Ultrastructure of Mikrocytos mackini, the cause of Denman Island disease in oysters Crassostrea spp. and Ostrea spp. in British Columbia, Canada

Diseases of Aquatic Organisms

N. Cochennec-Laureau¹  G. R. Meyer¹  F. C. J. Berthe¹  P. M. Hine¹  S. M. Bower¹ 

关键词: Mikrocytos mackini;    Crassostrea gigas;    Ultrastructure;    Amitochondriate protozoan;    Denman Island disease;   

DOI  :  10.3354/dao045215

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: An ultrastructural study was carried out on Mikrocytos mackini, the cause of Denman Island disease in Pacific oysters Crassostrea gigas in western Canada. Three forms were identified, quiescent cells (QC), vesicular cells (VC) andendosomal cells (EC). QC occurred in the vesicular connective tissue (VCT), haemocytes (hyalinocytes), adductor and heart myocytes, and extracellularly. They had a central round to ovoid nucleus, <7 cisternae of inactive nuclear membrane-bound Golgi,few vesicles and lysosome-like bodies. VC were rarely extracellular and usually occurred in adductor and heart myocytes, in close association with host cell mitochondria. The contents of the host cell mitochondria appeared to pass through a tubularextension into the cytoplasm of the parasite. Cytoplasmic vesicles resembled the tubular structure in appearance and size. EC occurred in the VCT, in haemocytes and extracellularly. They had a dilated nuclear membrane, sometimes containing a loopedmembranous structure that appeared to derive from the nucleus, and pass into the cytoplasm. A well-developed anastomosing endoplasmic reticulum connected the nuclear and plasma membranes, and endosomes were present in the cytoplasm. QC and EC cells werefrequently observed tightly against, or between, the nuclear membranes of the host cell. Few organelles occurred in all forms of M. mackini, especially QC. The lack of organelles found in most eukaryotic cells, including mitochondria ortheir equivalents, may be due to obligate parasitism and the utilization of host cell organelles reducing the need for parasite organelles. Alternatively, perhaps M. mackini is a primitive eukaryote. Although phylogenetic affinities could not bedetermined, it is not a haplosporidian. A developmental cycle is proposed from these findings.

【 授权许可】

Unknown