Descriptions of Mikrocytos veneroïdes n. sp. and Mikrocytos donaxi n. sp. (Ascetosporea: Mikrocytida: Mikrocytiidae), detected during important mortality events of the wedge clam Donax trunculus Linnaeus (Veneroida: Donacidae), in France between 2008 and 2011

Type Article
Date 2018-03
Language English
Author(s) Garcia Celine1, Haond Christophe1, Chollet Bruno1, Nerac Mirella1, Omnes Emmanuelle1, Joly Jean-Pierre1, Dubreuil Christine1, Serpin Delphine1, Langlade Aime2, Le Gal Dominique3, Terre-Terrillon Aouregan3, Courtois Olivier4, Guichard Benjamin1, Arzul IsabelleORCID1
Affiliation(s) 1 : IFREMER, RBE SG2M LGPMM, Stn La Tremblade, Ave Mus Loup, F-17390 La Tremblade, France.
2 : IFREMER, ODE LITTORAL LERMPL, Stn Trinite Mer, 12 Rue Resistants, F-56470 La Trinite Sur Mer, France.
3 : IFREMER, ODE LITTORAL LERBO, Stn Concarneau, Pl Croix, F-29185 Concarneau, France.
4 : IFREMER, ODE LITTORAL LERPC, Stn La Tremblade, Ave Mus Loup, F-17390 La Tremblade, France.
Source Parasites & Vectors (1756-3305) (Biomed Central Ltd), 2018-03 , Vol. 11 , N. 1 , P. 119 (16p.)
DOI 10.1186/s13071-018-2692-0
WOS© Times Cited 3
Keyword(s) Mikrocytos veneroides n. sp., Mikrocytos donaxi n. sp., Donax trunculus, Mortality, Microcell parasite
Abstract

Background: Microcell parasites are small intracellular protozoans mostly detected in molluscs and can be associated with mortalities. In 2010 and 2011, strong increases in mortality events were reported in different wild beds of the wedge clam Donax trunculus Linnaeus, along the Atlantic coast of France and the presence of potential pathogens, including microcells, was investigated.

Methods: Clams collected in different beds showing mortality were examined by histology. Based on histological observations, confirmatory analyses were carried out, including transmission electron microscopy (TEM) and molecular characterization.

Results: Histological analyses revealed the presence of small protozoans similar to microcell parasites in different tissues of Donax trunculus , particularly in muscular and connective tissues. TEM examination confirmed the intracellular localization of the protozoans. Moreover, the lack of haplosporosomes and mitochondria suggested that the observed parasites belong to the genus Mikrocytos Farley, Wolf & Elston,  1988. Mikrocytos genus-specific PCR and in situ hybridization results supported the microscopic observations. Sequence fragments of the 18S rRNA gene shared 75–83% identity with the different Mikrocytos spp.  described previously, including Mikrocytos mackini Farley, Wolf & Elston, 1988 and M. boweri Abbott, Meyer, Lowe, Kim & Johnson, 2014. Phylogenetic analyses confirmed that the microcell parasites observed in Donax trunculus in France belong to the genus Mikrocytos and suggest the existence of two distinct species.

Conclusions: Based on morphological, ultrastructural, molecular data and host information, the two microcell parasites detected in Donax trunculus belong to the genus Mikrocytos and are distinct from previously described membersofthisgenus.This  is the first report of Mikrocytos spp. found in France and infecting the clam Donax trunculus. Mikrocytos veneroïdes n. sp. was detected in different wild beds and Mikrocytos donaxi n. sp. was detected only in Audierne Bay.

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Figure S1. Alignment of Mikrocytos small subunit ribosomal gene sequences obtained in the present study. 5 127 KB Open access
Figure S2. Transmission electron microscopy of Mikrocytos veneroïdes n. sp. at different stages. 2 352 KB Open access
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Garcia Celine, Haond Christophe, Chollet Bruno, Nerac Mirella, Omnes Emmanuelle, Joly Jean-Pierre, Dubreuil Christine, Serpin Delphine, Langlade Aime, Le Gal Dominique, Terre-Terrillon Aouregan, Courtois Olivier, Guichard Benjamin, Arzul Isabelle (2018). Descriptions of Mikrocytos veneroïdes n. sp. and Mikrocytos donaxi n. sp. (Ascetosporea: Mikrocytida: Mikrocytiidae), detected during important mortality events of the wedge clam Donax trunculus Linnaeus (Veneroida: Donacidae), in France between 2008 and 2011. Parasites & Vectors, 11(1), 119 (16p.). Publisher's official version : https://doi.org/10.1186/s13071-018-2692-0 , Open Access version : https://archimer.ifremer.fr/doc/00428/53989/