author(s)
Mekala Lakshman

abstract
The conventional Electron Microscopy {(EM -Transmission Electron Microscope(TEM) and Scanning Electron Microscope (SEM)} is one of the gold standard techniques to study the patho-morphological changes in cells of different diseases in the field of life science. Examination of tissues / cells under EM is otherwise called as "cell pathology" which deals with all membranous structural deviations, localization of disease etiological agents (bacteria, virus, fungi, rickettesia like organisms (ROL's), mycoplasma and parasitic infections). Visualization of localized and /or attached pathogens and therapeutic nanoparticles in different structures of the cells of aquatic animals is possible only with EM studies. Despite of accessibility to various laboratory techniques for accurate diagnosis and specific pathogen identification but, the EM technique is having its significance to support all molecular techniques due to the meticulous observation of all sub-cellular structural changes in response to the disease causing agents which target different structures in a cell or group of cells. The conventional EM is a multi-stepped, time consuming and expertise technique which needs to have continuous practice and up-date. In general, aquatic animal diseases are wide range beginning from nutritional, bacterial, viral, neoplastic, parasitic, RLO and many other conditions are being recorded all over the Globe. Most of the diseases are being diagnosed on the basis of pathognomonic lesions and conventional lightmicroscopy (LM) techniques like histopat hology (HP), immunohistochemistry (ICH) or immunocytochemistry (ICC) and flow cytometry (FCM). Advanced diagnostic tools like qRT-PCR techniques, Genomics and Proteomics were also being used. But demonstration of minute pathogens like virus and sub cellular structural alterations due to disease process are possible only with EM.