Reference: Biol. Bull. 161: 115-125. (August, 1981) AMESON MICHAELIS (MICROSPORIDA) IN THE BLUE CRAB, CALLINECTES SAP1DUS. PARASITE-INDUCED ALTERATIONS IN THE BIOCHEMICAL COMPOSITION OF HOST TISSUES A M. FINDLEY, 1 E. W. BLAKENEY, JR., AND E. H. WEIDNER Department of Zoology & Physiology, and Department of Biochemistry, Louisiana State University. Baton Rouge. Louisiana 70803 ABSTRACT Ameson michaelis' interaction with its blue crab host significantly altered the biochemical constituents of host tissues. Modifications in skeletal muscle protein and carbohydrate metabolism were reflected in substantial variations in hemolymph composition. Blood osmolality, Cl~, and Na + ion levels decreased with heavy par-asitic invasion, while K + ion and ninhydrin positive substances (NPS) levels in-creased in both light and heavy infections. Microsporidiosis resulted in a general increase in all hemolymph free amino acids detected except glutamic acid. Effects of A. michaelis sporogenesis were observed by comparing the biochem-ical composition of thoracic and cheliped skeletal musculature. Protein and car-bohydrate levels were lower in infected thoracic muscle. The opposite trend was observed for tissue free-amino-acids (ninhydrin-positive substances). The concen-tration of nine of the sixteen amino acids detected remained unchanged with in-fection. Skeletal muscle glutamate, proline, glycine, alanine, and arginine levels declined, while taurine and tyrosine levels increased. Lactic acid accumulated in the hemolymph, thoracic muscle, and hepatopan-creas of parasitized blue crabs. Lactate concentrations reached six to seven times their normal levels in hemolymph and skeletal muscle, and four times the control value in the hepatopancreas. Blood glucose levels declined during the terminal stages of microsporidan infection. INTRODUCTION The Microsporidae are a large group of highly specialized obligate intracellular protozoan parasites. Although they are best known as parasites of arthropods and fish, microsporidans are the etiological agents of various pathologies in amphibians, reptiles, birds, and a variety of mammals, including man (see Sinderman, 1970; Weiser, 1976; Canning, 1977). Despite these parasites' wide distribution in nature and their devastating effects on a variety of animals, relatively little is known about their physiological characteristics and the infections they produce. Disturbances in the biochemical composition of tissues infected by intracellular parasites are of interest because such infections often significantly alter the elec-trolyte, carbohydrate, protein, and free-amino-acid pools of host cells (see von Brand, 1973). Among parasitic protozoans, the microsporidan Ameson michaelis (=Nosema michaelis) massively invades host cells, proceeds rapidly through spo-rogenesis in host muscle, and inflicts widespread tissue damage. A. michaelis spo-rogenesis takes place in blue crab sarcoplasm. Ater entering myofibrils, schizonts Received 12 March 1981; accepted 1 June 1981. 1 Present address: Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 115
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