Osmoregulation in Onymacris rugatipennis, a free-ranging tenebrionid beetle from the Namib Desert.
Haemolymph levels of organic and inorganic constituents were investigated in the tenebrionid Onymacris rugatipennis during dehydration and rehydration. The major osmolar effectors are sodium (26%), chloride (24%), amino acids (18%), and sugars (11%); regulation of haemolymph osmotic pressure (OP) during dehydration is effected largely by a reduction in the haemolymph content of these constituents. Changes in amino acid levels are not the result of interchanges with soluble protein. During rehydration, the main contributors to osmoregulation are sodium (26%), chloride (24%), and an increase in haemolymph solute(s) not measured in this study (31%). Of the sodium removed from the haemolymph during dehydration, 21.2% was excreted. Faecal losses of potassium during dehydration far exceeded the amounts removed from the haemolymph; however, haemolymph potassium levels were strongly regulated during rehydration. Regulatory efficiency increases as desiccation proceeds, and is greatest only when this species is severely challenged.
Naidu
S G
SG
Department of Physiology, Nelson R Mandela School of Medicine, University of Natal, 719 Umbilo Road, 4041, Durban, South Africa. naidus15@med.und.ac.za
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose; D001835:Body Weight; D002712:Chlorides / Q000378:metabolism; D001517:Coleoptera / Q000502:physiology*; D003681:Dehydration; D003889:Desert Climate; D005243:Feces / Q000737:chemistry; D005440:Fluid Therapy; D006458:Hemolymph / Q000737:chemistry* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D014199:Trehalose / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology*
D000596:Amino Acids; D001786:Blood Glucose; D002712:Chlorides; D011506:Proteins; D012964:Sodium; D014199:Trehalose; D011188:Potassium