Abstract
Haemolymph levels of amino acids, sugars and glycerol were investigated in the tenebrionid Physadesmia globosa during dehydration and rehydration. The absolute amount of amino acid decreases during dehydration and increases during rehydration, indicating active regulation of this solute (the osmolal contribution of amino acids is large - approx. 25%). Changes in the amino acid content of the haemolymph during dehydration are not the result of interchange with soluble protein; the possibility exists during rehydration (between 1 h and 48 h). Trehalose and glucose are the only sugars found in appreciable quantity in the haemolymph of this species. Their osmolal contributions (total sugar: 2.6%), and contributions to osmoregulation, are not great. Glycerol is a minor osmolar effector in the haemolymph of Physadesmia, and changes in its levels do not contribute importantly to the regulation of haemolymph osmotic pressure.
Highlights
Capacities for osmoregulation have been demonstrated in a great variety of mesic and xeric beetles (Machin, 1975; Broza et al, 1976; Riddle et al, 1976; Coutchie & Crowe, 1979; Nicolson, 1980; Cohen et al, 1986; Naidu & Hattingh, 1986, 1988; Riddle, 1986; Naidu, 2001a, b)
Despite high concentrations of amino acids and sugars being found in the haemolymph of insects (Mullins, 1985), the literature does not abound with information on the contribution of these organic constituents to haemolymph osmotic pressure (OP) and to osmoregulation
Haemolymph amino acids in P. globosa are regulated during both dehydration and rehydration, and contribute approximately 40% and 25% to osmoregulation during dehydration and rehydration, respectively
Summary
Capacities for osmoregulation have been demonstrated in a great variety of mesic and xeric beetles (Machin, 1975; Broza et al, 1976; Riddle et al, 1976; Coutchie & Crowe, 1979; Nicolson, 1980; Cohen et al, 1986; Naidu & Hattingh, 1986, 1988; Riddle, 1986; Naidu, 2001a, b). In most of these studies, the role of major haemolymph cations and anions in osmoregulation has been explored. The present study, examines haemolymph amino acids, sugars, and glycerol in Physadesmia globosa (Haag) during dehydration and rehydration
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