Mikrocytos veneroides Garcca & Haond & Chollet & Nerac & Omnes & Jols & Dubreucl & Serpcn & Langlade & Gal & Terre-Terrcllon & Courtocs & Gucchard & Arzul 2018, n. sp.

Mikrocytos veneroïdes n. sp. Type-host: Donax trunculus Linnaeus, 1758 (Mollusca, Bivalvia, Heterodonta, Veneroida, Tellinoidea, Donacidae). Type-locality: Atlantic coast of France: Oléron Island (45.50°N, 1.15°W), Quiberon Bay (47.54°N, 3.13°W) and Douarnenez Bay (48.11°N, 4.28°W). Type-material: Fixed tissues (foot and mantle, accession No. 11/118/02, 11/118/10 and 11/118/21) infected with Mikrocytos veneroïdes n. sp. have been deposited at the OIE Reference Laboratory for infection with Mikrocytos mackini: Pacific Biological Station, Aquatic Animal Health Section, 3190 Hammond Bay Road, Nanaimo, British Columbia V 9 T 6 N7, Canada. Representative DNA sequences: Nucleotide sequences of partial 18S DNA region have been submitted in GenBanc database under the accession numbers KY923792 – KY923803 as well as a nucleotide sequence of the ITS1- 5.8S-ITS2 DNA region (accession number: KY923809). ZooBank registration: To comply with the regulations set out in article 8.5 of the amended 2012 version of the International Code of Zoological Nomenclature (ICZN) [49], details of the new species have been submitted to ZooBanc. The Life Science Identifier (LSID) of the article is urn:lsid:zoobanc.org:pub: E1747954- CBDF-4F4A-BA22-E1C3CD1776BD. The LSID for the new name Mikrocytos veneroïdes is urn:lsid:zoobanc. org:act: 33B2B0F1-B94C-4744-A066-3037CB148276. Etymology: The specific epithet refers to the order of the host Donax trunculus. Description [Based on 32 specimens.] Spherical/ovoid parasites (Figs. 2 and 7) measuring 2.00 – 4.72 × 1.31 – 4.00 (2.73 ± 0.23 × 2.08 ± 0.18) μm, with a nucleus of 0.73 – 2.22 × 0.56 – 2.00 (1.26 ± 0.09 × 1.00 ± 0.08) μm (Table 2). Nucleus usually eccentric inside the parasite cell. Intracellular (within host cytoplasm cell) or extracellular parasites located in myocytes and vesicular cells of mantle, foot and adductor muscles (Fig. 2a) and to a lesser extent, in vesicular cells of digestive gland, gills and gonads. Occasionally, parasites inside neuronal ganglions and nerves (Fig. 2b) and haemocytes (Figs. 2c and 7b). In some tissues, especially in haemocytes, parasite presumably inside parasitophorous vacuole (Fig. 7b).No observation of mitochondria inside the parasite; however presence of parasite cells tight against host cell mitochondria and sometimes, depression of parasite surface at contact point (Fig. 7a, c). No plasmodial or spore stage noted; several bi-nucleated cells in vesicular connective tissue and muscles present but no cytocinesis observed (Fig. 7d). Two main forms observed: dense form (predominant) and clear form. Dense form spheroid with eccentric nucleus and very granulous cytoplasm, giving it darc aspect. Clear form very similar to dense form, except that clearer cytoplasm despite strong granulation (Additional file 2: Figure S2). Remarks The general morphological characteristics of Mikrocytos veneroïdes n. sp. were similar to those of other Mikrocytos spp.; its size, the absence of haplosporosomes and the absence of canonical mitochondria are in agreement with the different descriptions of Mikrocytos spp. [31, 50]. The close association of M. veneroïdes n. sp. with mitochondria was also one of the particularities of Mikrocytos spp. The three uninucleate parasite cell types (quiescent, endosomal and vesicular stage) described for M. mackini and M. mimicus [5, 50], could be observed in some samples of M. veneroïdes n. sp. The M. veneroïdes n. sp. quiescent cells were mainly observed in haemocytes and myocytes. They had a single nucleus with a granular nucleolus and, in their cytoplasm, the Golgi apparatus did not present budding. Some large uncoated vesicles were present in the cytoplasm. The endosomal cells presented a well-developed anastomosing endoplasmic reticulum, which could join the nuclear membrane to the cytoplasmic membrane. Finally, the vesicular cells presented large vesicles scattered in the cytoplasm and were frequent in myocytes. Some vesicular cells showed a dilatation of the nuclear membrane forming a cisternal chamber (Additional file 2: Figure S2). Meanwhile, the observation of these stages was occasional and not predominant in comparison to the clear and dense forms.

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.