Histopathologic And Molecular Aspects Of Paramoebiasis In Lobster (Homarus americanus) With Emphasis On The Long Island Sound Die-Off   Salvatore Frasca Jr.1, Thomas Mullen Jr.1, Thomas Burrage2 and Richard A. French1   1Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT; 2United States Department of Agriculture, Agriculture Research Service, Plum Island Animal Disease Center, Greenport, Long Island, NY     Epizootic mortality of American lobster (Homarus americanus) occurred in western Long Island Sound during autumn of 1999. Necropsies were conducted on dead or dying, i.e. “limp”, lobsters to elucidate a pattern of lesions accountable for clinical signs of paresis, flaccid paralysis and death. Histologic evaluation of hemocoelomic viscera, nerve ring ganglia, ventral nerve cord and peripheral nerves revealed hemocytic neuritis and ganglioneuritis, with polysystemic interstitial hemocytic infiltrates and microgranulomata. An amoeba was identified in foci of neuritis, in hemocytic infiltrates, within neurons and between nerve fibers. This amoeba possessed a small, round, secondary nucleus differentially stained using the Feulgen technique.  Transmission electron microscopic examination of amoebae in ganglia confirmed the presence of this nucleus-like organelle, or Nebenkörper, considered a feature of members of genus Paramoeba Schaudinn, 1896. Molecular data for the family Paramoebidae is absent. However, by utilizing universal primers complementary to highly conserved regions of eukaryotic 18S small subunit (SSU) ribosomal RNA genes, we have PCR amplified, cloned and sequenced ribosomal DNA (rDNA) from twelve morphologically related species of lobose amoebae.  Consensus SSU rDNA sequences from these amoebae provide the essential data with which to construct phylogenetic trees using bioinformatic computer methods and to identify target sequences for PCR primer and in situ hybridization probe design for detection of this paramoeba in lobster tissue. DNA-based diagnostic techniques such as these are directly applicable to future management programs designed to assess and maintain the health of the LIS lobster population.