medio Rural e do Mar, Xunta de Galicia, 36620 Vilanova de Arousa, Spain
2Instituto Tecnolóxico para o Control do Medio Mariño de Galicia (INTECMAR), Consellería do Medio Rural e do Mar, Xunta de Galicia, 36611 Vilagarcía de Arousa, Spain
3Centro Tecnológico del Mar - Fundación CETMAR, 36208 Vigo, Spain
*Corresponding author:

ABSTRACT: The name ‘microcells’ is frequently used to refer to small-sized unicellular stages of molluscan parasites of the genera Bonamia (Rhizaria, Haplosporidia) and Mikrocytos (Rhizaria). Histological examination of Manila clams Ruditapes philippinarum revealed microcells in the connective tissue of adductor muscle, foot, mantle, gills, siphon and visceral mass. The clams had been collected from 4 beds on the coast of Galicia, Spain. The prevalence of these microcells ranged from 73 to 93% in surface clams and from 3 to 33% in buried clams. However, the detection of brown ring disease signs in clams from every bed prevented us from making the assumption that the microcells alone were responsible for clam mortality. PCR assays using primer pairs designed to detect Bonamia spp. and haplosporidians gave negative results, whereas positive results were obtained with primers for the genus Mikrocytos. A consensus sequence of 1670 bp of the ribosomal gene complex of the microcells was obtained. It contained a section of the 18S region, the whole first internal transcribed spacer, the 5.8S region, the second internal transcribed spacer and a section of the 28S region. Comparison of this sequence with those of M. mackini infecting Crassostrea gigas and Mikrocytos sp. infecting Ostrea edulis showed that the microcells of Galician clams were the most divergent among the compared parasites. This is the first report of a Mikrocytos-like parasite infecting Manila clams. Care must be taken to avoid the spread of this parasite through Manila clam transfers.


KEY WORDS: Ruditapes philippinarum · Manila clam · Microcells · Mikrocytos · PCR · Ribosomal gene


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Cite this article as: Ramilo A, Iglesias D, Abollo E, González M, Darriba S, Villalba A (2014) Infection of Manila clams Ruditapes philippinarum from Galicia (NW Spain) with a Mikrocytos-like parasite. Dis Aquat Org 110:71-79. https://doi.org/10.3354/dao02737

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